Pesticides & Waste Ch 22 & 23

1. Pesticides & WasteCh 22 & 23

2. PEST = any organism that interferes in some way with human welfare or activities. • PESTICIDE = toxic chemicals used to reduce the size of and control the pest population. • Grouped by their target organism Insecticide, Herbicide, Fungicide, Rodenticide • 85% of pesticides worldwide used for Agriculture.

3. “Ideal Pesticides” • Narrow-Spectrum= kill only target organism. • Breaks down easily into safe materials • Does not move around in the environment. • “Non-Ideal Pesticides” • Broad-Spectrum= kill more than just the target. • Persistent or Can degrade into other cmpds that can be more dangerous • Move around in the environment.

4. Pre-1940s (First-generation pesticides) • Inorganics (Minerals) • Contain lead, mercury, and arsenic • Very persistent & bioaccumulate • Organics (Botanicals) • Plant-derived • Break down readily • Post-1940s (Second-generation pesticides) • Synthetic Botanicals • Made by altering natural botanicals • Ex: dichlorodiphenyltrichloroethane (DDT)

5. INSECTICIDES : Classified by chemical structure • Chlorinated Hydrocarbons = organic cmpd + Cl • Broad-spectrum, persistent • Most are banned (DDT, endosulfan, etc) • Rachel Carson: Silent Spring • Organophosphates = organic cmpd + P • more poisonous than most others • not persistent, so they’ve replaced most chlorinated hydrocarbons • Carbamates = broad-spectrum, derived from carbamic acid • Less toxic to mammals (Carbaryl, Aldicarb)

6. HERBICIDES • Classified by how they act & what they kill • Selective Herbicides = kill only certain types of plants • Broad-leaf Herbicides • 2,4-D & 2,4,5-T common in 1940s • 2,4,5-T banned by EPA in 1979 due to possible harmful side effects realized after its use in the Vietnam War • Grass Herbicides • Nonselective Herbicides = kill all vegetation

7. VIETNAM WAR & HERBICIDES • US used mixtures of herbicides to kill vegetation in S.Vietnam to expose hiding places & destroy crops planted by Vietcong: Agent White, Agent Blue, & Agent Orange • Negative environmental impacts: • Mangrove forests & hardwood forests destroyed • Harmed ecology & economy of S.Vietnam • Negative health impacts: • Agent Orange = 2,4-D & 2,4,5-T combined. • Created highly toxic Dioxins during creation • Birth defects, stillbirths, female reproductive disorders, soft-tissue cancers • Bioaccumulated in fish = very high levels in Vietnamese people

8. DISEASE CONTROL • Malaria: carried mostly by female mosquitoes • Worldwide: 300-500M people currently suffer, 2.7M die each year. • DDT has helped the malaria problem greatly. • Sri Lanka: went from 2M cases each year to almost zero with the use of DDT. • When spraying stopped, more than 1M cases per year within 4 years. • Restarted DDT spraying in 1968 • DDT still used in at least 20 tropical countries to control mosquitoes.

9. CROP PROTECTION- We already know this… • 1/3 of world’s crops are eaten/destroyed by pests • Pesticides decrease crop loss due to weed competition, insect consumption, and plant diseases caused by pathogens = microorganisms that cause disease. • Many insects are considered pests, and ~200 species have the potential to cause large economic losses in agriculture. • Pesticide use is justified economically: • For every $1 spent by farmers on pesticides, $3-5 is saved from crop loss. • Monoculture = one variety of crop species is grown on large tracts of land. • Causes more pest destruction because it reduces the dangers and accidents that might befall a pest as it searches for food.

10. Genetic Resistance • any inherited characteristic that decreases the effect of a pesticide on a pest. • 520 insect & mite species & 84 weed species currently resistant • Evolution causes genetic resistance (any cumulative genetic change in a population of organisms). • Natural genetic traits protect some individuals from the pesticide, and their traits move onto the next generation. • Short generation times & large population sizes promote rapid evolution & quick adaptation.

11. Pesticide Treadmill = the cost of applying pesticides increases while their effectiveness decreases (due to genetic resistance) • Resistance Management = delay the evolution of genetic resistance to maximize the time a pesticide remains effective. • Maintain a nearby “refuge” of untreated plants. Pests there won’t be affected, and will breed with the newly resistant pests to keep the gene pool variable. • Avoid repeated use of same herbicide on the same field.

12. Ecosystem Imbalances • Pesticides affect species other than intended pests. • Beneficial insects, birds, and others are often killed. • Indirectly responsible for killing many natural enemies of the pests (may starve/migrate looking for food after pesticide use) • Kill natural enemies directly sometimes • eating prey who have pesticides in their bodies • Pest population rebounds soon due to lack of predators! • Creation of new pests (minor pests become major pests) • Pesticide may kill a certain pest’s natural predators, parasites, and competitors.

13. Persistence, Bioaccumulation & Biomagnification • DDT: falcons, pelicans. bald eagles, ospreys, and many other birds are very sensitive. Thin shells = chicks die. • 1972 – DDT banned. Bird reproduction increased.

14. 3 characteristics: • Persistence = natural decomposers haven’t yet evolved ways to degrade synthetic pesticides, so they accumulate in the environment. • Bioaccumulation / Bioconcentration = buildup of a persistent pesticide in the body (usually fatty tissues) • Biological Magnification / Amplification = those higher on the food chain have higher conc. of pesticides stored.

15. Mobility in the Environment • Pesticides tend to move through soil, water, & air, sometimes long distances. • Wash into rivers & streams to harm fishes (death or other health problems like bone degeneration). • 14.1M US residents drink water w/ traces of 5 common herbicides, causing slightly elevated cancer risk • Air mobility causes problems as well.

16. Short Term Effects • Mild poisoning: nausea, vomiting, headaches • More serious: permanent nervous system damage or other organs. • Globally: more than 3M poisoned, 220,000 die each year. • Worse in Developing nations – no safety training & lax laws. • Bhopal (India) Disaster – methyl isocyanate gas explosion. Converted to hydrogen cyanide (deadly) in the air. • 2500 died, survivors had serious respiratory, ophthalmic, intestinal, reproductive, and neurological problems. Survivors were paid $500 each. Cleanup still needs to be addressed.

17. Long Term Effects • Can cause cancer (lymphoma, leukemia, brain/lung/testicle/breast) • Sterility possible. • Higher rates of miscarriage • Greater risk: children of ag.workers (birth defects/stunted limbs) • Immune system suppression • Potential link to Parkinson’s.

18. Pesticide & Endocrine Disruptors • Reproductive problems in animals (endocrine disrupters) • River Otters: abnormally small penises • Female sea gulls: behavioral changes – pair with other females. • Our Stolen Future = 1996 book by Colburn/Dumanoski/Myers • Suggested human hormone systems may be disrupted, as well as other health problems (breast/testicular cancer, male birth defects, low sperm counts). • Cause-Effect relationship still not established. • Should DDT be banned immediately worldwide?? • May internationally ban 9 pesticides suspected of endocrine disruption.

19. Pesticides & Children • Household Pesticides greater threat to children • Play on floors/lawns w/ more pesticide exposure. • Bodies still developing • May cause brain cancer & childhood leukemia. • EPA estimate: 84% of US homes using pesticide products. • Pest strips, bait boxes, flea collars, bug bombs, etc. • Pesticide residue on food • May affect dev.of intelligence & motor skills of young children.

20. Cultivation Methods • Interplanting = alternating rows of different plants • Strip Cutting = harvest one crop at a time, leaving habitat for natural predators of the pests. • Planting around marginsto keep habitat for natural predators. • Proper timing & crop rotation

21. Genetic Controls • Create a pest-resistant crop by crossing pest-resistant plants w/ non-resistant. • Problems: fungi/bacteria/pathogens evolve quickly = must keep ahead! • Genetically Modified (GM) Plants can be created quickly ! It could harm other parts of the environment ! • Many varieties are selective. Modify the gene = more general & more widely effective!

22. Biological Controls • use naturally occurring disease organisms/ parasites/ predators to control pests. • >300 species have been introduced. • Careful that new control agents don’t become pests! (weevil/thistle) • Bt= soil bacterium that’s a great natural insecticide.

23. Quarantine • restrict import of exotic plants/animals that may harbor pests. • Effective, but not foolproof. • Ex: Mediterranean Fruit Flies (medflies) in California… it’s worked, but they keep coming back!

24. Pheromones & Hormones • Pheromones = natural substances produced by animals to stimulate a response within their species. • Use to lure insects into traps! • Hormones = natural chemicals produced by insects to regulate their own growth/metamorphosis. • Given at wrong time: abnormal development & possible death.

25. Integrated Pest Management (IPM) • Combine many methods of pest mgmt. • Pesticides are a last resort, and weak ones are used in low amts. • Important for Sustainable agriculture. • Used to MANAGE, not ERADICATE. • Determine when pest pop reaches an economic injury threshold when benefit of taking action exceeds cost. • Requires education on good strategies. • Overall, IPM use is low. Knowledge to use pesticides is less than to use IPM.

26. Reproductive Controls • Sterile Male Technique = sterilize males w/ radiation or chemicals. • Disadvantages: • Must be done continually to be effective - if discontinued, pest pop will rebound very quickly. • Expensive! $$$$$$

27. Irradiating Foods • Use ionizing radiation (gamma rays from cobalt 60) on harvested food to kill harmful microorganisms • First used in US: 1992 • Controversial, yet mostly safe. • Can cause free radicals (carcinogenic), but they normally occur produced by frying and boiling. • Don’t know the long-term effects yet.

28. FOOD, DRUG, and COSMETICS ACT (1938) • Recognized the need to regulate pesticides found in food • NO MEANS FOR REGULATION! • Made more effective in 1954: Pesticide Chemicals Amendment (AKA Miller Amendment) required establishment of acdeptable and unacceptable levels of pesticides in food. • Delaney Clause (1958): no substance capable of causing cancer in test animals or in humans would be permitted in processed food. • Didn’t cover raw foods, & lacked data on older pesticides. • Almost impossible for newer pesticides to pass standards

29. Federal Insecticide, Fungicide, and Rodenticide Act • (1947): regulate effectiveness of pesticides (restrict use of ineffective pesticides). • Now requires testing and registration of active ingredients • Don’t meet FDCA standards? No registration with FIFRA. • 1972: EPA gets regulatory authority, and has now banned or restricted use of many chlorinated hydrocarbons (DDT) • Amended FIFRA in 1988 to require registration of older pesticides, so now must face the same standards of new pestic. • Didn’t address groundwater cont., establish standards for residues on food or farm worker safety, require companies to disclose potentially harmful inert ingredients

30. Food Quality Protection Act • 1996: amended FDCA & FIFRA. • Established identical pesticide residue limits for raw produce and processed foods. • Must consider child susceptibility when considering pesticide residue limits. • Must set limits for all health risks, not just cancer. • Must test for endocrine-disrupting properties.