Toxicologist Highlights Difficulties of Using OELs for Developmental and Reproductive Toxicants

By Ed Rutkowski

June 9, 2015—In a presentation June 3 at AIHce 2015, Thomas A. Lewandowski, a toxicologist and principal with the environmental consulting firm Gradient, explained the challenges of deriving and applying occupational exposure limits (OELs) in circumstances where employees may be exposed to chemicals that have toxic effects to human development and reproduction. The challenges are of special concern to industrial and occupational hygienists given trends showing that large percentages of women will become pregnant at least once while employed and will continue to work for the majority of their pregnancies, Lewandowski said.

OEL values are intended to be safe for repeated daily exposures over a working lifetime, but may not be protective of pregnant women or developing fetuses, Lewandowski said. While most OELs are expressed as time-weighted averages, these may not be indicative of a fetal dose.
In addition, development includes periods of susceptibility before the end of the first trimester, when a woman may not know she’s pregnant or may not yet be ready to inform her employer. The effects of exposures to toxicants during these periods might not become apparent until years later, Lewandowski said.

Unlike cancer, developmental and reproductive effects require more than a single test to determine, and chemicals must be tested on multiple species. A full battery of tests for developmental and reproductive toxicants can cost more than $100,000, Lewandowski said.

The complexity of the developmental process also presents challenges for employers who are trying to determine how to protect pregnant workers. For example, the placenta, which at one time was considered to be a protective barrier between mother and child, is now known to allow some chemicals to pass through completely and can even increase the toxicity of certain chemicals, Lewandowski said. Other complicating factors include the mother’s hormonal changes and increased nutritional needs during pregnancy.

Given these complexities, Lewandowski advised industrial/occupational hygienists to be cautious in their communications to workers about developmental and reproductive toxicants, and suggested they ensure that workers do not become unduly concerned. “Hazard and risk are not the same thing,” he said. “A hazard does not necessarily mean there’s a risk.”

Ed Rutkowski is editor in chief of The Synergist.