biological monitoring, 1. a process of measuring the levels of various physiological substances, drugs, or metabolites within a patient during diagnosis or therapy. 2. the measurement of toxic substances in the environment and the identification of health risks to the population. Biological monitoring often uses indirect methods of identifying and measuring substances, such as analyses of samples of blood, urine, feces, hair, nails, sweat, saliva, or exhaled air and extrapolation from metabolic effects.
