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Analysis of the effects of ultrafine particulate matter while accounting for human exposure
Journal article

Analysis of the effects of ultrafine particulate matter while accounting for human exposure

Brian J Reich, Montserrat Fuentes and Janet Burke
Environmetrics (London, Ont.), Vol.20(2), pp.131-146
04/24/2008
DOI: 10.1002/env.915
PMCID: PMC2719864
PMID: 19655031
url
https://www.ncbi.nlm.nih.gov/pmc/articles/2719864View
Open Access

Abstract

Particulate matter (PM) has been associated with mortality in several epidemiological studies. The US EPA currently regulates PM 10 and PM 2.5 (mass concentration of particles with diameter less than 10 µm and 2.5 µm, respectively), but it is not clear which size of particles are most responsible for adverse heath outcomes. A current hypothesis is that ultra-fine particles with diameter less than 0.1µm are particularly harmful because their small size allows them to deeply penetrate the lungs. This paper investigates the association between exposure to particles of varying diameter and daily mortality. We propose a new dynamic factor analysis model to relate the ambient concentrations of several sizes of particles with diameters ranging from 0.01 to 0.40 µm with mortality. We introduce a Bayesian model that converts ambient concentrations into simulated personal exposure using the EPA’s Stochastic Human Exposure and Dose Simulator, and relates simulated exposure with mortality. Using new data from Fresno, CA, we find that the four-day lag of particles with diameter between 0.02µm and 0.08µm is associated with mortality. This is consistent with the small particles hypothesis.
ecological fallacy human exposure SHEDS dynamic factor model ultrafine particles

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