Biological monitoring and biological effect monitoring

Biological monitoring and biological effect monitoring are procedures used as part of screening in occupational health practice:22 biological monitoring screens for exposure, and biological effects monitoring attempts to detect early effects. As in other forms of screening, the principle is to detect adverse exposure or early alterations in biochemical parameters following workplace exposures, and then to take appropriate preventive measures to prevent the onset of overt health effects or clinical disease.

Biological monitoring involves the analysis of biological samples (urine, blood, or breath) for the presence of the chemical to which the individual worker is exposed, or for a metabolite. Examples amenable to monitoring are lead and mercury, and organic solvents such as trichloroethylene and xylene. Metabolites of organic solvents that can be detected in urine samples are trichloroacetic acid for trichloroethylene and 1,1,1,-trichloroethane, and mandelic acid for styrene. Some metabolites are non-specific and can result from several different exposures, both occupational and non-occupational, e.g. hippuric acid in the urine can occur from benzoate in foods or from occupational exposure to toluene. Other metabolites are more specific, e.g. methyl- hippuric acid in urine following exposure to xylene.

Biological effect monitoring attempts to detect changes in one or more biochemical parameters as an early effect of occupational exposure. Examples are the detection of elevated free erythrocyte protoporphyrin level in blood among those exposed to inorganic lead, and depression of serum cholinesterase in workers exposed to organophosphates. Tests such as the detection of DNA adducts in biological samples for exposure to carcinogens23 and markers of oxidative stress in workers exposed to pesticides24 are available, but are not indicated for routine biological effect monitoring.

Health surveillance

The periodic clinical and physiological assessment of workers for exposure to workplace hazards25 or for monitoring general health status forms an integral part of occupational medicine practice. For the prevention of work-related illness, emphasis should be on the former. Some of the components of health surveillance for specific purposes have been covered in the preceding sections.

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