Organic Contaminants’ Dermal Uptake, Air-water Gas Exchange And Anthropogenic Debris-mediated Distribution

The interfacial behavior is the driving force for the inter-compartmental mass transfer and dictates the geochemical process of organic contaminants at the regional and global scales. In the present study, dermal uptake from airborne organics, air-water gas exchange and anthropogenic debris-mediated distribution were conducted. First, atmospheric sizefractioned particle and gaseous samples were collected near an outdoor-barbecuing vendor stall(along with charcoal-grilled food items) in Xinjiang of Northwest China with a 10-stage Micro-Orifice Uniform Deposit Impactor and a PUF sampler and were analyzed for particulate matter and polycyclic aromatic hydrocarbons(PAHs). Examine the relative importance of inhalation, dermal contact and food ingestion in the human exposure routes. Furthermore, assess the potential human health risk associated with barbecue fume exposure in outdoor-barbecuing settings. Second, review available information about dermal exposure to chemicals via direct air-to-skin transfer. To examine the relative importance of inhalation and dermal contact as the human exposure pathways for residents dwelling in e-waste zones with extended exposure to outdoor air pollutants. Third, characterized concentration or fugacity profiles of hydrophobic organic contaminants near both sides of the air-water interface, obtained by the passive sampling device with relatively high resolution. Last, examine how antifouling paint flakes and other anthropogenic debris mediate the distribution patterns of the dichlorodiphenyltrichloroethanes(DDT) and its metabolites, organophosphorus flame retardants(OPFRs), phthalates(PAEs) and organotin compounds(OTs) in estuarine sediment.The highest levels of PM10, PM2.5, BaP and total PAHs were found at 2 m from the stove. The concentrations of PM10, PM2.5 and BaP(900–5300 μg m-3, 700–4100 μg m-3 and 7.2–8.8 ng m-3, respectively) near the stove exceeded the national ambient air quality standards of China. The average concentration of PAHs in charcoal-grilled foods(0.9±0.5 ng g-1 of BaPeq) were lower than 5 ng g-1, the European Commission‘s standard for smoked and grilled meat.Deposition efficiency and fluxes of particle-bound PAHs in the adult male‘s respiratory tract were calculated using measured size-fractioned concentrations of inhaled PAHs and the ICRP model. The results show that more than 90% of the amounts of ∑16PAH deposited in the bronchial region(BB), bronchiolar region(bb), and alveolar-interstitial region(AR) of the human respiratory tract were contributed by ?ne particles(aerodynamic diameter of <1.8 μm). Furthermore, exposure to PAHs through inhalation and dermal contact by consumers who spent one hour per day near a charcoal-grilled vendor for a normal meal(lunch or dinner) amounted to a Ba P equivalent(BaPeq) dosage of 3.0–77 ng d-1(inhalation: 2.8–27 ng d-1 of BaPeq; dermal contact: 0.2–50 ng d-1 of BaPeq), comparable to those(22–220 ng d-1 of BaPeq) through the consumption of charcoal-grilled meat assumed to be at the upper limit of 50–150 g. In addition, the potential health risk was in the range of 3.1×10-10–1.4×10-4 for people of different age groups subjected to inhalation and dermal contact exposure to PAHs once a day, with the 95% confidence intervals(1.2×10-8–1.2×10-5) comparable to the lower limit of the potential cancer risk range(1×10–6–1×10–4). These results indicated that outdoor exposure(particularly dermal contact) to BBQ fume may have become a significant but largely neglected source of health hazards to the general population and should be well recognized.Skin absorption of gaseous organic contaminants is an important and relevant mechanism in human exposure to such contaminants, but has not been adequately examined. We demonstrates that dermal uptake from airborne contaminants could be recognized as a significant exposure route for local residents subjecting to combustion fume from e-waste recycling activities. For example, the daily dermal intake of gaseous BDE-47 and BDE-99 through air-mediated transfer by adults in Guiyu, an e-waste recycling site, were 0.65 and 0.61 ng kg-1 d-1, respectively, during the warm period(September), exceeding those via inhalation of both gaseous and particle-bound BDE-47(0.55 ng kg-1 d-1) and BDE-99(0.33 ng kg-1 d-1). Thus, dermal uptake from airborne pollutants should be regarded as a significant pathway for human exposure to e-waste combustion fume, particularly for volatile organic pollutants with high dermal penetration rates or with low dermal penetration rates but abundant contents during e-waste combustion.Herein, we introduce a novel passive sampling device which is capable of measuring concentration(and therefore fugacity) gradients of hydrophobic organic contaminants across the air-water interface. Laboratory studies indicated that the fugacity values of polycyclic aromatic hydrocarbons(PAHs) from water to air were positively correlated to their volatilization half-lives. Results for field deployment were consistent between the passive sampler and an active method, i.e., a combination of grab sampling and liquid-liquid extraction. In general, the fugacity profiles of detected PAHs were indicative of an accumulation mechanism in surface microlayer in the study regions(Haizhu Lake and Hailing Bay of Guangdong Province, China), while p,p’-DDD tended to volatilize from water to the atmosphere in Hailing Bay. Furthermore, the fugacity profiles of the target analytes generally decreased and then increased towards the air-water interface, reflecting the complexity of environmental behavior of the target analytes near the air-water interface. Overall, the passive sampling device provides a novel mean to better characterize the airwater diffusive transfer of hydrophobic organic contaminants, facilitating the understanding of the global cycling of hydrophobic organic contaminants.Recently published literature indicated that dichlorodiphenyltrichloroethane(DDT)-containing antifouling paint flakes were heterogeneously distributed within estuarine sediments. However, the significance of antifouling paint flakes in the fate and transport of DDT compounds and other organic pollutants in estuarine sediment is yet to be adequately addressed. To fill this knowledge gap, estuarine sediment and paint flakes from cabin and boat surfaces were collected from a fishery base in Guangdong Province of South China and analyzed for DDT compounds. Coarse fractioned samples collected from the vicinity of boat maintenance facilities contained appreciable amounts of colorful particles, which were identified as paint flakes by Fourier transform infrared spectroscopy. The highest concentrations of DDXs(sum of DDTs and its metabolites) occurred in the heavy-density(>1.7 g cm-3) fraction of coarse-size(200–2000 μm) sediments from near the boat maintenance facilities, suggesting the importance of paint flakes in the distribution pattern of ―hot spots‖ in estuarine sediment. Moreover, the desorption rates of DDT compounds from paint flakes and the heavy-density fraction of coarse-size sediment were both extremely slow. Apparently, unevenly distributed paint flakes in sediment can artificially inflate the sorption capacity of heavy-density sediment for DDT compounds, and therefore can substantially change the environmental fate and behavior of hydrophobic organic chemicals in estuarine sediment. Finally, commonly used source diagnostic indices of DDT compounds were mostly grain-size and density dependent in sediment, as a result of the occurrence of paint flakes, which may strongly compromise the outcome of any source diagnostics efforts.Increasing evidence suggested that manufactured debris may alter the underlying mechanisms for biogeochemical cycling of organic compounds. To examine this assumption, estuarine sediment and embedded debris were collected from a fishery base in Guangdong Province of South China and analyzed for organophosphorus flame retardants(OPFRs), phthalates(PAEs) and organotin compounds(OTs). Coarse-size debris(> 200 μm) were heterogeneously distributed in sediment, and most abundant near the boat maintenance facilities, aquaculture zone and shipping channel. The median concentrations of OPFRs, OTs, PAEs and dichlorodiphenyltrichloroethanes in debris were 11, 0.2, 11 and 3.9 μg g-1 dry sample weight-1, respectively, 1 to 3 orders of magnitude greater than those in bulk sediment(19, 60, 240 and 570 ng g-1 dry sample weight-1, respectively). Furthermore, OPFRs, OTs and PAEs were mostly(> 99%) enriched in coarse-size(63–2000 μm) sediment, and there was no significant correlation(p > 0.05) between the concentrations of OPFRs, OTs and PAEs in bulk and size-fractioned sediment samples and total organic carbon or grain size. When distinct debris were removed from the light-density(<1.7 g cm-3) fraction of coarsesize(200–2000 μm) sediment, the concentration levels of OPFRs, OTs, PAEs and DDTs declined by 84%, 59%, 55% and 7%, respectively. Obviously, debris irregularly distributed in sediment can alter the sediment sorption capacity for OPFRs, OTs and PAEs, and thus may undermine the significance of organic matter and grain size to the distribution of organic chemicals in sediment. Finally, commonly used procedures for preparing sediment samples and screening of debris may disturb the grain size distribution or underestimate the abundance of heavy-density debris, resulting in flawed sediment quality assessment.