DDT 1874-2005DDT 1874-2005

Paul JepsonPaul JepsonIntegrated Plant Protection Center

Oregon State Universityjepsonp@science.oregonstate.edu

November 17th, 2005

Pre-1940’s Pre-1940’s insecticidesinsecticides

• Household– Clothes moth:

camphor, naphalene, p-dichlorbenzene

– Fumigation: ethylene oxide, hydrocyanic acid

• Garden and farm– Nicotine, methyl

bromide, acetonitrile, calcium copper and lead arsenates, pyrethrins, rotenone

Dipping apples in 1% hydrochloric acid for 4 min removes 66-73% of the arsenic residue: 1930

Average arsenic after treatment: 0.006 grains/lb

FDA tolerance:

1927: 0.025 grains/lb

1932: 0.01 grains/lb

Experimental hop Experimental hop duster, Corvallis duster, Corvallis Oregon, 1940Oregon, 1940

Applying 4,6-dinitro-o-cyclohexyl phenol dust in walnut shell flour for spider mite control

DDT

• Highly toxic• Very persistent• Low acute toxicity to humans• 1941, little interest expressed• 1944, use to manage typhus epidemic created high

demand in wartime• High use in agriculture from first year of introduction• Impacts on humans and environment overridden by

commercial imperatives• Facilitated establishment of modern environmental

movement

Chronology of the modern pesticide industry• World War I

– Increase in supply of agricultural products to USA and allies– Growth of chemical industry incl. Chemical Warfare Service (PDB)– Development of pest control as a metaphor for war and vice versa

• Between wars– Testing of war gases as insecticides– Attempts to establish “Chemical Peace Service”– Entomologists increasingly use war metaphor for pest control

• World War II– Total war concept feeds warfare and pest control (annihilation)– Factory capacity for production grows after DDT introduction

• US government enables scarce materials to be used to build 14 factories for 11 companies in 1944/4

• 35-100% tax relief given to companies– DuPont awarded post war license for DDT in exchange for production agreement– Wide scale spraying in vector control using chemical warfare equipment– Restrictions on wide use of DDT under war powers legislation, because of side-effects on

humans and wildlife, detected at an early stage• Aftermath of war

– Organophosphate nerve gases tested as pesticides– No license or patent restrictions on US industry initially– Surplus production capacity directed to agriculture– No legal powers of government to restrict sale of properly labeled chemicals– Wildlife and conservation groups and many entomologists raise concerns by 1945– War metaphor used nationally to promote DDT use– Efficiency in military use, and for medicine used as an argument for promoting use in

agriculture

Introduction and wide-scale use of Introduction and wide-scale use of organochlorine insecticides, 1946organochlorine insecticides, 1946

Pyrethrum flower imports peaked at 13 million lbs 1945, but feel sharply in 1946, not resuming until 1955

Early promise, early Early promise, early cautioncaution

• DDT, HCH: combined contact activity and high toxicity of pyrethrins, with stomach activity and persistence of arsenates

• But, were not the universal insecticides that popular accounts made it appear– Toxicity to beneficials (e.g.parasites, bees, beetles, flies)

reported in early 1940’s– Research prior to 1946 was more cautious (problems

with lack of selectivity in potato, invertebrate loss in carrots, mite outbreaks in apple)

DDT used widely in the house, farm and DDT used widely in the house, farm and zoozoo

(Leary, Fishbein & Salter, 1946)

Pesticide treatments by 13 commercial Pesticide treatments by 13 commercial applicators in Oregon, 1957applicators in Oregon, 1957 (Mumford, 1959)

Application type

No. jobs Acres treated

Mean area per job

Application charge per acre

Ground treatment

767(DDT 49)

10,272(DDT 386)

13.4 $2.60

Aerial spraying

1,841(DDT 714)

146,481(DDT

25,231)

80.0 $1.33

The Hale centrifugal sprayer, capable of projecting spray upwards 30ft

The Hurst hang-on sprayer

Mist blowers, 1952Mist blowers, 1952(Garman, 1953)

50 gals/min, 1mph, gives 11.2 gals per tree, at 20 ft tree spacing

Serious drift problems reported in 1950’s literature

Application efficiency was not high

Pesticide utilization efficiencyPesticide utilization efficiency (Graham-Bryce, 1977)

Pesticide Application method

Target Efficiency of utilization

Demeton-S-methyl

Foliar spray Aphids on sugar beet

0.000008%

Dieldrin Seed treatment

Wheat bulb fly larvae

0.0015%

Dimethoate Foliar spray Aphids on field beans

0.03%

Lindane Foliar spray Capsids on Cocoa

0.02%

Dieldrin Aerial swarm spray

Locusts 6.0%

Summary• Organochlorines seemed a vast improvement upon

what went before• They were inexpensive and often gave high economic

return• High persistence and broad spectrum of toxicity did not

require them to be used efficiently• Chemists were ignorant of how OC properties impacted

ecological processes• Over-optimism and over-marketing led to complacency• Pest outbreaks (caused by loss of natural enemies)

were common following OC use• Evidence of wildlife impacts emerged by the late 1950’s

but hazard was known in 1945• The ‘Green Revolution’ relied upon broad spectrum

pesticides

Silent Spring Silent Spring byby Rachel Rachel CarsonCarson

• Main arguments– Pesticides represent new risk, parallel with

radioactivity, that deserves to be watched critically

– The most severe problems are the long term genetic and ecological ones; ecologists have new responsibilities

– The administrative machinery is inadequate• Response in UK:

– All scientific claims and statistics checked for accuracy and errors (minor), published in Journal of Ecology, 1963

– Public and parliamentary focus on pollution, ecology, risks and benefits

– Gradual restriction of OC’s, 1962-1976

The peregrin falcon(Moriarty, 1999)

• 1960, UK racing pigeon owners thought that falcon predation was increasing

• Analysis revealed a falcon population decline since 1955

• 1962: 92% of pre-war territories deserted, only 2% of nests successful

• pp-DDE and dieldrin seed dressings implicated• Pigeon mortality common, and 2-3 pigeons

consumed could prove lethal to falcons• If dieldrin was responsible for the decline, what

explains the poor breeding success?

Changes in egg shell thickness index, 1845-1979, Changes in egg shell thickness index, 1845-1979, for British peregrine falcons (for British peregrine falcons (Falco peregrinusFalco peregrinus)) (Ratcliffe, 1993)

Shell strength Shell strength and thickness in and thickness in Falco peregrinusFalco peregrinus (Cooke, 1979)

Open circles: 1850-1942

Closed circles: 1970-1974

pp-DDE thickens eggs of bengalese finch, hen, quail and pheasant

DDE implicated in egg shell thinningDDE implicated in egg shell thinning

SOILSOIL

0.730.73

EARTHWORMEARTHWORMSS

1.631.63

BLACKBIRDSBLACKBIRDS

87.1 (liver)87.1 (liver)

BLACKBIRDBLACKBIRDSS

52.7 (eggs)52.7 (eggs)

THRUSHTHRUSH

119.5 (liver)119.5 (liver)

THRUSHTHRUSH

46.2 (eggs)46.2 (eggs)

MOLESMOLES

1.78 (liver)1.78 (liver)

JANJAN

MARMAR

MAYMAY

Food chain Food chain accumulation of accumulation of pppp-DDE in UK -DDE in UK orchards after orchards after April sprays April sprays (ppm)(ppm)Bailey et al. (1974)Many equivalent datasets: Clear lake; land and sea bird carcass

studies

Epidemiological criteria for inferring causation

Criterion Inference strengthened…

Problems

Strength of association

Cause associated with large increase in risk

Difficulties measuring exposure and effects

Probability of causal association

Statistical significance Requires large study population and large effect

Time order Introduction of cause precedes effects

Long latency

Specificity of association

Specific cause linked to specific effect

Chemicals cause suites of effects, and they interact with other chemicals and stresses to cause disease

Consistency of association

Different authors, places, times

Impacts vary in space and time

Dos-response relationship

High exposure, high effect

Difficulty in measuring exposure, variation in modifying factors between groups, non-linear relationships

Biological plausibility Known mechanism Many processes not well understood, epidemiological data often precede mechanism

Benefits of OC’s?Benefits of OC’s?

Locust control in Africa

Disease vector control

Band spraying with insect growth Band spraying with insect growth regulators, using ULV sprayers, regulators, using ULV sprayers,

replaces OC’s and OP’sreplaces OC’s and OP’s

Returns to approach used for dieldrin and the OC’s, but without the

environmental risk

Alternatives to DDT proving harder to find, but they do exist

DDT still used as a wall treatment, and against the vectors of sleeping sickness. Pyrethroid-treated bed nets are just as effective

Impact of the modern insecticide era on biological control?

Numbers of introduced natural Numbers of introduced natural enemies by decadeenemies by decade (Gurr, et al.,

2000)

0

100

200

300

400

500

600

700

800

900

1890-9 1900-9 1910-9 1920-9 1930-9 1940-9 1950-9 1960-9 1970-9 1980-9 1990-8

% Biological introductions leading to success, % Biological introductions leading to success,

establishment, failure (or unknown)establishment, failure (or unknown) (Gurr et al., 2000)

0

10

20

30

40

50

60

70

80

90

100

1880-9 1900-9 1910-9 1920-9 1930-9 1940-9 1950-9 1960-9 1970-9 1980-9 1990-8

SuccessEstablishmentFailure

How can success rate be improved?

The organochlorine legacyThe organochlorine legacy• Remaining OC residues and polar

accumulation• Human body burdens, declining,

but still there• Clean-up and disposal

internationally• Gradual shift towards more

effective chemicals• Chemophobia among public• Lack of public understanding of

agriculture• Regulation improving• Alternative technology

suppressed• Recycling of arguments about

causation with respect to human disease and environmental impact

• POP’s convention permits use in malaria management

OC’s in aquatic ecosystems of the Columbia Plateau (USGS)

Continued use of DDT in vector control

• Express the trade-offs in terms of costs and benefits

• Is lack of DDT the real underlying cause of malaria resurgence?

• Do advocacy groups contribute to or detract from progress?