Pesticides and pest control

1. Pesticides and pest control Chapter 20

2. US Pesticide Use (2001) EPA Report

3. US pesticide use by type Look at and understand Table 20-1.

4. Most common pesticides in US • Glyphosate (Round-up) • most heavily used pesticide in US • Safe? EPA Fact Sheets Nat’l Pesticide Information Ctr.

5. Atrazine • 2nd most heavily used pesticide in US • Broad spectrum herbicide that inhibits photosynthesis • Endocrine diisruptor in wildlife EPA Fact Sheets Nat’l Pesticide Information Ctr.

6. Ecological Effects of Atrazine • Data for 28 sites in Louisiana (1993)

7. Pesticides and human health • OPs are cause of most acute fatalities Cornell Human Health Site

8. Bhopal, India (1984) • "world's worst industrial accident“ • 5,000 - 15,000 deaths • 200,000 people suffered blindness and lung damage • Union Carbide paid $470 million in damages (could have prevented it for $1 million): December 3, 2004 – Global Day for Action

9. State of Toxicity Testing Based on 3,350 active and inert ingredients.

10. Pesticide Regulation New York Law: Standard contracts for homeowners (1/2004) and standard signage (1/2005) • Read about it in Miller Quebec, Canada Non-farm ban on all pesticides on public and private land "I consider health to be more important than a perfect lawn," Minister Boisclair added

11. Original pest population Introduction of pest control Economic threshold Pest density Equilibrium position Equilibrium position Reduced pest population Time IPM Strategy

12. 600 500 Gypsy moth caterpillar Boll weevil Insects and mites 400 Number of species 300 Plant diseases 200 Weeds 100 0 1950 1960 1970 1980 1990 2000 2010 Year Genetic Resistance

13. Pesticide Export • Pesticides return to the US in air and imported food items (coffee, cocoa, fruits and vegetables) • 25% of produce consumed in US is imported

14. FDA Market Basket Program • Why do you think this is? FDA Total Diet Study

15. Alternative Pest Control Strategies

16. DDT and Malaria The case for DDT (Science News)

17. Pesticides of Concern • Organochlorines • Orpganophosphates • Agent Orange (2,4,5-T) • Paraquat

18. Pesticides • Pesticides are designed to harm life (insects, plant, fungi, etc.) • many are considerably toxic to humans • many are persistent in the environment • lipophilic compounds bioaccumulate up food chains (to humans) • Risk vs. benefit or pesticide use • increases food production • effective against controlling insect-borne diseases (malaria, yellow fever, African sleeping sickness, viral encephalitis-NYC) • Human costs: • worldwide (according to WHO): • 1 million serious accidental poisonings and 2 million suicide attempts involving pesticides every year • higher rate of toxic episodes in developing countries where regulations are less strict and more poorly enforced • Sri Lanka (population 15 million) - 13,000 hospital admissions per year and 100 deaths • China: 100,000 cases of pesticide poisonings annually From: Philp, Chap. 9 and O'Malley, M. 1997. Clinical evaluation of pesticide exposure and poisonings. The Lancet 349(9059):1161-1167.

19. Pesticides • History of pesticide use: • natural pesticides used since ~1850 • root of derris plant for insect control in nutmeg plantation in Singapore • extract of derris root is rotenone • chrysanthemum flowers (pyrethrum) have been used as insecticidal agents for centuries • synthetic pesticides first used ~1900 • first synthetic production of pyrethrum was in 1828 • US imported 14 million tons in 1945 • arsenic compounds - arsphenamine effective against syphilis (1910) • white arsenic (arsenic trioxide) used against Colorado potato beetle • copper arsenate - slug bait • DDT • synthesized in 1854, but insecticidal properties not recognized until 1939 • 1950s - replaced other pesticides because highly effective • first agent to arouse environmental concern • focus of Rachel Carson's Silent Spring • over 1000 chemicals now registered as pesticides against ~2000 pest species • over $1 billion industry in US From: Philp, Chap. 9

20. Organophosphate pesticides • Organophosphate pesticides all contain O and P, and all act via the same mechanism • Most frequent cause of human poisonings by insecticides • History: • first OPs developed by Germans, in conjunction with chemical warfare agents (sarin, etc.) • TEPP, the first OP, was highly toxic to mammals, and biodegraded very quickly • parathion: synthesized in 1944, became most commonly used insecticide • but high mammalian toxicity by all exposure routes has decreased its use • causes most human fatal poisonings • being (or has been) phased out of production in 1990s • Includes parathion, malathion, dichlovoros, and diazinon (and many others) • Environmental Fate: • relatively quickly degraded in environment (relative to organochlorine compounds) • relatively water soluble - rapidly distributed throughout the body in blood • exposure is usually via skin or lungs • primarily an occupational (or recreational farming) hazard • Disposition: • OPs are bioactivated by the liver • ex: parathion (P=S) to paraoxon (P=O) • Toxicity • act by the phosphate irreversibly binding to and inhibiting acetylcholinesterase (the enzyme that breaks down the neurotransmitter in the nerve-muscle synapses and in brain) • there is often a delay before onset of symptoms (2 hrs) From: Philp, Chap. 9, Klaassen et al, Chap. 18

21. Organophosphate pesticides • Toxicity (continued) • symptoms: massive cholinergeric response: dizziness, disorientation, diarrhea, slowing of the heart (bradycardia), profuse sweating • response can be prolonged as OP is released from fat stores • and inhibition is irreversible, so effect of more exposure is cumulative • some OPs can caused OP-induced delayed peripheral neuropathy (OPIDN) • axonal dieback of peripheral nerves and demyelination • nutrients not transported down nerve fiber • humans and hens most sensitive (don't ask me why) • many exposures result from improper household storage, suicides, etc. • likely to have concurrent exposure to VOCs which are used as carriers for pesticides (toluene, xylene) which are listed as "inert" ingredients • treatment: • atropine, which blocks acetylcholine receptors (prevents action of neurotransmitter) • pralidoxime, which binds to OP stronger than OP binds to acetylcholinesterase • Carbamates: • similar to OPs, but binding to acetylcholinesterase is reversible • examples: • carbaryl, aldicarb, etc. From: Philp, Chap. 9, Klaassen et al, Chap. 18, ATSDR Case study #22 (1993).

22. Organophosphate pesticidesCase studies • Persian Gulf War Syndrome (UK-style) • Ministry of Defense denied for 2 years that British troops were exposed to OPs • then said malathion (a relatively nontoxic OP) was used to delouse Iraqi prisoners • 3 other OP pesticides were purchased in Gulf countries to treat tents, latrines, etc. • dimethyl phosphorothionate, diazinon, and axamathiphos • now conducted a long-term epidemiological study to track reproductive effects • southwestern Hungary village of Rhinya • 11 of 15 infants born between 1989 and 1990 had birth defects • normal rate in Hungary is 1 in 15 • cluster not linked to genetics, familial inheritance or other known teratogenic factors (inbreeding etc.) • 4 had Down's syndrome (223x higher than average Hungarian rate) • all mothers had eaten fish containing high concentrations of trichlorfon (releases dichlorvos) during pregnancy • fish farms had used insecticide (40% TCF) to treat parasitic infections in the fish • residents continued to eat fish even during government efforts to prohibit consumption • Case studies: • from: Bartel, H. 1991. Quiet sufferers of the silent spring. The New Scientist 130(1769):30-36. • Mrs. Chapman and the helicopter and the cows. From: Dean, M. UK Ministers misled over use of Gulf War pesticides. The Lancet 349(9053):7, and Czeizel, A E et al. 1993. Environmental trichlorfon and cluster of congenital abnormalities. The Lancet, 341(8844):539-543.