section 3: chemical hazards
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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?. - PowerPoint PPT PresentationTRANSCRIPT
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?