Researchers and investigators from the National Institute for Occupational Safety and Health offer an insider's glimpse into a health hazard evaluation of a workplace where metal furniture such as beds and cabinets are manufactured. Employees of a metal furniture manufacturer asked the National Institute for Occupational Safety and Health (NIOSH) to evaluate health hazards at their workplace. They were concerned about exposures to welding fumes and dust from powder painting and grinding operations. Some employees reported breathing problems, excessive tiredness and dust in their noses at the end of their work shifts. The company had 146 employees and was located in a 110,000-square foot building. Employees' work included cutting, bending and welding sheet metal to form end tables, lockers and beds. Most employees spoke Spanish as their primary language, and most were members of a union. The company had a safety committee, which met every 3 months.
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Employees bent metal furniture parts to the desired shapes and spot-welded the corners. Parts that could not be joined using a spot welder were welded by tacking the corners using a metal inert gas (MIG) welder. The total welding time per part was minimal.
MIG welders used welding wire that contained 1.4 percent to 1.8 percent manganese by weight. Some parts, such as bed frames, were made by cutting metal tubing with a saw and welding the pieces together. The welding area did not have its own ventilation system; however, one fume extractor was used while welding bed frames (Figure 1). Fourteen employees worked as MIG welders and 13 as spot welders.
After welding, employees in the grinding area used hand-held grinders to smooth the welds and remove sharp edges. Completed parts traveled on an overhead conveyor through a degreasing booth, where they were rinsed with phosphoric acid. As the parts exited the booth, an employee used a rag dipped in toluene for touch-up cleaning.
Metal parts were grounded with an electrostatic charge to attract paint particles to the part. The parts traveled on a conveyor through a powder paint spray booth in which permanently mounted spray guns coated the parts as they passed through. Painters stood at openings in the booth or sometimes stepped into the booth and manually powder painted any areas on the parts missed by the spray guns (Figure 2). Painted parts continued on the conveyor to a gas oven for curing, then to the packing and shipping departments. Painters regularly entered the spray booth and used a squeegee to remove paint overspray that had settled onto the floors and walls of the booth. The company had 15 painters.
What NIOSH Found: 1) Shortness of breath - Two of the employees we interviewed reported shortness of breath lasting a few minutes at a time. However, we concluded that these symptoms were not work-related. Two employees reported eye and throat irritation, and six employees reported no symptoms. 2) Fume exposure - We discovered that some of the MIG welders were exposed to manganese and carbon monoxide above recommended levels. Employees who welded tubing were exposed to higher concentrations of metal fumes than employees welding sheet metal. 3) Work practices - Sometimes employees' welding practices increased their risk of exposure. For example, we observed a welder leaning over a bed frame to weld an opposite corner, placing his breathing zone over a previously welded area that still was smoking (Figure 3). 4) Burns - Welders reported being injured by sparks that burned through their flame-retardant cloth aprons and sleeves. 5) Dust exposure - Some painters were exposed to TGIC, respirable dust and total dust above recommended limits. Lab analysis of bulk samples of powder paint showed that it did not contain silica or asbestos, but the particles were small enough to be inhaled deeply into the lungs. 6) Compressed air - We also observed that employees at the powder paint booth used compressed air to clean excess powder paint dust off their clothing. This practice increases the amount of dust in the air, and also increases the risk of eye injuries from particles blown toward the face as well as skin injuries from compressed air injection. 7) Breathing tests - We found that two painters had changes in their breathing tests that could suggest asthma due to paint exposure. 8) Ill-fitting respirators - Some employees wearing respirators had not been fit-tested and were not wearing their respirators properly. 9) Noise - Noise levels were above the recommended limits during grinding, welding and painting, and at the presses, which had the highest noise levels. 10) Muscle strains - Muscle strains were common injuries. We observed that most stations, tables and carts for the press brake and machining system were not adjustable. 11) Cuts - Cuts also were common injuries. Employees wore cotton gloves that did not always prevent cuts when handling sheet metal. Reducing Worker Exposure - We recommended a number of actions to improve employee health and safety at this facility and similar facilities.