Implications of seasonal control of PM2.5-bound PAHs: An integrated approach for source apportionment, source region identification and health risk assessment.

PM2.5-bound PAHs are ubiquitous in urban atmospheres and are characterized as carcinogenic, teratogenic and mutagenic upon inhalation. A total of 218 daily PM2.5 samples were collected during one year in the urban district of Beijing, China. Analysis showed that the annual mean concentration of total PAHs (TPAHs) was 66.2 ng/m3, with benzo(a)pyrene (BaP) accounting for 12.4%. High-molecular-weight (HMW, 4-6 rings) PAHs were the dominant components. Seasonal TPAH concentrations decreased in the order of heating season (156 ng/m3) > autumn (20.4 ng/m3) > spring (16.0 ng/m3) > summer (12.5 ng/m3) and were related to meteorological conditions and source emission intensity. The source-attributed mass contribution and source regions of three sources (i.e., (1) vehicle emissions; (2) coal combustion; and (3) petroleum volatilization, natural gas and biomass combustion) were identified by integrating the positive matrix factorization (PMF), potential source contribution function (PSCF) and conditional probability function (CPF). Vehicle emissions contributed the most mass (54.6%), followed by coal combustion (29.8%), on an annual basis. Combined with actual regional emissions, vehicle emissions were mainly derived from local sources, while coal combustion mainly came from regional transport from surrounding areas. Vehicle emissions and coal combustion have much higher mass contributions in the heating season. The source-attributed cancer risk was further evaluated based on source mass contribution and inhalation unit risk. Vehicle emissions contributed the largest risk (2.8 × 10-6, accounting for 71%) as a result of 30 years of exposure for local residents, exceeding the acceptable level (10-6). The heating season showed the most risk, especially in response to vehicle emissions and coal combustion. Overall, the source-attributed cancer risk was regarded as the better index for the development of a control strategy of PM2.5-bound PAHs for protecting residents. Based on this index, priority control sources in each season were identified to supply a more effective management solution.

Levels and health risks of PM2.5-bound toxic metals from firework/firecracker burning during festival periods in response to management strategies.

Daily PM2.5 was collected in the periods before, during and after the Chinese Spring Festival (CSF) in both 2016 and 2018 to clarify the annual variation in the concentrations and health risks of toxic metals under different firework/firecracker (FF) management strategies. PM2.5 and bound metals all decreased during the CSF from 2016 to 2018. According to relative abundance analysis, toxic metals, i.e., Ba, Pb, Cu and Cr, showed obvious peak concentrations and abundance levels on intensive FF burning days, i.e., New Year's Eve, Chinese New Year and the Lunar Festival. In both CSF periods, three sources of toxic metals, namely, FF burning, coal combustion, and resuspended dust and vehicle emissions, were identified by positive matrix factorization (PMF). Among them, the mass contribution of FF decreased from 0.83 µg m-3 (11%) in the 2016 CSF to 0.23 µg m-3 (9.0%) in the 2018 CSF. The FF-attributed noncancer and cancer risks due to metals for residents under long-term exposure were 0.02 (19.9%) and 1.76 × 10-7 (17.9%) in the 2016 CSF and 0.01 (20.2%) and 8.59 × 10-8 (14.7%) in the 2018 CSF. Although a policy shift from "restriction" to "prohibition" regarding FF has indeed decreased toxic metal concentrations and health risk, Cr(VI) and Ba should be examined more closely in the future because they have become dominant contributors to cancer risk and noncancer risk, respectively.

Emission control priority of PM2.5-bound heavy metals in different seasons: A comprehensive analysis from health risk perspective.

Source-specific health risks of PM2.5-bound metals were analyzed for emission control by integrating source apportionment with health risk assessments of residents affected via inhalation pathways. A total of 218 daily PM2.5 samples were collected in 2016 in the central urban district of Beijing, China. Analyses showed that the mean annual concentrations of total heavy metals (THMs) and PM2.5 were 0.39 and 104.37 µg m-3, respectively. The heating season had significantly higher concentrations of THMs and PM2.5 (0.61, 134 µg m-3) than the non-heating season (0.27, 88.1 µg m-3) (p < 0.05). Among all metals, arsenic had the largest incremental cancer risk of 7.04 × 10-6. Six sources were identified by positive matrix factorization combined with conditional probability function and potential source contribution function analyses. The order of contribution to PM2.5-bound metal concentrations was resuspended dust (61.0%), traffic emission (16.3%), Cu-related industry (14.1%), coal combustion (3.7%), Cr-related industry (3.4%), and fuel oil combustion (1.6%). During the heating season, the contribution of coal combustion decreased slightly, which may have been due to the countermeasure of substituting coal for gas or electric heat in 2016. However, in terms of cancer risk contribution, coal combustion was the top contributor in both heating (3.5 × 10-6, 51.6%) and non-heating (2.7 × 10-6, 59.6%) seasons due to high attributable contents of the toxic metals, As, Cd and Pb. The Cr-related and Cu-related industries were the next controlled sources in the heating and non-heating seasons, respectively. Thus, these sources should receive priority in the development of control measures.

Determination of arsenic speciation and the possible source of methylated arsenic in Panax Notoginseng.

Arsenic species and a possible source of methylated arsenic in a Panax Notoginseng (PN) medicinal plant were explored to further understand the change of inorganic arsenic to the less toxic methylated form to minimize the health risks associated with its medicinal use. Arsenic speciation in PN from major planting areas was determined using high-performance liquid chromatography coupled with hydride generator-atomic fluorescence (HPLC-HG-AFS). Pot experiments were performed to explore the source of methylated arsenic in PN, and the arsenite methyltransferase (arsM) gene abundance was determined using quantitative reverse transcription PCR (q-RTPCR). Methylated arsenic (monomethylarsonic acid (MMA) + dimethylarsinic acid (DMA)) accounted for 43% ± 30% of the total arsenic in PN from planting areas, while the primary species in soil was As(V) (94% ± 0.12%). In the pot experiments, methylated arsenic accounted for 37%-49% of the total arsenic in PN, and As (V) was the primary species in soil (>98%). The four detected arsenic species in PN increased as the amount of As added to soil increased. The methylated arsenic contents in the PN root were significantly positively correlated with the ArsM gene abundance in soil, suggesting that methylated arsenic in PN is likely from the planting soil.

Source apportionment and health risk assessment of heavy metals in soil for a township in Jiangsu Province, China.

Human activities contribute greatly to heavy metal pollution in soils. Concentrations of 15 metal elements were detected in 105 soil samples collected from a typical rural-industrial town in southern Jiangsu, China. Among them, 7 heavy metals-lead, copper, zinc, arsenic, chromium, cadmium, and nickel-were considered in the health risk assessment for residents via soil inhalation, dermal contact, and/or direct/indirect ingestion. Their potential sources were quantitatively apportioned by positive matrix factorization using the data set of all metal elements, in combination with geostatistical analysis, land use investigation, and industrial composition analysis. Furthermore, the health risks imposed by sources of heavy metal in soil were estimated for the first time. The results indicated that Cr, Cu, Cd, Pb, Ni, and Co accumulated in the soil, attaining a mild pollution level. The total hazard index values were 3.62 and 6.11, and the total cancer risks were 9.78 × 10-4 and 4.03 × 10-4 for adults and children, respectively. That is, both non-carcinogenic and carcinogenic risks posed by soil metals were above acceptable levels. Cr and As require special attention because the health risks of Cr and As individually exceeded the acceptable levels. The ingestion of homegrown produce was predominantly responsible for the high risks. The potential sources were apportioned as: a) waste incineration and textile/dyeing industries (28.3%), b) natural sources (45.4%), c) traffic emissions (5.3%), and d) electroplating industries and livestock/poultry breeding (21.0%). Health risks of four sources accounted for 23.5%, 32.7%, 7.4%, and 36.4% of the total risk, respectively.

Urbanization-related changes in soil PAHs and potential health risks of emission sources in a township in Southern Jiangsu, China.

Urbanization, which is characterized by population aggregation, industrial development, and increased traffic load, may change local polycyclic aromatic hydrocarbons (PAH) emissions and their associated health risks. To investigate these changes, we collected soil samples in 2009 and 2014 in a rapidly developing small town in Southern Jiangsu (China) and measured the concentrations of 16 PAHs via gas chromatography-mass spectrometry. Although the total PAHs decreased from 4586.6 to 640.6ng/g, the concentrations of the high-molecular-weight PAHs benzo(b)fluoranthene and benzo(a)pyrene increased due to changes in the PAH sources. Source apportionment by positive matrix factorization indicated that the two sources responsible for the highest soil PAH contributions changed from biomass combustion (42%) and coal combustion (32%) in 2009 to coal, biomass and natural gas combustion (35%) and diesel combustion (33%) in 2014. However, the two sources with the highest associated health risks were diesel and gasoline combustion in both years. The incremental lifetime cancer risk for residents exposed to PAHs in the soil via incidental ingestion and dermal contact decreased from 1.75×10-6 to 1.60×10-6. The ban on open burning of straw and the substitution of coal with natural gas offset the PAH health risks due to increased urbanization.

Levels of arsenic pollution in daily foodstuffs and soils and its associated human health risk in a town in Jiangsu Province, China.

The development of industries in rural areas can aggravate the arsenic (As) contamination of the local environment, which may pose unacceptable health risks to the local residents. This paper estimated the health risk posed by inorganic As (iAs) to residents via ingestion of soil, skin contact with soil and consumption of foodstuffs in a typical rural- industrial developed town in southern Jiangsu, China. The average concentrations of total As in soil, rice, fish, shrimp and crab, pork and eggs, vegetables and fruits were detected to be 10.367, 0.104 mg/kg dw (dry weight), 0.050, 0.415, 0.011, 0.013 and 0.017 mg/kg fw (fresh weight), respectively. All of these values are below the maximum allowable concentration in food and soil in China. The deterministic estimation results showed that the hazard quotient (HQ) and excess lifetime cancer risk (R) were 1.28 (0.78-2.31) and 2.38 × 10(-4) (2.71 × 10(-5)-5.09 × 10(-4)) for all age groups, respectively. Males in the age range of 2-29 years and females in the age range of 2-13 years and 18-29 years exhibited non-carcinogenic risk (HQ>1). Carcinogenic risk exceeded the acceptable level of 1 × 10(-)(5) for both genders at all ages. Furthermore, this risk rose with age. The probabilistic estimation results showed that about 28% of residents had non-carcinogenic risk due to over ingestion of iAs. The R value of 90% of residents was greater than 10(-)(5). The sensitivity analysis indicated that the cancer slope factor (SF), the ingestion rates of rice and the iAs concentration in rice were the most relevant variables affecting the assessment outcome. Based on these results, it is recommended that residents reduce their consumption of rice, though it should be noted that the assessment outcome has uncertainty due to estimating iAs from foodstuffs and not considering the bioaccessibility of iAs in foodstuffs. Nevertheless, measures like reducing industrial As emissions, forbidding the use of pesticides, fertilizers and sludge which contain As and optimizing water management in rice paddy fields should be taken to mitigate the risks.