Recently published scientific research sponsored by U.S. and European styrene industries indicates that worker exposure to styrene levels at 40 ppm over 15 years results in reduced hearing function.

As a result of this new research, which studied approximately 250 workers at a German boatbuilding plant, the international styrene industry associations will consider in early 2011 adoption of a revised 8-hour recommended Occupational Exposure Limit (OEL) for styrene of 20 ppm, and a recommended 15-minute limit of 70 ppm.

In addition to adjusting the industry recommendation to reflect the best science, these limits are consistent with the styrene worker exposure limits recently submitted under the European Union REACH program, as well as the ACGIH recommendation and the levels enforced by many countries.

Individual composite manufactures will need to determine how to respond to the new recommended OEL. U.S. OSHA and state-OSHAs may ultimately adopt these as official limits. Under OSHA’s General Duty Clause, it is possible that the agency would enforce compliance with what could be considered an industry standard.

Compliance with a 20 ppm 8-hour limit will likely require greater use of job rotation and respirators, as pollution prevention and ventilation may not be effective in reducing exposures below 50 ppm, especially for the open molding of larger or custom products. If respirators are part of a company’s program to limit exposures, compliance with the OSHA Respiratory Protection standard will be required. Many companies will have to allocate significant management resources to ensure successful respirators usage.

A Short History of Exposure Limits

The OSHA Permissible Exposure Limit (PEL) for styrene has long been 100 ppm, enforced as an 8-hour time-weighted-average. OSHA also has a short term 15-minute exposure limit of 200 ppm.

In the early 1990s, new data suggested that workers may suffer short-term and reversible neurotoxic effects such as drowsiness and slower reflexes at exposure in the 50 to 100 ppm range. OSHA attempted to update the styrene PEL to reflect these new data, but a court ruled that OSHA had not fully satisfied technical rulemaking requirements, and the official OSHA styrene PEL was returned to 100 ppm. California OSHA continues to enforce an 8-hour limit of 50 ppm, and the industrial hygiene professional association ACGIH recommends an exposure limit of 20 ppm.