Fine Particulate Air Pollution Exposure Linked to Risk of Cardiovascular Events

Long-term exposure to fine particulate air pollution (PM_2.5) is associated with an increased risk of incident acute myocardial infarction (AMI), ischemic heart disease (IHD) mortality, and cardiovascular disease (CVD) mortality, researchers reported in JAMA Network Open.

There is disagreement over whether the current National Ambient Air Quality Standard for PM_2.5 (12 μg/m³) is sufficiently protective. Investigators therefore conducted a retrospective cohort study to quantify the association of long-term PM_2.5 with incident AMI, IHD mortality, and CVD mortality among adults in the Kaiser Permanente Northern California (KPNC) health plan from 2007 to 2016.

The study included 3,798,078 adults (mean [SD] age, 41.1 [17.2] years; 52.5% female; 50.2% White) with at least 1 year of KPNC health plan membership with at least 1 outpatient visit who lived in the Northern California region for at least 1 year and had a home address that was geocoded and linked to the air pollution data. All participants were followed for up to 10 years. Individual-level time-updated 1-year mean PM_2.5 exposures were compiled for every participant and were updated monthly from baseline through the end of follow-up. The analysis was performed from January 2020 to December 2022.

Long-term PM_2.5 exposure was associated with an increased risk of each outcome in all analysis models. The minimally adjusted model 1 showed a 38% (95% CI, 32%-45%) increased risk of incident AMI, a 50% (95% CI, 40%-60%) increased risk of IHD mortality, and a 30% (95% CI, 24%-36%) increased risk of CVD mortality per 10 μg/m³ increase in 1-year mean PM_2.5. After the sequential addition of covariates, confounding by socioeconomic status (SES) and baseline comorbidities was observed, with negligible confounding by smoking, body mass index, and medication use. In the fully adjusted model, a 12% (95% CI, 7%-18%) increased risk of incident AMI, a 21% (95% CI, 13%-30%) increased risk of IHD mortality, and an 8% (95% CI, 3%-13%) increased risk of CVD mortality per 10 μg/m³ increase in 1-year mean PM_2.5 were observed.

Age-based analysis showed that the hazard ratio for CVD mortality varied from 1.35 at age 50 years, 1.25 at age 60 years, 1.16 at age 70 years, and 1.08 at age 80 years. The mean age of CVD death was 79.6 (13.1) years.

Evidence of effect modification by neighborhood SES for all outcomes was observed, with larger PM_2.5 associations occurring in those living in low SES neighborhoods vs high SES neighborhoods. In sensitivity analyses that included neighborhood income, similar effect modification results were found for IHD and CVD mortality, with no differences occurring for incident AMI.

PM_2.5 exposure at moderate concentrations (10.0 to 11.9 μg/m³ ) vs low concentrations (<8.0 μg/m³ ) was associated with a 6% (95% CI, 3%-10%) increased risk of incident AMI and a 7% (95% CI, 2%-12%) risk of IHD mortality, with no increase in CVD mortality risk.

PM_2.5 exposure at high concentrations above the regulation limit (12.0 to 13.9 μg/m³) was associated with a 10% (95% CI, 5%-16%) increased risk of incident AMI (95% CI, 5%-16%), a 16% (95% CI, 8%-25%) increased risk of IHD mortality, and an 8% (95% CI, 3%-14%) increased risk of CVD mortality, vs low concentrations (<8.0 μg/m³).

Study limitations include the lack of data on physical activity, diet, alcohol use, marital status, or detailed smoking history. Also, the use of single rather than multiple imputation for missing covariates may have underestimated standard errors.

“This study’s results add to the growing evidence that long-term PM_2.5 exposure is associated with increased risk of cardiovascular events and that the current regulatory standard of 12 μg/m³ is not sufficiently protective,” stated the investigators.