Exposure to VOCs in Auto Repair Shops in Tucson, Arizona
SWEHSC Members: Paloma Beamer, Dean Billheimer
Summary:
Auto repair shops employ approximately 1% of the U.S. labor force. Workers in this industry are routinely exposed to volatile organic compounds (VOCs), which are gases emitted from certain solids or liquids found in many products and processes. Exposure to VOCs is often associated with irreversible health effects, including asthma, cardiovascular disease, cancer, and cognitive and neurological symptoms. Despite these risks, VOC exposure studies are quite sparse.
The goal of this study was to assess which exposure factors were related to total personal and shop-level specific VOC exposures for full-time workers in marginalized and predominantly Spanish-speaking auto repair shops. Worker activities and ventilation conditions were monitored during July, August, and November of 2018, and personal VOC exposure was also measured. The activities with the highest average VOC exposures were bodywork, fluids, and tire work, while administration and breaktime were the lowest.
Across all shops, 30 VOCs were detected in at least one air sample using a SUMMA canister. Although activity type was significantly associated with total VOC concentrations, ventilation type was not. A substantial proportion of the variability in VOC concentrations was attributed to random effects related to the specific shop and shift, rather than activity or ventilation type. This study highlights the complexity of the exposure environment in auto repair shops and how critical it is to evaluate VOC levels for the health and well-being of the workers.
Figure 1. Mel and Enid Zuckerman College of Public Health undergraduate intern Joshua Doty (left), Rietta Wagoner (center), and Imelda Cortez (right), from Sonora Environmental Research Institute, assisting with field work.
Auto repair shops employ approximately 1% of the U.S. labor force. Workers in this industry are routinely exposed to volatile organic compounds (VOCs), which are gases emitted from certain solids or liquids found in many products and processes. Exposure to VOCs is often associated with irreversible health effects, including asthma, cardiovascular disease, cancer, and cognitive and neurological symptoms. Despite these risks, VOC exposure studies are quite sparse. The goal of this study was to assess which exposure factors were related to total personal and shop-level specific VOC exposures for full-time workers in marginalized and predominantly Spanish-speaking auto repair shops.
This project was led by Drs. Paloma Beamer, Scott Carvajal, Dean Billheimer, and Nathan Lothrop and Maia Ingram, all faculty at the Mel and Enid Zuckerman College of Public Health (MEZCOPH) and Ann Marie Wolf of the Sonora Environmental Research Institute (SERI). Drs. Beamer and Billheimer are also members of the Southwest Environmental Health Sciences Center (SWEHSC). Co-authors include many previous MEZCOPH students, Jocelyn Fimbres (MS), Carolina Quijada (BS), Marvin Chaires (BS, MPH), Fernanda J. Camargo (BS), Emma V. Gallardo (BS), Rietta Wagoner (BS, MPH, PhD), and Nicolas Lopez-Galvez (PhD) and Dr. Denise Moreno Ramirez, a NIEHS T32 Postdoctoral Fellow. Co-authors also include Flor Sandoval, Program Director, and Imelda Cortez, Environmental Health Promotora with SERI. This project was supported by the SWEHSC Data Science Core, which includes authors Dr. Shannon Gutenkunst and Elmira Torabzadeh.
What were the methods of data collection and analysis?
Participants were recruited at local auto repair shops with fewer than 25 employees through door-to-door outreach by community health workers from the Sonora Environmental Research Institute, Inc. (SERI) in the south metropolitan area of Tucson, Arizona, during July, August, and November 2018. Specific VOC concentrations were measured in 9 total auto repair shops for 22 workers over 35 shifts. To assess personal VOC exposures, the study team monitored four work shifts per shop, which could include any combination of single or multiple shifts for participants.
Following informed consent, community health workers administered participant demographic and background surveys. In addition to the surveys, study personnel from the University of Arizona recorded worker activities, room conditions, ventilation, nearby activity, and other relevant notes for real-time exposure assessment. Worker activities were categorized: 1) administration, 2) body work, 3) taking a break, 4) cleaning, 5) engine work, 6) fluids work, 7) tire work, and 8) unknown. Ventilation conditions were sequentially categorized by availability of outdoor air: 1) outside, 2) open bay/garage door, 3) fan, 4) swamp cooler, and 5)air conditioning. Personal total VOC exposure was measured using a calibrated ppbRAE 3000 monitor with tubing affixed in the worker’s breathing zone. The monitors were placed on the participant's belt, in a sling bag, or near their work area. Monitors logged 20-second interval averages, with concentrations reported in isobutylene units.
What were the results of this study?
The activities with the highest average VOC exposures were “bodywork”, “fluids work”, and “tire work”, whereas “administration” and “taking a break” were the lowest. While work activities were relatively evenly distributed across observation types, ventilation conditions were predominantly limited to open garages, bay doors, or outdoor settings, all of which were associated with the lowest mean VOC concentrations. Statistical modeling indicated that activity type was significantly associated with total VOC concentrations, whereas ventilation type was not. However, the direct effect of activity was minimal, explaining only 3% of the variability in VOC concentrations, compared to approximately 50% explained by random effects attributed to shop and shift.
Summa canisters (air sampling devices) were deployed in 9 shops. Across all shops, 30 VOCs were detected in every sample, with acetone and toluene found in all and benzene, ethylbenzene, and xylene in most (9–11 out of 14 samples; all but one shop). Workers were typically exposed to low background VOC levels punctuated by intermittent high peaks. The highest peaks (exceeding background concentrations by more than two orders of magnitude) were recorded during spraying of brake cleaner and painting activities in 22 of the 35 monitored shifts, as shown in Figure 2 below. This pattern of a sharp concentration spike followed by a decline to background levels is likely attributable to the fact that most work was performed outdoors or with open bay doors, allowing for continuous dilution with ambient air and, in some cases, resulting in non-detectable VOC concentrations.
Figure 2. Real-time total VOC concentration categorized by activity, with peaks labeled with specific activities for one shift.
Overall, average total VOC exposures were approximately an order of magnitude lower for activities not typically associated with VOC sources, such as administrative tasks (GM = 50 ppb) and breaks (GM = 45 ppb), compared with higher-exposure tasks such as body repair (GM = 419 ppb) and cleaning (GM = 165 ppb). While body repair had the highest average exposures, cleaning had a higher maximum exposure (396,801 ppb). Figure 3 below displays the total VOC concentrations stratified by activity and colored by shop. The black horizontal lines mark the first quartile (Q1), the median, and third quartile (Q3), while the black diamond marks the geometric mean (GM). Each point reflects the average value for an activity-ventilation span, calculated by combining the broader activity-ventilation groups step by step. As shown in Figure 3, the GM is lower for administrative tasks and breaks and higher for body repair and cleaning, highlighting the elevated VOC exposures associated with the latter activities.
Figure 3. Total VOC concentrations stratified by activity and colored by shop.
What is the importance of measuring VOC exposure in the work area, specifically auto repair shops?
This study highlights the complexity of the exposure environment for auto repair workers. For both total and specific VOCs, concentrations varied substantially. Total VOC exposures were more strongly associated with the specific shift and shop than with recorded activities or ventilation conditions. It is likely that differences in how tasks are performed, even by the same individual in the same shop, contribute to this variability, which can occur from day to day. In this study, 26 of the 35 monitored shifts involved tracking the same participant on two different days, either on back-to-back days or in the same week. Yet exposures for the same worker performing similar tasks were not necessarily comparable between shifts.
The results of this study show the unpredictability and variability of VOC levels in auto shops. Even for the same worker performing the same task, specific VOCs varied substantially in duplicate samples and within the same shops on consecutive days. A major strength of this project is the detail on total and specific VOCs collected among so many workers during full shifts, especially from such small shops in a very underserved and under-resourced community. This study confirmed what others have found: worker VOC exposures tend to be episodic peaks with highly variable levels among workers, shifts, activities, and shops. Future studies could enhance data collection methods to account for increased exposure factors (e.g., type of product, nearby activity) or monitor workers for more shifts over time to better model variation of VOC exposures.