Transboundary health impacts of transported global air pollution and international trade.

Millions of people die every year from diseases caused by exposure to outdoor air pollution. Some studies have estimated premature mortality related to local sources of air pollution, but local air quality can also be affected by atmospheric transport of pollution from distant sources. International trade is contributing to the globalization of emission and pollution as a result of the production of goods (and their associated emissions) in one region for consumption in another region. The effects of international trade on air pollutant emissions, air quality and health have been investigated regionally, but a combined, global assessment of the health impacts related to international trade and the transport of atmospheric air pollution is lacking. Here we combine four global models to estimate premature mortality caused by fine particulate matter (PM2.5) pollution as a result of atmospheric transport and the production and consumption of goods and services in different world regions. We find that, of the 3.45 million premature deaths related to PM2.5 pollution in 2007 worldwide, about 12 per cent (411,100 deaths) were related to air pollutants emitted in a region of the world other than that in which the death occurred, and about 22 per cent (762,400 deaths) were associated with goods and services produced in one region for consumption in another. For example, PM2.5 pollution produced in China in 2007 is linked to more than 64,800 premature deaths in regions other than China, including more than 3,100 premature deaths in western Europe and the USA; on the other hand, consumption in western Europe and the USA is linked to more than 108,600 premature deaths in China. Our results reveal that the transboundary health impacts of PM2.5 pollution associated with international trade are greater than those associated with long-distance atmospheric pollutant transport.

Revealing the hidden health costs embodied in Chinese exports.

China emits a considerable amount of air pollutants when producing goods for export. Previous efforts have emphasized the magnitude of export-related emissions; however, their health consequences on the Chinese population have not been quantified. Here, we present an interdisciplinary study to estimate the health impact of export-related air pollution. The results show that export-related emissions elevated the annual mean population weighted PM2.5 by 8.3 µg/m(3) (15% of the total) in 2007, causing 157,000 deaths and accounting for 12% of the total mortality attributable to PM2.5-related air pollution. Compared to the eastern coastal provinces, the inner regions experience much larger export-related health losses relative to their economic production gains, owing to huge inter-regional disparities in export structures and technology levels. A shift away from emission-intensive production structure and export patterns, especially in inner regions, could significantly help improve national exports while alleviating the inter-regional cost-benefit inequality. Our results provide the first quantification of health consequences from air pollution related to Chinese exports. The proposed policy recommendations, based on health burden, economic production gains, and emission analysis, would be helpful to develop more sustainable and effective national and regional export strategies.

Initial transport and retention behaviors of ZnO nanoparticles in quartz sand porous media coated with Escherichia coli biofilm.

The significance of biofilm on the transport and deposition behaviors of ZnO nanoparticles were examined under a series of environmentally relevant ionic strength at two fluid velocities of 4 m-d(-1) and 8 m-d(-1). Biofilm enhanced nanoparticles retention in porous media under all examined conditions. The greater deposition was also observed in extracellular polymeric substances (EPS) coated surfaces by employment of quartz microbalance with dissipation (QCM-D) system. Derjaguin-Landau-Verwey-Overbeek (DLVO) failed to interpret more ZnO nanoparticles deposition on biofilm (EPS) coated silica surfaces. Chemical interaction and physical morphology of biofilm contributed to this greater deposition (retention). Biofilm affected the spacial distribution of retained ZnO nanoparticles as well. Relatively steeper slope of retained profiles were observed in the presence of biofilm, corresponding to the greater deviation from colloid filtration theory (CFT). Pore space constriction via biofilm induced more nanoparticle trapped in the column inlet, leading to greater deviations (σln k(f)) from the CFT.

Influence of natural organic matter on the transport and deposition of zinc oxide nanoparticles in saturated porous media.

The significance of natural organic matter (NOM, both humic acid and alginate) on the transport and deposition kinetics of ZnO nanoparticles (NPs) in irregular quartz sand was examined by direct comparison of both breakthrough curves and retained profiles with NOM present in NPs suspension versus those obtained without NOM. Packed column experiments were conducted in both NaCl and CaCl(2) solutions under a series of environmentally relevant ionic strengths. Under all examined conditions, breakthrough plateaus with NOM even at concentration as low as 1 mg L(-1) of total organic carbon (TOC) were higher than those without NOM, indicating that presence of NOM in NPs suspensions enhanced ZnO NPs transport. Although hyper-exponential retained profiles were observed both in the presence and absence of NOM, the amount of retained ZnO NPs acquired in the presence of NOM decreased slowly as the transport distance increased. Straining induced by concurrent aggregation is found to cause the hyper-exponential decrease. In the presence of NOM, electrosteric interaction effectively reduced the ZnO NPs deposition on collector surfaces and NPs-NPs aggregation. Subsequently, the amount of NPs that jammed in the column inlet in the absence of NOM were markedly decreased, which therefore exhibited as flatter retained profiles.

Influence of natural organic matter on the deposition kinetics of extracellular polymeric substances (EPS) on silica.

The influence of humic acid and alginate, two major components of natural organic matter (NOM), on deposition kinetics of extracellular polymeric substances (EPS) on silica was examined in both NaCl and CaCl(2) solutions over a wide range of environmentally relevant ionic strengths utilizing a quartz crystal microbalance with dissipation. Deposition kinetics of both soluble EPS and bound EPS extracted from four bacterial strains with different characteristics was investigated. EPS deposition on humic acid-coated silica surfaces was found to be much lower than that on bare silica surfaces under all examined conditions. In contrast, pre-coating the silica surfaces with alginate enhanced EPS deposition in both NaCl and CaCl(2) solutions. More repulsive electrostatic interaction between EPS and surface contributed to the reduced EPS deposition on humic acid-coated silica surface. The trapping effect induced by the rough alginate layer resulted in the greater EPS deposition on alginate-coated surfaces in NaCl solutions, whereas surface heterogeneities on alginate layer facilitated favorable interactions with EPS in CaCl(2) solutions. The presence of dissolved background humic acid and alginate in solutions both significantly retarded EPS deposition on silica surfaces due to the greater steric and electrostatics repulsion.

Deposition kinetics of zinc oxide nanoparticles on natural organic matter coated silica surfaces.

The deposition kinetics of ZnO nanoparticles on silica surfaces and surfaces that pre-coated with Suwannee River humic acid (SRHA) were examined over a wide range of environmentally relevant ionic strengths in both monovalent and divalent solutions by employing a quartz crystal microbalance with dissipation (QCM-D). Deposition efficiencies of ZnO nanoparticles on bare silica surfaces increased with increasing ionic strength in both NaCl and CaCl(2) solutions, which agreed with the trends of interaction forces between nanoparticle and silica surface and thus was consistent with classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The presence of divalent cation Ca(2+) in solutions greatly enhanced the deposition kinetics of ZnO nanoparticles on silica surfaces. Pre-coated SRHA on silica surfaces hindered the deposition of ZnO nanoparticles in both monovalent and divalent solutions, which was not consistent with classic DLVO theory. Steric repulsion, a non-DLVO interaction, was found to be a major mechanism controlling the deposition of ZnO nanoparticle on SRHA-coated silica surfaces.

Contribution of extracellular polymeric substances on representative gram negative and gram positive bacterial deposition in porous media.

The significance of extracellular polymeric substances (EPS) on cell transport and retained bacteria profiles in packed porous media (quartz sand) was examined by direct comparison of the overall deposition kinetics and retained profiles of untreated bacteria (with EPS) versus those of treated cells (without EPS) from the same cell type. Four representative cell types, Pseudomonas sp. QG6 (gram-negative, motile), mutant Escherichia coli BL21 (gram-negative, nonmotile), Bacillus subtilis (gram-positive, motile), and Rhodococcus sp. QL2 (gram-positive, nonmotile), were employed to systematically determine the influence of EPS on cell transport and deposition behavior. Packed column experiments were conducted for the untreated and treated cells in both NaCl (four ionic strength ranging from 2.5 mM to 20 mM) and CaCl(2) (5 mM) solutions at pH 6.0. The breakthrough plateaus of untreated bacteria were lower than those of treated bacteria for all four cell types under all examined conditions (in both NaCl and CaCl(2) solutions), indicating that the presence of EPS on cell surfaces enhanced cell deposition in porous media regardless of cell type and motility. Retained profiles of both untreated and treated cells for all four cell types deviated from classic filtration theory (log-linear decreases). However, the degree of deviation was greater for all four untreated cells, indicating that the presence of EPS on cell surfaces increased the deviation of retained profiles from classic filtration theory. Elution experiments demonstrated that neither untreated nor treated cells preferentially deposited in secondary energy minima. Furthermore, the release of previously deposited cells in the secondary energy minima did not change the shape of retained cell profiles, indicating that deposition in secondary energy minima did not produce the observed deviations of retained profiles from classic filtration theory.