Human exposure assessment: finding out what's getting in.

A s the number of people dying worldwide from noncommunicable diseases such as cancer and heart disease continues to rise, being able to measure and qualify people's exposure to harmful environmental agents is becoming increasingly important. Exposure assessment is emerging as a scientific field thanks in large part to revolutionary advances in genetics, molecular biology, and microenvi-ronmental and personal measurement technology. "As the methods of exposure assessment become more robust, sensitive, and inexpensive, they will dramatically change the field," says Richard Jackson, director of the National Center for Environmental Health at the Centers for Disease Control and Prevention in Atlanta, Georgia. Jackson was one of a group of more than 400 government, academic, and industry scientists and policy makers that met in September 1999 to discuss the role of human exposure ass ent et tion of environmental disease. "When we're talking about creating a new science for the field of exposure assessment, what we're really talking about is new ways of understanding the dose-response relationship necessary to understand risk assessment,"-ys Samuel Wilson, deputy director of the NIEHS. "Exposure analysis provides the bridge ... between traditional environmental science and toxicology and epidemiology," says Paul Lioy, deputy director of the Environmental and Occupational Health Sciences Institute in Piscataway, New Jersey. According to Lioy, researchers are developing an entirely new conceptual framework to understand how environmental exposures affect public health. However, George Lucier, director of the NIEHS's Environmental Toxicology Program, considers it a stretch to call exposure assessment a new science and says the field just needs some reinventing. "It is an old science that has languished, that hasn't gotten the support it deserved," he says. But he acknowledges that the discipline needs to be rethought, especially in terms of disease and determining individual sensitivity. Whether exposure assessment is emerging as a newly defined field or merely a rein-vented one, a new paradigm to link human exposure assessment to disease is crystallizing. Most experts agree that the key lies in linking the many new tools being developed for examining exposure to hypothesis-driven research. Researchers can approach the exposure disease relationship from two directions. From the exposure end they can learn how a person's exposure to a chemical may lead to disease. From examining a disease trend in the population or a subpopulation, they can work backward to exposure. "There's a recognition that both observational kinds of research for