Atmospheric chemistry and cancer risk assessment of Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs over a semi-arid site in the Indo-Gangetic plain.

Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs were collected over a year at a traffic dominated site in Agra, to determine the dominant partitioning mechanism. During the entire sampling period, total PAHs and Nitro-PAHs were 3465 ± 3802 and 26.1 ± 25.9 ng m-3 respectively. The gas-particle partitioning behavior of PAHs was studied by applying the Pankow model, Absorption model, and Dual model. Amongst all the partitioning models, the Dual model fits well and indicates that the partitioning of PAHs at the traffic site in Agra depends on both the physical adsorption of PAHs on the Total Suspended Particulate (TSP) surface and absorption of PAHs into the organic layer present on the TSP surface. Pankow model indicates that PAHs are emitted from the source close to the sampling point and due to this PAHs do not get enough time to get partitioned in between both the phases. Incremental lifetime Cancer Risk (ILCR) shows that adults and children are more prone to cancer risk in comparison to infants for both PAHs and Nitro-PAHs. Cancer risk by inhalation was minimum in comparison to both ingestion and dermal exposure. Nitro-PAHs in the particulate phase were high enough to exceed the minimum permissible limit (10-6) of causing cancer by ingestion and dermal exposure.

Mutagenic and Cancer Risk Estimation of Particulate Bound Polycyclic Aromatic Hydrocarbons from the Emission of Different Biomass Fuels.

Smoke samples from combustion of different biomass fuels were analyzed for the particulate bound Polycyclic Aromatic Hydrocarbons (PAHs) due to their carcinogenic and mutagenic nature. Out of 16 priority PAHs, 11 PAHs were detected in the emission of fuels, while the remaining 5 PAHs (chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[g,h,i]perylene) were below the detection limit. The highest emission factor for the sum of all the PAHs was found for coal (353.08 mg kg-1), charcoal (27.28 mg kg-1), and the various wood types. Emission rates of total PAHs ranged from 0.37 to 5.15 mg h-1 with the highest value for bituminous coal (5.15 mg h-1) and lowest for Polyalthia longifolia (0.37 mg h-1). A cancer risk assessment was done for infants, children, and adults using the incremental lifetime cancer risk (ILCR) model via ingestion, inhalation, and dermal contact pathway. The ILCR values ranged from 10-11 to 10-6, and a higher cancer risk was observed for children and adults in comparison to infants. PAH concentrations emitted from biomass emissions shows a direct correlation with mutagenesis to humans, indicating a higher potential for the frameshift mutation as compared to base-pair mutation for dung, bituminous coal, charcoal, Dalbergia sissoo, Psidium guajava, Ziziphus mauritana, Polyalthia longifolia, and Ailanthus trithesa.

Chemical fractionation, bioavailability, and health risks of heavy metals in fine particulate matter at a site in the Indo-Gangetic Plain, India.

In the present study, the distribution and chemical fractionation of heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in PM2.5 collected at Sikandarpur in Agra from September 2015 to February 2016 were carried out to evaluate their mobility potential, environmental, and human health risk through inhalation. Sequential extraction procedure was applied to partition the heavy metals into four fractions (soluble and exchangeable fraction (F1); carbonates, oxides, and reducible fraction (F2); bound to organic matter, oxidizable, and sulphidic fraction (F3); and residual fraction (F4)) in PM2.5 samples. The metals in each fraction were analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Daily PM2.5 concentration ranged between 13 and 238 µg m-3 during the study period. For more than 92% of the days, the mass concentrations were greater than the National Ambient Air Quality Standard (NAAQS) set at 60 µg m-3. The total mass concentration of the eight metals was 3.3 µg m-3 that accounted for 2.5% of the PM2.5 mass concentration and followed the order Fe > Zn > Cu > Mn > Pb > Ni > Cd > Cr in dominance. The carcinogenic metals (Cd, Cr, Ni, and Pb) comprised 10% of the total metal determined. Almost all the metals had the highest proportion in the residual fraction (F4) except Ni, which had the highest proportion in the reducible fraction (F2). Chemical fractionation and contamination factor (CF) showed that Pb and Ni are readily mobilized and more bioavailable. Risk assessment code (RAC) showed that Cd, Cu, Mn, Ni, Pb, and Zn had medium environmental risk, while Cr and Fe had low risk. When the bioavailable (F1 + F2) concentrations were applied to calculate non-carcinogenic and carcinogenic risk, the results showed that the value of hazard index (HI) for toxic metals was 1.7 for both children and adults through inhalation. The integrated carcinogenic risk was 1.8 × 10-6 for children and 7.3 × 10-6 for adults, with both values being higher than the precautionary criterion (1 × 10-6). Enrichment factor (EF) calculations showed that Cd, Pb, Zn, and Ni were enriched being contributed by anthropogenic activities carried out in the industrial sectors of the city.

Chemical fractionation of heavy metals in fine particulate matter and their health risk assessment through inhalation exposure pathway.

Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24 µg m-3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2 ng m-3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10 µg dL-1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5 µg dL-1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10-6).

Chemical partitioning of fine particle-bound As, Cd, Cr, Ni, Co, Pb and assessment of associated cancer risk due to inhalation, ingestion and dermal exposure.

The bioavailability and human health risks of As, Pb, Ni, Co, Cr and Cd in fine particulate matter (PM2.5) at an urban site on a National highway in Agra, India were investigated. Inductively coupled plasma-optical emission spectrometer was used for metal analysis in sequentially extracted samples to ascertain the highly mobile, reducible, bioavailable and immobile fractions of the metals. Cancer risk resulting from inhalation, dermal and ingestion exposure to each metal in these fractions was calculated according to US EPA models. The average mass concentration of PM2.5 was 87.16 ± 62.51 µg/m3. Cr, Ni and Pb were the most abundant metals. The results showed that Pb and Cr were higher in the mobile fraction. Cd and Co had high bioavailability. Ingestion is the major exposure pathway for all heavy metals except Cr to infants, children and adults followed by inhalation and dermal contact. The cumulative risk for Cr(VI) due to dermal and inhalation routes exceed the maximum acceptable limit for children of age 1-7 years, 8-15 years and adults when total concentration is considered, but the estimated risks are within the acceptable limit when the bioavailable, water soluble and mobile fraction are taken into account. Hence the study shows that children and adults living in the vicinity of this site are more susceptible, hence more attention should be paid to protect them from pollution hazards. The study indicates the importance of metal speciation in assessing associated human health risks.

Atmospheric concentrations and gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs at Indo-Gangetic sites.

Aerosol samples in the dual-phase (gaseous and particulate) were collected simultaneously for the first time in Agra at a rural and a traffic dominated site during post-monsoon and winter seasons to investigate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). The samples were collected using a high volume sampler on quartz micro-fiber filter papers and polyurethane foam plugs for particulate and gas phases respectively. The samples were extracted in a mixture of DCM and n-hexane. 16 priority PAHs and two nitro-PAHs were analyzed using gas chromatograph-mass spectrometry. The total concentration of PAHs (gas + particulate) was 4015 and 624 ng m-3 at the traffic and rural sites respectively. Two and three ring PAHs were dominant in the gas phase while four, five and six ring PAHs were abundant in the particle phase. A statistically significant correlation (r2 = 0.69-0.98, p < 0.001) for log Kpvs. was obtained for individual PAHs at both sites where slopes varied between -2.83 and -0.04 at the traffic site and from -3.15 to -0.06 at the rural site. Regression statistics of Clausius-Clapeyron plots suggest that the concentration of highly volatile PAHs in the atmosphere is influenced by temperature. The gas-particle partitioning coefficient Kp in its logarithmic form correlated with 1/T (r2 = 0.5-0.95, p < 0.001) and a positive slope for individual PAHs was found. In health risk assessment DbA was found to be the most carcinogenic and mutagenic as compared to other PAHs followed by BaP. 1-NPyr had a larger contribution to BaP-TEQ than 3-NFla.