Scientific Criteria Document for the Development of the ......Canadian Water Quality Guidelines for...

Scientific Criteria Document for the Development of the

Canadian Water Quality Guidelines for the Protection of Aquatic Life

TRICHLORFON

PN 1466

ISBN 978-1-896997-82-7 PDF

© Canadian Council of Ministers of the Environment, 2012

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon ii

NOTE TO READERS

The Canadian Council of Ministers of the Environment (CCME) is the primary minister-led intergovernmental forum for collective action on environmental issues of national and international concern. This document provides the background information and rationale for the development of the Canadian Water Quality Guidelines for trichlorfon. They were developed by the National Guidelines and Standards Office of Environment Canada. For additional scientific information regarding these water quality guidelines, please contact: National Guidelines and Standards Office Environment Canada Fontaine 200 Sacré-Cœur Blvd. Gatineau, QC K1A 0H3 Phone: 819-953-1550 Email: [email protected] Website: http://www.ec.gc.ca This scientific supporting document is available in English only. Ce document scientifique du soutien n’est disponible qu’en anglais avec un résumé en français. Reference listing: CCME. 2012. Canadian Water Quality Guidelines: Trichlorfon. Scientific Criteria Document. Canadian Council of Ministers of the Environment, Winnipeg. PN 1466 ISBN 978-1-896997- 82-7 PDF © Canadian Council of Ministers of the Environment, 2012

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon iii

SCIENTIFIC CRITERIA DOCUMENT - CANADIAN WATER QUALITY GUIDELINES FOR TRICHLORFON

TABLE OF CONTENTS

Note to readers ............................................................................................................................. ii Table of Contents ........................................................................................................................ iii List of Figures .............................................................................................................................. iv List of Tables................................................................................................................................ iv Executive Summary ...................................................................................................................... i Résumé......................................................................................................................................... iii 1.0 INTRODUCTION .............................................................................................................. 5 2.0 PHYSICAL AND CHEMICAL PROPERTIES .............................................................. 5

2.1 Identity: ............................................................................................................. 5 2.2 Analytical Methods............................................................................................ 6

3.0 PRODUCTION AND USES ............................................................................................ 6 4.0 SOURCES TO THE ENVIRONMENT .......................................................................... 8 5.0 ENVIRONMENTAL FATE AND BEHAVIOUR............................................................. 8

5.1 Transformation Products................................................................................... 8 5.2 Fate in Water and Sediment ............................................................................. 8 5.3 Fate in Soil ........................................................................................................ 9 5.4 Fate on Vegetation.......................................................................................... 10 5.5 Bioconcentration and Bioaccumulation ........................................................... 10

6.0 CONCENTRATIONS IN CANADIAN WATERS ........................................................ 10 6.1 Guidelines from Other Jurisdictions ................................................................ 11

7.0 ENVIRONMENTAL TOXICITY..................................................................................... 11 7.1 Mode of Action ................................................................................................ 11 7.2 Freshwater Aquatic Toxicity ............................................................................ 12 7.3 Toxicity to Fish ................................................................................................ 12

7.3.1 Toxicity to Invertebrates .............................................................................. 14 7.3.2 Toxicity to Algae and Plants ....................................................................... 15 7.3.3 Toxicity to Amphibians ................................................................................ 15 7.3.4 Field Studies ................................................................................................. 15 7.3.5 Marine Toxicity.............................................................................................. 16 7.3.6 Toxicity-Modifying Factors .......................................................................... 16 7.3.7 Toxicity of Transformation Products.......................................................... 16

8.0 GUIDELINE DERIVATION ........................................................................................... 17 8.1 Protection of Freshwater Aquatic Life

8.1.1 Short-term Freshwater Benchmark Concentration ................................. 18 8.1.2 Long-term Freshwater CWQG ................................................................... 22

8.2 Protection of Marine Life ................................................................................. 23 8.3 Data Gaps and Research Recommendations................................................. 23 8.4 Implementation and Other Considerations...................................................... 23

9.0 REFERENCES ............................................................................................................... 24 APPENDIX A – TOXICITY VALUES FOR FRESHWATER AQUATIC SPECIES EXPOSED TO TRICHLORFON............................................................................................... 30

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon iv

LIST OF FIGURES

Figure 2.1. Chemical structure of trichlorfon.............................................................................. 5 Figure 5.1 Structure of dichlorvos, the primary transformation product of trichlorfon............. 8 Figure 8.1 Short-term log-normal SSD representing the toxicity of trichlorfon in freshwater.21

LIST OF TABLES

Table 3.1 Physical-chemical properties of trichlorfon.............................................................. 7 Table 6.1 Water quality criteria and guidelines for the protection of freshwater aquatic life. 11 Table 8.1 Final aquatic toxicity data selected for short-term SSD development.................... 20 Table 8.2 Studies used to derive geometric means for short-term freshwater SSD................ 21 Table 8.3 Short-term freshwater SSD for trichlorfon resulting from generic SSD method ... 22

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon v

List of Acronyms

AChE Acetylcholinesterase a.i. Active ingredient BCF Bioconcentration factor CAS Chemical Abstract Service CCME Canadian Council of the Ministers of the Environment CDF Cumulative distribution function ChE Cholinesterase CL Chemiluminescence CWQG Canadian Water Quality Guideline ECXX Effective concentration on XX percent of the population FAO Food and Agriculture Organization HSDB Hazardous Substances Data Bank IARC International Agency for Research on Cancer ICXX Inhibitory concentration on XX percent of the population IPCS International Programme on Chemical Safety IUPAC International Union of Pure and Applied Chemistry LCXX Lethal concentration on XX percent of the population LOEC Lowest observable effects concentration MATC Maximum acceptable toxicant concentration MPC Maximum permissible concentration NC Negligible concentration NOEL No observable effects level NOEC No observable effects concentration PMRA Pest Management Regulatory Agency SSD Species sensitivity distribution SSRD Special Review and Reregistration Division TLm Median tolerance limit US EPA United States Environmental Protection Agency WHO World Health Organization

EXECUTIVE SUMMARY

This report describes the development of Canadian Water Quality Guidelines (CWQG) for the protection of freshwater aquatic life for the pesticide active ingredient trichlorfon. While information regarding formulations is compiled and summarized, environmental quality guideline values are derived using toxicity data generated using the technical active ingredient trichlorfon (> 90% active ingredient). Trichlorfon is an organophosphate insecticide used to control pests such as cockroaches, crickets, silverfish, bedbugs, fleas, cattle grubs, flies, ticks, leafminers and leaf-hoppers (EXTOXNET, 1996). Trichlorfon is manufactured by Bayer CropScience Inc. It is produced in soluble powder, granular, emulsifiable concentrate, and fly bait formulations. It was first registered in Canada in 1980, and is currently registered under the trade names Dylox 420, Dipterex, Neguvon pour-on cattle insecticide, and Dylox 80% (PMRA, 2004). Trichlorfon has a molecular weight of 257.4 g/mol. It has a melting point between 83 and 84ºC and a density of 1.73 g/cm3 at 25ºC (HSDB, 1999). It has a Henry's Law constant of 1.72 x 10-9 kPa·m3/mol (HSDB, 1999) and a vapour pressure of 1.04 x 10-6 kPa (HSDB, 1999). These values indicate that it is non-volatile. Trichlorfon is highly soluble in water, with a solubility of 154,000 mg/L at 25ºC (HSDB, 1999). The log Kow for trichlorfon ranges from 0.40 to 1.70, suggesting that it will partition to water-based substances more so than organics. The log Koc ranges from 0.78 to 1.90, indicating that trichlorfon will preferentially stay in solution, rather than partitioning to sediment or suspended solids (HSDB, 1999). Trichlorfon is considered to be non-persistent in the aqueous environment based on its high rate of hydrolysis under neutral and alkaline conditions. Reported half-lives of 588, 67, and 22 hours are reported at pHs of 6, 7, and 8, respectively (Chapman and Cole 1982). Trichlorfon is one of the few organophosphates that transforms into a more toxic compound (Howe et al., 1994). Dichlorvos, the primary metabolite of trichlorfon, inhibits cholinesterase at ≥100 times the rate of trichlorfon (Hofer, 1981). Transformation to the neurotoxin dichlorvos occurs when trichlorfon is hydrolyzed in water, biological fluids, and tissues at pH levels greater than 5.5 (IPCS, 1992). The short-term and long-term freshwater Canadian Water Quality Guidelines for trichlorfon for the protection of aquatic life were developed. The short-term freshwater CWQG was developed using the statistical approach, as sufficient data existed to meet the requirements for SSD. The data requirements were not satisfied to derive a long-term freshwater CWQG using the SSD approach. Therefore, following the tiered approach, a long-term freshwater interim CWQG was developed. There were insufficient data to develop either a short- or long-term marine CWQG. The short-term and long-term freshwater guideline values are summarized in the table below. Due to the rapid transformation of trichlorfon to dichlorvos, additional site-specific guidance may be required to ensure aquatic life is not being impacted, especially in regions elevated in pH and/or temperature.

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon ii

Canadian Water Quality Guidelines (CWQG) for Trichlorfon for the Protection of Aquatic Life (µg a.i./L)

Long-Term Exposure

Short-Term Exposure

Freshwater 0.009* 1.1** Marine NRG NRG

NRG = no recommended guideline * interim value calculated from short-term low-effect data using lowest endpoint approach ** value calculated from LC50 data using the SSD approach

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon iii

RÉSUMÉ

Le présent rapport décrit le processus d’élaboration des Recommandations canadiennes pour la qualité des eaux (RCQE) relatives au trichlorfon, matière active utilisée comme pesticide, en vue de la protection de la vie aquatique en milieu d’eau douce. Bien que des études soient menées au sujet des préparations, on se sert des données sur la toxicité de la matière active de qualité technique trichlorfon (> 90 % de matière active) pour établir les valeurs des recommandations. Le trichlorfon est un insecticide organophosphoré utilisé pour lutter contre certains organismes nuisibles, tels les coquerelles, les grillons, les lépismes argentés, les punaises de lits, les puces, les hypodermes des bovins, les mouches, les tiques, les mineuses des feuilles et les cicadelles (EXTOXNET, 1996). Le trichlorfon est produit par Bayer CropScience Inc. et se présente sous forme de poudre soluble, de granulés de concentré émulsifiable et de préparations d’appât pour mouches. Il a été homologué pour la première fois au Canada en 1980 et est actuellement homologué sous les noms commerciaux suivants : Dylox 420, Dipterex, Neguvon à verser – insecticide pour bovins, et Dylox 80 % (ARLA, 2004). La masse moléculaire du trichlorfon est de 257,4 g/mol. Son point de fusion se situe entre 83 et 84 ºC et sa densité est de 1,73 g/cm3 à 25 ºC (HSDB, 1999). La constante de la loi d’Henry du trichlorfon est de 1,72 × 10-9 kPa m3/mol (HSDB, 1999), et sa pression de vapeur est de 1,04 × 10-6 kPa (HSDB, 1999). Ces valeurs indiquent que ce produit n’est pas volatil. Le trichlorfon est très soluble dans l’eau, à savoir 154 000 mg/L à 25 ºC (HSDB, 1999). La valeur du log Koe pour le trichlorfon varie de 0,40 à 1,70, ce qui semble indiquer que le trichlorfon se retrouvera dans l’eau plus facilement que dans les substances organiques. Le log Kco varie de 0,78 à 1,90, indiquant que le trichlorfon aura tendance à rester dissous, plutôt que de se répartir dans les sédiments ou les solides en suspension (HSDB, 1999). Le trichlorfon est considéré comme non persistant en milieu aqueux, compte tenu de son taux élevé d’hydrolyse dans des conditions neutres et alcalines. Des demi-vies de 588, de 67 et de 22 heures ont été indiquées à des pH de 6, 7, et 8, respectivement (Chapman et Cole, 1982). Le trichlorfon est un des rares composés organophosphorés qui se transforme en un composé plus toxique (Howe et al., 1994). En effet, le dichlorvos (le métabolite primaire du trichlorfon) inhibe la cholinestérase à un taux plus de 100 fois supérieur à celui de l’inhibition produite par le trichlorfon (Hofer, 1981). Le trichlorfon se transforme en une neurotoxine appelée dichlorvos, lorsqu’il est hydrolysé dans l’eau, les liquides biologiques et les tissus à un pH supérieur à 5,5 (PISSC, 1992). Des recommandations canadiennes pour la qualité des eaux (RCQE) visant le trichlorfon en vue de la protection de la vie aquatique exposée à court et à long terme ont été élaborées. La RCQE concernant l’exposition à court terme en eau douce a été élaborée à l’aide de la méthode statistique, car on disposait de suffisamment de données pour satisfaire aux exigences pour la DSE. Les données n’étaient toutefois pas suffisantes pour établir des recommandations concernant l’exposition à long terme en eau douce au moyen de la méthode de la DSE. Par conséquent, selon la démarche à plusieurs volets, on a élaboré une RCQE provisoire pour une exposition à long terme en eau douce. Les données n’étaient pas suffisantes pour élaborer des RCQE pour les expositions à court et à long terme en milieu marin. Les RCQE pour les expositions à court et à long terme en eau douce sont résumées dans le tableau ci-dessous. De

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon iv

plus, à cause de la transformation rapide du trichlorfon en dichlorvos, d’autres directives propres à chaque site pourraient aussi être nécessaires afin de s’assurer que la vie aquatique n’est pas touchée, spécialement dans les régions où le pH ou la température sont élevés. Recommandations canadiennes pour la qualité des eaux (RCQE) : protection de

la vie aquatique – trichlorfon (µg m.a./L)

Exposition à long terme

Exposition à court terme

Eaux douces 0,009* 1,1** Eaux marines AR AR

AR = aucune recommandation * valeur calculée à partir des données sur les doses produisant un effet faible à court

terme, selon la méthode du plus petit paramètre d’effet ** valeur calculée à partir des données sur la CL50, selon la méthode de la DES

1.0 INTRODUCTION

The Canadian Water Quality Guidelines (CWQG) for the Protection of Aquatic Life are developed through compilation and interpretation of aquatic toxicity data, thereby providing an important tool in the evaluation of ambient water quality. Trichlorfon concentrations monitored in the environment can be compared to the guideline value to help predict whether sensitive species will be impacted in the ecosystem. Exceedance of the guideline values does not denote definite negative impacts to the environment, but rather that further investigation is necessary, for example site-specific analysis of water chemistry parameters and sensitive species residing in the ecosystem. The Water Quality Task Group of the Canadian Council of the Ministers of the Environment (CCME) is charged with overseeing the development of Canadian Water Quality Guidelines for the Protection of Aquatic Life. In 2007, the guideline derivation protocol was revised. The goals of the revised protocol include: (i) accounting for the unique properties of contaminants which influence their toxicity; and (ii) incorporating the species sensitivity distribution (SSD) method, which uses acceptable data as outlined in the protocol (provided these data pass quality control criteria) in a more flexible approach. The structure of the criteria document for trichlorfon has been built to accommodate the changes in the protocol for guideline derivation. All of the customary components of scientific criteria documents have been included (physical and chemical properties, production and uses, environmental fate and behaviour, environmental concentrations, toxicity data). In addition, new cornerstones of the protocol, such as bioaccumulation/bioconcentration, and toxicity modifying factors have been given attention.

2.0 PHYSICAL AND CHEMICAL PROPERTIES

2.1 Identity:

Trichlorfon is an organophosphate insecticide used to control pests such as cockroaches, crickets, silverfish, bedbugs, fleas, cattle grubs, flies, ticks, leafminers and leaf-hoppers (EXTOXNET, 1996). It has the IUPAC chemical name of dimethyl (2,2,2-trichloro-1-hydroxyethyl) phosphate (CAS RN 52-68-6; Figure 2.1). Trichlorfon-containing products are used in agriculture, horticulture, forestry, food storage, gardening, households and animal husbandry (Tomlin, 1997).

Figure 2.1. Chemical structure of trichlorfon

Canadian Water Quality Guidelines for the Protection of Aquatic Life for Trichlorfon 6

The physical and chemical properties of trichlorfon are presented in Table 2.1. Trichlorfon has a melting point between 83 and 84ºC and a density of 1.73 g/cm3 at 25ºC (Mackay et al., 1999; HSDB, 1999). It has a Henry's Law constant of 1.72 x 10-9 kPa·m3/mol and a vapour pressure of 1.04 x 10-6 kPa (HSDB, 1999). These values indicate that it is non-volatile. Trichlorfon is highly soluble in water, 120,000 mg/L at 25ºC (HSDB, 1999). Trichlorfon is also highly soluble in chloroform (750,000 mg/L), ether (170,000 mg/L) and benzene (152,000 mg/L) (Budavari, 1996). It is poorly soluble in carbon tetrachloride, and insoluble in petroleum oils (IARC, 1983). Trichlorfon is stable in alcohols and organic solutions (Clayton and Clayton, 1981-1982). The log Kow for trichlorfon ranges from 0.40 to 1.70, suggesting that it will partition to water-based substances more so than organics. The log Koc ranges from 0.78 to 1.90, indicating that trichlorfon will preferentially stay in solution, rather than partitioning to sediment or suspended solids (HSDB, 1999).

2.2 Analytical Methods

The standard procedures for residue detection involve extraction with acetonitrile and re-extraction with ether, followed by gas chromatography detection using flame photometric detection or flame thermionic detection. During chromatography, trichlorfon is thermally decomposed to dimethyl phosphite for detection and quantification (Ferreira and Fernandes, 1980). Acetylation or trimethylsilylation can be used to stabilize trichlorfon for gas chromatography, thus avoiding decomposition (Vilceanu et al., 1973; Bowman and Dame, 1974). Recent analytical methods using a column (e.g., Thermon 3000, Shimalite TPA) can detect trichlorfon without decomposition. Gas chromatography using the flame thermionic method can be based on column using acetic anhydride (Conrad et al., 1987). Geiß and Gebert (2006) found that octadecyl silica materials were most suitable for the extraction of trichlorfon from water.

3.0 PRODUCTION AND USES

Trichlorfon was introduced to the commercial market in 1952 (Lorenz et al., 1955). Trichlorfon is primarily used to control insects on field crops (e.g., corn, alfalfa, barley, and tobacco), fruits, vegetables, and ornamentals. Other applications include the control of pests around domestic areas and on animals and fish, as fly bait, and to treat intestinal and ectoparasites of fish. Trichlorfon is produced in soluble powder, granular, emulsifiable concentrate, and fly bait formulations. The amount of trichlorfon in these products ranges from 1% active ingredient in bait products to 98% active ingredient in technical grade product (USEPA, 1997). In Canada, the Pest Management Regulatory Agency (PMRA) regulates the use of active ingredients under the Pest Control Products Act. Pesticides are registered for use in agricultural/forestry, industrial, and social applications. Trichlorfon was first registered in Canada in 1980, and was re-evaluated by PMRA in 2008 (PMRA, 2008). The re-evaluation eliminated a number of uses, including essentially all residential uses and restricted other uses considerably. Bayer CropScience Inc. is the registrant for these products.


Table 2.1 Physical-chemical properties of trichlorfon.

Dylox 420, containing 420 g a.i./L, is a liquid insecticide applied aerially to field crops (e.g., alfalfa, grains, corn, tobacco), fruits (e.g., berries), vegetables, and ornamentals (e.g., flowers, shrubs, trees). Application rates for field crops typically range from 1.5 to 2.75 L/ha. Tobacco application rates range from 2.75 to 7.25 L/ha. Application rates for vegetables range from 2.75 to 4 L/ha (PMRA, 2004). Dylox 80% is a soluble powder, containing 80% trichlorfon, that is applied to field crops, vegetables, and ornamentals. Application rates for field crops typically range from 0.35 to 2.25 kg/ha, but are higher for tobacco with a range of 1.5 to 4 kg/ha. Typical application rates for vegetables and ornamentals are 0.70 to 2.25 and 1 to 2.25 kg/ha, respectively (PMRA, 2004). Neguvon pour-on cattle insecticide is used to control lice and grubs on cattle. It is a liquid formulation (8% trichlorfon) and is applied directly to the animals’ backs (PMRA, 2004).

Physical-Chemical Property Trichlorfon Reference(s) Appearance

White crystals Budavari, 1996; USEPA, 1997

Common Name Trichlorfon USEPA, 1997 Trade Name Anthon, Bovinos, Briten,

Chlorofos, Chlorophos, Ciclosom, Dipterex, Ditrifon, Dylox, Dyrex, Equino-Aid, Foschlor, Leivasom, Neguvon, Masoten, Pronto, Phoschlor, Proxol, Totalene, Trichlorophene, Trichlorphon, Trichlorophon, Trinex, Tugon and Vermicide Bayer 2349.

EXTOXNET, 1996

Class organophosphate EXTOXNET, 1996 Chemical Name

CAS: 52-68-6 IUPAC: dimethyl (2,2,2-trichloro-1-hydroxyethyl) phosphate

USEPA, 1997

Chemical Formula C4H8Cl3O4P Mackay et al.1999 CAS Registry Number 52-68-6 EXTOXNET, 1996 Molecular Weight 257.4 Mackay et al. 1999 Water Solubility 120,000 mg/L @ 25ºC HSDB, 1999 Density 1.73 g/cm3 @ 25ºC HSDB, 1999 Melting Point 83-84ºC Mackay et al. 1999 Vapour Pressure 1.04 x 10-6 kPa @ 20°C HSDB, 1999 Partition Coefficient (log Kow)

0.40-1.70 Mackay et al. 1999

Soil Adsorption Coefficient (log Koc)

0.78-1.90 HSDB, 1999

Henry’s Law Constant 1.72 x 10-9 kPa·m3/mol HSDB, 1999


4.0 SOURCES TO THE ENVIRONMENT

Trichlorfon is administered using spray and aerial application methods. These applications to soil and vegetation can expose non-target terrestrial organisms to trichlorfon. Most trichlorfon-containing products used in agriculture (e.g., DYLOX 420) are applied multiple times throughout the year, thus prolonging the exposure period to non-target organisms. Although trichlorfon is not to be applied directly to water bodies (PMRA, 2004), the pesticide may enter these systems by leaching, runoff, or spray drift, thus exposing aquatic organisms to residues (USEPA, 1997). Losses as a result of volatilization following application may be significant depending on environmental conditions. The presence of pesticides in air, water and ice in the arctic and other regions of the world where these compounds are neither produced nor used may occur as a result of long-range atmospheric transport from agricultural and urban areas. Transport of these compounds in the atmosphere is a function of both vapour pressure and water solubility. Environments of low oxidation, high vapour pressure, and low water solubility (Sw) allow for the presence of organic compounds to remain in the gas phase for longer periods of time.

5.0 ENVIRONMENTAL FATE AND BEHAVIOUR

5.1 Transformation Products

Dichlorvos (2,2,-dichlorovinyl dimethyl phosphate) is the major transformation product of trichlorfon (Figure 5.1; Hofer, 1981; USEPA, 1997). Biotransformation in soil and hydrolysis in water are the primary methods of trichlorfon transformation (HSDB, 1999). The transformation to dichlorvos in water occurs by dehydrochlorination (IPCS, 1992). The rate of transformation increases at greater water alkalinities (IPCS, 1992). Trichlorfon can be transformed to dichlorvos through photolysis. The rate of photolysis is slower in solid than aqueous environments (Giovanoli-Jakbczak et al., 1971). In plant tissues, trichlorfon is transformed to dichlorvos by dechlorination. Dichlorvos is then hydrolyzed to phosphoric acid and dichlorovinyl alcohol (Hartley and Kidd, 1987). Diclorvos was demonstrated to be non-persistent in okra plants (Zaidi et al., 1993) and meat (Millar and Aitken, 1964).

Figure 5.1 Structure of dichlorvos, the primary transformation product of trichlorfon

5.2 Fate in Water and Sediment

The high water solubility and low octanol-water partition coefficient of trichlorfon indicate that it will preferentially remain in water rather than partition to organic matter. This is supported by


a low soil adsorption coefficient, indicating that trichlorfon does not have an affinity for sediment or suspended solids (HSDB, 1999). Transformation of trichlorfon occurs more rapidly with increasing water alkalinity. Approximately 99% of trichlorfon applied to a pond with a pH of 8.5 transformed (to dichlorvos) in 2 hours. Trichlorfon was stable after 2 hours in a pond administered the same application, but with a pH of 5 (Purdue University, 1987). Chapman and Cole (1982) reported half-lives of 588, 67, and 22 hours at pHs of 6, 7, and 8, respectively. A similar range was reported by USEPA (1997) with hydrolysis half-lives of 104 days (pH 5), 34 hours (pH 7), and 31 minutes (pH 9). A hydrolysis half-life of 526 days was reported for trichlorfon in water with a pH between 1 and 5 and a temperature of 20ºC (Mühlmann and Schrader, 1957). Faust and Suffet (1966) also considered the influence of temperature in transformation. Half-lives at 10, 20, 30, 50 and 70 ºC, and pHs of 1, 2, 3, 4, and 5 were 2400, 526, 140, 10.7, and 1.13 days, respectively (Faust and Suffet, 1966). Hydrolysis is more rapid in non-sterile (natural) than sterile (laboratory) water (HSDB, 1999). A higher rate of decomposition was reported in river water (pH 7.39) than distilled water (pH 7.3-7.5), indicating that biotransformation aids in transformation of trichlorfon in water (HSDB, 1999).

5.3 Fate in Soil

Trichlorfon is considered to be highly mobile in soil, based on its water solubility (154,000 mg/L) and soil adsorption coefficient (log Koc = 0.78-1.90) (HSDB, 1999). Soil organic matter content and texture do not significantly affect the mobility of trichlorfon (HSDB, 1999; EXTOXNET, 1996). These properties suggest that groundwater contamination could occur. However, the rapid transformation of trichlorfon in soil could minimize such contamination (Purdue University, 1987; USEPA, 1997). In non-sterile soil, trichlorfon transforms rapidly with an average half-life of 10 days, and a range from 1 to 27 days (Purdue University, 1987; Wauchope et al., 1992; IARC, 1983; Domine et al., 1993). Half-lives for transformation in sterile soil are greater than 40 days (Purdue University, 1987). Field studies have observed the influence of soil pH on the transformation rate of trichlorfon. Trichlorfon applied to soil at a rate of 2 mg/kg transformed completely in 1.5 months at a pH range of 3 to 4.6, and in 0.5 months at a pH range of 8.7 to 9.05 (HSDB, 1999). Rapid transformation was observed in trees sprayed with 1.14 kg/ha of trichlorfon (Sundaram and Varty, 1989). Shortly after application, soil concentrations of trichlorfon were 3 mg/kg. Two weeks after the application, concentrations were below the limit of detection (0.05 μg/kg) (Sundaram and Varty, 1989). Rapid transformation limits the movement of trichlorfon to deeper soil layers. Ten days after the last of two applications to an orchard (application rate not reported), trichlorfon was detected in 0 to 10 cm and 10 to 20 cm soil layers (Naishtein et al., 1973). Significant movement into lower layers was not reported following application of 2.4 kg/ha (Baida, 1970). At an application rate of 60 kg/ha, trichlorfon penetrated 60 cm into the soil (Naishtein, 1976). The presence of plants (e.g., tomato, potato, cabbage) has been associated with more rapid transformation than fields without vegetation (Ivanova and Molozhanova, 1974).


5.4 Fate on Vegetation

Trichlorfon does not persist in leaves or leaf litter (USEPA, 1997). Half-lives for trichlorfon applied to stems or leaves of tomato, potato, and cotton plants ranged from 20 to 57 hours. Half-lives for trichlorfon applied to plums, cherries, apples, peas, and wheat ranged from 0.5 to 0.75 hours (Dedek et al., 1979). The residual period for trichlorfon on plants was reported to be 7 to 10 days (USEPA, 1997).

5.5 Bioconcentration and Bioaccumulation

Bioconcentration factors (BCF) are a measure of the tendency of a substance to migrate from water to the body tissues of aquatic organisms where it can accumulate and become concentrated (Rand et al., 1995). An estimated BCF of 3 is reported for aquatic organisms exposed to trichlorfon. This suggests that the potential for bioconcentration is low (HSDB, 1999). This is supported by the rapid rate of transformation and low octanol-water partition coefficient reported for trichlorfon. These factors indicate that trichlorfon will have a low persistence in water and is unlikely to partition to the lipids of aquatic organisms. The results of Lopes et al. (2006) support this, as they found a BCF of 0.41 l/kg in the South American ray-finned fish Piaractus mesopotamicus (Pacu) and they found a half-life time of 57h (2.5d) for trichlorfon in water. Therefore bioaccumulation and biomagnification of trichlorfon is unlikely to occur.

6.0 CONCENTRATIONS IN CANADIAN WATERS

The National Water Research Institute, Environment Canada recently completed a three year surveillance program of pesticides in each of the five Environment Canada regions (Atlantic, Québec, Ontario, Prairie & Northern and Pacific Yukon) (Environment Canada, 2011). Trichlorfon was analyzed in surface waters in Ontario. Trichlorfon was not detected in surface waters sampled in 2003 (n=27) in water sampled around the Great Lakes. In isolated Ontario lakes, trichlorfon was rarely detected (3 of 163 samples) but had the highest concentration detected relative to 44 other pesticides (0.065 µg/L) (Environment Canada, 2011). The International Programme on Chemical Safety reports the results of two monitoring studies in Canada (IPCS, 1992). In 1976, water samples collected in forests sprayed with trichlorfon ranged from 0.062 to 1.0 μg/L (Sergeant and Zitko, 1979). In 1977, the maximum concentration measured was 0.058 μg/L (Sergeant and Zitko, 1979). Water samples collected two weeks after application at a rate of 1.14 kg/ha of trichlorfon to a forest in New Brunswick had trichlorfon concentration ranging from below detection limit (0.05 μg/L) to 95 μg/L (Sundaram and Varty, 1989). Dichlorvos, the primary transformation product of trichlorfon, was monitored in the Pacific and Yukon Region of Canada during 2003 and 2004. Samples in this region were collected, following storm events, from areas of high pesticide use. Dichlorvos concentrations from <0.000001 to 0.00181 μg/L were measured in surface water samples collected from the Lower Fraser Valley and Okanagan Basin, with a detection limit of 0.000001 μg/L. Sampling efforts in the Québec Region focused on the tributaries entering the St. Lawrence River, and concluded that dichlorvos was not detected in the Yamaska, Nicolet, Saint-François, or St. Lawrence Rivers in 2004, with respect to a detection limit of 0.01 to 0.02 μg/L (Environment Canada, 2011).


6.1 Guidelines from Other Jurisdictions

A water quality guideline for the protection of aquatic life for trichlorfon has been derived by the Netherlands (Table 6.1). The Netherlands preferentially uses statistical extrapolation methods to derive water quality guidelines, but uses assessment factors when there are insufficient data (Crommentuijn et al., 1997). The maximum permissible concentration (MPC) for freshwater aquatic species exposed to trichlorfon was derived by applying an assessment factor of 100 to an LC50 of 0.1 μg/L for the midge Chironomus plumosus (Crommentuijn et al., 1997). The resulting MPC for freshwater aquatic species is 0.001 μg/L. A negligible concentration (NC) of 0.00001 μg/L was derived by applying an assessment factor of 100 to the MPC (Crommentuijn et al., 1997). The NC is the value expected to cause negligible effects, and accounts for possible toxicity from multiple substances. Table 6.1 Water quality criteria and guidelines for the protection of freshwater aquatic

life. Chemical Water

Category F=fresh M=marine E=estuarine

Guideline (μg a.i./L)

Application (C=criterion) (G=guideline) (S=standard)

Jurisdiction Reference

Trichlorfon F 0.001a G Netherlands Crommentuijn et al. 1997 Trichlorfon F 0.00001b G Netherlands Crommentuijn et al. 1997

Notes: a Maximum Permissible Concentrations (MPC): The standard at which all aquatic species should be protected

from adverse effects. b Negligible Concentration (NC): Derived by dividing the MPC by 100, this is the value expected to cause

negligible effects, accounting for possible toxicity from multiple substances.

7.0 ENVIRONMENTAL TOXICITY

This section presents a review of the scientific literature on the toxicity of trichlorfon to aquatic biota. The focus of the review is on the short- and long-term effects of trichlorfon to the survival, growth, and reproduction of aquatic organisms. Effects data identified in the open literature were evaluated using the CCME (2007) data acceptability criteria for water quality guideline derivation.

7.1 Mode of Action

The primary mode of action for organophosphorus pesticides, like trichlorfon, is cholinesterase (ChE) inhibition. Cholinesterase is the enzyme that breaks down acetylcholine (AChE), the neurotransmitter responsible for nerve impulses between nerves and their receptors. Inhibition of cholinesterase leads to an accumulation of acetylcholine, causing disruptions in the central nervous system of affected animals. Acetylcholine is an important neurotransmitter across a wide range of taxa. Symptoms of toxicity include hyperactivity, tremors, terminal convulsions and death (IPCS, 1986; Jensen and Gaufin, 1964b).


Trichlorfon is one of the few organophosphates that transforms into a more toxic compound (Howe et al., 1994). Dichlorvos inhibits cholinesterase at ≥100 times the rate of trichlorfon (Hofer, 1981). Transformation to the neurotoxin dichlorvos occurs when trichlorfon is hydrolyzed in water, biological fluids, and tissues at pH levels greater than 5.5 (IPCS, 1992). Uptake of trichlorfon can occur through all routes of exposure (oral, dermal and inhalation), and rapidly permeates to all tissues (IPCS, 1992). Although the primary mode of action is the inhibition of cholinesterase, trichlorfon has also been observed to impede the immune response of fish (Chandrasekara and Pathiratne, 2005; Dunier et al., 1991). Trichlorfon is moderately toxic to fish and generally more toxic to aquatic invertebrates (Appendix A). The primary mode of action of trichlorfon on cyanobacteria is the inhibition of nitrogen metabolism, resulting in the alteration of growth, cell composition, ultrastructure and physiological processes (Marco et al., 1990; Martinez et al., 1991).

7.2 Freshwater Aquatic Toxicity

A positive relationship exists between increasing pH and temperature, and the toxicity of trichlorfon. As pH and temperature increase so too does the dehydrochlorination of trichlorfon to dichlorvos. Higher temperatures can also increase ectothermic metabolism, resulting in greater chemical uptake (Howe et al., 1994). Common symptoms of toxicity include increased excitability, sporadic movement, and loss of equilibrium (Kozlovskaya et al., 1984; Hinton and Eversole, 1980). The mechanism of lethal action in fish primarily involves impaired functioning of the central nervous system due to increased acetylcholine. Levels of acetylcholinesterase (AChE) have been observed to fall to 55-57% of controls after 24-h exposure to trichlorfon (Chandrasekara and Pathiratne, 2005). AChE inhibition is reversible, with enzyme activity slowly recovering to normal levels once fish are removed from trichlorfon treated water (Kozlovskaya et al., 1984). Trichlorfon has also been observed to retard fish growth at sublethal concentrations (Kimura et al., 1971).

7.3 Toxicity to Fish

Short-term Effects Trichlorfon is moderately to highly toxic to freshwater fish (IPCS, 1992). Toxicity values available from the literature ranged from a 96h-LC50 of 234 g a.i./L for bluegill sunfish (Lepomis macrochirus) to a 96h-TLm of 140,000 g a.i./L for fathead minnow (Pimephales promelas) (Mayer and Ellersieck, 1986; Pickering et al., 1962). Differences in species behaviour, feeding ecology, choline receptor sensitivity, and pharmacokinetics likely account for some of the variation between species. Toxicity values were reported for several fish species including goldfish (Carassius auratus), carp (Cyprinus carpio), rainbow trout (Oncorhynchus mykiss), channel catfish (Ictalurus punctatus), bluegill sunfish (Lepomis macrochirus), and fathead minnow (Pimephales promelas). Trout and salmon species were among the most sensitive to trichlorfon, with reported 96h-LC50s of 243 g a.i./L for brook trout (Salvelinus fontinalis), 300 g a.i./L for Atlantic salmon (Salmo salar), and 550 g a.i./L for Lake trout (Salvelinus namaycush) (Mayer and Ellersieck, 1986).


Because the rate of trichlorfon transformation to dichlorvos increases under alkaline conditions, pH levels can have a marked influence on toxicity. In a static short-term toxicity test using rainbow trout (Oncorhynchus mykiss), fish were exposed to trichlorfon at varying temperatures and pH levels (Howe et al., 1994). At a water temperature of 7°C the 96h-LC50s were 40,900 and 520 g a.i./L at pH levels of 6.5 and 9.5, respectively (Howe et al., 1994). Using 17ºC test water, 96h-LC50s of 2,500 and 330 g a.i./L were reported at pH levels of 6.5 and 9, respectively (Howe et al., 1994). Thus, this study also observed greater sensitivity to trichlorfon at higher temperatures (Howe et al., 1994). Woodward and Mauck (1980) observed the same relationship between pH and toxicity using cutthroat trout (Salmo clarkii). Ninety-six hour LC50s reported for cutthroat trout were 375, 620, 1,680, and 4,750 g a.i./L at pH levels of 8.5, 7.8, 7.5, and 6.5, respectively (Woodward and Mauck, 1980). Higher water temperature was also observed to increase toxicity with 96h-LC50s of 5,750 and 1,680 g a.i./L reported at 7 and 12ºC, respectively (Woodward and Mauck, 1980). Toxicity values for bluegill sunfish ranged from a 96h-LC50 of 234 g a.i./L to a 72h-LC50 of 100,000 g a.i./L (Mayer and Ellersieck, 1986). The former value was derived using trichlorfon at 98% active ingredient, while the latter value was derived using trichlorfon at 8% a.i. The most sensitive toxicity value for bluegill sunfish reported from primary or secondary data was a 96h-LC50 of 234 g a.i./L (Appendix A; Mayer and Ellersieck, 1986). Similar sensitivities were reported for channel catfish (Ictalurus punctatus) and black bullhead (Ictalurus melas). Ninety-six hour LC50s for channel catfish ranged from 880 to 7600 g a.i./L (Sanders et al., 1983). The 96h-LC50 for black bullhead was 515 g a.i./L (Mayer and Ellersieck, 1986). A number of different species had similar levels of tolerance to trichlorfon. Ninety-six hour LC50s reported for largemouth bass (Micropterus salmoides), guppy (Lebistes reticulatus) and fathead minnow (Pimephales promelas) were 3,450, 7,100, and 7,900 g a.i./L, respectively (Pickering et al., 1961; Mayer and Ellersieck, 1986). Ninety-six hour LC50s for the American eel (Anguilla rostrata) ranged from 1,310 to 8,570 g a.i./L (Hinton and Eversole, 1980). Among carp (Cyprinus carpio), greater sensitivity was reported for juveniles (1.1 g) with a 48h-TLm of 6,200 g a.i./L, compared to adults with a 96h-LC50 of 9,272 g a.i./L (Nishiuchi and Hashimoto, 1969; Anton and Ariz, 1994). Toxicity values reported for early life stages included 24h-LC50s of 8,800, 11,000, and 15,000 g a.i./L for the floating fry, sac fry and eyed eggs (Hashimoto et al., 1982). Thomaz et al. (2009) found that short-term sublethal exposure (0.5 mg/L) to trichlorfon induced oxidative stress in the heart of Oreochromis niloticus (Nile tilapia). The heart was found to be the most sensitive organ when compared to the liver and gills. This indicated a reduced capacity of the fish to survive prolonged hypoxic conditions. Long-term Effects Little information or data on long-term effects to fish were available. Siwicki et al. (1990) reported a 56d-LOEC for immunological response in carp (Cyprinus carpio) of 400,000 g a.i./L. Two percent active ingredient was used in this study and may explain why the organism was so tolerant. This study was classified as unacceptable.


Guimarães and Calil (2008) showed that Oreochromis niloticus treated with trichlorfon were on average 4.2 % smaller than controls in the lab (4.8% smaller in the field), however the results were not statistically significant, and the study was classified as unacceptable.

7.3.1 Toxicity to Invertebrates

Short-term Effects Trichlorfon is highly toxic to most aquatic invertebrates (IPCS, 1992). This group of species is generally more sensitive to trichlorfon than freshwater fish species or algae (Appendix A). Short-term values for freshwater invertebrates ranged from a 48h-EC50 of 0.18 g a.i./L for Daphnia pulex (water flea) to a 24h-LC50 of 51,970 g a.i./L for Brachionus calyciflorus (rotifer) (Mayer and Ellersieck, 1986; Ferrando and Andreu-Moliner, 1991). Sublethal symptoms of toxicity included hyperactivity, tremors and convulsions (Jensen and Gaufin, 1964b). Recovery was observed in organisms placed in clean water following exposure (Jensen and Gaufin, 1964b). Forty-eight hour EC50 and LC50 values for Simocephalus serrulatus (water flea) were 0.32 and 0.7 g a.i./L, respectively (Sanders and Cope, 1966; Mayer and Ellersieck, 1986). Toxicity values for Daphnia magna varied, with 48h-EC50s from 0.08 to 0.52 g a.i./L (Sanders et al., 1983; Yoshimura and Endoh, 2005). For stoneflies, the 96h-LC50 reported for Pteronarcella badia ranged from 5.3 to 11 g a.i./L, and was 24 g a.i./L for Skwala sp. (Mayer and Ellersieck, 1986; Sanders and Cope, 1968). Pteronarcys californica were slightly more tolerant, with values ranging from a 96h-LC50 of 35 g a.i./L to a 96h-TLm of 690 g a.i./L (Sanders and Cope, 1966; Gaufin et al., 1965). Howe et al. (1994) studied the influence of temperature and pH on trichlorfon toxicity to the amphipod Gammarus pseudolimnaeus and rainbow trout (Oncorhynchus mykiss). Trichlorfon was approximately four times more toxic to G. pseudolimnaeus than to rainbow trout. There were similar trends of increased toxicity with increased pH or temperature in both species, with pH apparently having the greater influence. For Gammarus, the 96h-LC50s at 7°C and pH of 6.5 and 9.5 were 10,900 and 70 g a.i./L, respectively. Higher temperature also increased sensitivity. Ninety-six hour LC50s reported at 17°C and pH 6.5 and 9.5 were 140 g a.i./L and 20 g a.i./L, respectively (Howe et al., 1994). Other toxicity values reported for G. pseudolimnaeus included 96h-LC50s of 52 and 108 g a.i./L calculated at pH levels of 8.5 and 7.5, respectively (Woodward and Mauck, 1980). The most tolerant invertebrate species was the rotifer, Brachionus calyciflorus. In two static short-term bioassays, the 24h-LC50 values for neonate rotifers exposed to trichlorfon were 47,000 g a.i./L (Snell et al., 1991) and 51,970 g a.i./L (Ferrando and Andreu-Moliner, 1991).


Long-term Effects A limited number of long-term studies were available for invertebrates. Jensen and Gaufin (1964b) investigated long-term effects of trichlorfon to behaviour and survival of stonefly nymphs (Pteronarcys californica and Acroneuria pacifica) by exposing the species to Dylox in a flow-through system for up to 30 days. The 30d-TLm for P. californica was 9.8 g a.i./L. Similar sensitivity was reported for A. pacifica with a 30d-TLm of 8.7 g a.i./L (Jensen and Gaufin, 1964b). Symptoms of toxicity observed in surviving stonefly naiads included hyperactivity, tremors, and convulsions. Molting of A. pacifica ceased in all test concentrations by 20 days (Jensen and Gaufin, 1964b). For water fleas (Daphnia magna) exposed to trichlorfon in a flow-through system a 21d-LOEC of 5.6 g a.i./L was reported (SSRD, 1997). A 10d-LC50 of 2,200 g a.i./L was reported for adult Pila globosa (gastropod) (Singh and Agarwal, 1981).

7.3.2 Toxicity to Algae and Plants Few studies have been performed on the toxicity of trichlorfon to algae and aquatic plants. Trichlorfon has been shown to alter growth, cell composition, ultrastructure and physiological processes in cyanobacteria, with toxicity attributed to the inhibition of nitrate uptake (Marco et al., 1990). However, available studies have shown the algae Chlorella vulgaris to be highly tolerant of trichlorfon with 72h-LOECs ranging from 25,000 to 100,000 g a.i./L for effects to photosynthesis and physiological processes, respectfully (Martinez et al., 1991).

7.3.3 Toxicity to Amphibians One study reported effects to amphibians from exposure to trichlorfon. Szubartowska et al. (1990) reported 1, 2, and 3 week LOECs of 4,000 g a.i./L for effects on hematocrit levels (the percentage of whole blood that is composed of red blood cells) and mean corpuscular volume in the green frog (Rana esculenta).

7.3.4 Field Studies Microcosm and mesocosm studies offer a number of advantages over laboratory studies. They account for the diversity of natural ecosystems and allow for the simultaneous observation of effects to different taxonomic groups. These studies allow for the observation of predation and competition between species, and thus demonstrate some of the indirect effects of the stressor. Microcosm and mesocosm studies demonstrate the processes of ecological recovery that occur after the removal of the stressor. The exposure scenarios in field studies are more realistic because they account for the influence that competing fate processes have on the availability of a substance to ecological receptors (Giesy et al., 1999). Trichlorfon was applied at a concentration of 0.25 mg a.i./L to fertilized culture ponds that were stocked with 5-day-old reciprocal-cross hybrid striped bass fry (Ludwig, 1993). The effects on zooplankton population dynamics and fingerling production were recorded. Trichlorfon application significantly decreased the fingerling survival. Rotifer populations were also adversely affected from trichlorfon application, initially due to the toxic properties of trichlorfon and subsequently from the pesticide-induced changes in the competitive and predatory


interactions among the fry, other invertebrates, and zooplankton. Low fry survival rates were related to low concentrations of rotifers at, and immediately following, stocking (Ludwig, 1993).

7.3.5 Marine Toxicity No acceptable marine toxicity studies for trichlorfon were found.

7.3.6 Toxicity-Modifying Factors

pH The pH of exposure media significantly influences the toxicity of trichlorfon. As noted above, trichlorfon is transformed into dichlorvos under pH conditions greater than 5.5 (IPCS, 1992). The greater the number of hydroxyl ions in water, the more rapid the transformation of trichlorfon to dichlorvos. Thus, as pH increases, so too does toxicity (Howe et al., 1994, Woodward and Mauck, 1980). This was demonstrated using rainbow trout (Oncorhynchus mykiss) and Gammarus pseudolimnaeus (Howe et al., 1994). Temperature The toxicity of trichlorfon is also greater at higher temperatures. Similar to the effect of pH, increased temperature increases the rate of transformation of trichlorfon to dichlorvos. By increasing metabolism, higher temperatures also increase the rate of trichlorfon uptake (Howe et al., 1994; Woodward and Mauck, 1980).

7.3.7 Toxicity of Transformation Products The major transformation product of trichlorfon is dichlorvos. This compound causes the inhibition of cholinesterase at a rate ≥100 times that of trichlorfon (Hofer, 1981). For freshwater fish, dichlorvos 96h-LC50s ranged from 200 μg a.i./L for lake trout (Salvelinus namaycush) to 8,900 μg a.i./L for walking catfish (Clarias batrachus) (IPCS, 1988). Using trichlorfon, the 96h-LC50 reported for lake trout was 550 μg a.i./L (Mayer and Ellersieck, 1986). Ninety-six hour LC50s reported for invertebrates exposed to dichlorvos ranged from 0.1 μg a.i./L for Pteronarcys californica to 0.5 μg a.i./L for Gammarus lacustris (IPCS, 1988). The 96h-LC50s for trichlorfon for P. californica and G. lacustris were 35 and 40 μg a.i./L, respectively. The hydrolysis half-life of dichlorvos in lakes and rivers is approximately 4 days, varying from 20 to 80 hours from pH 4 to 9 (HSDB, 1999; Howard, 1991). A benchmark was identified for dichlorvos for use in comparing to Canadian pesticide surveillance data. The benchmark was 1 ng/L. Similar benchmarks were also derived for 106 pesticides lacking Canadian Water Quality Guidelines. These benchmarks were derived either by using the most sensitive endpoint from a set of readily available toxicity data together with application factors in a fashion similar to CCME (1991) or adopting pre-existing water quality guideline using professional judgement (Environment Canada, 2011).


8.0 GUIDELINE DERIVATION

A CWQG for trichlorfon addresses its use in Canada and potential impacts to freshwater and marine aquatic systems. A CWQG provides a numeric value to risk assessors and risk managers in Canada on the level of trichlorfon in an aquatic system, below which protection of the most sensitive species and lifestage is expected to be maintained indefinitely. The water quality guidelines for trichlorfon are here adopted from the Ideal Performance Standards developed for the National Agri-Environmental Standards Initiative (Environment Canada 2006). The short-term guideline was developed using the statistical approach with a species sensitivity distribution (SSD) following a draft version of CCME (2007). The long-term freshwater interim guideline was developed using the lowest-endpoint and an application of a safety factor (CCME 1991). There were no marine studies available, so no marine guidelines were developed. An SSD is a statistical distribution that represents the variation in toxicological sensitivity among a given set of species to a contaminant. The species sensitivity distribution, often expressed as a cumulative distribution function (CDF), is composed of effect and no-effect concentrations obtained during toxicity testing (e.g., LC50, EC50, LOEL, or NOEL) on the horizontal axis and cumulative probability on the vertical axis (Posthuma et al., 2002). The number of data points used to construct the curve depends on the number of species tested for the endpoint of interest. Emphasis is placed on organism-level effects (e.g., survival, growth, reproduction) that can be more confidently used to predict ecologically-significant consequences at the population level (Forbes and Calow, 1999; Meador, 2000; Suter et al., 2005). With the SSD method, the concentration of a substance in water that will be protective of at least 95% of aquatic biota is estimated. For the purposes of Canadian Water Quality Guideline development, both a short-term SSD based on acceptable short-term L/EC50 data is derived, along with a long-term SSD based preferentially on long-term no-effect data where possible. If insufficient data are available for deriving a CWQG using the statistical approach, the CWQG can be developed using the lowest endpoint approach. The following sections describe the derivation of CWQGs for the protection of freshwater in surface water for the insecticide trichlorfon. The derived CWQGs are national in scope and do not take into account watershed-specific conditions.

8.1 Protection of Freshwater Aquatic Life The complete set of toxicity data considered for use in CWQG derivation (including data classified as primary, secondary, and unacceptable) is presented in Appendix A. A CWQG provides guidance separately for both short and long-term exposure. The short-term benchmark is not intended to protect all species indefinitely, but rather is to protect most species against lethality during severe, but transient, events – this is referred to as a short-term benchmark concentration. Examples include inappropriate application or disposal of the pesticide in question. This may include application under worst case conditions and/or through improper use of label instructions (e.g. heavy precipitation/wind events), and spill events. The long-term exposure value of the CWQG is intended to protect against negative effects to all species and life stages during indefinite exposure. Aquatic life may be chronically exposed to a pesticide as a result of persistence in the environment, including gradual release from


soils/sediments and gradual entry through groundwater/runoff, multiple applications within the same localized region, and long range transport events.

8.1.1 Short-term Freshwater Benchmark Concentration To be considered for inclusion in CWQG development, the aquatic toxicity studies must meet minimum data quality requirements as specified in the water quality protocol (CCME, 2007). Both primary and secondary data as described in the protocol (CCME, 2007) are considered acceptable for deriving the short-term freshwater SSD for trichlorfon. For a short-term freshwater SSD, LC/EC50s constitute acceptable endpoints. There were sufficient data to derive a short-term freshwater SSD. Some of the studies reported in Appendix A are for the same species, effect, endpoint or life stage, though the values of the LC50s are different. This variation may be the result of differences in experimental conditions, species strain, and/or bioassay protocol. Multiple bioassay results for the same species should not be used in an SSD regression analysis. This is particularly important when there is a large amount of data available for very few test species. For the derivation of an SSD for trichlorfon, intra-species variability was accounted for by taking the geometric mean of the studies considered to represent the most sensitive lifestage and endpoint, when experiment duration was the same. Table 8.1 presents the final dataset that was used to generate the fitted SSD for short-term freshwater exposure to trichlorfon. Values reported in Table 8.1 range from a 48-h EC50 of 0.18 μg a.i./L for the water flea Daphnia pulex (Mayer and Ellersieck, 1986), to a 24-h LC50 of 49,423 μg a.i./L for the rotifer Brachionus calyciflorus (Snell et al., 1991; Ferrando and Andreu-Moliner, 1991). Geometric mean values were calculated for Brachionus calyciflorus, and Isogenus sp (Table 8.2). Effect concentrations reported for the remaining species were taken from single studies. The short-term SSD was fitted using LC50 and TLm data and the final short-term benchmark concentration for trichlorfon was the 5th percentile of the short-term SSD. Each species for which appropriate short-term toxicity data was available was ranked according to sensitivity and its centralized position on the SSD was determined using the following standard equation (Aldenberg et al., 2002; Newman et al., 2002):

N

i 5.0

where i = the species rank based on ascending EC50s and LC50s N = the total number of species included in the SSD derivation

These positional rankings, along with their corresponding EC50 and LC50s were used to derive the SSD. Several cumulative distribution functions (CDFs) (normal, logistic, Gompertz, Weibull, and Fisher-Tippett) were fit to the data (both in arithmetic space and log space) using regression methods. Model fit was assessed using statistical and graphical techniques. The best model was


selected based on consideration of goodness-of-fit and model feasibility. Model assumptions were verified graphically and with statistical tests.


Table 8.1 Final aquatic toxicity data selected for short-term SSD development

Study No.

Organism Life Stage Endpoint Effect

Concentration (μg a.i./L)

References

1 Daphnia pulex (water flea) 1st instar 48-h EC50 0.18 Mayer and Ellersieck, 1986 – see note below

2 Simocephalus serrulatus (water flea)

1st instar 48-h LC50 0.7 Mayer and Ellersieck, 1986

3 Pteronarcella badia (stonefly)

Year 96-h LC50 5.3 Mayer and Ellersieck, 1986

4 Acroneuria pacifica (stonefly)

Naiad 96-h LC50 16.5 SRRD, 1997

5 Hexagenia (mayfly) Naiad 24-h TLm 17 Carlson, 1966

6 Isogenus sp. (stonefly) 1st instar 96-h LC50 17* Mayer and Ellersieck, 1986

7 Gammarus pseudolimnaeus (amphipod)

Adult 96-h LC50 17** Mayer and Ellersieck, 1986

8 Claasenia sabulosa (stonefly)

Year 96-h LC50 22 Mayer and Ellersieck, 1986

9 Skwala sp. (stonefly) Nymph 96-h LC50 24 US DIFWS, 1980

10 Pteronarcys californica (stonefly)

Year 96-h LC50 35 Mayer and Ellersieck, 1986

11 Gammarus lacustris (amphipod)

Adult 96-h LC50 40 Mayer and Ellersieck, 1986

12 Lepomis macrochirus (bluegill sunfish)

0.8g 96-h LC50 234** Mayer and Ellersieck, 1986

13 Salvelinus fontinalis (brook trout)


14 Salmo salar (Atlantic salmon)


15 Oncorhynchus mykiss (rainbow trout)

0.6-1.0g 96-h LC50 330** Howe et al. 1994

16 Oncorhynchus clarki (cutthroat trout)


17 Ictalurus melas (black bullhead)

NR 96-h LC50 515 Mayer and Ellersieck, 1986

18 Salvelinus namaycush (lake trout)

2.3g 96-h LC50 550 Mayer and Ellersieck, 1986

19 Ictalurus punctatus (channel catfish)

1.6g 96-h LC50 880 Mayer and Ellersieck, 1986

20 Hydropsyche (caddisfly) Naiad 24-h TLm 910 Carlson, 1966

21 Morone saxatilis (striped bass)

Alevin 96-h LC50 2000 SSRD, 1997

22 Micropterus salmoides (largemouth bass)

0.8g 96-h LC50 3,450 Mayer and Ellersieck, 1986

23 Procambarus sp. (crayfish) Adult 96-h LC50 7,800 Mayer and Ellersieck, 1986

24 Pimephales promelas (fathead minnow)

0.9g 96-h LC50 7,900 Mayer and Ellersieck, 1986

25 Anguilla rostrata (American eel)

114-340g 96-h LC50 8,570 Hinton and Eversole, 1980

26 Brachionus calyciflorus (rotifer)

Neonate 24-h LC50 49,423* Snell et al., 1991; Ferrando and Andreu-Moliner, 1991

*value shown is the geometric mean of species values; individual values and references can be seen in table 8.2 **Only the most sensitive value of the acceptable data was used in the SSD due to the wide range of pH values used in the toxicity tests Highlighted rows identify data selected to meet the minimum data requirements for an interim long-term water quality guideline (CCME 1991). See 8.1.2


Table 8.2 Studies used to derive geometric means for short-term freshwater SSD

Organism Endpoint Effect

Concentration (μg a.i./L)

Geometric Mean

(μg a.i./L) Reference

47,000 Snell et al. 1991 Brachionus

calyciflorus (rotifer) 24h-LC50

51,970 49,423 Ferrando and Andreu-

Moliner, 1991

12 Mayer and Ellersieck,

1986 Isogenus sp. (stonefly)

96h-LC50 24

17 Mayer and Ellersieck,

1986

The log normal CDF model provided the best fit of the models tested (Anderson-Darling Statistic (A2) = 0.334). The equation of the fitted normal CDF model is of the form:

where x is the concentration metameter, and the functional response, f(x), is the proportion of taxa affected at the given concentration. The location and scale parameters, µ and σ, are the mean and standard deviation of the theoretical population, respectively, and erf is the error function (a.k.a. the Gauss error function). The scale parameter of the normal model must always be positive. For the fitted model µ = 2.2481 and σ = 1.3447.

0.0

0.2

0.4

0.6

0.8

1.0

0.01 1 100 10000 1000000

Concentration (µg/L)

Pro

po

rtio

n o

f S

pe

cie

s A

ffe

cte

d

Short-term median effects SSD

95% fiducial limit

Invertebrate

Fish

5th percentile

L. macrochirus

Skwala sp.P. californica

G. lacustris

G. pseudolimnaeus

S. fontinalis

O. clarkiO. mykiss

I. melasS. namaycush

I. punctatusHydropsyche

M. saxatilis

P. promelas

M. salmoidesProcambarus sp.

A. rostrataB. calyciflorus

D. pulexS. serrulatus

P. badia

A. pacifica

HexageniaIsogenus sp.

C. sabulosa

S. salar

0.1 10 1000

Figure 8.1 Short-term log-normal SSD representing the toxicity of trichlorfon in freshwater.


The fitted SSD derived using the log-normal CDF model and LC50 data for freshwater organisms is presented in Figure 8.1.

The short-term SSD for freshwater aquatic organisms is presented in Figure 8.1. This consists of acceptable short-term LC50s, EC50s, and TLms of 26 aquatic species versus proportion of species affected. The dashed line at the bottom of the graph denotes the 5th percentile and the corresponding short-term guideline. Summary statistics for the shorter-term SSD are presented in Table 8.3. The 5th percentile on the short-term SSD is 1.1 μg a.i./L. The lower fiducial limit (5%) on the 5th percentile is 0.7 μg a.i./L, and the upper fiducial limit (95%) on the 5th percentile is 1.7 μg a.i./L. The final short-term benchmark concentration value for trichlorfon is the 5th percentile on the SSD. Table 8.3 Short-term freshwater SSD for trichlorfon resulting from generic SSD method

Short-term guideline metric Concentration SSD 5th percentile 1.1 µg a.i./L SSD 5th percentile, 90% LFL (5%) 0.7 µg a.i./L SSD 5th percentile, 90% UFL (95%) 1.7 µg a.i./L

Therefore, the short-term exposure benchmark concentration indicating the potential for severe effects (e.g., lethality or immobilization) to sensitive freshwater life during transient events is 1.1 µg a.i./L, for trichlorfon.

8.1.2 Long-term Freshwater Interim CWQG The long-term endpoints identified from the primary and secondary studies consisted of three invertebrate species. Available long-term toxicity data were not sufficient to derive a guideline using any of the methods in the current CCME (2007) protocol. Therefore, the Ideal Performance Standard for trichlorfon (Environment Canada 2006) that followed CCME (1991), was adopted as the long-term interim Canadian Water Quality Guideline. The IPS was developed using a safety factor of 20 applied to the short-term EC50 of the most sensitive species, that of juvenile Daphnia pulex 0.18 µg a.i./L (48-h EC50 D. pulex; Mayer and Ellersieck, 1986; see Table 8.1, where minimum dataset is also highlighted). The application factor of 20 was used because trichlorfon is considered relatively nonpersistent in water. The CWQG is calculated as follows: CWQG = EC50 ÷ AF = 0.18 ÷ 20 µg a.i./L (48-h EC50 D. pulex; Mayer and Ellersieck, 1986) = 0.009 µg a.i./L where, AF = Application factor


Therefore, the long-term freshwater interim Canadian Water Quality Guideline value for the protection of freshwater life in surface water is 0.009 µg a.i./L, for trichlorfon.

8.2 Protection of Marine Life

No acceptable marine studies were found, therefore there were insufficient data to derive short- or long-term guidelines for the protection of marine life.

8.3 Data Gaps and Research Recommendations

Trichlorfon is a reasonably well-studied pesticide, particularly with regard to short-term effects on freshwater fish and invertebrates. There are limited toxicity data available for algae and aquatic plants. The data available for these species suggests that they have a high tolerance for trichlorfon. Additional studies using algae and aquatic plants would be useful in confirming this assumption. Long-term data are lacking for all receptor groups. Acceptable long-term data are currently available for the waterflea Daphnia magna, and the stonefly species Acroneuria pacifica, and Pternornarcys californica. Additional data could be used to derive a long-term SSD to account for possible multiple applications of trichlorfon. The higher toxicity of the transformation product dichlorvos needs to be studied further. The amount of dichlorvos that becomes available to aquatic organisms as a result of trichlorfon application is unclear. If significant concentrations of dichlorvos are produced, it may be necessary to derive a CWQG for that pesticide. The dataset available for trichlorfon would benefit from more detailed information. Data reported by EFED (2000), SSRD (1997) and PMRA (2002, 2005) lacked information on test conditions, organism life stage, and other parameters. This made it difficult to compare toxicity data between studies.

8.4 Implementation and Other Considerations

The above guideline was developed using only toxicity data derived using the active ingredient. Formulated products which include trichlorfon may be more or less toxic than the active ingredient. In regions of concern, additional sampling may be considered for formulants to ensure aquatic life is not being impacted by other substances. Furthermore, due to the rapid transformation of trichlorfon to dichlorvos, additional site specific guidance may be required to ensure aquatic life is not being impacted, especially in regions elevated in pH and/or temperature.


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Yeh, S-P., T-G. Sung, C-C. Chang, W. Cheng, and C-M. Kuo. 2005. Effects of an organophosphorus insecticide, trichlorfon, on haematological parameters of the giant freshwater prawn, Macrobrachium rosenbergii (de Man). Aquaculture 243:383-392.

Yoshimura, H. and Y.S. Endoh. 2005. Acute Toxicity to Freshwater Organisms of Antiparasitic Drugs for Veterinary Use. Environmental Toxicology 20:60-66.

Zaidi, A.A., A. Ilahi, R. Tanvir and S. Ruby. 1993. Persistence of dichlorvos residues in Okra and its effects on sugar content of the vegetable. Pakistan Journal of Agricultural Sciences 30 (2): 224-227.

APPENDIX A – TOXICITY VALUES FOR FRESHWATER AQUATIC SPECIES

EXPOSED TO TRICHLORFON

Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Plants/Algae

Anabaena Cyanobacteria NR LOEC (growth, photosynthetic

pigments) 300,000 97 S,N 26 NR NR NR Marco et al., 1990 U

Anabaena Cyanobacteria NR

4d-NOEC (growth,

biochemical processes)

300,000 97 S,M 26 NR NR NR Marco and Orus, 1992 U

Chlamydomonas reinhardtii

green algae NR 72h-NOEC

(physiological processes)

100000 97 S,M 26 NR NR NR Martinez et al., 1991 U

Chlorella vulgaris green algae NR 72h-LOEC

(physiological processes)

100,000 97 S,M 26 NR NR NR Martinez et al., 1991 U

Scenedesmus quadricauda green algae NR 72h-LOEC

(photosynthesis) 25,000 97 S,M 26 NR NR NR Martinez et al., 1991 U

Invertebrates

Acroneuria pacifica stonefly Naiad 30d-TLm 8.7 89 F,N 12.8 9-11 NR 7.8-8.2

Jensen and Gaufin, 1964b 2



Acroneuria pacifica stonefly Larvae 96h-TLm 16.5 NR S,N 10.5-12.2

NR NR NR Gaufin et al., 1965 U

Acroneuria pacifica stonefly Naiad 96h-TLm 16.5 89 S,N 40129 7.4-13.5 122-210 7.9-8.3

Jensen and Gaufin, 1964a U

Acroneuria pacifica stonefly Naiad 96h-LC50 16.5 98 S,NR NR NR NR NR SSRD, 1997 1

Acroneuria pacifica stonefly Naiad 72h-TLm 22 89 S,N 40129 7.4-13.5 122-210 7.9-8.3




Acroneuria pacifica stonefly Naiad 48h-TLm 27 89 S,N 40129 7.4-13.5 122-210 7.9-8.3



Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Acroneuria pacifica stonefly Naiad 15d-TLm 107 89 F,N 12.8 9-11 NR 7.8-8.2


Aedes cantans mosquito 4th instar 24h-LC50 72.4 NR S,N 20-23 NR NR NR Rettich, 1977 U Aedes communis mosquito 4th instar 24h-LC50 139.7 NR S,N 20-23 NR NR NR Rettich, 1977 U Aedes excrucians mosquito 4th instar 24h-LC50 42.3 NR S,N 20-23 NR NR NR Rettich, 1977 U Aedes punctor mosquito 4th instar 24h-LC50 178.2 NR S,N 20-23 NR NR NR Rettich, 1977 U Aedes vexans mosquito 4th instar 24h-LC50 104.7 NR S,N 20-23 NR NR NR Rettich, 1977 U Biomphaloria alexandrina snail Adult 48h-LC50 26000 NR S,NR 17 NR NR NR Atalluh and Ishak, 1971 U Biomphaloria alexandrina snail Adult 48h-LC90 137000 NR S,NR 17 NR NR NR Atalluh and Ishak, 1971 U

Brachionus calyciflorus rotifer Neonate 24h-EC50

(immobilization) 37400 97 S,N 25 NR NR NR Yoshimura and Endoh, 2005 U

Brachionus calyciflorus rotifer Neonate 24h-LC50 47000 NR S,N 25 NR NR NR Snell et al., 1991 2

Brachionus calyciflorus rotifer Neonate 24h-LC50 51970 NR S,N 25 NA 80-100 7.4-7.8

Ferrando and Andreu-Moliner, 1991

2

Chironomus plumosus midge 4th instar 48h-EC50

(immobilization) 0.1 99 S,N 17 NR NR 7.4 Sanders et al., 1983 U

Chironomus plumosus midge 4th instar 48h-EC50

(immobilization) 0.12

80WP

S,N 17 NR NR 7.4 Sanders et al., 1983 U

Chironomus tentans midge 4th instar 96h-EC50 89.93 98 S,N 20 7.67 NR 7.95 Pape-Lindstrom and Lydy, 1997 U Claassenia sabulosa stonefly 1st year 96h-LC50 22 98 S,NR 16 NR 40 7.1 Mayer and Ellersieck, 1986 1 Claassenia sabulosa stonefly Naiad 96h-LC50 22 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Claassenia sabulosa stonefly Instar 96h-LC50 22 TG S, N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Claassenia sabulosa stonefly Naiad 48h-LC50 70 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Claassenia sabulosa stonefly Naiad 24h-LC50 110 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U

Colpidium campylum holotrichous ciliate

Life Cycle

43h-MAD >10,000 NR S,N 20 NR NR NR Dive et al., 1980 U

Culex pipiens mosquito 4th instar 24h-LC50 89.86 NR NR NR NR NR NR Cui et al., 2006 U Culex pipiens mosquito 4th instar 24h-LC50 41.11 NR NR NR NR NR NR Cui et al., 2006 U Culex pipiens molestus mosquito 4th instar 24h-LC50 58.2 NR S,N 20-23 NR NR NR Rettich, 1977 U Culex pipiens pipiens mosquito 4th instar 24h-LC50 94.6 NR S,N 20-23 NR NR NR Rettich, 1977 U Culiseta annulata mosquito 4th instar 24h-LC50 243.6 NR S,N 20-23 NR NR NR Rettich, 1977 U

Daphnia magna water flea Neonate 48h-EC50

(immobilization) 0.26 97 S,N 20 NR NR NR Yoshimura and Endoh, 2005 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Daphnia magna water flea Neonate 24h-EC50

(immobilization) 0.52 97 S,N 20 NR NR NR Yoshimura and Endoh, 2005 U

Daphnia magna water flea Life cycle

21d-LOEC 5.6 TG F,NR NR NR NR NR SSRD, 1997 1

Daphnia magna water flea 1st instar 48h-EC50

(immobilization) 0.08

80WP

S,N 17 NR NR 7.4 Sanders et al., 1983 U

Daphnia magna water flea 1st instar 48h-EC50

(immobilization) 0.12 99 S,N 17 NR NR 7.4 Sanders et al., 1983 U

Daphnia pulex water flea 1st instar 48h-EC50 0.18 98 S,NR 16 NR 40 7.1 Mayer and Ellersieck, 1986 1 Daphnia pulex water flea Adult 3h-TLm 65 NR S,N 24-26 NR NR NR Nishiuchi and Hashimoto, 1969 U Ephemeralla grandis mayfly Larvae 96h-TLm 140 NR S,N 8.9-10 NR NR NR Gaufin et al., 1965 U Gammarus lacustris amphipod NR EC50 40 TG NR NR NR NR NR PMRA 2002, 1 Gammarus lacustris amphipod Adult 96h-TLm 50 NR S,N 15 NR NR NR Gaufin et al., 1965 U Gammarus lacustris amphipod Adult 96h-LC50 40 98 S,NR 21 NR 40 7.1 Mayer and Ellersieck, 1986 1 Gammarus lacustris Sars amphipod Adult 96h-TLm 50 NR S,N 15 NR NR NR Nebeker and Gaufin, 1964 U Gammarus pseudolimnaeus amphipod Adult 96h-LC50 20 98 S,M 17 >5.0 40-48 9.5 Howe et al., 1994 2 Gammarus pseudolimnaeus amphipod NR 96h-LC50 52 99 S,N 12 NR 40 8.5 Woodward and Mauck, 1980 U Gammarus pseudolimnaeus amphipod Adult 96h-LC50 70 98 S,M 7 >5.0 40-48 9.5 Howe et al., 1994 2 Gammarus pseudolimnaeus amphipod NR 96h-LC50 108 99 S,N 12 NR 40 7.5 Woodward and Mauck, 1980 U Gammarus pseudolimnaeus amphipod Adult 96h-LC50 140 98 S,M 17 >5.0 40-48 6.5 Howe et al., 1994 2 Gammarus pseudolimnaeus amphipod Adult 96h-LC50 10900 98 S,M 7 >5.0 40-48 6.5 Howe et al., 1994 2 Gammarus pseudolimnaeus amphipod Adult 96h-LC50 17 80 S,NR 17 NR 40 7.4 Mayer and Ellersieck, 1986 1 Gammarus pseudolimnaeus amphipod Adult 96h-LC50 32 98 S,NR 17 NR 320 7.4 Mayer and Ellersieck, 1986 1

Gammarus pseudolimnaeus amphipod Adult 96h-LC50 1.7 80

WP S,N 17 NR NR 7.4 Sanders et al., 1983 U

Gammarus pseudolimnaeus amphipod Adult 96h-LC50 48 99 S,N 17 NR NR 7.4 Sanders et al., 1983 U Hexagenia mayfly Naiad 24h-TLm 17 99 S,N 26-25 7.8-3 NR NR Carlson, 1966 2 Hydropsyche caddisfly Naiad 24h-TLm 910 99 S,N 21-22 7.9-6.8 NR NR Carlson, 1966 2

Isogenus sp. stonefly 1st instar 96h-LC50 12 80

WP S,NR 7 NR 42 7.5 Mayer and Ellersieck, 1986 1

Isogenus sp. stonefly 1st instar 96h-LC50 24 98 S,NR 7 NR 42 7 Mayer and Ellersieck, 1986 1 Lymnaea acuminata gastropod Adult 240h-LC50 58 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Lymnaea acuminata gastropod Adult 168h-LC50 220 NR S,N NR NR NR NR Singh and Agarwal, 1981 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Lymnaea acuminata gastropod Adult 96h-LC50 300 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Lymnaea acuminata gastropod Adult 72h-LC50 650 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Lymnaea acuminata gastropod Adult 48h-LC50 2200 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Macrobrachium rosenbergii

freshwater prawn

Juvenile 96h-LC50 460 80 S,N 27 7 15.4 NR Juarez and Rouse, 1983 U

Macrobrachium rosenbergii

freshwater prawn



freshwater prawn



freshwater prawn

15-20g Haematological

parameters NR NR S, R 28 NR 100

7.3-7.5

Yeh et al., 2005 U


freshwater prawn

intermolt 24h-LC50 773.9 NR S, R 27 NR 100 7.3-7.5

Chang et al., 2006 U


freshwater prawn




freshwater prawn




freshwater prawn



Melanopsis dufouri gastropod 1.4-

1.8mm length

96h-LC50 10350 NR S,NR 29 NR 250 7.9 Almar et al., 1988 U


1.8mm length



1.8mm length


Moina macrocopa water flea Adult 3h-TLm 750 NR S,N 24-26 NR NR NR Nishiuchi and Hashimoto, 1969 U Pila globosa gastropod Adult 240h-LC50 2200 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Pila globosa gastropod Adult 168h-LC50 2800 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Pila globosa gastropod Adult 96h-LC50 8000 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Pila globosa gastropod Adult 72h-LC50 19000 NR S,N NR NR NR NR Singh and Agarwal, 1981 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Pila globosa gastropod Adult 48h-LC50 25400 NR S,N NR NR NR NR Singh and Agarwal, 1981 U Procambarus clarkii crayfish Adult 96h-LC50 200 NR S,NR 19 NR 250 7.8 Andreu-Moliner et al., 1986 U Procambarus clarkii crayfish Adult 96h-LC20 800 NR S,NR 19 NR 350 8.4 Andreu-Moliner et al., 1986 U Procambarus clarkii crayfish Adult 96h-LC50 990 >99 S,M 20e NR 250 7.9 Cebrian et al., 1991 U Procambarus clarkii crayfish Adult 72h-LC50 1160 >99 S,M 20e NR 250 7.9 Cebrian et al., 1991 U Procambarus clarkii crayfish Adult 48h-LC50 2190 >99 S,M 20e NR 250 7.9 Cebrian et al., 1991 U Procambarus clarkii crayfish 21.8g 96h-LC50 5000 NR R,N 20 NR NR NR Repetto et al., 1988 U Procambarus clarkii crayfish Adult 24h-LC50 5140 >99 S,M 20 NR 250 7.9 Cebrian et al., 1991 U

Procambarus clarkii crayfish Adult 24h-LC50 5155 80 S,N 25 >5.0 80-85 7.5-8.0

Jimenez et al., 2003 U

Procambarus sp. crayfish Adult 96h-LC50 7800 98 S,NR 12 NR 40 7.5 Mayer and Ellersieck, 1986 1 Pseudodactylogyrus anguillae

nemotode 0-12h Hatching rate NR NR S, NR 28 NR NR NR Umeda et al., 2006 U

Pseudodactylogyrus bini nemotode 0-12h Hatching rate NR NR S, NR 28 NR NR NR Umeda et al., 2006 U Pteronarcella badia stonefly Year 96h-LC50 5.3 98 S,NR 12 NR 40 8.5 Mayer and Ellersieck, 1986 1 Pteronarcella badia stonefly Naiad 96h-LC50 5.3 99 S,N 12 NR 40 8.5 Woodward and Mauck, 1980 U Pteronarcella badia stonefly Naiad 96h-LC50 9.8 99 S,N 12 NR 40 7.5 Woodward and Mauck, 1980 U Pteronarcella badia stonefly Naiad 96h-LC50 11 98 S,NR 16 NR 40 7.1 Mayer and Ellersieck, 1986 1 Pteronarcella badia stonefly Naiad 96h-LC50 11 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcella badia stonefly Instar 96h-LC50 11 TG S, N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcella badia stonefly Naiad 48h-LC50 22 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcella badia stonefly Naiad 24h-LC50 50 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcella badia stonefly Naiad 96h-LC50 100 99 S,N 12 NR 40 6.5 Woodward and Mauck, 1980 U

Pteronarcys californica stonefly Naiad 30d-TLm 9.8 89 F,N 12.8 9-11 NR 7.8-8.2


Pteronarcys californica stonefly Naiad 25d-TLm 33 89 F,N 12.8 9-11 NR 7.8-8.2


Pteronarcys californica stonefly Year 96h-LC50 35 98 S,NR 16 NR 40 7.5 Mayer and Ellersieck, 1986 1 Pteronarcys californica stonefly Naiad 96h-LC50 35 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcys californica stonefly Instar 96h-LC50 35 TG S, N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U

Pteronarcys californica stonefly Naiad 20d-TLm 41 89 F,N 12.8 9-11 NR 7.8-8.2


Pteronarcys californica stonefly Naiad 15d-TLm 63 89 F,N 12.8 9-11 NR 7.8- Jensen and Gaufin, 1964b 2


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

8.2

Pteronarcys californica stonefly Naiad 72h-TLm 69 89 S,N 40129 7.4-13.5 122-210 7.9-8.3






Pteronarcys californica stonefly Naiad 48h-LC50 180 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U Pteronarcys californica stonefly Naiad 24h-LC50 320 TG S,N 15.5 39879 NR 7.1 Sanders and Cope, 1968 U

Pteronarcys californica stonefly Larvae 96h-TLm 690 NR S,N 10.5-12.2

NR NR NR Gaufin et al., 1965 U

Simocephalus serrulatus cladoceran 1st instar 48h-EC50

(immobilization) 0.32 NR S,N 21.1 NR NR

7.4-7.8

Sanders and Cope, 1966 U

Simocephalus serrulatus daphnid 1st instar 48h-LC50 0.7 98 S,NR 16 NR 40 7.1 Mayer and Ellersieck, 1986 1 Simulium aokii and S. Venustum

blackfly Larvae 10min (1.8%

mortality) 1000

10WP

S,N 19-21 NR NR NR Matsuo and Tamura, 1970 U

Simulium aokii and S. Venustum

blackfly Larvae 1min (1.8% mortality)

10000 10

WP S,N 19-21 NR NR NR Matsuo and Tamura, 1970 U

Skwala sp. stonefly Nymph 96h-LC50 24 98 S,NR 7 NR 40-50 7.2-7.5

U.S. DIFWS, 1980 1

Streptocephalus seali fairy shrimp Adult 24h (36% mortality)

100 80 S,N 24 NR 120 8.5 Moss, 1978 U

Streptocephalus seali fairy shrimp Adult 48h (82.2 % mortality)

100 80 S,N 24 NR 120 8.5 Moss, 1978 U


250 80 S,N 24 NR 120 8.5 Moss, 1978 U


250 80 S,N 24 NR 120 8.5 Moss, 1978 U

Fish Anguilla anguilla eel 20-30g 96h-LC50 3380 98 S,N 20 NR 250 7.9 Ferrando et al., 1991 U Anguilla anguilla eel 20-30g 72h-LC50 3420 98 S,N 20 NR 250 7.9 Ferrando et al., 1991 U Anguilla anguilla eel 20-30g 48h-LC50 3800 98 S,N 20 NR 250 7.9 Ferrando et al., 1991 U Anguilla anguilla eel 20-30g 24h-LC50 5000 98 S,N 20 NR 250 7.9 Ferrando et al., 1991 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Anguilla rostrata American eel NR 96h-LC50 1310 NR S,NR 22 NR 40-48 7.2-7.6

Hinton and Eversole, 1980 U

Anguilla rostrata American eel NR 96h-LC50 1320 NR S,NR 22 NR 40-48 7.2-7.6

Hinton and Eversole, 1980 U

Anguilla rostrata American eel 114-340g 96h-LC50 8570 100 S,N 22 >4.99 40-48 7.2-7.6

Hinton and Eversole, 1980 2

Carassius auratus goldfish Adult 96h-LC50 48360 97 S,N 18 7.19-8.99

NR 6.8-8 Anton and Ariz, 1994 U

Carassius auratus goldfish Adult 96h-LC50 54000 97 S,N 18 7.19-8.99


Carassius auratus goldfish 1-2g 96h-TLm 99000 99 S,N 25 39911 20 7.4-7.5

Pickering et al., 1961 U

Carassius auratus goldfish Juvenile 48h-LC100 150000 80 R,N 20 NR NR 7.85-8.0

Kozlovskaya et al., 1984 U

Carassius auratus goldfish Adult 96h-LC50 >1,600 97 S,N 18 7.19-8.99


Carassius auratus goldfish NR 12h (AChE

activity) 1,000 NR S,N 20-21 NR NR 6.5 Weiss, 1959 U

Carassius auratus goldfish NR 12h (AChE

activity) 1,000 NR S,N 20-21 NR NR 8 Weiss, 1959 U

Carassius auratus goldfish 1.04g 48h-TLm >10000 NR S,N 23.5 NR NR NR Nishiuchi and Hashimoto, 1969 U Cyprinus carpio carp 1.1g 48h-TLm 6200 NR S,N 23.5 NR NR NR Nishiuchi and Hashimoto, 1969 U

Cyprinus carpio carp Floating

fry (Stage I)

24h-LC50 8800 NR S,N 25 NR NR 6.9-7.2

Hashimoto et al., 1982 U

Cyprinus carpio carp Adult 96h-LC50 9272 97 S,N 18 7.19-8.99


Cyprinus carpio carp Sac fry

(Stage 0) 24h-LC50 11000 NR S,N 25 NR NR

6.9-7.2


Cyprinus carpio carp Stage II 24h-LC50 14000 NR S,N 25 NR NR 6.9-7.2


Cyprinus carpio carp Stage IV 24h-LC50 14000 NR S,N 25 NR NR 6.9-7.2



Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Cyprinus carpio carp Eyed egg (Stage E)

24h-LC50 15000 NR S,N 25 NR NR 6.9-7.2


Cyprinus carpio carp Stage III 24h-LC50 15000 NR S,N 25 NR NR 6.9-7.2


Cyprinus carpio carp Stage V 24h-LC50 15000 NR S,N 25 NR NR 6.9-7.2


Cyprinus carpio carp Stage VI 24h-LC50 15000 NR S,N 25 NR NR 6.9-7.2


Cyprinus carpio carp 100-150g 72h-LOEC

(immunological response)

400000 2 S,N 20 NR NR NR Siwicki et al., 1990 U

Cyprinus carpio carp 100-150g 56d-LOEC

(immunological response)

400000 2 S,N 20 NR NR NR Siwicki et al., 1990 U

Cyprinus carpio carp 50-100g 15min exposure 20x106 NR S,N 20 NR NR 7.6 Cossarini-Dunier et al., 1990 U

Cyprinus carpio L. carp 150-160g 1h or 24h exposure

250 50 S,N 27-28 5.9-6.6 NR 7.2-2.6

Chandrasekara and Pathiratne, 2005

U

Gambusia affinis mosquitofish 2.5-3.0

cm 24h-LC0 500 NR S,N 21.1 NR NR NR Lewallen, 1959 U

Ictalurus melas black bullhead NR 96h-LC50 515 98 S,NR 18 NR 272 7.4 Mayer and Ellersieck, 1986 1 Ictalurus punctatus channel catfish NR 96h-LC50 7600 99 S,N 22 NR NR 7.4 Sanders et al., 1983 U

Ictalurus punctatus channel catfish NR 96h-LC50 7800 80


Ictalurus punctatus channel catfish 1.6g 96h-LC50 880 98 S,NR 18 NR 44 7.1 Mayer and Ellersieck, 1986 1

Lebistes reticulatus guppy 0.1-0.2g 96h-TLm 7100 99 S,N 25 39911 20 7.4-7.5


Lepomis macrochirus bluegill sunfish NR 96h-LC50 1000 80


Lepomis macrochirus bluegill sunfish NR 96h-LC50 3300 99 S,N 22 NR NR 7.4 Sanders et al., 1983 U Lepomis macrochirus bluegill sunfish 0.8g 96h-LC50 234 98 S,NR 22 NR 40 9.0 Mayer and Ellersieck, 1986 1 Lepomis macrochirus bluegill sunfish 0.6g 96h-LC50 2400 80 S,NR NR NR NR NR EFED, 2000 1

Lepomis macrochirus bluegill sunfish 1.0g 96h-LC50 5200 40EC

S,NR 17 NR 44 7.4 Mayer and Ellersieck, 1986 1


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Lepomis macrochirus bluegill sunfish NR 72h-LC50 100000 8 S,NR NR NR NR NR SSRD, 1997 1 Lepomis macrochirus bluegill sunfish 0.75g 48h-LC50 <23,000 TG S,NR NR NR NR NR EFED, 2000 1

Lepomis macrochirus bluegill sunfish 1-2g 96h-TLm 3800 99 S,N 25 39911 20 7.4-7.5


Lepomis macrochirus bluegill sunfish 0.87-2.4g 24h-LC50 41000 50 S,N 18 NR 51.3 7 McCann and Jasper, 1972 U Lepomis macrochirus bluegill sunfish 0.5-0.97g 24h-LC50 >52,000 8 S,N 18 NR 51.3 7 McCann and Jasper, 1972 U

Micropterus salmoides largemouth bass

0.8g 96h-LC50 3450 98 S,NR 18 NR 272 7.4 Mayer and Ellersieck, 1986 1

Morone saxatilis striped bass Alevin 96h-LC50 2000 80 S,NR NR NR NR NR SSRD, 1997 1 Oncorhynchus masou cherry salmon Juvenile 96h-TLm 1100 NR R,N 17.6 NR NR NR Kimura et al., 1971 U Oncorhynchus clarkii cutthroat trout 0.6g 96h-LC50 375 98 S,NR 12 NR 44 8.5 Mayer and Ellersieck, 1986 1 Oncorhynchus clarkii cutthroat trout NR 96h-LC50 375 99 S,N 12 NR 40 8.5 Woodward and Mauck, 1980 U Oncorhynchus clarkii cutthroat trout NR 96h-LC50 620 99 S,N 12 NR 320 7.8 Woodward and Mauck, 1980 U Oncorhynchus clarkii cutthroat trout NR 96h-LC50 1680 99 S,N 12 NR 40 7.5 Woodward and Mauck, 1980 U

Oncorhynchus clarkii cutthroat trout 0.9g 96h-LC50 3250 80


Oncorhynchus clarkii cutthroat trout NR 96h-LC50 4750 99 S,N 12 NR 40 6.5 Woodward and Mauck, 1980 U Oncorhynchus clarkii cutthroat trout NR 96h-LC50 5750 99 S,N 7 NR 40 7.5 Woodward and Mauck, 1980 U

Oncorhychus mykiss rainbow trout 9-11cm 48h-LC0 100000 10

WP S,N 9-13.5 NR NR NR Matsuo and Tamura, 1970 U

Oncorhynchus mykiss rainbow trout 0.6-1.0g 96h-LC50 330 98 S,M 17 >5.0 40-48 9.5 Howe et al., 1994 2 Oncorhynchus mykiss rainbow trout 0.2g 96h-LC50 430 98 S,NR 12 NR 40 8.5 Mayer and Ellersieck, 1986 1 Oncorhynchus mykiss rainbow trout 0.6-1.0g 96h-LC50 520 98 S,M 7 >5.0 40-48 9.5 Howe et al., 1994 2

Oncorhynchus mykiss rainbow trout NR 96h-LC50 700 80


Oncorhynchus mykiss rainbow trout 1.2g 96h-LC50 780 80


Oncorhynchus mykiss rainbow trout NR 96h-LC50 1100 99 S,N 17 NR NR 7.4 Sanders et al., 1983 U Oncorhynchus mykiss rainbow trout 0.33g 96h-LC50 1200 80 S,NR NR NR NR NR EFED, 2000 1 Oncorhynchus mykiss rainbow trout 1.2g 96h-LC50 1800 98 S,NR NR NR NR NR EFED, 2000 1 Oncorhynchus mykiss rainbow trout 0.6-1.0g 96h-LC50 2500 98 S,M 17 >5.0 40-48 6.5 Howe et al., 1994 2 Oncorhynchus mykiss rainbow trout NR 96h-LC50 4850 TG S,N 12 NR <60 NR Marking and Mauck, 1975 U Oncorhynchus mykiss rainbow trout Juvenile 24 to 72h-LC0 10000 NR S,N 8 NR NR NR Lewallen and Wilder, 1962 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Oncorhynchus mykiss rainbow trout 0.6-1.0g 96h-LC50 40900 98 S,M 7 >5.0 40-48 6.5 Howe et al., 1994 2

Oncorhynchus mykiss rainbow trout NR 96h-LC50 <37,100 12.2

S,NR NR NR NR NR SSRD, 1997 1

Oncorhynchus mykiss rainbow trout 100-150g 30min

immunological exposure

400 NR S,N 10.5-12 NR NR NR Kodama et al., 2004 U

Oreochromis niloticus tilapia NR Growth rate

index NR 80 S, R

23.2-25.5

4.4-8.5 NR 5.9-6.2

Guimarães and Calil, 2008 U

Oreochromis niloticus tilapia alevin Histopathology NR NR NR NR NR NR NR Guimarães et al., 2007 U

Oreochromis niloticus tilapia alevin Acetylcholinesterase activity

NR NR NR NR NR NR NR Guimarães et al., 2007 U

Pimephales promelas fathead minnow

0.9g 96h-LC50 7900 98 S,NR 18 NR 44 7.1 Mayer and Ellersieck, 1986 1


1-2g 96h-TLm 140000 99 S,N 25 39911 20 7.4-7.5



NR 96h-LC50 >100,000 99 S,N 22 NR NR 7.4 Sanders et al., 1983 U


NR 96h-LC50 >100,000 80



1-1.5g 96h-TLm 51000 99 S,N NR 39911 400 6.5-8.5

Henderson and Pickering, 1955 U


1-1.5g 48h-TLm 180000 99 S,N NR 39911 400 6.5-8.5



1-1.5g 96h-TLm 180000 99 S,N NR 39911 20 6.5-8.5



1-1.5g 24h-TLm 560000 99 S,N NR 39911 400 6.5-8.5



1-1.5g 48h-TLm 1000000 99 S,N NR 39911 20 6.5-8.5



1-1.5g 24h-TLm 1800000 99 S,N NR 39911 20 6.5-8.5


Pseudorasbora parva topmouth gudgeon

1-5g 96h-IC50 54062 NR S, N NA NA NA NA Kanazawa, 1983 U


Organism Common

name Life

Stage Endpoint

Effect Conc. (µg

a.i./L)

% a.i.

Test Type

Temp (oC)

DO (mg/L)

Hardness (mg/L)

pH Reference Rank

Rana esculenta L. green frog NR 1w-LOEC

(physiological response)

4,000 97.8

R,N 15 NR NR NR Szubartowska et al., 1990 U



4,000 97.8




4,000 97.8


Salmo salar Atlantic salmon 0.2g 96h-LC50 300 98 S,NR 12 NR 40 8.5 Mayer and Ellersieck, 1986 1 Salvelinus fontinalis brook trout 0.8g 96h-LC50 240 98 S,NR 12 NR 44 9.0 Mayer and Ellersieck, 1986 1 Salvelinus namaycush lake trout 2.3g 96h-LC50 550 98 S,NR 12 NR 162 7.4 Mayer and Ellersieck, 1986 1

Notes: F - Flowthrough; S - Static; R - Renewal; M - Measured; N - Nominal. 1 - Primary; 2 - Secondary; U - Unacceptable. NR = Not reported

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