One of the largest reported outbreaks of work-related respiratory illness in the machining environment in the United States raises new concerns for the estimated one million workers exposed to metal-working fluids on the job, according to an investigation conducted by NIOSH.

In January 2001, three machinists at a TRW, Inc., brake manufacturing plant in Mount Vernon, Ohio, were hospitalized with a respiratory illness called hypersensitivity pneumonitis. Union and management representatives at the facility asked NIOSH to help determine the cause and how to prevent further illness.

In November 2001, investigators reviewed records and found that 107 (27 percent) of 400 workers had been placed on work restriction by their treating physicians during the preceding 11 months because of respiratory conditions; 37 (35 percent) of these 107 workers remained on medical leave and 70 (65 percent) had returned to work.

NIOSH investigators concluded that the illnesses were likely related to occupational exposure to the metalworking fluids used in this facility. Similar illnesses have been documented among workers in other machining plants in the U.S. and Canada.

Medical records through October 2001 were reviewed for 32 (86 percent) of the 37 workers remaining on medical leave. All 32 workers had either full- or part-time work duties in the machining side of the plant; the median length of time working at the plant was 18 years.

No new newly symptomatic workers have been identified since April of 2001.

NIOSH stresses that employees, unions, manufacturing companies involved in machining processes and private and public health professionals must be educated about appropriate prevention and control measures, including appropriate engineering controls, metal-working fluid management practices, and use of personal protective equipment.

Early recognition of potential occupational illness in workers in the machining environment and ongoing medical surveillance for these workers also are needed to detect and prevent both acute illness and irreversible respiratory impairment, according to NIOSH.

OSHA's Metalworking Fluids Best Practices Manual (strictly advisory) can be accessed on OSHA's Web site at: