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.)

Thalidomide Children

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 , 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?