Pure and Applied Chemistry

Abstract: The precautionary principle is controversial, and critics invoke the need to wait for "sound science" before taking "costly" regulatory action. For human health effects, epidemiologic results are often considered more valuable than toxicologic studies in animals. Direct human evidence on the endocrine effects of environmental chemicals has been slow to accumulate because of inherent sample size limitations of exposed populations and over-conservative hypothesis testing approaches. Moreover, human health outcomes may take decades to emerge. Indeed, even huge population-based studies of hormone replacement therapy have been inconclusive regarding both benefits and risks. This paper argues that certain intrinsic standard epidemiologic methods are stacked to avoid making a type I error. Moreover, these combine with extrinsic limitations (long latency, high cost), leading me to conclude that reliance solely on epidemiology to provide definitive answers, will almost inevitably delay the discovery of meaningful associations warranting timely action for protection of public health. There are several ways in which the inherent conservatism of epidemiology is arrayed against preventative regulatory steps, hence a precautionary approach is warranted while awaiting the results of additional studies which for various reasons may be very long delayed or even impossible.