Daily Archives: September 15, 2013

Water Vapor – The most important greenhouse gas

This study finds a 30% difference between modeled and observed solar energy absorbed by the atmosphere.

Juan Du, Li Huang, Qilong Min, Lei Zhu. The influence of water vapor absorption in the 290-350 nm region on solar radiance: Laboratory studies and model simulation. Geophysical Research Letters. DOI: 10.1002/grl.50935

Water vapor is an important greenhouse gas in the earth’s atmosphere. Absorption of the solar radiation by water vapor in the near UV region may partially account for the up to 30% discrepancy between the modeled and the observed solar energy absorbed by the atmosphere. But the magnitude of water vapor absorption in the near UV region at wavelengths shorter than 384 nm is not known. We have determined absorption cross sections of water vapor at 5 nm intervals in the 290-350 nm region, by using cavity ring-down spectroscopy. Water vapor cross section values range from 2.94 × 10-24 to 2.13 × 10-25 cm2/molecule in the wavelength region studied. The effect of the water vapor absorption in the 290-350 nm region on the modeledradiation flux at the ground level has been evaluated using radiative transfer model.

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Should drinking water expsoure be considered in pregnancy-birth cohorts?

This study argues that drinking water contamination has not been adequately considered in studies pf pregnancy-birth cohorts. Indeed, there have been several studies in the US drinking water and pregnancy outcomes. There may be a legitmate reason for not considering drinking water…..in that the exposure of contaminants in drinking water is typically very low relative to other exposures. A weak statistical significant finding in a typical epidemiology study does not necessarily imply or prove biological plausibility.

Makris KC, Andra SS. Limited representation of drinking-water contaminants in pregnancy-birth cohorts. Science of the Total Environment. 2013 Sep 5;468-469C:165-175. doi: 10.1016/j.scitotenv.2013.08.012.

Water contamination and noise have been consistently the least assessed environmental/lifestyle exposures in pregnancy-birth cohorts (PBC). Water quality surveillance data collected during the past decade within urban drinking-water distribution systems call for re-evaluation of water and health issues in the developed world. The objectives of this scientific commentary were to (i) highlight the extent of appraisal of water contamination in exposure assessment studies of PBC, worldwide, and (ii) propose recommendations to increase awareness of emerging water-related risks through their improved representation into PBC study designs in urban centers. Three scientific literature databases (Scopus, PubMed, and Web of Science) were used for a systematic search on worldwide PBC and their publications that considered water contamination and health outcomes. Publicly-available e-databases (ENRIECO, BIRTHCOHORTS, and CHICOS) were also employed for detailed exploration of existing European Union (EU)-based PBC. Out of the 76 PBC identified in the EU territory, only 12 of them incorporated water contamination into their study designs. Among which only 6 PBC published scientific articles that either included data on water contamination and/or water intake estimates. Trihalomethanes but not other disinfection by-products were mostly studied in the PBC around the globe, while fluoride, atrazine, perfluorinated compounds, tetrachloroethylene, and lead were studied to a lesser extent as water contaminants. It appears that chemical-based water contamination and corresponding human exposures represent a largely underappreciated niche of exposure science pertaining to pregnant mother and children’s health in PBC. Future PBC studies should grasp this opportunity to substantially reform elements of water contamination in their exposure assessment protocols and effectively combine them with their epidemiological study designs.

Click here for full paper (fee).