By Cynthia Hines, MS, CIH
You may have seen water bottles labeled “BPA Free” or heard that certain foods contain BPA. BPA (or bisphenol A) has been in the news over the past several years. BPA is weakly estrogenic; that is, BPA may mimic some of the hormone-like effects of estrogen. BPA is used primarily in making polycarbonate plastic and some epoxy resins. The general population is exposed to BPA mainly through diet. Trace levels of BPA may be present in food or beverages in contact with polycarbonate containers or epoxy resins coatings on the inside of cans. As a result, BPA has been detected in the urine of over 92% of the general population. But what about the exposures of people who work with BPA? The few studies that have measured worker exposure to BPA have focused mainly on cashiers handling point-of-sale thermal receipt paper coated with BPA and workers in Chinese factories. No published data were available on the BPA exposure of workers in U.S. factories.
BPA Use in Industry
In addition to BPA’s use in making polycarbonate and epoxy resins, BPA is used in making phenolic resins and certain specialty waxes used in the “lost wax” process for casting metal parts. Resins made with BPA contain only trace levels of BPA; that is nearly all of the BPA has been chemically-reacted in making the resin. Therefore, under normal conditions of use, touching products such as polycarbonate safety glasses does not lead to BPA exposure. By contrast, BPA remains intact in waxes and thermal paper made with BPA; that is the percentage of BPA used in making the wax or paper remains in the final product.
The NIOSH BPA Exposure Study
The National Institute for Occupational Safety and Health (NIOSH) undertook a study in 2013-2014 to measure BPA exposure in U.S. manufacturing workers. The NIOSH study included six companies that either made BPA, BPA-based resins, or made and used BPA-filled waxes. A total of 78 workers participated in the study. Over two consecutive work days, each participant provided seven urine samples. BPA was measured in the samples. On average, workers in the NIOSH study had BPA levels in their urine ~70 times higher than adults in the U.S. general population (based on data from the 2013-2014 National Health and Nutrition Examination Survey, a representative sample of the U.S general population). Unlike the general population, these workers handled raw BPA, often in large quantities. And unlike the general population, workers in the NIOSH study were exposed to BPA mainly by inhalation and dermal absorption. NIOSH investigators found that work tasks such as handling bags or sacks of BPA and taking process or bulk samples containing BPA for quality control testing were associated with increased urinary BPA levels in the workers. Workers who handled a resin product where only trace levels of BPA remained, had the...Click here to read the rest of the blog post.