In 1996, the allied styrene industry associations signed a voluntary agreement with OSHA to encourage compliance with an industry exposure guideline of 50 ppm for an 8-hour average and 100 ppm for 15-minute exposure. The agreement with OSHA requires composites manufacturers to use engineering controls, including pollution prevention techniques such as low-styrene resin as well as ventilation, and administrative controls such as job rotation, to reduce exposures to 100 ppm. Then, if necessary, personal protective equipment (respirators) can be used to achieve the 50 ppm limit. Using low-emitting processes, ventilation and respirators, the large majority of composite manufacturers are complying with these recommended exposure limits.
Questions remained, however, regarding the appropriate level to ensure worker health and safety. While the extensive studies with more than 55,000 styrene workers did not show any styrene-related excess of cancer or other chronic disease, there have long been a number of short-term studies that suggested that exposures of 20 ppm or lower could cause mild and temporary neurtoxic effects, although these studies are of questionable validity and can be difficult to interpret. This most recent research used a large number of subjects to carefuly study a range of possible effects including color vision, coordination and balance, and psychological factors. Hearing was the only measure that showed an effect related to styrene exposure.