1. Chemicals and Disease
Three major types of toxic agents:

2. Mutagens:
Chemicals or radiation that produces mutations in DNA

3. Teratogens
Chemicals, radiation, or viruses that cause birth defects during pregnancy

4. Carcinogens
Chemicals, radiation, or viruses that cause or promote cancerous cells.
Environmental and lifestyle factors account for up to 80% of all cancers

5. Long term exposure to various toxic chemicals in the environment can disrupt the body’s immune, nervous, and endocrine systems

6. Immune system: cells and tissues that protect the body against disease
Nervous system: brain, spinal cord, and peripheral nerves
Endocrine system: releases hormones into bloodstream

7. Hormone disrupters: chemicals similar to estrogens (female hormone)
Hormone blockers: chemicals that prevent natural (male) hormones from working correctly

8. “Gender benders”
Thyroid disrupters: affect growth and weight, may cause behavioral disorders.

9. Toxicology and Human Health
Toxicity: a measure of how harmful a substance is.
Depends on:
Dose: the amount of a substance ingested, inhaled, or absorbed through the skin

10. Frequency of exposure
Age/body size
Body detox
Genetic make-up

11. Persistence: resistance to breakdown
Harm caused by a toxin depends on:
Solubility
Water: water supply
Oil/fat: penetrate cell membranes
Persistence: resistance to breakdown

12. Bioaccumulation: toxin absorbed and stored in organs, muscles, and/or tissues
Biomagnification: levels of a toxin are magnified as they pass through/up food chains

13. Interactions
Chemical
Synergistic
Response: they type/amount of health damage
Acute: immediate
Chronic: long lasting

14. Pesticides
Chapter 23

16. The IDEAL pesticide would:
Kill ONLY the target species
(Harm NO other species)
Breakdown easily
(No persistence)
NOT cause genetic resistance in target species
Be CHEAP!

18. The 2 Major Categories:
Broad Spectrum: kills target and non-target species (kills everything)
Narrow Spectrum: (selective) kills specific group of pests

19. Specific Categories Insecticides Chlorinated hydrocarbons
DDT – banned in 1972
HIGH persistance
Organophosphates
Carbamates
Botanicals

20. Herbicides Contact (atrazine) Systemic Soil Sterilants
AGENT ORANGE: used in the Vietnam war – cause birth defects in animals and humans as well as cancer

21. Fungicides Fumigants (spays) Rodenticides Nematocides
(Carbon tetrachloride: CCl4)
HIGH persistance…
Rodenticides
Nematocides

22. POP’s
Persistent Organic Pollutants: man-made chemicals that do NOT break down
Pesticides (DDT)
Industrial chemicals
By-products & contaminants

23. Although some pesticides such as DDT are banned in the U. S
Although some pesticides such as DDT are banned in the U.S. – companies can still manufacture and export them to other countries…
Note: the U.S. stopped manufacturing DDT in 1985

24. Problems
Genetic resistance
Remember: insects are r-strategists so they reproduce A LOT and ADAPT/EVOLVE QUICKLY
Remember: anti-biotic resistant bacteria… SAME THING!

25. Pesticide Treadmill: when “farmers” increase the amount of pesticide sprayed on their crops due to increased genetic resistance
Greater amounts have been shown to be ineffective…

26. Broad Spectrum pesticides kill NON-TARGET species: natural predators and parasites that HELP maintain populations of pest species

27. Wiping out natural predators can unleash new pests whose populations had previously held in check
Pesticides are also killing honey bees which are a keystone species because of the vital job of pollination

28. Some pesticides bioaccumulate leading to disastrous problems for higher organisms (biomagnification!)

34. Human Health Affects…
Cancers
Nervous disorders
Reproductive disorders
Immune system disorders
Birth defects
??????

35. Pesticide Benefits Combat insect-borne diseases (malaria)
Increases food supplies
Lowers food costs (?)
Faster/Efficient

36. Regulation
Department of Health and Human Services: FDA
USDA
EPA
Pesticide regulations: HAND-OUT!!

37. Reductions in Pesticide Use
IPM: Integrated Pest Management
Goal: NOT to eradicate pest populations, but to reduce crop damage at an economically tolerable level…

38. Uses cultivation, biological, and chemical methods as part of an overall program.
Need experts
Initial costs are higher
Hindered by subsidies

39. “Alternative” Methods of Controlling Pests
Cultivation Practices:
Crop rotation
Intercropping, polyculture, polyvarietal practices
Adjust planting times

40. Biological pest control:
Provide habitats for pests’ natural enemies (spiders’ huts in China)
Spiders kill more insects than insecticides do!!!
Import natural predators (also bacteria, viruses, parasites)

41. Lure pests away using pheromones Disrupt life cycles using hormones
Insect birth control
Sterilize the males
Lure pests away using pheromones
Disrupt life cycles using hormones
Hot water

42. Organic methods: Soap spray Tobacco spray Alcohol spray
Bt (Bacillus thurengienses)
Neem
Pyrethrins (from chrysanthemum)
Cayenne pepper
Citrus oil

43. Create GMO’s (Bt Corn)
Irradiation