2020 News & Events

Using Near-Field Exposure Modeling to Inform Ambient Air Emissions and Models

5 October 2020
adapted from the research highlight by the EPA

paint pots

Understanding the role of volatile chemical products (VCPs) on air quality and health requires information on product usage, the fraction of product emitted to air, and the reaction pathways that result in ozone and secondary organic aerosol (SOA). In recent work led by the EPA, with CSL researcher Brian McDonald, the High-Throughput Stochastic Human Exposure and Dose Simulation (SHEDS-HT) model was used to estimate product usage and the emissions of volatile organic compounds (VOCs), while the Community Multiscale Air Quality Modeling System (CMAQ) model along with observational constraints from the California Nexus (CalNex) field campaign were used to bound the role of VCPs in ozone and SOA formation. SHEDS-HT, literature, and top-down constraints imposed by ambient observations suggest that emissions of VOCs from VCPs are likely underestimated in the NEI for California and potentially across the United States. After remedying emission magnitudes and SOA formation potential, CMAQ indicates VCPs are responsible for ~41% of fresh SOA and ~17% of maximum daily 8-hr average ozone in summer Los Angeles. Inhalation was also estimated to be more competitive with dermal and ingestion exposure to organic compounds than previously thought.

Qin, M., B.N. Murphy, K.K. Isaacs, B.C. McDonald, Q. Lu, S.A. McKeen, L. Koval, A.L. Robinson, C. Efstathiou, C. Allen, and H.O.T. Pye, Criteria pollutant impacts of volatile chemical products informed by near-field modeling, Nature Sustainability, doi:10.1038/s41893-020-00614-1, 2020.


Consumer, industrial and commercial product use is a source of exposure to potentially hazardous chemicals. In addition, cleaning agents, personal care products, coatings and other volatile chemical products (VCPs) evaporate and react in the atmosphere, producing secondary pollutants. Here, we show that high air emissions from VCP use (>e;14 kg per person per yr, at least 1.7× higher than current operational estimates) are supported by multiple estimation methods and constraints imposed by ambient levels of ozone, hydroxyl radical reactivity and the organic component of fine particulate matter (PM2.5) in Pasadena, California. A near-field model, which estimates human chemical exposure during or in the vicinity of product use, indicates that these high air emissions are consistent with organic product use up to ~75 kg per person per yr, and the inhalation of consumer products could be a non-negligible exposure pathway. After the PM2.5 yield is constrained to 5% by mass, VCPs produce ~41% of the photochemical organic PM2.5 (1.1 ± 0.3 µg m−3) and ~17% of the maximum daily 8 hr average ozone (9 ± 2 ppb) in summer in Los Angeles. Therefore, both toxicity and ambient criteria pollutant formation should be considered when organic substituents are developed for VCPs in pursuit of safer and more sustainable products and cleaner air.