Hazard evaluation and technical assistance report: HETA-99-0144-2797, Case Corporation, Burlington, Iowa.
In March 1999, the National Institute for Occupational Safety and Health (NIOSH) received a Health Hazard Evaluation (HHE) request from the International Union, United Automobile, Aerospace, and Agricultural Implement Workers of America (U.A.W.), Local 807, representing workers at Case Corporation, Burlington, Iowa. The request cited concerns about respiratory symptoms and skin rashes among employees who worked with metalworking fluid (MWF) in departments 680 and 681; during the course of the HHE, concerns were also raised regarding the Hazard Communication Program. On November 3-5, 1999, NIOSH representatives conducted medical and industrial hygiene surveys. The medical survey consisted of a questionnaire given to all employees in departments 665, 680, and 681, and follow-up peak expiratory flow (PEF) testing for some participants. The industrial hygiene survey consisted of personal breathing zone (PBZ) air sampling for thoracic particulate (the portion of the particulate that penetrates beyond the larynx), welding fume, and volatile organic compounds (VOCs), and area air sampling for both thoracic and total particulate. Process and concentrated MWF samples were collected for microbial (culturable fungi and bacteria counts, and endotoxin counts) and amine (triethanolamine and monoethanolamine, as well as nitrosamines) analysis. Issues related to the Hazard Communication Program were also reviewed. The highest air contaminant concentrations we found during our survey were from air samples from welders in department 680. Several PBZ concentrations exceeded the American Conference of Governmental Industrial Hygienists’ Threshold Limit Value (TLV) for iron and manganese. All results for aluminum and nickel were at least one order of magnitude below their lowest exposure limits. Based on the cumulative mass concentration of the different metals, and on the thoracic particulate mass samples collected separately, several welders’ exposure to welding fume exceeded the TLV of 5 milligrams per cubic meter of air (mg/m3). NIOSH recommends reducing welding fume exposures to the lowest feasible concentration due to its carcinogenic potential. The typical exposure of non-welders (primarily machinists) to thoracic particulate on these days was above the NIOSH Recommended Exposure Limit (REL) for MWF of 0.4 mg/m3. The mean thoracic particulate exposure for welders in departments 680/681 was 4.79 mg/m3, but because only a small fraction of the particulate was extractable, much of this was likely due to welding fume and not to MWF. Welders in departments 680/681 had a mean extractable exposure = 0.35 mg/m3, which still indicates a relatively high exposure to MWF aerosol with respect to the REL. The MWF circulating through the central coolant system in departments 680/681 had very low levels of culturable fungi and bacteria, with concentrations of fungi below 10 colony forming units per milliliter (CFU/mL) of MWF, and bacteria below 110 CFU/mL. Low levels of endotoxin ( trace - 137 endotoxin units per milliliter of MWF) present in these samples indicates that in the recent past these culturable fungi and bacteria levels have been low also. A sample taken from a machine with a self-contained MWF sump had the highest level of microbial contamination, 4.6 x 105 CFU/mL bacteria, predominantly Gram-negative species. One hundred twenty-seven workers participated in the medical component of this survey; participation by department ranged from 82% - 100%. The most frequently reported symptom among all participants was ‘sinus problems,’ which was reported by 79 (62 %) participants. Among those symptoms reported to be work-related, ‘irritation of the eyes, nose, or throat’ was reported by the most participants (73%). In general, employees reporting job duties of either welding, or both welding and machining, had higher percentages of reported respiratory symptoms compared to those whose reported job duties included neither welding nor machining. A larger percentage of machinists than welders reported rash or skin irritation. Of the 10 persons completing PEF testing, one had patterns of decreasing PEF during the workshift with improved PEF measurements away from work, suggesting that decrements in PEF for that person were related to work. The data from our questionnaire survey suggest that exposure to welding fume (which exceeded the TLV in some cases) may be playing a greater role in the occurrence of respiratory symptoms among department 680/681 workers than exposure to MWF aerosols. In addition, nearly all employees in department 680/681 were exposed to MWF concentrations above the NIOSH REL for MWF. Recommendations are made in this report concerning further evaluation and control of exposures to welding fume and MWF. In addition, improvements in the implementation of the Hazard Communication Program are recommended.