| Indoor environment is main space for human daily life, and also a place where human expose to different hazardous substances. Hazardous substances in indoor environment may have a negative impact on human health through non-dietary ingestion, including indoor air inhalation, dust ingestion and dust dermal absorption, and the route of exposure has a higher influence on children than adults. PAHs have become a hot research topic for their harmful to human health. In China, up to now, research on PAHs in indoor environment is mainly concentrated in some special polluted areas, such as e-waste sites, but little in common indoor environment. In this research, 81 indoor dust samples were collected from 23 provinces of China from different types of indoor environment,including 45 family homes and 36 non family homes (including public places, laboratories and offices), and the concentration, spatial distribution characteristic, composition and sources of PAHs in these samples were studied. In addition,12 dust and air samples were concurrently gathered in same indoor environment,and the correlationship,composition,level of exposure to human and cancer risk were investigated.Three extraction methods-ultrasonic extraction, soxhlet extraction and microwave extraction-were compared. Short extraction time, low extraction solvent and higher recovery method were used in this study.Through the research we find that the concentration of PAHs in indoor dust is ranged from 1.0 to 470μg/g dry weight in China, which is moderate compared to other countries. The concentration of PAHs of indoor dust in family homes is higher than public places, and lower than offices. The higher PAHs level in indoor dust was found in northeast and north areas, and lower in south, and has no significant difference between urban and rural family homes. High-molecular weight PAHs (≧4 ring) are predominant PAHs in indoor dust, 68% of the total PAHs in family homes, and 84.6% of the total PAHs in non family homes. 4 ring PAHs is the main compounds in family homes, while 5 ring PAHs in non family homes. The results of analysis by using diagnostic ratios and principal component analysis (PCA) indicate that there are different sources of PAHs for different types of indoor environment. The PAHs were mainly from pyrogenic sources and petrogenic sources from outside and cooking sources from inside in both urban and rural family homes. The outdoor sources were the main sources in public place.Opsite to the case in indoor dust, PAHs in air is mainly low ring compounds, and 2 and 3 ring PAHs account for 85% in total PAHs, among which phenanthrene, fluorine and naphthane were the most predominant PAHs. The concentration of PAHs in indoor air and dust have significant logarithmic correlation. The concentrations of PAHs in indoor air in China were ranged from 15.0 to 73.1 ng/m3, which was calculated by logarithmic correlation in indoor air and dust.The trend of human exposure to PAHs by dust ingestion, indoor air inhalation and dust dermal absorption increased along with the ages of the residences. For infants, the total absorption of PAHs in indoor environment was 4 to 5 times higher than adults. Among three absorption ways metioned above, the dust ingestion was dominated, followed by the indoor air inhalation and the dust dermal absorption, and the dust dermal absorption was two order of magnitude lower than other two ways. The BaP has the highest cancer toxicity in indoor dust followed by BaA and DahA, and Acy and Ace had the lowest cancer risk. The cancer risks of PAHs in indoor dust were also increased along with ages similar to human exposure. The infants have the highest cancer risk, which was 2 order of magnitude higher than adults. Compared with guidelines of cancer risk, we find that the cancer risks of PAHs for youths, callans and adults were in a lower level, but for infants, it was in a higher but still moderate level. |
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