National Human Exposure Assessment Survey (NHEXAS)
In the spring of 1994, the U.S. Environmental Protection Agency (EPA) awarded RTI a large grant to launch the pilot program for the National Human Exposure Assessment Survey (NHEXAS), a far-reaching and long-term study of the ways that humans are exposed to potentially toxic chemicals in the environment. The toxins studied were lead and arsenic, benzene and related volatile organic compounds, and various pesticides. Although the pilot program focused on the upper Midwest, the results of the study and the methods for collecting data will be expanded and applied to a nationwide survey.
Building on Decades of Prior Research
EPA chose RTI to anchor this new research because of the long and distinguished work of Dr. Edo D. Pellizzari in assessing chemical exposure in human populations. Beginning in the 1970s with his research for EPA's Total Exposure and Assessment Methodology (TEAM), which evolved into NHEXAS in the 1990s, Dr. Pellizzari and RTI scientists used statistically sampled populations to discover the relationship between chemical exposure in an individual and that person’s "body burden"---the amount of a specific chemical absorbed in body fluids and tissue.
Innovations in Data Collection
To understand body burden, RTI field technicians analyzed samples of study participants' blood and urine. Participants kept daily logs of their activities and completed questionnaires so that researchers could find the pathways by which these chemicals enter the body and relate these pathways to absorption levels. Innovative personal monitoring packs---worn on the back or around the waist---were designed by RTI scientists to be unobtrusive, comfortable, and convenient.
This comprehensive approach to collecting data at the personal level and weighing it against statistical models that predict exposures in whole populations has contributed significantly to progress in public health and regulatory policy in the U.S. The integration of these different scientific methods for assessing chemical exposure and risk, designed and implemented first by the RTI team, is now a central part of the nationwide survey planned by NHEXAS.