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Rochelle W. Tyl

RTI International, Research Triangle Park, North Carolina, USA

Abstract
Background: Myers et al. [Environ Health Perspect 117:309–315 (2009) ] argued that Good Laboratory Practices (GLPs) cannot be used as a criterion for selecting data for risk assessment, using bisphenol A (BPA) as a case study. They did not discuss the role(s) of guideline-compliant studies versus basic/exploratory research studies, and they criticized both GLPs and guideline-compliant studies and their roles in formal hazard evaluation and risk assessment. They also specifically criticized our published guideline-compliant dietary studies on BPA in rats and mice and 17β-estradiol (E₂) in mice.

Objectives: As the study director/first author of the criticized E₂ and BPA studies, I discuss the uses of basic research versus guideline-compliant studies, how testing guidelines are developed and revised, how new end points are validated, and the role of GLPs. I also provide an overview of the BPA guideline-compliant and exploratory research animal studies and describe BPA pharmacokinetics in rats and humans. I present responses to specific criticisms by Myers et al.

Discussion and conclusions: Weight-of-evidence evaluations have consistently concluded that low-level BPA oral exposures do not adversely affect human developmental or reproductive health, and I encourage increased validation efforts for “new” end points for inclusion in guideline studies, as well as performance of robust long-term studies to follow early effects (observed in small exploratory studies) to any adverse consequences.

Key words: basic/exploratory studies, bisphenol A, end points, 17β-estradiol, guideline-compliant studies, routes of administration. Environ Health Perspect 117:1644–1651 (2009) . doi:10.1289/ehp.0900893 available via http://dx.doi.org/ [Online 29 June 2009]

Address correspondence to R.W. Tyl, RTI International, 124 Hermann, 3040 Cornwallis Rd., P.O. Box 12194, Research Triangle Park, NC 27709-2194 USA. Telephone: (919) 541-5972. Fax: (919) 541-5956. E-mail: rwt@rti.org

I thank RTI International’s Fellows Program for time to write this article ; the senior and technical staff at RTI for their extraordinary dedication and expertise on the bisphenol A (BPA) and 17β-estradiol (E₂) studies discussed ; C.A. Winkie for her patient typing and retyping of the manuscript ; and the Environmental Health Perspective reviewers.

The BPA and E₂ studies performed at RTI (a contract research organization) were funded by the American Plastics Council of the American Chemistry Council. The time to write this article was provided by the RTI Fellows Program (R.W.T. is a Distinguished Fellow) .

Received 15 April 2009 ; accepted 29 June 2009.

Correction

In Table 1 of the original manuscript published online, the age of F₁ animals at termination was given at 16 weeks. The animals actually ranged in age from 16 to 19 weeks, based on time during the cohabitation period that mothers were inseminated and when pups were delivered [Tyl RW. Ages of mice in the two-generation BPA study (Letter) . Toxicol Sci (in press) ]. The table has been corrected here.