Transcript Slide 1

November 17th, 2005
DDT 1874-2005
Paul Jepson
Integrated Plant Protection Center
Oregon State University
[email protected]
Pre-1940’s
insecticides
• Household
– Clothes moth:
camphor, naphalene, pdichlorbenzene
– 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
duster, Corvallis
Oregon, 1940
Applying 4,6-dinitro-ocyclohexyl phenol dust in
walnut shell flour for spider
mite control
DDT
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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
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World War I
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Between wars
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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
Testing of war gases as insecticides
Attempts to establish “Chemical Peace Service”
Entomologists increasingly use war metaphor for pest control
World War II
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Total war concept feeds warfare and pest control (annihilation)
Factory capacity for production grows after DDT introduction
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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 sideeffects on humans and wildlife, detected at an early stage
Aftermath of war
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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
organochlorine insecticides, 1946
Pyrethrum flower imports peaked at 13
million lbs 1945, but feel sharply in 1946,
not resuming until 1955
Early promise, early
caution
• 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 zoo
(Leary, Fishbein & Salter, 1946)
Pesticide treatments by 13 commercial
applicators in Oregon, 1957 (Mumford, 1959)
Application
type
No. jobs
Acres
treated
Mean
area
per
job
Application
charge per
acre
Ground
treatment
767
10,272
13.4
$2.60
(DDT 49)
(DDT 386)
1,841 146,481 80.0
$1.33
Aerial
spraying
(DDT
714)
(DDT 25,231)
Mist blowers, 1952
(Garman, 1953)
50 gals/min, 1mph, gives 11.2 gals per tree, at 20 ft tree
spacing
The Hale centrifugal sprayer,
capable of projecting spray upwards
30ft
The Hurst hang-on
sprayer
Serious drift problems reported in 1950’s literature
Application efficiency was not high
Pesticide utilization efficiency
(Graham-Bryce, 1977)
Pesticide
Application
method
Target
Efficiency of
utilization
Demeton-Smethyl
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 by Rachel
Carson
• 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, for
British peregrine falcons (Falco peregrinus) (Ratcliffe,
1993)
DDE implicated in egg shell thinning
Shell strength and
thickness in Falco
peregrinus (Cooke,
1979)
Open circles: 18501942
Closed circles: 19701974
pp-DDE thickens eggs of
bengalese finch, hen,
quail and pheasant
MAY
THRUSH
BLACKBIRDS
46.2 (eggs)
52.7 (eggs)
THRUSH
119.5 (liver)
MAR
87.1 (liver)
MOLES
1.78 (liver)
EARTHWORM
S
1.63
JAN
BLACKBIRDS
SOIL
0.73
Food chain
accumulation of
pp-DDE in UK
orchards after
April sprays (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?
Locust control in Africa
Disease vector control
Band spraying with insect growth
regulators, using ULV sprayers, replaces
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
enemies by decade (Gurr, et al., 2000)
900
800
700
600
500
400
300
200
100
0
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,
establishment, failure (or unknown)
(Gurr et al., 2000)
100
90
80
70
60
Success
Establishment
Failure
50
40
30
How can
success rate
be
improved?
20
10
0
1880-9
1900-9
1910-9
1920-9
1930-9
1940-9
1950-9
1960-9
1970-9
1980-9
1990-8
The organochlorine legacy
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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?