Polycyclic aromatic hydrocarbon exposure, oxidative potential in dust, and their relationships to oxidative stress in human body: A case study in the indoor environment of Guangzhou, South China.

A comparative study of internal and external exposure is a good method to comprehensively understand human exposure to environmental contaminants that may trigger oxidative stress in human body. Information is limited regarding the influences of reactive oxygen species (ROS) on human health from the environment. In addition, data on the contribution of polycyclic aromatic hydrocarbons (PAHs) from indoor environments, especially air, to total human exposure are still insufficient. The present study measured PAHs in paired indoor dust (n = 101), gas (polyurethane foams, n = 100), and particle samples (quartz fiber filters, n = 100) and their hydroxy metabolites (OH-PAHs) in 205 urine samples from 101 families in Guangzhou, South China. The oxidative potential (OP) in dust samples was quantified with a dithiothreitol (DTT) assay to reflect the oxidizability of ROSs, and explore the relationship between environmental ROSs and oxidative stress in humans (using urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a biomarker). The estimated daily intakes (EDIs) of Σ16PAH via air inhalation were much higher than those from gas dermal contact, dust dermal contact, and dust ingestion (mean: 19.5 > 4.27 > 3.75 > 1.60 ng/kg_bw/day). Generally, approximately 16% of naphthalene, 28% of fluorene, 9% of phenanthrene, and 3% of pyrene were derived from indoor environments for all residents when compared with the total PAH exposure amount from all sources. Significantly positive relationships were found between OH-PAHs and 8-OHdG (coefficients ß: 0.129-0.366, p < 0.05) checked by linear mixed effect models, and males seemed to be more susceptible than females to the DNA oxidative damage related to PAH exposure. The mean OP value in dust was 7.14 ± 6.68 pmol/(min·µg). Individual PAHs in dust gradually intensified the oxidizability of dust particles as their molecular weight increased. A potential but not significant dose-relationship was found between dusty OP and urinary 8-OHdG. Further work should determine the impact of chemical profiles on OP in different environmental media and continuously explore the potential to use OP as a useful indicator to reflect the total oxidizability of several groups of environmental pollutants.

[Ozone Pollution Trend in the Pearl River Delta Region During 2006-2019].

Based on the monitoring data of the Guangdong-Hong Kong-Macao Pearl River Delta Regional (PRD) Air Quality Monitoring Network from 2006 to 2019, the ozone trend in RRD was analyzed using the Mann-Kendall test method, Sen's slope method, and the Pettitt change point test. The results show that:① the average ozone concentration in the PRD has increased significantly from 2006 to 2019 (P<0.05), with an average growth rate of 0.80 µg·(m3·a)-1. After 2016, the rate of ozone increase has accelerated. ② The average annual ozone concentration in the central PRD increased significantly, while in the peripheral areas of the PRD, this is not obvious. Ozone increases significantly in summer but not in other seasons.③ From 2006 to 2019, the concentration of NO2 in the central PRD decreased remarkably, so the titration effect weakened and resulted in an increase in the ozone concentration. The concentration of NO2 in the marginal areas of the PRD has little change, so the ozone concentration in these areas has little change. ④ With the changes of VOCs and NO2 concentrations, the chemical sensitivity of O3 production in the PRD is changing. The VOC-limited regimes are continuously decreasing, and the mixed NOx-VOC-limited regimes and NOx-limited regimes are increasing. In order to deal with regional ozone pollution, the cooperative control of VOCs and NOx needs to strengthen.

Levels and sources of PBDEs and PCBs in human nails from e-waste, urban, and rural areas in South China.

Human nails have been increasingly used as a biomarker for human exposure to persistent organic pollutants (POPs). In the present study, the fingernails of e-waste-dismantling workers from Longtang town, Qingyuan city, rural residents from Shijiao town, Qingyuan city, and urban residents from Guangzhou city, respectively, were collected from South China to monitor the human burdens of polybrominated diphenyl ether (PBDEs) and polychlorinated biphenyl (PCBs). The median concentrations of in the nails of the e-waste-dismantling workers, and urban and rural residents were 412, 129, and 82.1 ng g-1, respectively, and the median concentrations of were 108, 8.4, and 22.1 ng g-1, respectively. The levels of PCBs and PBDEs in the nails of e-waste-dismantling workers were significantly higher as compared to those for urban and rural residents (p < 0.05), implying the continuous and greater exposure to these chemicals in the e-waste recycling areas. BDE 209 (92-98%) was the major congener of PBDEs and CB 52 (26-51%) was the main congener of PCB in nail samples. However, no significant gender difference was observed for PBDE and PCB levels in nails from all three investigated areas, and no significant correlation was found between their levels and the age of the participants. The enantiomer fractions (EFs) of CBs 95 and 132 indicated that the external sources (e.g. dust and/or air) were the primary sources for CBs 95 and 132 in human nails from the e-waste area, while the contribution from the internal sources (e.g. serum) could be in a small percentage. The results of this study indicate that human nails can be used as a proper indicator of human exposure to PCBs and PBDEs, and further studies are needed by a comprehensive investigation of the relationships between the PCB and PBDE levels in the nails and serum and/or other internal tissues.

[Impact of Meteorological Factors on the Ozone Pollution in Hong Kong].

Based on ozone monitoring and meteorological data from 2000 to 2015 in Hong Kong, the characteristics of ozone pollution and the influence of meteorological factors on the ozone pollution were analyzed. The results show that:① A seasonal variation of the ozone concentration in Hong Kong is notable:autumn > spring > winter > summer. Days of ozone exceeding the standard value are concentrated in summer and autumn and rarely occur in winter and spring. ② The annual mean ozone concentration of the maximum daily 8-h average (MDA8) in Hong Kong increases from 2000 to 2015, with an average growth rate of 0.77 µg·(m3·a)-1. The 90th percentile concentration of the ozone MDA8 also increases, with an average rate of 1.49 µg·(m3·a)-1. ③ Higher temperatures are necessary for ozone pollution in Hong Kong. The higher the temperature is, the more ozone pollution likely occurs. ④ In most cases, the ozone concentration is negatively correlated with the relative humidity. The higher the relative humidity is, the lower are the ozone and 90th percentile concentrations in Hong Kong. ⑤ When ozone pollution occurs in Hong Kong, prevailing winds tend to shift from northerly or easterly to westerly. In addition, with the increase of the wind speed, the average ozone concentration changes little, but the 90th percentile ozone concentration significantly decreases. ⑥ Precipitation and cloud cover are important factors affecting the ozone concentration. Weather conditions without or with little rain for many consecutive days are necessary for the occurrence of ozone pollution events. However, with the increase of the cloud cover, the average ozone and 90th percentile concentrations continue to decrease. ⑦ In the case of a total solar radiation ≤ 20 MJ·m-2 or sunshine duration ≤ 10 h, the ozone concentration is positively correlated with the solar radiation and sunshine duration. However, in the case of intense solar radiation (total solar radiation>20 MJ·m-2 or duration of sunshine>10 h), the ozone concentrations decrease with increasing solar radiation or duration because strong solar radiation often occurs in the background of sunny weather after rain. At the same time, southerly winds from the sea often prevail, making it difficult for ozone pollution to occur in Hong Kong. ⑧ Ozone excess days in Hong Kong are often accompanied by changes of a series of meteorological conditions including less rain on sunny days, stronger radiation, higher boundary layer height, lower relative humidity, smaller wind speeds, and higher temperatures. The end of the pollution process is accompanied by the opposite weather changes.