Airborne particulates and hospital admissions for cardiovascular disease: A quantitative review of the evidence

This is a quantitative review of studies characterizing the relationship be tween exposure to airborne particulates and hospital admissions for cardiov ascular disease. A MEDLINE search and a review of reference lists were cond ucted to identify time-series studies that considered particles less than 1 0 pm or 2.5 mum in diameter (PM10 and PM2.5, respectively) and their associ ation with day-to-day variation in cardiovascular admissions. The results o f these studies were standardized to give estimates of the percentage incre ase in hospital admissions associated with an increase in ingestion of ambi ent particles of 10 mug/m(3). The results were grouped and compared on the basis of the specific outcomes and exposure measures. When studies that con sidered the association between PM10 exposure and specific cardiovascular o utcomes were pooled (after exclusion of outliers), a 10-mug/m(3) increase i n PM10 was associated with increases in admission rates of 0.8% (95% confid ence interval [Cl]: 0.5, 1.2%) for congestive heart failure, 0.7% (95% Cl: 0.4, 1.0%) for ischemic heart disease, and 0.2% (95% Cl: -0.2, 0.6%) for ce rebrovascular accidents. These effects tended to diminish substantially whe n gaseous co-pollutants were considered. The extent to which these effects are due to fine particles Is unclear. The available studies indicate that e xposure to airborne particles is associated with hospital admissions for ca rdiovascular disease; but the magnitude of this effect depends strongly on the specific disease category being considered, the time lag used in the an alysis, and the type and amount of co-pollutants. Future studies should inc lude careful consideration of the role of co-pollutants in this association , the interaction of particles with temperature, the impact of particle siz e on, this effect, and the extent to which the observed effect involves sho rt-term "harvesting.".