Basic research versus guideline studies on BPA.

Tyl (p. 1644) responds to a previous commentary [Myers et al.; Environ Health Perspect 117:309-315 (2009)] that argued against the exclusive use of guideline-compliant studies performed using Good Laboratory Practices (GLPs) for bisphenol A (BPA) risk assessment. Tyl contrasts guideline-compliant studies designed to detect reproducible effects of exposures using relevant doses, routes and animal models, with basic/exploratory research studies of unvalidated outcomes that are typically of shorter duration and smaller size. She also discusses how testing guidelines are developed and how new end points may be validated and incorporated; provides an overview of the methods and findings of guideline-compliant and exploratory animal studies of BPA; describes BPA pharmacokinetics in rats and humans and its relevance to study design; and presents responses to specific criticisms by Myers et al. Tyl argues that weight-of-evidence evaluations have consistently concluded that low-level oral BPA exposures do not adversely affect human developmental or reproductive health endpoints, but she also recommends increasing studies to validate "new" end points used in exploratory research.