Ambient particulate matter, ozone, and neurologic symptoms in U.S. Gulf states adults

Research on neurologic effects of air pollution has focused on neurodevelopment or later-life neurodegeneration; other effects throughout adulthood have received less attention. We examined air pollution levels and neurologic symptoms among 21,467 adults in US Gulf Coast states. We assigned exposure using Environmental Protection Agency estimates of daily ambient particulate matter 2.5 (PM_2.5) and ozone. Gulf Long-term Follow-up Study participants reported neurologic symptoms at enrollment (2011-2013). We estimated cross-sectional associations between each air pollutant and prevalence of "any" neurologic, central nervous system (CNS), or peripheral nervous system (PNS) symptoms. Ambient PM_2.5 was consistently associated with prevalence of neurologic symptoms. The highest quartile of 30-day PM_2.5 was associated with any neurologic symptom (prevalence ratio [PR] = 1.16; 95% confidence interval [CI] = 1.09, 1.23) and there were increasing monotonic relationships between 30-day PM_2.5 and each symptom category (P-trend ≤ 0.01). Associations with PM_2.5 were slightly stronger among nonsmokers and during colder seasons. The highest quartile of 7-day ozone was associated with increased prevalence of PNS symptoms (PR = 1.09; 95% CI = 1.00, 1.19; P-trend = 0.03), but not with other outcomes. Ozone concentrations above regulatory levels were suggestively associated with neurologic symptoms (PR = 1.06; 95% CI = 0.99, 1.14). Mutual adjustment in co-pollutant models suggests that PM_2.5 is more relevant than ozone in relation to prevalence of neurologic symptoms.