PMean: My research contributions to reproductive toxicology

The U.S. National Institutes of Health (NIH) has a new biosketch format where they ask you to summarize “up to five of your most significant contributions to science.” Here’s a first draft of my research contributions to reproductive toxicology.

At the National Institute for Occupational Safety and Health (NIOSH), a branch of the Centers for Disease Control and Prevention, I worked with a toxicologist, Steven M. Schrader, on male reproductive toxicology. I should note that Dr. Schrader also supervised a strong program in female reproductive toxicology, and while I learned quite a bit about both sides of the equation, a different statistician served as co-author on the publications on female reproductive toxicology.

I was fortunate to arrive at NIOSH shortly after completion of a major longitudinal study of sperm samples in a healthy cohort of unexposed males. The longitudinal design required novel statistical measures and graphical displays. This data set produced many publications including two which won a major annual award, The Alice Hamilton award, for the best publication of the year in occupational safety and health.

One of the smaller findings from the longitudinal study, but one which illustrates some of the important considerations needed during the statistical planning of research studies, examined the general practice of requiring three separate blood draws to assess hormone levels such as testosterone. Since hormones are pulsatile, the three blood draws were assumed to help produce a more precise estimate of hormone levels for an individual. While this is certainly true, in an occupational health study, where the emphasis is often on comparing group means between exposed and unexposed populations, the three blood draws could possibly be “penny wise and pound foolish.” The prospect of having three separate blood draws could reduce overall participation rates in a study and the longitudinal data set showed some hypothetical examples. Even a decrease in participation as small as 10 or 20% could wipe out all the gains in precision by requiring three blood draws rather than one.

In addition to the longitudinal study, I worked on the planning of studies in humans examining occupational exposures to non-ionizing radiation and lead, and helped develop a novel rabbit model for lead exposure.

My research in male reproductive toxicology taught me how to handle the complexities associated with longitudinal data and exposure studies.

As a side note, the lead author of the publication winning the Alice Hamilton award is asked to give a lecture at the following year’s award ceremony. Since Dr. Schrader won in two consecutive years, he graciously allowed me to speak in place of him the second time around. I chose as my topic of my talk, a biography of W. Edwards Deming. I ended the talk with an exhortation that NIOSH should adopt the principles of quality control that Dr. Deming advocated. This talk led to the adoption of a Total Quality Management program at NIOSH and I served on the first quality improvement committee formed at NIOSH.

Grajewski B, Cox C, Schrader SM, Murray WE, Edwards RM, Turner TW, Smith JM, Shekar SS, Evenson DP, Simon SD, Conover DL. Semen quality and hormone levels among radiofrequency heater operators. J Occup Environ Med. 2000 Oct;42(10):993-1005.

Schrader SM, Langford RE, Turner TW, Breitenstein MJ, Clark JC, Jenkins BL, Lundy DO, Simon SD, Weyandt TB. Reproductive function in relation to duty assignments among military personnel. Reprod Toxicol. 1998 Jul-Aug;12(4):465-8.

Moorman WJ, Skaggs SR, Clark JC, Turner TW, Sharpnack DD, Murrell JA, Simon SD, Chapin RE, Schrader SM. Male reproductive effects of lead, including species extrapolation for the rabbit model. Reprod Toxicol. 1998 May-Jun;12(3):333-46.

Schrader SM, Turner TW, Ratcliffe JW, Welch LS, Simon SD. Combining reproductive studies of men exposed to 2-ethoxyethanol to increase statistical power. Occupational Hygiene 1996: 2; 411-415.

Weyandt TB, Schrader SM, Turner TW, Simon SD. Semen analysis of military personnel associated with military duty assignments. Reprod Toxicol. 1996 Nov-Dec;10(6):521-8.

Schrader SM, Ayers-Cumbo M, Turner TW, Simon SD, Ratcliffe J, Welch L, Grajewski B, Weyandt T. Semen quality across populations. Molecular Andrology 1995: 7; 105-121.

Schrader SM, Turner TW, Breitenstein MJ, Simon SD. Measuring male reproductive hormones for occupational field studies. J Occup Med. 1993 Jun;35(6):574-6.

Schrader SM, Turner TW, Simon SD. Longitudinal study of semen quality of unexposed workers. Sperm motility characteristics. J Androl. 1991 Mar-Apr;12(2):126-31.

Schrader SM, Breitenstein MJ, Turner TW, Simon SD. Longitudinal study of semen quality of unexposed workers: seminal plasma characteristics. In: Baccetti B ed. Comparative spermatology 20 years after. 1991; Vol. 75. New York NY: Serno Symposia Publications; 905-908.

Schrader SM, Turner TW, Simon SD. Sources of variation of the sperm penetration assay under field study conditions. ARTA 1991: 2(Suppl 4); 63-74.

Schrader SM, Turner TW, Simon SD. Longitudinal study of semen quality of unexposed workers: sperm head morphometry. J Androl. 1990 Jan-Feb;11(1):32-9.

Schrader SM, Turner TW, Breitenstein MJ, Simon SD. Longitudinal study of semen quality of unexposed workers. I. Study overview. Reprod Toxicol. 1988;2(3-4):183-90.

Here’s a picture of Dr. Schrader, from a webpage on careers in Andrology.