Lung Function and Short-Term Ambient Air Pollution Exposure: Differential Impacts of Omega-3 and Omega-6 Fatty Acids

Rationale: Exposure to air pollution is associated with adverse respiratory effects. Polyunsaturated omega 3 (n-3) fatty acids (FAs) appear to attenuate the health effects of air pollution. Objectives: This panel study evaluated whether n-3 FA intake and blood levels of polyunsaturated omega 6 (n-6) FAs can modulate the associations between respiratory effects and short-term exposure to ambient air pollution in healthy adults. Methods: Sixty-two healthy adults were enrolled into either high or low n-3 FA groups on the basis of n-3 FA intake and erythrocyte n-3 FA concentrations. Low and high n-6 FA groups were dichotomized on the basis of blood n-6 FA levels. Participants underwent three to five testing sessions separated by at least 7 days. At each session, the forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), and plasma markers of inflammation (IL-6 [interleukin-6]) and oxidative stress (ox-LDL [oxidized low-density lipoprotein]) were measured. Associations between the ambient ozone and fine particulate matter (PM) (PM with an aerodynamic diameter ⩽2.5 μm [PM_2.5]) levels and the lung function and blood markers were assessed by using mixed-effect models stratified by FA levels. Results: Average levels of ozone (40.8 ± 11.1 ppb) and PM_2.5 (10.2 ± 4.1 μg/m³) were below national ambient air quality standards during the study period. FVC was positively associated with ozone at a lag of 0 days (lag0) in the high n-3 FA group, whereas the association was null in the low n-3 FA group (for an interquartile range increase in ozone of 1.8% [95% confidence interval (CI): 0.5% to 3.2%] vs. 0.0% [95% CI: -1.4% to 1.5%]); however, the association shifted to being negative at lag4 (-1.9% [95% CI: -3.2 to -0.5] vs. 0.2% [95% CI: -1.2% to 1.5%]) and lag5 (-1.2% [95% CI: -2.4% to 0.0%] vs. 0.9% [95% CI: -0.4% to 2.3%]). A similar pattern was observed in the low n-6 FA group compared with the high n-6 FA group (lag0: 1.7% [95% CI: 0.3% to 3.0%] vs. 0.5% [95% CI: -0.9% to 2.0%] and lag4: -1.4% [95% CI: -2.8% to 0.0%] vs. -0.5% [95% CI: -1.8% to 0.9%]). The associations between FEV₁ and ozone and between FVC and PM_2.5 also followed a similar pattern. Elevated ozone levels were associated with an immediate decrease in ox-LDL in the high n-3 FA group at lag0 (-12.3% [95% CI: -24.8% to 0.1%]), whereas there was no change in the low n-3 FA group (-7.5% [95% CI: -21.4% to 6.5%]) and there was a delayed increase in IL-6 in the high n-3 FA group compared with the low n-3 FA group (lag4: 66.9% [95% CI: 27.9% to 106.0%] vs. 8.9% [95% CI: -31.8% to 49.6%], lag5: 58.2% [95% CI: 22.4% to 94.1%] vs. -7.4% [95% CI: -48.8% to 34.0%], and lag6: 45.8% [95% CI: 8.7% to 82.9%] vs. -8.5% [95% CI: -49.7% to 32.6%]). Conclusions: We observed lag-dependent associations between short-term ambient air pollutants and lung function that were differentially modulated by n-3 and n-6 FAs, suggesting that n-3 and n-6 FAs counteract the respiratory response to low levels of ambient air pollution in healthy adults.Clinical trial registered with clinicaltrials.gov (NCT02921048).