Ultrafine and Accumulation Mode Particles and Hospital Admissions in Children and Elderly in Copenhagen

Abstract

ISEE-260 Objective: Evidence on the health risks associated with exposure to ambient ultrafine particles is limited, although toxicologic evidence points to importance of this fraction of particulate matter. We studied the association between urban background levels of total number concentration of particles (NCtot, 10–700 nm in diameter) measured at a single site (May 15, 2001, to December 31, 2004) and hospital admissions due to cardiovascular (CVD) and respiratory disease (RD) in the elderly (aged ≥65 years) and asthma in children (aged 5–18 years). We examined these associations in the presence of PM10, PM2.5, and ambient gases and used data on the size distribution to assign NCtot to 4 modes with mean diameters 12, 23, 57, and 212 nm and examine the role of different size fractions on health. Material and Methods: We used a time-series Poisson generalized additive model adjusted for overdispersion, season, day of the week, public holidays, school holidays, influenza, pollen, and meteorology, with up to 5 days lagged exposure. Results: We found that adverse health effects of PM on CVD and RD hospital admissions in elderly were mainly mediated by PM10 and accumulation mode particles with lack of effects of UFPs. For pediatric asthma, results indicated relevance of accumulation mode particles as well as UFPs and nitrogen oxides relevant for traffic related sources, whereas PM10 seemed to have little effect. Conclusions: Our results suggest relevance of particle volume/mass for CVD and RD admissions in elderly, and possibly of particles numbers from traffic sources for pediatric asthma.