Occupational Exposure to Bisphenol A (BPA) in U.S. Manufacturing CompaniesPosted on by
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 lowest urinary BPA levels. Among the highest exposed workers were those who worked with molten casting wax containing BPA. The NIOSH study findings are described in more detail in a recently published article in the Annals of Work Exposures and Health (formerly the Annals of Occupational Hygiene).
NIOSH did not evaluate the health of workers who participated in the study; however, an earlier cross-sectional study conducted by other researchers reported changes in male hormones, semen quality and sexual function in Chinese factory workers who had urinary BPA levels comparable to levels found in the current NIOSH study.
As no single study can establish cause and effect, additional research is needed in other worker populations to confirm or refute these findings.
Minimizing BPA Exposure
Neither NIOSH, the Occupational Safety and Health Administration (OSHA,) nor the American Conference of Governmental Industrial Hygienists (ACGIH) have occupational exposure limits for BPA. As good practice and as part of continuous improvement efforts, NIOSH encourages companies to review work processes and practices for ways to minimize worker exposure to BPA by following the hierarchy of controls.
Exposure reduction steps could include:
- Eliminating BPA or substituting other chemicals for BPA. In applications where BPA is an essential building block (component) of a material, such as in polycarbonate plastic, substitution may not be an option.
- Containing BPA dust and vapor emissions with either full enclosures or local exhaust ventilation.
- Minimizing the time workers spend in BPA production areas.
- Cleaning surfaces in production areas, offices and lunch rooms regularly to remove BPA residues.
- As a last resort, using personal protective equipment (PPE) and assuring that PPE is properly fitted, worn, maintained, and cleaned. PPE may include respirators, chemically-resistant gloves and suits, and eye and face protection.
- Implementing a sampling program for BPA to evaluate the efficacy of controls and surface decontamination efforts.
The NIOSH study contributes new information on worker exposure to BPA in one U.S. sector, manufacturing. This information, however, is only one step on the path to assessing the health and safety of working with BPA.
Other research questions arising from the NIOSH study include:
- Is BPA affecting the health of exposed workers?
- How does the body handle BPA after inhalation and dermal exposure?
- Is BPA stored in the body after repeated long-term exposure to BPA at occupational levels?
- In industrial processes where BPA is heated, does BPA vaporize? If so, at what temperature and what is the physical state of the exposure?
- Do family members of workers have “take-home” exposure to BPA?
- Is additional toxicological research needed at exposure levels and patterns relevant to workers? NIOSH welcomes your thoughts on this study and suggestions for future research on BPA.
If you work with BPA or are responsible for health and safety at a facility with BPA, NIOSH is also interested in learning how information from this study has affected the way you work with BPA or handle BPA in your facility.
Cynthia Hines, MS, CIH, is a Senior Research Industrial Hygienist in the NIOSH Division of Surveillance, Hazard Evaluations, and Field Studies.