Volatile Chemical Product Enhancements to Criteria Pollutants in the United States

Abstract

Volatile chemical products (VCPs) are a significant source of reactive organic carbon emissions in the United States with a substantial fraction (>20% by mass) serving as secondary organic aerosol (SOA) precursors. Here, we incorporate a new nationwide VCP inventory into the Community Multiscale Air Quality (CMAQ) model with VCP-specific updates to better model air quality impacts. Model results indicate that VCPs mostly enhance anthropogenic SOA in densely populated areas with population-weighted annual average SOA increasing 15-30% in Southern California and New York City due to VCP emissions (contribution of 0.2-0.5 μg m^-3). Annually, VCP emissions enhance total population-weighted PM_2.5 by ∼5% in California, ∼3% in New York, New Jersey, and Connecticut, and 1-2% in most other states. While the maximum daily 8 h ozone enhancements from VCP emissions are more modest, their influence can cause a several ppb increase on select days in major cities. Printing Inks, Cleaning Products, and Paints and Coatings product use categories contribute ∼75% to the modeled VCP-derived SOA and Cleaning Products, Paints and Coatings, and Personal Care Products contribute ∼81% to the modeled VCP-derived ozone. Overall, VCPs enhance multiple criteria pollutants throughout the United States with the largest impacts in urban cores.

Keywords: PM2.5; air quality impacts; ozone; reactive organic carbon; secondary organic aerosol; volatile chemical products.

Figure 1.

Modeling performance metrics for OC, PM_2.5, and maximum daily 8-hour O₃, disaggregated by season and region. Note: NE – U.S. EPA Regions 1, 2, 3; SE – U.S. EPA Region 4; MW – U.S. EPA Region 5; PL – U.S. EPA Regions 6, 7, 8; SW – U.S. EPA Region 9; NW – U.S. EPA Region 10; SON – fall months; DJF – winter months; MAM – spring months; JJA – summer months; NMB – normalized mean bias. See Table S3 in the supporting information for additional data related to the model evaluation.

Figure 2.

(Center) Annual-average SOA enhancements attributable to VCP emissions. (Side Panels) Diurnal, population-weighted SOA enhancements attributable to VCP emissions for select counties. Line indicates the average VCP enhancements for each hour and shading represents the VCP enhancements for 95% of all days. Note: colormap is non-linear.

Figure 3.

(Center) Summertime-average MDA8 O₃ enhancements attributable to VCP emissions. (Side Panels) Diurnal, population-weighted O₃ enhancements attributable to VCP emissions for select counties. Line indicates the average VCP enhancements for each hour and shading represents the VCP enhancements for 95% of all days. Note: colormap is non-linear.

Figure 4.

Percent contributions to national emissions, population-weighted, annual average SOA concentrations, and population-weighted, summertime average MDA8 O₃ concentrations by Product Use Category for the VCP sector.