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Determination of LD50 of Propoxur on American Nymph cockroaches
Joseph Scott - 11986573
Pharmacology 1 - 91707
May 26, 2017
Introduction
The purpose of this experiment has the purpose to determine the definitive LD 50 of the Carbamate
insecticide Prodoxur when given to American nymph cockroaches.
The American nymph cockroach (Periplaneta Americana) at adult hood grow up to a average
length of 30-40mm in length (University Library University of Illinois at Urbana-Champaign) This is
the specimen used during this experiment. The selection criteria for the cockroaches used within this
experiment are of an approximate size of 2cm in length lacking the stage of their development giving
them wings. The point in the life cycle between birth and adult hood is referred to the nymph stage in
their development (Bell & Adiyodi 1981).
These cockroaches can become a public health hazard due to their association with human waste,
disease and their ability to move from sewers into households or commercial constructs. Their
presence is of epidemiological significance with at least 22 species of pathological human bacteria,
viruses, fungi and protozoans isolated from field collected American cockroaches (Rust MK, Reierson
DA, Hansgen KH. 1991).
Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573
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Figure 1: Life cycle of the nymph cockroach (University Library University of Illinois at Urbana-Champaign 2014)
Figure 2: American nymph
cockroaches and their excrement
(L.J. Buss, TR Fasulo, University
of Florida)
Many insecticides have been developed throughout the world. One of the most common forms of
insecticides used commercially in households are Organophosphate Carbamates which is the
generalized term for this category of insecticides. Within carbamates we focus on the use of Propoxur
Carbamates are used to kill or control insects. They are made from carbamic acid and come in many
forms, each different in how they work and their toxic effects towards the targeted insect.
Carbamates have low effect on the surrounding environment long term as they break down within
the environment in weeks to months (Delaware Health and Social Services). Carbamates work as
reversible inhibitor of cholinesterase, which is an essential nervous system enzyme of insects, this
results in a fast immobilization and death of the insects (Hayes 1982).
Propoxur is a non-synthetic insecticide that was introduced in the year 1959. Propoxur has a fast
knockdown and extended residual effect towards insects such as flies, fleas, ticks and as in the
experiment against cockroaches, in the household or environment. (Hayes & Laws 1990). There are
many forms purchasable of this product which affect its concentration spread and release such as
liquid and aerosol forms which are ready to use. (USDA 1992). The type used within this experiment
is in the form of powder, diluted into different concentrations.
Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573
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Figure 3: Carbamate mode of
action (University of
Technology Sydney 2017)
Figure 4: Chemical Structure
of Propoxur (university of
Technology Sydney 2017)
LD50 is referred to the Lethal Dose expected to eliminate half of an exposed population of individuals
(Stenersen 2004). The usual unit of dosage is in mg per kg (mg/kg). When there is only needed a
small dose to reach the LD50 than there is a higher level of toxicity while a higher dose required to
achieve the LD50 means there is a lower level of toxicity from the substance towards the organism.
The LD50 test is a procedure in which a substance such as insecticides is applied to animals such as
cockroaches with the purpose to determine the substances concentration needed to achieve a
predetermined rate of death reaching 50% of the test population (NSW Department of Primary
Industries 2013).
Method
Refer to pages 28-35 Pharmacology 1 Subject Number 91707 Course Practical Manuel, Autumn
Semester 2017 (University of Technology, Sydney 2017).
Results
Notes:
Concentrations determined by demonstrator.
Purity of stock samples of propoxur (97.6%).
Table 1. The death percentage of American Nymph cockroaches to propoxur at varied concentrations (group and class results).
Concentrations (% W/V) Roach Fidty (RF) % Death Class average % DeathControl 0.00 0.00
0.01 20.00 16.250.02 70.00 42.500.05 70.00 68.750.10 100.00 83.75
Notes:
Class Average result from all 8 Groups.
Roach Fidty (RF) singled out as our own group.
There is a duplicate of 2 cups for each concentration to achieve greater accuracy.
The percentage of death is calculated by the measurement of the number of dead cockroaches
after a 24-hour period after cockroaches have been exposed to propoxur to the presence of 5
cockroaches per 1 cup.
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Data shows that as dose concentration increases so does death rate.
Average Weight of each cockroache from RF = 0.56g. from Class = 0.48g.
Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573
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Figure 5: Log-Linear
graph based on
experimental results of
RF and Class average to
determine the LD50.
Figure 6: Log-Probit
graph based on
experimental results of
RF and Class average to
determine the LD50.
Table 2: LD50 average w/v determination based off experimental result graphs.
Log Linear Log Probit AverageLD50 Group RF (w/v) 0.021 0.018 0.039LD50 Class (w/v) 0.030 0.031 0.0305Average 0.0255 0.0245
Table 3: Calculation from percentage w/v to mg/kg.
LD50 From Log Linear Group LD50 From Log Probit Group= 0.021 w/v= 0.021 g/100ml= 0.00021 g/ml= 0.00021 mg/ul – per cockroach injection divided by average weight from RF group= 0.00021 mg/0.56g= 0.000375 mg/g= 0.375 mg/kg
= 0.018 w/v= 0.018 g/100ml= 0.00018 g/ml= 0.00018 mg/ul – divided from average weight per 1 cockroach RF group= 0.00018 mg/0.56g= 0.000321 mg/g= 0.321 mg/kg
LD50 From Log Linear Class LD50 from Log Probit Class= 0.03 w/v= 0.0003 mg/ulDivide by average class weight= 0.0003 mg/0.48g= 0.000625 mg/g= 0.625 mg/kg
= 0.31 w/v= 0.00031 mg/ulDivide by average class weight= 0.00031 mg/0.48g= 0.000646 mg/g=0.646 mg/kg
Table 4: Propoxur LD50 of American nymph cockroaches by group and class results calculated from
linear and probit log graphs
Log Linear Log Probit AverageLD50 Group (mg/kg) 0.375 0.321 0.348LD50 Class (mg/kg) 0.625 0.646 0.636Average 0.500 0.484
Discussion
The LD50 found by RF and Class results of Propoxur on American Nymph Cockroaches were
0.348 mg/kg and 0.636 mg/kg respectively.
In 1999 a study was performed by Valles, Koehler and Brenner of which they determined
the LD50 of propoxur towards American Nymph Cockroaches was 0.65mg/kg. the class
Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573
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results closely represent the same result as their experiment, while the RF group was below
their experimental found value.
There can be many sources of variation within the experiment, a few of these can include
but are not limited to:
Different size / length of cockroaches used (measurement of individual cockroaches
was difficult due to their nature to move run around).
The RF group has an outlier on the 0.2 w/v propoxur concentration that caused a higher
line of best fit giving a lower Ld50.
Application of 1ul dose to cockroaches as application due to cockroach movement was
difficult which could have caused bad placement of propoxur.
Recommendations for the improvement of this experiment for future studies.
Weighing of individual cockroaches to get more consistent and specific results.
Exact measure each individual cockroach between group and class as to assure less
variation.
Differentiate females to males as their weights vary.
Maintain health of test population.
Produce more test samples, more cockroaches per cup/ more cups for greater accuracy.
Table 4 has shown that the average calculation for the log linear as well as the log probit
graphs provide similar results. The log probit graph shows better results than that of the log
linear graph for the class results but not as good for the RF results. This result for RF may be
due to the outlier on the 0.2 w/v concentration pushing the Ld50 backwards. These
improved results on the Log probit graph may be due to its extended section between the
10/90 range for horizontal observation. By following the line of best fit we can see that on
the log probit graph the results are much easier to determine while the log linear graph
raises results quickly over a small area making it difficult to determine the LD50
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References
1. Bell WJ, Adiyodi KG. 1981. The American Cockroach. Chapman and Hall, London.
2. Fasulo TR. (2002). Cockroaches and Pest Ants. University of Florida
3. Hayes, W. J. 1982, Pesticides studied in man, Williams and Wilkins, Maryland.
4. Hayes, W.J. & Laws E.R. (ed.). 1990, Handbook of pesticide toxicology, Vol. 3, Classes of
pesticides. Academic Press Inc, New York
5. University Library University of Illinois at Urbana-Champaign 2014, IPM photo reference,
viewed 20th May 2017,
6. University of Technology Sydney. 2017, ‘Pharmacology 1 autumn semester 2017’, UTS
Online Subject 91707, course Manual
7. University of Technology Sydney. 2017, ‘Pharmacology 1 autumn semester 2017’, Lecture
insecticides 1/2 'Pharmacol1 L1-2 Insecticides.pdf
8. USDA. 1992, The biologic and economic assessment of propoxur. NAPIAP, Extension Service,
USDA, Washington, DC.
9. NSW Department of Primary Industries 2013, LD50 and lethality testing, viewed 20th May
2017, <http://www.animalethics.org.au/accreditation-and-licensing/ld50-and-lethality-
testing>.
10. Valles, S. M., Koehler, P. G., Brenner, R. J. 1999, Comparative insecticide susceptibility and
detoxification activities among pestiferous Blattodea. Elsevier Science enzyme
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