Aerosols, Global Climate, and the Human Health Co-Benefits of Climate Change Mitigation - Aerosols: Measurement, Dosimetry, and Health Effects - page 349

13.3.3 H ealtH e FFects oF PM c onstituents
PM is a complex mixture of a wide array of chemical constituents, and PM's chemical composition
varies seasonally and regionally (Bell et al., 2007). While most past studies have investigated the
effects of the PM mass concentration on human health effects, newer studies have begun to evaluate
the mortality impacts of PM by source-speciic components, including two key aerosol components
that affect climate change: sulfates and elemental BC soot.
With regard to acute effects of PM components, Thurston et al. (2005) found that coal-burning-
related sulfate-containing aerosols were among those most associated with increases in daily mor-
tality. Bell et al. (2009) found that communities with higher PM 2.5 content of nickel (Ni), vanadium
(V), and elemental carbon (EC) and/or their related sources were found to have higher risk of hospi-
talizations associated with short-term exposure to PM 2.5 . Lall et al. (2011) similarly found that EC of
trafic origins were associated with higher risk of cardiovascular disease (CVD) hospital admissions
in New York than PM 2.5 mass in general. In a study of New York City mortality, Ito et al. (2011)
have reported that coal-combustion-related components (e.g., selenium [Se] and sulfur) were associ-
ated with CVD mortality in summer, whereas the trafic-related EC showed associations with CVD
mortality throughout the year. Zhou et al. (2011) investigated the PM 2.5 components and gaseous
pollutants associated with mortality in Detroit, MI and Seattle, WA. These authors similarly found
that CVD and respiratory mortality were most associated with warm season secondary aerosols
(e.g., sulfates) and trafic markers (e.g., EC) in Detroit, while in Seattle, the component species
most closely associated with mortality included those for cold season trafic and other combustion
sources, such as residual oil and wood burning. In addition, recent evidence has implicated diesel-
trafic-derived EC as a factor in increased risk of acute asthma morbidity (Spira-Cohen et al., 2011).
Overall, these studies of PM 2.5 components and constituents suggest that both EC and sulfate, and
their associated sources, including diesel trafic and coal burning, may be among the most explana-
tory of the acute adverse health effects of PM 2.5 , although the health impacts of the particulate
mixture are not well understood
With regard to the long-term effects of PM air pollution, Ozkaynak and Thurston (1987) con-
ducted the irst source apportionment of PM 2.5 -mortality effects, inding that sulfate-related par-
ticles, largely from coal burning, were most associated with the mortality impacts of long-term
exposure to PM 2.5 . More recently, Ostro et al. (2007) examined daily data from 2000 to 2003 on
mortality and PM 2.5 mass and components, including EC and OC, nitrates, sulfates, and various
metals. The authors examined associations of PM 2.5 and its constituents with daily counts of several
mortality categories: all-cause, CVD, respiratory, and mortality age >65 years, inding the stron-
gest associations between mortality and sulfates and several metals. Ostro et al. (2010) used data
from a prospective cohort of active and former female public school professionals to develop esti-
mates of long-term exposures to PM 2.5 and several of its constituents, including EC, OC, sulfates,
nitrates, iron (Fe), potassium (K), silicon (Si), and zinc (Zn), inding increased risks of all-cause
and cardiopulmonary mortality from exposure to constituents derived from combustion of fossil
fuel (including diesel), as well as those of crustal origin. In addition, Smith et al. (2010) undertook
a meta-analysis of existing time-series studies, as well as an analysis of a cohort of 352,000 people
in 66 U.S. cities during 18 years of follow-up of the American Cancer Society cohort, inding total
mortality effects from long-term exposure to both the elemental BC and sulfate components of
PM 2.5 aerosols.
13.4 SULFATES AND GEOENGINEERING OF CLIMATE CHANGE
One of the repeatedly raised theories regarding how to mitigate climate change is the deliberate
injection of sulfates into the atmosphere because of their aforementioned climate cooling properties
(Rasch et al., 2008; Ammann et al. 2010; Ban-Weiss and Caldeira, 2010). The theory behind this
proposal is that the higher level of sulfates would cool the global environment much in the manner