Determining the etiologic effects of environmental contaminants on public health: some methodological challenges

Philip C. Nasca, MS, PhD, FACE
School of Public Health: University at Albany
Rensselaer, New York, USA

Since the middle of the 20th century, the scientific community has been assembling an impressive array of data regarding the human health effects of chemical pollutants. Much of what we know about chemical mutagenesis and carcinogenesis has been derived from chemical structure analysis using large data bases and sophisticated computer programs, short term studies in sub-mammalian species and carefully conducted animal studies. Epidemiologic studies of occupational cohorts exposed to moderate to high levels of various chemicals and industrial processes have also shed light on the etiologic relevance of these exposures. Experimental and epidemiologic studies have also contributed to our knowledge regarding the relationships between various environmental exposures to chemicals and other health outcomes such as adverse reproductive outcomes and neurologic impairments. Despite these advances our current scientific methods make it difficult to always draw firm conclusions regarding environmental exposures and adverse health outcomes. Chemical structure and short term assays while useful as tools for screening large numbers of chemicals for potential mutagenic or carcinogenic properties, can only suggest specifics chemicals that require further study through animal assays and epidemiologic studies in human populations. The problems of extrapolating from animal studies are well known as are the problems of exposure measurement in epidemiologic studies. There is a critical need to develop better biomarkers of exposure, intermediate cellular effects of exposure, and measures of host susceptibility. We are already seeing challenges to the environment caused by increasing levels of environmental contamination accompanied by the trend toward global warming. These challenges have the potential to change the ecology of the planet to a degree where both chemical and biologic alterations will pose new and more dangerous threats to public health. Sustaining our fragile environment in concert with rationale economic development is needed now.

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