| Abstract |
| On March 14, 2000, the National Institute for Occupational Safety and Health (NIOSH) received a joint management/union request for a health hazard evaluation (HHE) at the Thyssen-Dover Elevator facility in Middleton, Tennessee. The request asked NIOSH to determine if workplace exposures are related to health problems that some employees have experienced. Specific areas of concern identified in the request included both traditional welding and laser metal cutting processes. Reported symptoms were muscle weakness, tingling fingers, weight loss, and diverticulitis. On May 1-3, 2000, NIOSH researchers conducted a site visit at the Thyssen-Dover Elevator facility. During the site visit, integrated personal air sampling was conducted to evaluate employee exposure to welding fume during the first and second work shifts in Departments 544, 543, 591, 597, and at the Bystronic laser. Instantaneous air samples were collected for carbon monoxide (CO), oxides of nitrogen (NOx), and ozone (O3) at various locations in the manufacturing area. Bulk samples for asbestos analysis were obtained from ceiling insulation and the Department 544 oven. Company accident and illness records were reviewed. Confidential interviews were conducted with 24 first and second shift employees. The laser cutting operation was reviewed. The personal air sampling results showed that employees in Department 544 were exposed to total welding fume, above the American Conference of Governmental Industrial Hygienists (ACGIH) ® threshold limit value (TLV) of 5 milligrams per cubic meter (mg/m 3 ). Full shift time-weighted average (TWA) exposures for the two employees in this department were 5.44 mg/m3 and 6.10 mg/m3 . NIOSH recommends controlling welding fume to the lowest feasible concentration and meeting the exposure limit for each welding fume constituent. Element-specific analyses of the welding fume components showed that manganese exposure for the two Department 544 workers exceeded the ACGIH TLV of 0.2 mg/m3 on the day of the monitoring. TWA concentrations measured were 0.23 mg/m3 and 0.31 mg/m3 . The NIOSH recommended exposure limit (REL) for manganese fume is 1.0 mg/m3 . One sample from a Department 544 welder found exposure to lead in excess of the 30 micrograms per cubic meter Action Level established by the Occupational Safety and Health Administration. No other samples indicated the presence of lead above the limit of quantification. The source of the lead was not determined. In general, air contaminant concentrations were lower during the second (evening) work shift. General dilution ventilation is the primary ventilation control at this facility. Carbon monoxide concentrations of 8-12 parts per million (ppm) were measured at various locations of the manufacturing area during the first shift. The NIOSH REL for CO is 35 ppm and the ACGIH TLV for CO is 25 ppm. The primary source of the CO is likely the propane-powered lift trucks. Low concentrations of NOx were measured at some welding stations and ozone was not detected in any of the samples. No asbestos was found in any of the bulk samples. A limited review of the laser cutting operation indicated that protective shielding to prevent eye exposure to beam radiation may not be adequate. Worker complaints were grouped into three general categories; gastro-intestinal symptoms, neurological symptoms, and chronic sinusitis. Symptoms that were reported appeared to be associated with the work (i.e., symptoms appeared after reporting for work and improved or resolved after the employee left work). However, no work exposures could be found that would be the primary cause of chronic sinusitis or gastrointestinal symptoms. Welders complained of neurologic symptoms that were suggestive of manganese poisoning. Manganese exposure levels measured during this site visit would not be expected to result in manganese poisoning, but higher past exposure levels, or chronic exposure to elevated manganese levels, may account for the symptoms described by welders at this plant. Industrial hygiene monitoring found Department 544 worker exposure to total welding fume and manganese in excess of established criteria. One sample from this department showed lead exposure in excess of regulatory criteria. Because the facility is an open manufacturing environment, incorporates numerous processes, and relies on general dilution ventilation as the primary control, the worker exposure profile in the manufacturing area is complex. Contaminant concentrations were generally lower on the second shift. Shielding to prevent eye exposure to beam radiation on a high power laser cutter may have been altered. Workers reported gastro-intestinal symptoms, neurological symptoms, and chronic sinusitis. The temporal pattern for the gastrointestinal and chronic sinusitis was consistent with a workplace exposure, however, no workplace exposures were found that would explain these symptoms. Manganese levels measured at this site would not be expected to result in the neurologic symptoms observed and/or reported, however, higher past exposures or chronic exposures over time may account for these symptoms. Recommendations to provide respiratory protection as an interim measure, improve ventilation, conduct additional monitoring, utilize welding shields, review and modify the laser cutter, and reduce carbon monoxide emissions are in the Recommendations section of this report. |
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