AAAR Particulars - October 2009

Decrease in PM2.5 Linked to Increase in Life Expectancy

Pope et al. (New England Journal of Medicine 2009; 360:376-86) compiled data on life expectancy, socioeconomic status, and demographic characteristics for 211 county units in the 51 U.S. metropolitan areas with matching data on fine-particulate air pollution for the late 1970s and early 1980s and the late 1990s and early 2000s. Their regression modeling revealed that a decrease of 10 μg per cubic meter in the concentration of PM2.5 was associated with an estimated increase in mean life expectancy of 0.61 year. The investigators were acknowledged for their "pioneering attempts to document the population health benefits of reducing ambient air pollution by correlating past reductions in ambient PM2.5 concentrations with increased life expectancy", according to an editorial article that appeared in the same issue of the journal.

"Global Dimming" Trend for the Past Three Decades Examined

Researchers at University of Maryland and University of Texas demonstrated that visibility inverse (Vil, in km-1) climatology be used to characterize the spatial and temporal variability of over-land aerosols for the past several decades (Science 2009; 323: 1468-1470). The calculated Vil's from National Climatic Data Center (NCDC) Global Summary of Day (GSOD) database indicated that visibility in the clear sky has decreased substantially from 1973 to 2007 over South and East Asia, South America, Australia and Africa, resulting in net global "dimming" over land by the presence of atmospheric aerosols. In contrast, the visibility has increased over Europe during the same period, consistent with the reported European "bringtening".

Toxicity of Atmospheric Aerosols on Marine Phytoplankton Revealed

Previous studies have suggested that atmospheric deposition of nutrients and trace metals can stimulate phytoplankton growth of the phytoplankton community. Using aerosol samples from different back trajectories in incubation experiments with natural communities, an international team of researchers showed that the response of phytoplankton growth to aerosol additions depends on specificcomponents in aerosols and differs across phytoplankton species (www.pnas.org/cgi/doi/10.1073/pnas.0811486106). High concentrations of copper (and possibly other elements) in some aerosols may induce toxicity that affects phytoplankton growth. One of the implications is that aerosol deposition canpotentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.

Sub-2 nm Particle Detection Close to Operational Implementation

Iida et al. (AS&T, 43(1): 81-96) at University of Minnesota studied ﬁve working ﬂuids for which the predicted cutoff diameter is below 2 nm ina laminar-ﬂow ultraﬁne condensation particle counter (UCPC). Diethylene glycol (DEG) was recommended as the working ﬂuid for atmospheric aerosol sampling because of the smaller sizes of detected particles, the relatively low saturator temperature, and its relatively high vapor pressure (so that particles can grow larger for detection). The performance of the UCPC using DEG was shown to be sufficiently steady for unattended operation. In the same issue of AS&T, Brunelli et al. (AS&T, 43(1): 53-59), design, construction, and calibration of a radial differential mobility analyzer suitable for sizing aerosol nanoparticles with mobility diameters as small as 1 nm.