The synergistic effects of Particle Radioactivity (Gross Beta Activity) and PM2.5 on Cardiovascular Diseases Mortality

Abstract

BACKGROUND: Although the effects of fine particulate matter (particulate matter ≤2.5 μm aerodynamic diameter; PM₂.₅) on cardiovascular diseases (CVD) morbidity and mortality are well established, little is known about CVD health effects of particle radioactivity (PR). In addition, there are still questions about which of the PM₂.₅ physical, chemical, or biological properties are mostly responsible for its toxicity. METHODS: We investigated the association between PR, measured as gross β-activity from highly resolved spatiotemporal predictions, and mortality for CVD, myocardial infarction, stroke, and all-cause non-accidental mortality in Massachusetts (2001-2015). Within both difference-in-difference (DID) approach and generalized linear mixed-effect model frameworks, we fit gross β-activity-alone, PM2.5 alone, gross β-activity&PM₂.₅ models and examined the interaction between PM₂.₅ and gross β-activity. RESULTS: We found significant associations between gross β-activity/PM₂.₅ and each mortality cause. Using the DID approach and adjusting for PM₂.₅, we found the highest associations with MI (RR=1.16, 95% CI: 1.08, 1.24) and stroke (RR=1.11, 95% CI: 1.04, 1.18) for an IQR increase (0.055 mBq/m3) in gross β-activity. We found a significant positive interaction between PM₂.₅ and gross β-activity, with higher associations between PM₂.₅ and mortality at a higher level of gross β-activity. We also observed that the associations varied across age groups. The results were comparable between the two statistical methods with and without adjusting for PM₂.₅. CONCLUSIONS: This is the first study that, using highly spatiotemporal predictions of gross β-activity, provides evidence that PR increases CVD mortality and enhances PM₂.₅ CVD mortality. Therefore, PR can be an important property of PM₂.₅ that must be further investigated. Addressing this important question can lead to cost-effective air quality regulations. KEYWORDS: cardiovascular disease; death; particle radioactivity; death