| Polycyclic aromatic hydrocarbons (PAHs), a kind of semivolatile organic compounds (SVOCs) prevailing in all kinds of environmental media, have produced potential and long-term harm to the natural environment and human health. Scientists in the world have carried out studies on occurrence of PAHs in different environment media; most of these studies however, were focused on relatively small areas for short time, and lacking comprehensive information at the national scale for different countries, and thus are not cable to fully understand the residues, environmental fate, and health risk of PAHs on a large scale. In order to fill this gap, the International Joint Research Center for Persistent Toxic Substances (IJRC-PTS) carried out a large scale monitoring program, the Asia Soil and Air Monitoring Program (Asia-SAMP), under which a large amount of air and soil samples were collected in five Asian countries, including China, Japan, South Korea, Vietnam and India. This study is a part of the Asia-SAMP. In this study, concentrations of PAHs in these air and soil samples were measured; the spatial distribution, time variances, and transformations of PAHs in air and soil in these countries were analyzed. The carcinogenic risk caused by respiratory exposure to PAHs in these countries was also evaluated with the help of epidemiological data. The results of this study can describe comprehensively the contamination trends by PAHs in on a national scale in these countries, present a scientific support for the pollution control of PAHs, and provide a exploration direction for the future environmental remediation and pollutants treatment for these five countries.Under Asia-SAMP, air samples were collected using passive air samplers with polyurethane foam disks over four consecutive three-month periods from September 2012 to August 2013 to measure the seasonal concentrations of PAHs at 176 sites (11 background,83 rural and 82 urban) across the five countries. The annual concentrations of total 47 PAHs (?47PAHs) at all sites in the five countries ranged from 6.29 to 688 ng/m~3 with mean of 128 ng/m~3. Air concentrations of PAHs in China, Vietnam and India were greater than those in Japan and South Korea. As expected, the air concentrations (ng/m~3) were highest at urban sites (143±117) followed by rural (126±147) and background sites (22.4±11.4). In Chinese and India air, higher concentrations of PAHs was found in the east part of country with relatively denser population, traffic-congest, and higher industrial activities, and declined from east to west. In Vietnam, the highest levels of PAHs were measurement in more developed and populated zone, but it was geographically uniform in Japan and South Korea. Significant positive correlations were found between PAH concentrations and atmosphere aerosol optical depth.PAHs were also analyzed in 169 concurrently collected soil samples in 2012 across China, Japan, South Korea, Vietnam and India. In terms of the compositional profiles of PAHs, benzo(b)fluoranthene was the most abundant compound found in most soil samples, followed by fluoranthene, phenatherene, and pyrene. The annual concentrations of total 47 PAHs at all sites ranged from 13.1 to 7310 ng/g dw with mean of 128 ng/g dw. Higher concentrations of ?PAHs were found in urban soil, follow by rural and background soil, similar to the distribution pattern in air. Compared with the published data, the PAHs pollution levels in present study were similar to those in Africa, and much lower than those in Europe. Significant positive correlations were found between PAH concentrations and soil organic matter for China, South Korea, Vietnam and India, while the distribution of PAHs in Japanese soil were influenced by the population density and air PAHs concentrations in this country.The soil-air exchange of PAHs was investigated by calculating the flux of PAHs between air and soil using fugacity model in the study areas. Differences in soil-air exchange patterns were observed for different PAH congeners and in different seasons. The main soil-air exchange trend was volatilization for 2-ring PAHs, but deposition for 5-and 6-ring PAHs in whole study regions and in all the seasons.. For the 3- & 4-ring PAHs tendenciesof accumulation in soils in cold regions/seasons and re-volatilization to atmosphere in warm regions/seasons were observed. It was found that air temperature was the most important factor affecting the exchange direction of PAHs between soil and air.Using "Equivalent Toxicity Coefficient", the average benzo(a)pyrene equivalent concentration (BaPeq) was calculated to be 5.61 ng/m~3 in the five countries It was estimated that the annual BaPeq concentrations at 78.8% of the sampling sites exceeded the WHO guideline level. The overall population attributable fractions (PAFs) for lung cancer due to inhalation exposure to outdoor PAHs were 8.8‰ (0.056‰-52‰) for China,7.5‰ (0.26‰-27‰) for Vietnam,3.2%o (0.047‰-20‰) for India,0.85%o (0.042‰-4.5‰) for South Korea, and 0.38‰ (0.007‰-3.2‰) for Japan. We estimated the numbers of lifetime excess lung cancer cases caused by exposure to PAHs ranged from 27.8 to 2,200,1.36 to 108,2.45 to 194,21.8 to 1,730, and 9.10 to 720 per million people for China, Japan, South Korea, Vietnam and India, respectively. Overall, the lung cancer risk in China and Vietnam were higher than in Japan, South Korea and India. |
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