Size-resolved gas-particle partitioning characteristics of typical semi-volatile organic compounds in urban atmosphere.

Understanding particle size distribution and size-resolved gas-particle partitioning of semi-volatile organic compounds (SVOCs) is important for characterizing their fate in atmosphere. However, the size-resolved gas-particle partitioning characteristics of SVOCs has not been adequately considered. To address this issue, the present study collected gaseous and size-fractioned particulate samples both in and outside of schools, offices, and residences in three districts of different urbanization levels in a megacity, Guangzhou, South China during two seasons. Typical SVOCs, including 15 polycyclic aromatic hydrocarbons (PAHs), six organophosphate esters and seven phthalic acid esters were measured. Emission sources, physicochemical properties, and environmental conditions at the sampling sites considerably impacted the spatiotemporal distribution patterns and particle size distribution of target SVOCs. Not all observed gas-particle partition coefficients (Kp) of target SVOCs were negatively correlated with subcooled liquid-vapor pressures (PL0), probably because certain factors, such as the non-exchangeable part of the particle-bound SVOCs, were not considered in traditional gas-particle partition theories. Particle size was an important factor affecting gas-particle partitioning. Adsorption was the dominant mechanism for PAHs with high molecular weight in different particle modes. A new model was established to predict size-resolved Kp of PAHs with high molecular weight based on PL0 and particle size.

A comprehensive risk assessment of human inhalation exposure to atmospheric halogenated flame retardants and organophosphate esters in an urban zone.

Inhalation exposure to flame retardants used as additives to minimize fire risk and plasticizers is ubiquitous in human daily activities, but has not been adequately assessed. To address this research gap, the present study conducted an assessment of human health risk for four age groups through inhalation exposure to size fractionated particle-bound and gaseous halogenated flame retardants (polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs)) and organophosphate esters (OPEs) at indoor and outdoor environments (school, office, and residence) in three districts of a megacity (Guangzhou, China). Results demonstrated that OPEs were the dominant components among all targets. Indoor daily intakes of PBDEs and OPEs were 13-16 times greater than outdoor levels for all age groups. Gaseous OPEs contributed significantly greater than particle-bound compounds to daily intakes of all target compounds. Based on the different life scenarios, hazard quotient (HQ) and incremental life cancer risk (ILCR) from adults exposure to PBDEs and OPEs in indoor and outdoor settings were the greatest, followed by adolescents, children, and seniors. The estimated HQ and ILCR for all age groups both indoors and outdoors were lower than the safe level (HQ = 1 and ILCR = 10-6), indicating that the potential health risk for local residents in Guangzhou via inhalation exposure to atmospheric halogenated flame retardants and OPEs was low.

Assessment of airborne polycyclic aromatic hydrocarbons in a megacity of South China: Spatiotemporal variability, indoor-outdoor interplay and potential human health risk.

Although a number of studies have assessed the occurrence of atmospheric polycyclic aromatic hydrocarbons (PAHs) in indoor environment, few studies have systemically examined the indoor-outdoor interplay of size-dependent particulate PAHs and potential health risk based on daily lifestyles. In the present study, size-dependent particle and gaseous samples were collected both indoors and outdoors within selected schools, offices and residences located in three districts of Guangzhou, China with different urbanization levels during the dry and wet weather seasons. Results from measurements of PAHs showed that higher total PAH concentrations occurred in residential areas than in other settings and in indoor than in outdoor environments. Compositional profiles and size distribution patterns of particle-bound PAHs were similar indoors and outdoors, predominated by 4-and 5-ring PAHs and the 0.56-1.0 µm particle fraction. Statistical analyses indicated that outdoor sources may have contributed to 38-99% and 62-100% of the variations for indoor particle-bound and gaseous PAH concentrations, respectively. Incremental life cancer risk (ILCR) from human exposure to indoor and outdoor PAHs based on different lifestyles followed the order of adults > children > adolescents > seniors. All average ILCR values for four age groups were below the lower limit of the Safe Acceptable Range (10-6). In addition, the ILCR value for adults (average: 7.2 × 10-7; 95% CI: 5.4 × 10-8‒2.5 × 10-6), estimated from outdoor air PAH levels with 24-h exposure time, was significantly higher than our assessment results (average: 5.9 × 10-7; 95% CI: 6.3 × 10-8‒1.9 × 10-6), suggesting the significance of assessing human inhalation exposure risks of indoor and outdoor PAHs in urban air based on daily lifestyles.

Occurrence of halogenated flame retardants in sediment off an urbanized coastal zone: association with urbanization and industrialization.

To examine the impacts of urbanization and industrialization on the coastal environment, sediment samples were collected from an urbanized coastal zone (i.e., Daya Bay and Hong Kong waters of South China) and analyzed for 20 polybrominated diphenyl ethers (PBDEs) and 10 alternative halogenated flame retardants (AHFRs). The sum concentration of PBDEs was in the range of 1.7-55 (mean: 17) ng g(-1), suggesting a moderate pollution level compared to the global range. The higher fractions of AHFRs (i.e., TBB+TBPH, BTBPE and DBDPE) than those of legacy PBDEs (i.e., penta-BDE, octa-BDE and deca-BDE) corresponded with the phasing out of PBDEs and increasing demand for AHFRs. Heavy contamination occurred at the estuary of Dan'ao River flowing through the Daya Bay Economic Zone, home to a variety of petrochemicals and electronics manufacturing facilities. The concentrations of HFRs in surface sediments of Hong Kong were the highest in Victoria Harbor, which receives around 1.4 million tons of primarily treated sewage daily, and a good relationship (r(2) = 0.80; p < 0.0001) between the HFR concentration and population density in each council district was observed, highlighting the effect of urbanization. Moreover, the AHFR concentrations were significantly correlated (r(2) > 0.73; p < 0.05) with the production volume of electronic devices, production value of electronic industries and population size, demonstrating the importance of industrializing and urbanizing processes in dictating the historical input patterns of AHFRs.

Correlation between genomic DNA copy number alterations and transcriptional expression in hepatitis B virus-associated hepatocellular carcinoma.

Human hepatocellular carcinoma (HCC) is one of the most common tumors worldwide, in which the genetic mechanisms of oncogenesis are still unclear. To investigate whether the genomic DNA copy number alterations may contribute to primary HCC, the cDNA microarray-based comparative genomic hybridization (CGH) analysis was here performed in 41 primary HCC infected by hepatitis B virus and 12 HCC cell lines. The resulting data showed that, on average, 7.25% of genome-wide DNA copy numbers was significantly altered in those samples (4.61+/-2.49% gained and 2.64+/-1.78% lost). Gains involving 1q, 6p, 8q and 9p were frequently observed in these cases; and whilst, losses involving Ip, 16q and 19p occurred in most patients. To address the correlation between the alteration of genomic DNA copy numbers and transcriptional expression, the same cDNA microarray was further applied in 20 HCC specimens and all available cell lines to figure out the gene expression profiles of those samples. Interestingly, the genomic DNA copy number alterations of most genes appeared not to be in generally parallel with the corresponding transcriptional expression. However, the transcriptional deregulation of a few genes, such as osteopontin (SPP1), transgelin 2 (TAGLN2) and PEG10, could be ascribed partially to their genomic aberrations, although the many alternative mechanisms could be involved in the deregulation of these genes. In general, this work would provide new insights into the genetic mechanisms in hepatocarcinogenesis associated with hepatitis B virus through the comprehensive survey on correlation between genomic DNA copy number alterations and transcriptional expression.