Answer to Question 1
The two classes of chemicals are heavy metals and persistent organic compounds.
Heavy metals are extremely toxic because, as ions or in certain compounds, they are soluble in water and may be readily absorbed into the body, where they tend to combine with and inhibit the functioning of particular vital enzymes. Even very small amounts can have severe physiological or neurological consequences.
The trait that makes heavy metals and nonbiodegradable synthetic organics particularly hazardous is their tendency to accumulate in organisms.
Answer to Question 2
Our use constitutes only one step in the total product life cycle, a term that encompasses all steps, from obtaining raw materials to final disposal of the product. Implicit in our use of hair spray, for example, is that raw materials were obtained and various chemicals were produced to make both the spray and its container. Chemical wastes and by-products are inevitable in production processes. In addition, consider the risk of accidents or spills occurring in the manufacturing process and in the transportation of raw materials, the finished product, or wastes. Finally, what are the risks of breathing hair spray? What happens to the container you throw into the trash, which still holds some of the hair spray when the propellant is used up?
Local/long distance cell Signaling
Example of the Table of Drugs and Chemicals.
Vapor Densities of Selected Chemicals
Risk factor for children age 2 to 3
Summer squash exhibiting various fruit-shape phenotypes, including disc, long, and sphere