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ABSTRACT
In order to study effects of ambient particulate matter (PM) it was previously necessary to have access to a comprehensive air monitoring network. However, there are locations in the world where PM levels are above generally accepted exposure standards but lack a monitoring infrastructure. This is true in Iraq and other locations in Southwest Asia and Afghanistan where U.S. and other coalition troops were deployed beginning in 2001. Since aerosol optical depth (AOD), determined by satellite, and visibility are both highly related to atmospheric PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) concentrations, we employed a novel approach that took advantage of historic airport visibility measurements to calibrate the AOD–visibility relationship and determine visibility spatially and temporally (2006–2007) over an approximately 17,000 km2 region of Iraq. We obtained daily visibility predictions that were highly associated with satellite-based 1x1 km AOD daily observations (R2=0.87). Based on a previously derived calibration between PM2.5 and visibility, we were able to predict spatially and temporally resolved PM2.5 concentrations. Variability of PM2.5 among sites was high, with daily concentrations differing by as much as ~30 μg/m3. This study demonstrates the feasibility of characterizing historic PM2.5 exposures in Iraq and other locations in Southwest Asia and Afghanistan with similar climate characteristics. This is of utility for epidemiologists seeking to assess the potential health effects related to PM2.5 exposures among previously deployed military personnel and of the population of the region.
Implications: This study demonstrates the ability to utilize aerosol optical depth to successfully estimate visibility spatially and temporally in Southwest Asia and Afghanistan. This enables for the estimation of spatially resolved PM2.5 concentrations in the region. The ability to caracterize PM2.5 concentrations in Southwest Asia and Afghanistan is highly important for epidemiologists investigating the relationship between chronic exposure to PM2.5 and respiratory diseases among military personnel deployed to the region. This information will better position policy makers to draft meaningful legislation relating to military health.
Acknowledgment
The authors appreciate the assistance of Mike Hunsucker and Jeff Zautner, 14th Weather Squadron (U.S. Air Force), Asheville, NC.
Funding
This work was supported by the VA Cooperative Studies Program No. 595: Pulmonary Health and Deployment to Southwest Asia and Afghanistan, from the U.S. Department of Veterans Affairs, Office of Research and Development, Clinical Science Research and Development, Cooperative Studies Program. This publication was also made possible by U.S. Environmental Protection Agency (EPA) grant RD-83479801. Its contents are solely the responsibility of the grantee and do not necessarily represent the official views of the EPA, U.S. Department of Veterans Affairs, or U.S. Government.
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Notes on contributors
Shahir Masri
Shahir Masri is a doctor of science recently graduated from the Department of Environmental Health, Harvard T.H. Chan School of Public Health, in Boston, MA.
Eric Garshick
Eric Garshick is associate chief physician of the Pulmonary, Allergy, Sleep, and Critical Care Medicine Section of the V.A. Boston Healthcare System, and professor of medicine at the Harvard Medical School.
Brent A. Coull
Brent A. Coull is a professor of biostatistics at the Harvard T.H. Chan School of Public Health.
Petros Koutrakis
Petros Koutrakis is a professor of environmental sciences at the Harvard T.H. Chan School of Public Health.