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

• 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?