Assessment of biodegradation and toxicity of alternative plasticizer di(2-ethylhexyl) terephthalate: Impacts on microbial biofilms, metabolism, and reactive oxygen species-mediated stress response.

Although di(2-ethylhexyl) terephthalate (DOTP) is being widely adopted as a non-phthalate plasticizer, existing research primarily focuses on human and rat toxicity. This leaves a significant gap in our understanding of their impact on microbial communities. This study assessed the biodegradation and toxicity of DOTP on microbes, focusing on its impact on biofilms and microbial metabolism using Rhodococcus ruber as a representative bacterial strain. DOTP is commonly found in mass fractions between 0.6 and 20% v/v in various soft plastic products. This study used polyvinyl chloride films (PVC) with varying DOTP concentrations (range 1-10% v/v) as a surface for analysis of biofilm growth. Cell viability and bacterial stress responses were tested using LIVE/DEAD™ BacLight™ Bacterial Viability Kit and by the detection of reactive oxygen species using CellROX™ Green Reagent, respectively. An increase in the volume of dead cells (in the plastisphere biofilm) was observed with increasing DOTP concentrations in experiments using PVC films, indicating the potential negative impact of DOTP on microbial communities. Even at a relatively low concentration of DOTP (1%), signs of stress in the microbes were noticed, while concentrations above 5% compromised their ability to survive. This research provides a new understanding of the environmental impacts of alternative plasticizers, prompting the need for additional research into their wider effects on both the environment and human health.

Advanced optical photothermal infrared spectroscopy for comprehensive characterization of microplastics from intravenous fluid delivery systems.

Growing attention is being directed towards exploring the potential harmful effects of microplastic (MP) particles on human health. Previous reports on human exposure to MPs have primarily focused on inhalation, ingestion, transdermal routes, and, potentially, transplacental transfer. The intravenous transfer of MP particles in routine healthcare settings has received limited exploration in existing literature. Standard hospital IV system set up with 0.9 % NaCl in a laminar flow hood with MP contamination precautions. Various volumes of 0.9 % NaCl passed through the system, some with a volumetric pump. Fluid filtered with Anodisc filters washed with isopropyl alcohol. The IV cannula was immersed in Mili-Q water for 72 h to simulate vein conditions. Subsequently, the water was filtered and washed. Optical photothermal infrared (O-PTIR) microspectroscopy is used to examine filters for MP particles. All filters examined from the IV infusion system contained MP particles, including MPs from the polymer materials used in the manufacture of the IV delivery systems (polydimethylsiloxane, polypropylene, polystyrene, and polyvinyl chloride) and MP particles arising from plastic resin additives (epoxy resin, polyamide resin, and polysiloxane-containing MPs). The geometric mean from the extrapolated result data indicated that approximately 0.90 MP particles per mL of 0.9 % NaCl solution can be administered through a conventional IV infusion system in the absence of a volumetric pump. However, with the implementation of a pump, this value may increase to 1.57 particles per mL. Notably, over 72 h, a single cannula was found to release approximately 558 MP particles including polydimethylsiloxane, polysiloxane-containing MPs, polyamide resin, and epoxy resin. Routine IV infusion systems release microplastics. MP particles are also released around IV cannulas, suggesting transfer into the circulatory system during standard IV procedures.

The passive sampler assisted human exposure risk characterization for tetrachloroethene soil vapor intrusion scenario.

The potential human health risks associated with soil vapor intrusion and volatile organic compounds (VOCs) exposure were characterized at an industrialized site by the quantification of gaseous VOCs in soil pores using a passive sampling technique. The gaseous tetrachloroethene (PCE) in soil pores varied between 12 and 5,400 µg m-3 showing 3 orders of magnitude variation with dependence on groundwater PCE concentrations. Though the PCE concentration in the air only varied between 0.45 and 1.5 µg m-3 showing negligible variations compared to the variation observed in soil pores. The PCE concentration in the air varied between 0.45 and 1.5 µg m-3. The calculation of fugacity suggested that the PCE in the test site originated from groundwater. Measured PCE in groundwater ranged from 14 to 2,400 times higher than PCE in soil gas. This indicates that conducting a vapor intrusion risk assessment using passive soil gas sampling is critical for accurate risk characterization and assessment. Estimated PCE inhalation cancer risks for street cleaners and indoor residents varied between 10-6 and 10-4 with a low plausible hazard, and between 10-3 and 10-2 with a high risk, respectively. The results of this study demonstrate that passive sampling offers a significantly lower cost and labor-intensive approach compared to traditional methods for assessing pollution distribution in contaminated sites and characterizing risks. This highlights the potential for wider application of passive sampling techniques in environmental studies.

Profiling and occupational health risk assessment study on coal ashes in terms of polycyclic aromatic hydrocarbons (PAHs).

Profiling and cancer risk assessment on the polycyclic aromatic hydrocarbons (PAHs) content of coal ashes produced by the major coal combustion plants from the eastern coalfield region in India was conducted. Thirteen PAHs were detected on coal ashes collected from ash deposition sites of major thermal power plants and the profiling of the PAHs was done. Benzo[a]pyrene equivalents (BaPeq) for individual PAHs were calculated and applied to the probabilistic assessment model from US EPA (1989). Monte Carlo simulations were conducted to assess the risk of inhabitants exposed to PAHs through the dust of the coal ash deposition site. In fly ash, the range of total amount of carcinogenic PAHs was from 3.50 to 6.72 µg g-1 and for the bottom ash, the range was 8.49 to 14.91 µg g-1. Bottom ashes were loaded with ample amounts of 5- and 6-ring carcinogenic PAHs, whereas fly ashes were dominated by medium molecular weight PAHs. The simulated mean cancer risks from fly ashes were 2.187 E-06 for children and 3.749 E-06 for adults. For the case of bottom ash, the mean risks were 1.248 E-05 and 2.173 E-05 respectively for children and adults. Among all the three exposure routes, dermal contact was the major and caused 81% of the total cancer risk. The most sensitive parameters were exposure duration and relative skin adherence factor for soil, which contributed the most to total variation. The 90% risks calculated from the bottom ashes (2.617 E-05 for children and 4.803 E-05 for adults) are marginally above the acceptable limit (>1.000 E-06) according to US EPA. In this study, a comprehensive risk assessment on carcinogenic PAHs present in coal ashes was done for the first time that may be helpful to develop potential strategies against occupational cancer risk.

UV stabilizers can foster early development of biofilms on freshwater microplastics.

Interactions between microbes and microplastics are important as of emerging plastic loads in the global environment. Although diverse plastic additives are used in large amounts, there are very few studies on a quantitative comparison of plastisphere on plastics with different plastic additives. We studied the effects of two widely used UV stabilizers (benzotriazole-type UV-327 and benzophenone-type UV-531 were selected based on their persistence and toxicity) in low-density polyethylene (LDPE) on freshwater microbes. This is the first study on the sole effects of UV stabilizers used as plastic additives on freshwater in situ plastisphere biofilm development. Confocal laser scanning microscopy, assisted with proper differentiating fluorochromes and threshold-based 3D segmentation of data, was used to visualize and quantify biofilm. On the first week of biofilm growth, there was very little biovolume and a negligible amount of phototrophs on pristine LDPE contrasting other substrates. Biovolumes were significantly higher on LDPE with UV stabilizers (up to 159% higher than pristine LDPE), although the biomass was mostly dead due to toxicity (>100% higher dead biovolume than live biovolume in LDPE with UV stabilizers). After the fourth week, marginally higher biovolumes along with a revival of the biomass on LDPE with UV stabilizers were observed. The ability to induce microorganismic intracellular reactive oxygen species by UV stabilizers was detected, which may stimulate biofilm growth during the primary phase of biofilm development. Atomic force microscopy analysis denoted that LDPE with UV stabilizers exhibit considerably stronger adhesion force than pristine LDPE. These observations suggest that UV stabilizers can foster the early attachment of microbes to microplastics while killing the surface contacting layer. An alive upper layer of microbes can get developed on the dead biofilm without much disruption due to the toxicity of UV stabilizers. This occurrence can eventually boost the early development of biofilms on plastics.

Differential staining lowers the false positive detection in a novel volumetric measurement technique of microplastics.

A novel method for the volumetric detection of microplastics in various environmental (soil, water) and food (fish, meat) matrices was developed. The method is based on the Nile Red staining of microplastics while eliminating probable interference by other organic polymers such as lignin, chitin, cellulosic materials, and other organic substances using a mixture of three water-based dyes (Calcofluor White, Evans Blue, and 4,6-diamidino-2-phenylindole [DAPI]). The excitation/emission 'sweet spot' was determined for water based blue dyes to detect them in a single channel for effective elimination of probable contaminations. Detection of microplastic particles using the Nile Red method was validated by comparing with traditional detection of microplastics via Fourier transform infrared spectroscopy (FTIR). Volumetric measurements of the microplastics present in environmental samples were made possible using Z-stack confocal microscopy images backed by threshold-based 3D segmentation. Regularly shaped microplastic materials were used to validate the volumetric measurement method. The proposed volumetric determination method will be very useful for screening microplastics in diverse media and improving the prevailing method using FTIR.

Profiling and assessing soil-air exchange of polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil using ex situ equilibrium passive sampling.

Cancer risk can be associated with exposure to polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil. This study investigated the profiles and sources of PAHs from poured rubber-surfaced playground dust and uncovered playground surface soil, by applying an ex-situ equilibrium passive sampling technique. Surface dust and soil samples were collected from 15 different playgrounds in Seoul, Republic of Korea. The total 16 EPA PAHs concentrations in surface dust and soil varied from 198 to 919 µg kg-1 dw and 68-169 µg kg-1 dw, respectively. 4- to 6-ring PAHs were dominant, accounting for approximately 53.8%-94.5% of the total PAHs in surface dust and soil. The diagnostic ratios and principal component analysis suggested that a mixed coal combustion and vehicular emission was likely the main source of PAHs in the surface dust and soil. The higher total organic carbon content can explain the higher PAH accumulation and lower fugacities of PAHs. The fugacity comparison of phenanthrene and pyrene in dust, soil, air, and playground surface material indicated that atmospheric deposition is the main source of PAHs in the dust and soil on rubber-surfaced and uncovered surfaced playgrounds. This study contributes to the understanding of PAHs sources in dust and soil samples in children's playground and helps policymaker determine the right contamination sources for risk management.

Profiling of seasonal variation in and cancer risk assessment of benzo(a)pyrene and heavy metals in drinking water from Kirkuk city, Iraq.

Water samples at 13 sites were analyzed to evaluate heavy metals (cobalt, lead, manganese, copper) and benzo(a)pyrene using 2 methods of analysis (high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) kits). The Lesser Zap River is the main tributary of the Tigris and is used as a main source of drinking water in Kirkuk city through the General Kirkuk project. Risk evaluation for benzo(a)pyrene and lead in water samples was accomplished by Monte Carlo simulation. The highest concentrations of B(a)P were recorded at sites S7 and S5, with levels of 0.192 and 0.122 µg L-1 detected by HPLC and ELISA, respectively. The WHO guidelines for benzo[a]pyrene in drinking water recommend 0.7 µg L -1, and none of the samples surpassed this level; moreover, B(a)P levels exceeded EPA standards in 2014 (0.01 µg L-1), particularly when the liquid-liquid extraction method with HPLC was used. Carcinogenic risks for human adults and children exist and are highest during the rainy season as compared with the carcinogenic risk during the dry season and risks for children exceed those of adults. This indicates that the 2nd round of sampling (winter season) harbors more carcinogenic risk than the 1st round of sampling (dry season).

Biofilm development of Bacillus siamensis ATKU1 on pristine short chain low-density polyethylene: A case study on microbe-microplastics interaction.

A low-density polyethylene (LDPE) degrading bacterial strain (ATKU1) was isolated (99.86% similar with Bacillus siamensis KCTC 13613T) from a plastic dumping site to study interactions between microplastics (< 5 mm) and microorganisms. The strain was found (by scanning electron microscopy) to form biofilm on the microplastic surface after its interaction with LDPE (avg. Mw~4,000 Da and avg. Mn~1,700 Da) as a sole carbon source. Atomic force microscopy (AFM) showed the biofilm's 3-D developmental patterns and significantly increased Young's modulus of the LDPE surface after microbial treatment. Most of the viable bacteria attached to biofilms rather than media, which suggested their ability to utilize LDPE. Absorption bands of carbonyl, alkenyl, acyl, ester, primary-secondary alcohol, alkene groups and nitric oxides were found on the treated LDPE particles using Fourier-transform infrared spectroscopy. Fourier transform-ion cyclotron resonance mass spectrometry of the media indicated compositional shifts of the compounds after treatment (i.e., increase in the degree of unsaturation and increment in oxygen-to-carbon ratio) and presence of unsaturated hydrocarbons, polyketides, terpenoids, aliphatic/peptides, dicarboxylic acids, lipid-like compounds were hinted. The plastic degrading abilities of Bacillus siamensis ATKU1 suggest its probable application for large scale plastic bioremediation facility.

Microplastics in Food: A Review on Analytical Methods and Challenges.

Human exposure to microplastics contained in food has become a significant concern owing to the increasing accumulation of microplastics in the environment. In this paper, we summarize the presence of microplastics in food and the analytical methods used for isolation and identification of microplastics. Although a large number of studies on seafood such as fish and shellfish exist, estimating the overall human exposure to microplastics via food consumption is difficult owing to the lack of studies on other food items. Analytical methods still need to be optimized for appropriate recovery of microplastics in various food matrices, rendering a quantitative comparison of different studies challenging. In addition, microplastics could be added or removed from ingredients during processing or cooking. Thus, research on processed food is crucial to estimate the contribution of food to overall human microplastic consumption and to mitigate this exposure in the future.

Assessment of Serratia sp. isolated from iron ore mine in hexavalent chromium reduction: kinetics, fate and variation in cellular morphology.

Serratia sp. strain SU.ISM.1 was isolated from Noamundi iron ore mines for the first time and was observed for hexavalent chromium reduction, and growth kinetics modelling was applied for bacterial chromium reduction. For 4-8 ppm of hexavalent chromium concentration, complete reduction was observed within 36 h when the selected isolate was applied, and for 12-20 ppm chromium concentration, complete reduction was achieved within 48 h. The viable biomass concentration increased up to 36 h of treatment time, after which the biomass concentration gradually declined. The Aiba model of product inhibition growth kinetics best described the growth of biomass in the presence of hexavalent chromium. The total mass conversion of Cr(VI) to Cr(III) for 4, 8, 12, 16 and 20 ppm was found to be 94.9%, 88.5%, 74.66%, 70.75% and 78.8%, respectively. The AFM and FESEM studies showed that the roughness of the cell surface increased with increasing concentration of hexavalent chromium, probably due to adsorption of chromium.

Profiling and potential cancer risk assessment on children exposed to PAHs in playground dust/soil: a comparative study on poured rubber surfaced and classical soil playgrounds in Seoul.

Children can get affected by polycyclic aromatic hydrocarbons (PAHs) while they interact with play area soil/rubber surfacing and exposed to PAHs by dermal contact, inhalation and hand-to-mouth activity. A comparative study has been conducted on PAHs profiling and probable cancer risk of children from PAHs present in uncovered playground surface soil and poured rubber surfaced playground dust. Surface soil and dust samples have been collected from 14 different children parks around the Korea University campus, Seoul, Republic of Korea. Concentrations of 16 PAHs in the soils/dust were found to be in a range of 2.82-57.93 µg g-1. Profiling of the PAHs from the playground soils/dust reveals 3-ring PAHs are dominating with 79.9% of total PAHs content, on an average. The diagnostic ratio analysis confirms that vehicular exhaust and fossil fuel burning are likely the main sources of high molecular weight carcinogenic PAHs, whereas low molecular weight PAHs have pyrogenic origin. The probabilistic health risk assessment using Monte Carlo simulations for the estimation of the 95% cancer risk exposed to the PAHs from the surfaced playgrounds shows a little higher value than the USEPA safety standard (1.3 × 10-5). Sensitivity analysis revealed exposure duration and relative skin adherence factor for soil as the most influential parameters of the assessment. Noticeably, cancer risk is approximately 10 times higher in poured rubber surfaced playgrounds than in uncovered soil playgrounds.

Discussion on the technical note entitled, "public health risk assessment following exposure to PAH-contaminated soils - specific considerations for bioaccessibility and other exposure parameters".

This is a discussion on the technical note entitled, "Public Health Risk Assessment following Exposure to PAH-contaminated Soils - Specific Considerations for Bioaccessibility and Other Exposure Parameters". Presence of some serious issues in the technical note on understanding the scopes and concepts of the original research article have been highlighted. The prevailing unclear definition of bioaccessibility and bioavailability in the scientific community may have been caused the misunderstanding of the scope of our original study. On an effort to clear this idea we feel privileged to write this discussion.

Health risk assessment and source study of PAHs from roadside soil dust of a heavy mining area in India.

The total concentrations of 13 detected polycyclic aromatic hydrocarbons (PAHs) in different traffic soil samples of Dhanbad heavy mining area, India, were between 8.256 and 12.562 µg/g and were dominated by four ring PAHs (44%). Diagnostic ratio study revealed that fossil fuel burning and vehicular pollution are the most prominent sources of the PAHs in roadside soil even at a heavy coal mining area. The 90th percentiles cancer risks determined by probabilistic health risk assessment (Monte Carlo simulations) for both the age groups (children and adults) were above tolerable limit (>1.00E-06) according to USEPA. The simulated mean cancer risk was 1.854E-05 for children and 1.823E-05 for adults. For different exposure pathways, dermal contact was observed to be the major pathway with an exposure load of 74% for children and 85% for adults. Sensitivity analysis demonstrated relative skin adherence factor for soil (AF) is the most influential parameter of the simulation, followed by exposure duration (ED).

Effect of bioflocculants on the coagulation activity of alum for removal of trihalomethane precursors from low turbid water.

Reactivity of chlorine towards hydrophobic groups present in natural organic matter (NOM) provokes the formation of carcinogenic disinfection byproducts such as trihalomethanes in chlorinated water. The present study aimed to investigate the variations in coagulant activity of alum using two different bioflocculants (coagulant aid) namely, Moringa oleifera and Cyamopsistetragonoloba for the removal of hydrophobic fractions of NOM and subsequent chlorine consumption by treated water. Effect of dual coagulants on trihalomethane surrogate parameters such as total organic carbon, dissolved organic carbon, UV absorbing materials and prominent hydrophobic species such as phenolic groups along with aromatic chromophores, polyhydroxy aromatic moiety have also been studied. The concept of differential spectroscopy and absorbance slope index has been employed to understand the combined effects of alum-bioflocculants on the reactivity of NOM with chlorine. Our result shows that the combination of alum and C. tetragonoloba is more efficient for reducing trihalomethane surrogates from chlorinated water as compared to M. oleifera. C. tetragonoloba elicited synchronized effects of sweep coagulation and particle bridging-adsorption which eventually facilitated efficient removal of hydrophobic fractions of NOM. The variation in the mechanistic approach of bioflocculants was due to the presence of cationic charge on M. oleifera and adhesive property of C. tetragonoloba.

Biofilm development of Bacillus thuringiensis on MWCNT buckypaper: Adsorption-synergic biodegradation of phenanthrene.

Adsorption-synergic biodegradation of a model PAH (phenanthrene, Phe) on MWCNT buckypaper surface with a potential PAH biodegrading bacterial strain Bacillus thuringiensis AT.ISM.11 has been studied in aqueous medium. Adsorption of Phe on buckypaper follows Dubinin-Ashtakhov model (R2 = 0.9895). MWCNT generally exerts toxicity to microbes but adsorbed layer of Phe prevents the direct contact between MWCNT and bacterial cell wall. FESEM study suggests that formation of biofilms occurred on buckypaper. Lower layer cells are disrupted and flattened as they are in direct contact with MWCNT but the upper layer cells of the developed biofilm are fully intact and functional. Force-distance curves of Bacillus thuringiensis AT.ISM.11 with buckypaper indicates adhesion forces varied from -10.3 to -15.6 nN with increasing contact time, which supports the phenomenon of biofilm formation. AFM surface statistical data of buckypaper suggests increase in bacterial cell count increases the Rms roughness (95.7242-632.565) while adhering to the buckypaper surface to form biofilm. We observed an enhanced Phe biodegradation of 93.81% from that of the 65.71% in 15 days' study period, using buckypaper as a bio-carrier or a matrix for the microbial growth. GC-MS study identified phthalic acid ester as metabolite, which is the evidence of protocatechuate pathway degradation of Phe. Current study enlightens the interaction between hydrocarbons and microbes in presence of MWCNT buckypaper matrix in aqueous system for the first time. An enhancement in biodegradation of Phe by 28.10% has also been reported which can be a basis for CNT aided enhanced biodegradation studies in future.

Public health risk assessment with bioaccessibility considerations for soil PAHs at oil refinery vicinity areas in India.

Populations living in the vicinity of oil refinery sludge deposition sites may be at greater risk of potential exposure to polycyclic aromatic hydrocarbons (PAHs) through inhalation, ingestion, and direct contact with contaminated media. Three Indian oil refinery sludge deposition sites (at Haldia, Barauni and Guwahati) were chosen for study. Soil samples were collected from three different locations at each site. Mild solvent extraction by butanol and exhaustive extraction by acetone/hexane have been conducted to estimate the bioaccessible PAHs beside the total extractable PAHs content of the soil samples. Concentrations of 13 PAHs in the soils were found to be in a range of 67.02-95.21µg/g and bioaccessible PAHs were in a range of 19.296-36.657µg/g. A probabilistic health risk assessment with bioaccessibility considerations was carried out using Monte Carlo simulations for the estimation of the cancer risk exposed to the PAHs. The 90th percentiles cancer risks with bioaccessibility considerations of soil PAHs for children is 6.506E-05 and for the adults the risk is 6.609E-05. Risk assessments on extracted PAHs from exhaustive solvent extraction can overestimate the risk by 2.87-2.89 folds at 90% confidence level with respect to the biomimetic mild extraction procedure using butanol. According to USEPA above 1×10-6 extra risk of cancer is an alarm towards management. So, public health issues due to PAHs is imminent in these oil refinery vicinity areas. Sensitivity analysis revealed exposure duration (ED) and relative skin adherence factor for soil (AF) as the most influential parameters of the assessment. The profiling and risk assessment study with bioaccessibility considerations of PAHs from soil indicates that high PAHs concentration can lead to higher cancer risk for the vicinity area residents and local government should take immediate management actions.

Cancer Risk Assessment of Polycyclic Aromatic Hydrocarbons in the Soils and Sediments of India: A Meta-Analysis.

A carcinogenic risk assessment of polycyclic aromatic hydrocarbons in soils and sediments was conducted using the probabilistic approach from a national perspective. Published monitoring data of polycyclic aromatic hydrocarbons present in soils and sediments at different study points across India were collected and converted to their corresponding BaP equivalent concentrations. These BaP equivalent concentrations were used to evaluate comprehensive cancer risk for two different age groups. Monte Carlo simulation and sensitivity analysis were applied to quantify uncertainties of risk estimation. The analysis denotes 90% cancer risk value of 1.770E-5 for children and 3.156E-5 for adults at heavily polluted site soils. Overall carcinogenic risks of polycyclic aromatic hydrocarbons in soils of India were mostly in acceptance limits. However, the food ingestion exposure route for sediments leads them to a highly risked zone. The 90% risk values from sediments are 7.863E-05 for children and 3.999E-04 for adults. Sensitivity analysis reveals exposure duration and relative skin adherence factor for soil as the most influential parameter of the assessment, followed by BaP equivalent concentration of polycyclic aromatic hydrocarbons. For sediments, biota to sediment accumulation factor of fish in terms of BaP is most sensitive on the total outcome, followed by BaP equivalent and exposure duration. Individual exposure route analysis showed dermal contact for soils and food ingestion for sediments as the main exposure pathway. Some specific locations such as surrounding areas of Bhavnagar, Raniganj, Sunderban, Raipur, and Delhi demand potential strategies of carcinogenic risk management and reduction. The current study is probably the first attempt to provide information on the carcinogenic risk of polycyclic aromatic hydrocarbons in soil and sediments across India.

Estimation of decrease in cancer risk by biodegradation of PAHs content from an urban traffic soil.

The role of preferential biodegradation in the reduction of cancer risk caused by polycyclic aromatic hydrocarbons (PAHs) has been studied. A consortium of microorganisms isolated from aged oil refinery exposed soil was used to degrade 13 PAHs content extracted from an urban traffic site soil. The biodegradation arranged in a batch process with a mineral salt broth, where PAHs were the sole carbon source. 70.46% biodegradation of the total PAHs occurred in an incubation period of 25 days. Sequential or preferential biodegradation took place as the lower molecular weight (LMW) PAHs were more prone to biodegradation than that of the higher molecular weight (HMW) PAHs. Microorganisms from the isolated consortia preferred the simpler carbon sources first. The relatively higher carcinogenicity of the HMW PAHs than that of the LMW PAHs leads to only 40.26% decrement in cancer risk. Initial cancer risk for children was 1.60E-05, which was decreased to 9.47E-06, whereas, for the adults, the risk decreased to 1.01E-05 from an initial value of 1.71E-05. The relative skin adherence factor for soil (AF) turned out to be the most influential parameter with 54.2% contributions to variance in total cancer risk followed by the exposure duration (ED) for children. For the adults, most contributions to the variance in total cancer risk were 58.5% by ED and followed by AF.

Polycyclic aromatic hydrocarbons (PAHs) concentration levels, pattern, source identification and soil toxicity assessment in urban traffic soil of Dhanbad, India.

Present study was carried out to assess and understand potential health risk and to examine the impact of vehicular traffic on the contamination status of urban traffic soils in Dhanbad City with respect to polycyclic aromatic hydrocarbons (PAHs). Eight urban traffic sites and two control/rural site surface soils were analyzed and the contents of 13 priority PAHs was determined. Total PAH concentration at traffic sites ranged from 1.019 µg g(-1) to 10.856 µg g(-1) with an average value of 3.488 µg g(-1). At control/rural site, average concentration of total PAHs was found to be 0.640 µg g(-1). PAH pattern was dominated by four- and five-ring PAHs (contributing >50% to the total PAHs) at all the eight traffic sites. On the other hand, rural soil showed a predominance of low molecular weight three-ring PAHs (contributing >30% to the total PAHs). Indeno[123-cd]pyrene/benz[ghi]perylene (IP/BgP) ratio indicated that PAH load at the traffic sites is predominated by the gasoline-driven vehicles. The ratio of Ant/(Ant+Phe) varied from 0.03 to 0.44, averaging 0.10; Fla/(Fla+Pyr) from 0.39 to 0.954, averaging 0.52; BaA/(BaA+Chry) from 0.156 to 0.60, averaging 0.44; and IP/(IP+BgP) from 0.176 to 0.811, averaging 0.286. The results indicated that vehicular emission was the major source for PAHs contamination with moderate effect of coal combustion and biomass combustion. Carcinogenic potency of PAH load in traffic soil was nearly 6.15 times higher as compared to the control/rural soil.