Identifying and Reducing Employee Exposure to Methylene Chloride
The Occupational Safety and Health Administration (OSHA), On-Site Consultation Program, offers no-cost and confidential occupational safety and health services to small and medium-sized businesses in all 50 states, the District of Columbia, and several U.S. territories, with priority given to high-hazard worksites. On-Site Consultation services are separate from enforcement and do not result in penalties or citations. Consultants from state agencies or universities, work with employers to identify workplace hazards, provide advice for compliance with OSHA standards, and assist in establishing and improving safety and health programs.
OSHA On-Site Consultation Program is voluntary. At the employer's request, state agencies, such as Utah Occupational Safety and Health (UOSH) Consultation and Education Services conduct no-cost, confidential workplace safety and industrial hygiene hazard assessment visits and services. During one such visit, a UOSH consultant observed approximately 90 to 100 employees working in a small clean room where methylene chloride was being used as a bonding agent for plastic tubing during the manufacture of biomedical devices. Employees poured methylene chloride from quart-sized bottles into dispensers used in the manufacturing process. A localized exhaust ventilation system with small vacuum type hoses was mounted above an opening on each dispenser. An air velocity reading of approximately 10 feet per minute was noted.
The UOSH consultant conducted air sampling measurements to determine the amount of the employees' inhalation exposure to methylene chloride. One employee's exposure was more than 8 times the permissible exposure level over an 8-hour, time-weighted average and more than 5 times the level employees may be exposed to over a 15-minute period.
Inhalation of methylene chloride vapor is one of the predominant means of exposure, and it can cause mental confusion, light-headedness, nausea, vomiting, and headache in the short-term. Continued exposure may cause light-headedness, staggering, unconsciousness, and even death. Some studies have shown that certain cancers, such as biliary and brain cancer, are associated with long-term exposure to methylene chloride.
After sampling, results showed employees were exposed to methylene chloride at levels above permissible exposure limits, the employer implemented interim protection measures. These measures included requiring employees to wear supplied air respirator hoods.
The employer made changes to the ventilation system and further air sampling was conducted. The results found that the methylene chloride levels were still above permissible exposure limits.
At the employer's request, the UOSH Consultant conducted real-time measurements of methylene chloride in and around the ventilation system. The UOSH Consultant recommended pulling air from below the work area. The specific gravity of methylene chloride is heavier than air. The engineers used this information, and relocated the ventilation system below the workstation. This change proved effective in abating the hazard. Sampling results showed employee exposure to methylene chloride was now less than half the 8-hour time-weighted average permissible exposure limit of 25 parts per million (ppm). It was also below the level to which employees may be exposed over a 15-minute period (125 ppm).
The redesign of the system had a positive impact on improving work conditions for the employees. In addition, the employer did not have to pay for the services provided by UOSH Consultation. This cost savings could be used for the redesign and reconstruction of the ventilation system.
Source: Kathryn A. McNeill, Manager, UOSH Consultation and Education Services