Student Research: Grace Liao
Objectives: The purpose of this study was to characterize workers’ exposure to emerging waterborne coatings used in automotive refinishing systems and observe other work practices associated with using these products.
Methods: Ten auto body shops in King County, Washington that use waterborne coatings were recruited to participate in this study. Based on reviews of MSDSs, 14 target compounds were selected to characterize exposures to components of waterborne basecoats. Task-based personal air sampling was conducted on 11 painters when applying basecoats. Samples were collected at 100 and 400 ml/min, an attempt to achieve the limit of detection of sorbent tubes and prevent analyte breakthroughs. Sampling results were summarized and compared to MSDSs and historical exposure studies of solvent-based paints. Painters’ work practices were also recorded to determine other possible routes of exposure. Work practices recorded included the use of PPE, gun-cleaning procedures, waste disposal, and paint booth maintenance.
Results: Breathing zone concentrations of aromatic hydrocarbons and polar volatile organic compounds were typically below their respective method limits of quantitation (MLOQ). On average 11% (SD= 16%) of the aromatic hydrocarbon samples and 23% (SD=19%) of the polar compound samples exceeded their respective MLOQs. All analyte concentrations had threshold limit value (TLV) parametric exceedance fractions below 0.03, and had National Institute of Occupational Safety and Health (NIOSH) odor parametric exceedance fraction below 0.05. VOC exposure levels when spraying wateroborne painter were 5 to 72 times higher than historical studies on VOC exposures to solvent-based paints. Procedures for cleaning paint guns and disposing of waterborne paint wastes varied between shops. Several shops disposed of waste in the municipal solid waste stream without chemical characterization, in violation of state regulations. Painters were observed using lacquer thinner to clean their waterborne paint guns, which is not recommended by manufacturers. Painters were also observed handling waterborne waste with inadequate exposure control. We observed that the flow rates in spray booths typically failed to meet OSHA requirements.
Conclusions: Workers’ exposures to target compounds when applying waterborne basecoats were typically below their respective MLOQs and regulatory limits. The levels were also lower than the historical exposure levels of spraying solvent-based paints. However, without maintaining adequate airflow in the paint booths adequate guidelines on all aspects of handling the paints, workers can still be at risk to different routes of hazardous exposures. Therefore, more information is needed on the chemical composition of the waste generated from waterborne paint systems to establish best practices for spray gun cleaning and waste disposal.