HEALTH NEWS

Study Title:

Monitoring Human Tissues for Toxic Substances.

Study Abstract

The National Human Monitoring Program (NHMP) was established in 1967 to determine and assess changes in detectability and concentrations of pesticide residues in the national general population. The program was initially an activity of the U.S. Public Health Service, but was transferred to the new Environmental Protection Agency (EPA) in 1970. The NHMP now consists of the National Human Adipose Tissue Survey (NHATS); EPA planned to introduce a National Blood Network (NBN), but it has not been implemented.

It is difficult or impossible to remove persistent xenobiotics effectively from the tissues of living animals or people, so precautions must be taken against unnecessary and excessive exposures. Precautions against exposure are, however, greatly complicated by the dependence of modern society on synthetic chemicals; even the cleanest-looking environments now contain toxic contaminants. Therefore, it is prudent to assess and try to reduce their effects. An essential part of the management of toxic chemicals is regular sampling of the population to determine magnitudes of exposure and contamination.

Neither detection nor determination of concentration of a chemical in tissues of individuals or the general population provides a quantitative estimate of risks to human health. For example, people living downstream from a defunct DDT plant in Triana, Alabama, were chronically exposed to DDT in their diets for many years and have several times the national geometric mean for DDT and related chemicals (e.g., DDD and DDE) in their serum. However, a survey of the health status of 499 of them, out of approximately 600, indicated that total DDT body burdens were not associated with specific illness or ill health (Kreiss et al, 1981). But some chemicals can be degraded so rapidly that they cannot be detected in tissues even a few hours after exposure (Lynn et al., 1984). Such chemicals include benzidine (a known human carcinogen), aflatoxin, vinyl chloride, formaldehyde, and many other toxic or carcinogenic chemicals. Therefore, failure to detect a chemical in human tissues does not mean that potentially toxic exposure to it has not occurred.