Use of visual range measurements to predict fine particulate matter exposures in Southwest Asia and Afghanistan

Abstract

Military personnel deployed to Southwest Asia and Afghanistan were exposed to high levels of ambient particulate matter (PM) indicating the potential for exposure-related health effects. However, historical quantitative ambient PM exposure data for conducting epidemiological health studies are unavailable due to a lack of monitoring stations. Since visual range is proportional to particle light extinction (scattering and absorption), visibility can serve as a surrogate for PM2.5 concentrations where ground measurements are not available. We used data on visibility, relative humidity (RH), and PM2.5 ground measurements collected in Kuwait from years 2004 to 2005 to establish the relationship between PM2.5 and visibility. Model validation obtained by regressing trimester average PM2.5 predictions against PM2.5 measurements in Kuwait produced an r2 value of 0.84. Cross validation of urban and rural sites in Kuwait also revealed good model fit. We applied this relationship to location-specific visibility data at 104 regional sites between years 2000 and 2012 to estimate monthly average PM2.5 concentrations. Monthly averages at sites in Iraq, Afghanistan, United Arab Emirates, Kuwait, Djibouti, and Qatar ranged from 10 to 365 µg/m3 during this period, while site averages ranged from 22 to 80 µg/m3, indicating considerable spatial and temporal heterogeneity in ambient PM2.5 across these regions. These data support the use of historical visibility data to estimate location-specific PM2.5 concentrations for use in future epidemiological studies in the region.

Faculty Opinions recommendation of Respiratory Health after Military Service in Southwest Asia and Afghanistan. An Official American Thoracic Society Workshop Report.

“…For example, in daily sampling conducted in Kuwait City in 2004-2005 using equipment suitable for a desert environment, the annual average PM 2.5 value was 53 mg/m 3 (2,29), within the range of mean PM 2.5 concentrations found by EPMSP. As noted in this document (see below and Figure 2), the PM 2.5 levels estimated based on military airport visibility data in Iraq, Afghanistan, Kuwait, and other countries in Southwest Asia (18) were also similar to the EPMSP concentrations.…”

“…A strength of SHADE is an exposure assessment approach that does not rely on self-reported exposure. Historical NASA satellite and military airport visibility (visual range assessment) records will be used to reconstruct deploymentrelated PM 2.5 at each veteran's deployment locations (17,18). This approach integrates ground-level PM 2.5 data obtained from monitoring stations, airport visibility data in the countries where U.S. military personnel were deployed, and high-resolution AOD data available from NASA satellites (E. Garshick, workshop presentation).…”

A novel calibration approach using satellite and visibility observations to estimate fine particulate matter exposures in Southwest Asia and Afghanistan

“…In our previous work, daily-integrated PM 2.5 concentration data collected at several monitoring sites in Kuwait during the period 2004-2005 was used to calibrate a model for the relationship between PM 2.5 and visibility, with relative humidity as a covariate (Masri et al 2015). This study produced PM 2.5 predictions that correlated well with observed averages (r2=0.84) and performed well through 10-fold internal cross validation.…”

“…To convert visibility to spatially- and temporally-resolved PM 2.5 concentrations in the current study, we used the calibration equation coefficients generated from this previous work. The prediction equation is as follows: $${\mathrm{PredPM}}_{2.5\mathrm{ij}}={\gamma }_{\mathrm{normalo}}+{\gamma }_{\mathrm{normalv}}\left(\frac{1}{{\mathrm{PredVIS}}_{\mathrm{ij}}}\right)+{\gamma }_{\mathrm{normalm}}\left({\mathrm{RH}}^2\right)$$ where PredPM 2.5ij is the predicted PM 2.5 for cell i on a day j; PredVIS ij is the daily visibility predicted for cell i on a day j; RH 2 is the square of relative humidity for cell i on day j; γ o , γ v , and γ m are the coefficients estimated from our previous analysis, which are equal to +39.3691, +732372, and −0.00319, respectively (Masri et al 2015). Grid- and day-specific PM 2.5 predictions over varying periods were then calculated and a map of grid-cell specific averaged PM 2.5 estimates over the entire study period was projected onto a map for visual representation.…”

“…In a recent study, we established the relationship between visibility and PM 2.5 in Southwest Asian and Afghanistan (Masri et al 2015). This relationship with visibility is due to the light extinction (scattering and absorption) effects of particles with sizes similar to the wavelengths of visible light, which has been empirically shown in a number of studies (Burt, 1961; Noll et al 1968; Charlson, 1969; Waggoner and Weiss, 1980; Abbey et al 1995).…”