Air pollution is known to cause adverse health effects.Fine particle pollution,or PM2.5,is of particular concern.This pollutant is emitted from motor vehicles,power plants,industry,and forest fires,and unlike summertime ozone,can occur year-round.Particle pollution is a contributor to heart attacks and sudden death or morbidity in people with cardiovascular disease or risk factors for the disease such as high blood pressure or high cholesterol.Everyone is exposed to some level of air pollution,the attributable health burden can be high,particularly for susceptible populations.Interventions can be effective actions to reduce the health impacts of air pollution.Dietary fatty acid supplementation has been shown to decrease cardiovascular risk through multiple mechanisms.We conducted studies evaluated the efficacy of supplementation with marine fish oil(FO)or olive oil(OO)in protecting against cardiovascular effects induced by controlled exposure of middle-aged healthy volunteers to concentrated ambient air pollution particles.Subjects(ages 50 to72 years),were randomly assigned to receive 3 g/d of fish oil(FO,1.2 g EPA and 0.82 g DHA),or olive oil(OO,3g/d)for 28 days.Supplementation resulted in statistically significant increases in plasma EPA levels in the FO group and oleic acid levels in OO group.Subjects were then exposed to concentrated ambient air pollution particles(CAP,mean mass concentration 253±16 Bg/m3)or filtered air for 2 hours on sequential days.Heart rate variability(HRV),plasma lipids,coagulation markers,and endothelial function measured by flow-mediated dilation of the brachial artery(FMD)were assessed pre-,immediately post-,and 20 hours post-exposure.Short-term exposure to CAP resulted in autonomic nervous system imbalance and impaired vascular endothelial function.FO supplementation attenuated CAP-induced reductions in HF/LF ratio,elevations in nLF domain of HRV,and increases in plasma triglycerides and VLDL.OO supplementation ameliorated CAP-induced reduction of FMD and changes in blood markers associated with vasoconstriction and fibrinolysis.The study of healthy middle-aged adults found that short-term exposure to ambient air pollution particles results in acute cardiovascular effects in healthy middle-aged adults,and suggest that supplementation with FO is protective against changes in autonomic balance and plasma lipids,while OO supplementation blunts adverse vascular responses of air pollution inhalation.This study could have impact on public health: people at risk of heart disease can change their behavior during bad air quality days to limit their exposure.The study also suggests that fish oil may provide protection from harmful cardiac effects and olive oil may provide protection from the harmful vascular effects of air pollution exposure.This abstract of a proposed presentation does not necessarily reflect EPA policy.