Abstract
BackgroundThere is ample evidence of adverse associations between short-term exposure to ambient particle mass concentrations and health but little is known about the relative contribution from various sources. MethodsWe used air particle composition and number networks in London between 2011 and 2012 to derive six source-related factors for PM10 and four factors for size distributions of ultrafine particles (NSD). We assessed the associations of these factors, at pre-specified lags, with daily total, cardiovascular (CVD) and respiratory mortality and hospitalizations using Poisson regression. Relative risks and 95% confidence intervals (CI) were expressed as percentage change per interquartile range increment in source-factor mass or number concentration. We evaluated the sensitivity of associations to adjustment for multiple other factors and by season. ResultsWe found no evidence of associations between PM10 or NSD source-related factors and daily mortality, as the direction of the estimates were variable with 95% CI spanning 0%. Traffic-related PM10 and NSD displayed consistent associations with CVD admissions aged 15–64years (1.01% (95%CI: 0.03%, 2.00%) and 1.04% (95%CI: −0.62%, 2.72%) respectively) as did particles from background urban sources (0.36% for PM10 and 0.81% for NSD). Most sources were positively associated with pediatric (0–14years) respiratory hospitalizations, with stronger evidence for fuel oil PM10 (3.43%, 95%CI: 1.26%, 5.65%). Our results did not suggest associations with cardiovascular admissions in 65+ or respiratory admissions in 15+ age groups. Effect estimates were generally robust to adjustment for other factors and by season. ConclusionsOur findings are broadly consistent with the growing evidence of the toxicity of traffic and combustion particles, particularly in relation to respiratory morbidity in children and cardiovascular morbidity in younger adults.
Highlights
A number of detailed reviews of the health effects of short-term exposure to particles have been published (Adar et al, 2014; Atkinson et al, 2014; WHO, 2013)
Using data collected from the Clearflo project, supplemented by national and local network measurements made at the North Kensington (NK) urban background site in London, U.K., we assembled a database of over 100 metrics for 2011–2012, that included daily concentrations of particle mass (for particles with aerodynamic diameter b 10 μm (PM10)), particle number and size distribution (NSD) as a measure of ultrafine particles, as well as particle chemical composition and a wood smoke tracer derived using the aethalometer model (Fuller et al, 2014)
The total of the four sources falls well short of the total number count from the CPC because the CPC covers a wider range of particle sizes, and corrections applied for internal particle losses in the SMPS may be an underestimate
Summary
A number of detailed reviews of the health effects of short-term exposure to particles have been published (Adar et al, 2014; Atkinson et al, 2014; WHO, 2013) These highlight an increasing focus on better identification of specific particle components and/or sources in order to target measures for the protection of public health. These are two quite different approaches: the former addresses single components of ambient particulates that may have a dominant source under certain climatic conditions (for example during warm periods urban elemental carbon is dominated by vehicle exhaust) while the latter addresses clusters of components as defined by source apportionment that may better represent a specific source. PM10 source-related Oil 1 − 0.16 Non-exhaust
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