I. Toxicity Threshold II. Bioaccumulation III. Biomagnification IV. Carcinogens V. Teratogens A. Chemicals that cause or support cancer B. Substances that cause mutations and birth defects C. The dose of a chemical above which there is a measurable decline in the health measure D. The process by which chemicals are stored in the tissues of living organisms E. Concentrations of a chemical increase at each higher level of the food web