On September 3, 2004, the National Institute for Occupational Safety and Health (NIOSH) received a health hazard evaluation (HHE) request from the management at Kewaunee Fabrications, LLC, Kewaunee, Wisconsin. The request asked NIOSH to evaluate employee exposures to hexamethylene diisocyanate (HDI) during spray painting. Additionally, exposure to volatile organic compounds (VOCs), particulates, and silica was measured. Two ventilation systems were examined and confidential medical interviews with 13 employees were performed. Full-shift air samples for HDI, VOCs, particulates, and silica were collected between December 13-15, 2004. No air samples collected for HDI monomer exceeded the NIOSH Recommended Exposure Limit (REL) of 35 micrograms per cubic meter (microg/m3). There is no Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for HDI monomer or other species of HDI. However, the United Kingdom Health and Safety Executive (UK-HSE) does publish a Total Reactive Isocyanate Group (TRIG) 8-hour time-weighted average (TWA) criteria of 20 microg/m3 and a Ceiling Limit criteria of 70 microg/m3. Of the 15 painters sampled for HDI exposure, six workers' had PBZ levels that exceeded the UK-HSE TRIG 8-hour TWA criteria of 20 microg/m3 while four workers' HDI levels exceeded the UK-HSE TRIG Ceiling Limit criteria of 70 microg/m3. Workers wore supplied air respirators, full-body Tyvek suits, boot covers, and latex gloves while spray painting, so actual exposure to airborne HDI may be lower. However, latex gloves do not provide adequate protection against HDI and other solvents used in the paint shops. Two sanding/prep workers' particulate exposure levels exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV), (10 milligrams per cubic meter of air [mg/m3]). Levels for another worker engaged in the same activity also exceeded the OSHA PEL of 15 mg/m3. No silica (quartz and cristobalite) was found in these samples. Disposable filtering-facepiece respirators were available on a voluntary basis and sporadically used by some workers engaged in sanding/prep activities. All samples collected for VOCs were well below relevant occupational exposure criteria. Air velocities, measured at the exhaust outlets, were three to seven times higher in the West paint shop than in the East paint shop. This likely accounted for the lower airborne concentration of HDI in the West paint shop. No consistent respiratory symptoms were noted among the 13 workers interviewed, and symptoms reported were not those commonly found among workers exposed to HDI. However, a common work practice reported by workers involved the use of methyl ethyl ketone (MEK) to wash their skin and remove paint. This practice should be discontinued because MEK can be absorbed through the skin. NIOSH investigators conclude that a health hazard exists from exposure to particulates during the sanding/prep work activity and the use of solvents such as MEK to clean skin. Recommendations to increase the level of protection for workers engaged in sanding/prep activities include mandatory use of NIOSH-approved, single-use filtering-face piece N-95 respirators. Additionally, exhaust ventilation in the East paint shop should be increased to at least 100 feet per minute (fpm), as an average air velocity across the exhaust outlet to reduce the potential health hazard from exposure to isocyanates.
Region-5; Hazard-Confirmed; Solvents; Solvent-vapors; Isocyanates; Ketones; Ventilation-systems; Ventilation; Exhaust-ventilation; Particulates; Particulate-dust; Aerosols; Aerosol-particles; Volatiles; Organic-compounds; Organic-solvents; Painting; Paint-shops; Respiratory-protection; Respiratory-protective-equipment; Personal-protective-equipment