Spatial and temporal variability in desert dust and anthropogenic pollution in Iraq, 1997–2010

ABSTRACT

Satellite imaging has emerged as a method for monitoring regional air pollution and detecting areas of high dust concentrations. Unlike ground observations, continuous data monitoring is available with global coverage of terrestrial and atmospheric components. In this study we test the utility of different sources of satellite data to assess air pollution concentrations in Iraq. SeaWiFS and MODIS Deep Blue (DB) aerosol optical depth (AOD) products were evaluated and used to characterize the spatial and temporal pollution levels from the late 1990s through 2010. The AOD and Ångström exponent (an indicator of particle size, since smaller Ångström exponent values reflect a source that includes larger particles) were correlated on 50 × 50 km spatial resolution. Generally, AOD and Ångström exponent were inversely correlated, suggesting a significant contribution of coarse particles from dust storms to AOD maxima. Although the majority of grid cells exhibited this trend, a weaker relationship in other locations suggested an additional contribution of fine particles from anthropogenic sources. Tropospheric NO₂ densities from the OMI satellite were elevated over cities, also consistent with a contribution from anthropogenic sources. Our analysis demonstrates the use of satellite imaging data to estimate relative pollution levels and source contributions in areas of the world where direct measurements are not available.

Implications: The authors demonstrated how satellite data can be used to characterize exposures to dust and to anthropogenic pollution for future health related studies. This approach is of a great potential to investigate the associations between subject-specific exposures to different pollution sources and their health effects in inaccessible regions and areas where ground monitoring is unavailable.

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Acknowledgments

The authors appreciate the suggestions of Planning Committee members the VA Cooperative Studies Program #595: Respiratory Health and Deployment to Iraq and Afghanistan: Nicholas L. Smith, Ph.D., Rebecca B. McNeil, Ph.D., and Jaime E. Hart, Sc.D. The authors also acknowledge the MODIS mission scientists and associated NASA personnel for the production of the data used in this research developed and maintained by the NASA GES DISC.

Funding

This work is supported by the U.S. Department of Veterans Affairs, Office of Research and Development, Clinical Science Research and Development, Cooperative Studies Program, U.S. Environmental Protection Agency (EPA) grant RD 83479801, and National Science Foundation Grant AGS-111916. Its contents are solely the responsibility of the authors and do not represent the official views of the EPA, U.S. Department of Veterans Affairs, or the U.S. Department of Defense/Army. Further, EPA, U.S. Department of Veterans Affairs, and the U.S. Department of Defense/Army do not endorse the purchase of any commercial products or services mentioned in the publication.

Additional information

Funding

This work is supported by the U.S. Department of Veterans Affairs, Office of Research and Development, Clinical Science Research and Development, Cooperative Studies Program, U.S. Environmental Protection Agency (EPA) grant RD 83479801, and National Science Foundation Grant AGS-111916. Its contents are solely the responsibility of the authors and do not represent the official views of the EPA, U.S. Department of Veterans Affairs, or the U.S. Department of Defense/Army. Further, EPA, U.S. Department of Veterans Affairs, and the U.S. Department of Defense/Army do not endorse the purchase of any commercial products or services mentioned in the publication.

Notes on contributors

A. Alexandra Chudnovsky

A. Alexandra Chudnovsky is an Assistant Professor at Tel-Aviv University and a visiting Scientist at the Harvard T.H. Chan School of Public Health. Her interests focus on developing modeling methods to predict and evaluate the contribution of local and regional pollution sources to the urban air quality. Petros Koutrakis is a Professor of Environmental Sciences at Harvard T.H. Chan School of Public Health and the Director of the EPA/Harvard University Center for Ambient Particle Health Effects. His research activities focus on the development of human exposure measurement techniques and the investigation of sources, transport, and the fate of air pollutants. Alex Kostinski is a Professor of Physics at MTU. His recent research has been in cloud, aerosol, and precipitation physics; radar meteorology; astrophysics; wave propagation in random media; turbulent fluids; adaptive optics; and polarization optics. Susan P. Proctor is a research scientist at U.S. Army Research Institute of Environmental Medicine (USARIEM), with appointments as a Research Scientist at the VA Boston Healthcare System and Research Associate Professor at Boston University. Her research interests focus on exposure assessment, health outcomes and environmental/occupational epidemiology. Eric Garshick is Associate Chief, Pulmonary, Allergy, Sleep, and Critical Care Medicine Section at the Veterans Affairs Boston Healthcare System; Professor of Medicine, Harvard Medical School; and a Research Physician at the Channing Division of Network Medicine, Brigham and Women’s Hospital. His research includes the study of the health effects of air pollution and diesel exhaust on respiratory health and the study of respiratory health in patients with chronic spinal cord injury.