Olfaction impairment (OI) is an often underreported, common sensory deficit that can lead to a host of adverse health conditions, quality of life issues, and is a predictor of 5-year mortality. Environmental exposures, including very fine particulate matter (PM2.5), are believed to be a potential risk factor in the loss of smell but previous research into this association has been limited. We therefore collaborated with the National Institute of Environmental Health Sciences' Sister Study, which had been originally designed to examine the relationship between environmental exposures and cancer, to test a large sub-sample (n=4020) of their population in order to identify participants with olfaction impairment. Our multivariable logistic regression analysis found that those in the highest exposure group were more likely to suffer from olfaction impairment when compared to those in the lowest exposure group, with an OR = 1.55 (95% CI: 1.40, 1.72) after adjusting for all relevant confounders. Results were similar for all instances of PM2.5 yearly average measurements. Further quantile regression analyses showed that the greatest effect of ambient air pollutants on olfaction was for those whose smell tests fell below the 42nd quantile, indicating that PM2.5 may exacerbate OI rather than instigate it. We conclude that higher levels of PM2.5 were associated with olfaction impairment and that the effect may have been greater for those with an already declining sense of smell.
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