Mixture effects of point source air pollutants on outpatient visits for respiratory illness in New York State: evidence for synergistic interactions between VOC and criteria air pollutants (2010-2018)
Background: Mixtures of criteria air pollutants (CAPs) and volatile organic compounds (VOCs) can interact synergistically, causing greater respiratory harm than the individual components, including asthma exacerbation and reduced lung function. However, while VOCs are recognized air pollutants and potential for synergy is known, prior work on mixture effects is limited to CAP mixtures. Objectives: Using data from the National Emissions Inventory, we assessed county level mixture effects of zip code level point source air pollution emissions on emergency room (ER) visits for asthma and COPD in New York State from 2010 to 2018. Methods: We explored mixture effects of 10 air pollutants on outpatient admissions for asthma and chronic obstructive pulmonary disease (COPD), using a complementary multi-model approach, including linear regression, random forest, and mixture models to assess single pollutant and mixture effects. Results: Significant pairwise interactions were identified between VOC and most CAP pollutants for both asthma and COPD. While standardized single pollutant effects were small for both conditions, standardized mixture effects for asthma without interactions were moderate (0.36, 95%CI: 0.32, 0.41, per quantile mixture increase). Including significant pairwise interactions in the model results in a 3-fold adjusted increase (1.07, 95%CI: 0.64, 1.50). Results for COPD are similar but less striking. Conclusion: Our findings show that point source pollution offers a significant contribution to risk of asthma and COPD-related visits, effects vary by illness and location, and pairwise interactions between mixture components, especially between VOC and CAPs, may dramatically increase case rates.