  There is increasing focus on whether air pollution originating from different
sources has different health implications. In particular, recent evidence
suggests that fine particulate matter (PM2.5) with chemical tracers suggesting
coal combustion origins is especially harmful. Augmenting this knowledge with
estimates from causal inference methods to identify the health impacts of PM2.5
derived from specific point sources of coal combustion would be an important
step towards informing specific, targeted interventions. We investigated the
effect of high-exposure to coal combustion emissions from 783 coal-fired power
generating units on ischemic heart disease (IHD) hospitalizations in over 19
million Medicare beneficiaries residing at 21,351 ZIP codes in the eastern
United States. We used InMAP, a newly-developed, reduced-complexity air quality
model to classify each ZIP code as either a high-exposed or control location.
Our health outcomes analysis uses a causal inference method - propensity score
matching - to adjust for potential confounders of the relationship between
exposure and IHD. We fit separate Poisson regression models to the matched data
in each geographic region to estimate the incidence rate ratio for IHD
comparing high-exposed to control locations. High exposure to coal power plant
emissions and IHD were positively associated in the Northeast (IRR = 1.08, 95%
CI = 1.06, 1.09) and the Southeast (IRR = 1.06, 95% CI = 1.04, 1.08). No
significant association was found in the Industrial Midwest (IRR = 1.02, 95% CI
= 1.00, 1.04), likely the result of small exposure contrasts between
high-exposed and control ZIP codes in that region. This study provides targeted
evidence of the association between emissions from specific coal power plants
and IHD hospitalizations among Medicare beneficiaries.
