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Section 3: Chemical Hazards. What are toxic and hazardous chemicals? What are some possible impacts from chemical hazards? Are hormonally active agents a human health threat? Why do scientists no so little about the impacts of chemicals on human health? Is pollution prevention the answer?.
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Section 3: Chemical Hazards What are toxic and hazardous chemicals? What are some possible impacts from chemical hazards? Are hormonally active agents a human health threat? Why do scientists no so little about the impacts of chemicals on human health? Is pollution prevention the answer?
What are toxic and hazardous chemicals? Toxic Chemical: a chemical that can cause temporary or permanent harm or death Hazardous Chemical: can harm humans because it is flammable or explosive
Types of Toxic Agents Mutagens: chemicals that change DNA (ex: radiation, arsenic, etc.) Teratogens: chemicals that cause birth defects to fetus or embryo (ex: alcohol, thalidomide, etc.) Carcinogens: cause cancer and tumors (ex: asbestos, cigarettes, etc.)
Impacts of Chemicals on Humans Chemicals may also impact: • Immune System • Nervous System • Endocrine System
The Endocrine System • Glands secrete hormones (chemical messengers) into the bloodstream • Hormones then travel to specific target cells and bind with their receptors • The body’s responses to hormones are much slower and longer lasting than its responses to nerve impulses
Hormonally Active Agents • Exposure to low level certain synthetic chemicals may disrupt a bodies hormone levels • These chemicals are known as “endocrine disrupters” or “hormonally active agents”
Examples of Endocrine Disruptors • DDT – may inhibit reproduction organ development, lower sperm count, increase obesity • BPA – may increase rates of cancer, cause earlier onset of puberty, lower sperm count • BHA – may decrease reproductive ability, increase rate of tumor development
Example: Mudsuckers • Normal ovaries • “Ovotestes” from fish in contaminated waterways
Case Study – DES • DES (diethylstilbestrol, a synthetic form of estrogen) was prescribed to pregnant women to prevent miscarriages and premature births • 1938-1971, 5 to 10 million women were exposed to the drug
Case Study – DES • “DES daughters” have a higher risk of developing cervical and breast cancer, as well as reproductive problems • “DES sons” have a higher risk of developing genital abnormalities • “DES granddaughters and grandsons” may also develop health problems
Establishing Guilt Is Difficult • Under current laws, most chemicals are considered innocent until proven guilty • “Toxicologist know a great deal about a few chemicals, a little about many, and nothing about most.”
Establishing Guilt Is Difficult • U.S. National Academy of Sciences estimates that only 10% of the 80,000 chemicals in commercial use have been tested for toxicity • Why? • Not required (considered innocent) • Lack of funds, personnel, facilities • Expensive • Difficult to test interactions
Pollution Prevention Model • Where do we go from here? • We do not know much about all of the chemicals inside us and around us • Eliminating them may create other problems
Pollution Prevention Model Precautionary Principle: where there is plausible, but incomplete, scientific evidence of significant harm we need to take action to reduce the risk “Better Safe Than Sorry”
Pollution Prevention Model First: new chemical technologies would be considered harmful until studies say otherwise. Second: existing chemicals that appear to be harmful would be removed from use.
Review Chapter 10 Section 3 • What are toxic and hazardous chemicals? • What are some possible impacts from chemical hazards? • Are hormonally active agents a human health threat? • Why do scientists no so little about the impacts of chemicals on human health? • Is pollution prevention the answer?