Benzene homologues in environmental matrixes from a pesticide chemical region in China: Occurrence, health risk and management

Risk assessment of Benzene, Toluene, Ethyl benzene, and Xylene (BTEX) in the atmospheric air around the world: A review

Volatile organic compounds, such as BTEX, have been the subject of numerous debates due to their detrimental effects on the environment and human health. Human beings have had a significant role in the emergence of this situation. Even though US EPA, WHO, and other health-related organizations have set standard limits as unhazardous levels, it has been observed that within or even below these limits, constant exposure to these toxic chemicals results in negative consequences as well. According to these facts, various studies have been carried out all over the world - 160 of which are collected within this review article, so that experts and governors may come up with effective solutions to manage and control these toxic chemicals. The outcome of this study will serve the society to evaluate and handle the risks of being exposed to BTEX. In this review article, the attempt was to collect the most accessible studies relevant to risk assessment of BTEX in the atmosphere, and for the article to contain least bias, it was reviewed and re-evaluated by all authors, who are from different institutions and backgrounds, so that the insights of the article remain unbiased. There may be some limitations to consistency or precision in some points due to the original sources, however the attempt was to minimize them as much as possible.

Spatiotemporal characteristics and dynamic risk assessment of a multi-solvents abandoned pesticide-contaminated site with a long history, in China

With the development of the economy and the adjustment of urban planning and layout, abandoned pesticide sites are widely distributed in major and medium cities in China. Groundwater pollution of a large number of abandoned pesticide-contaminated sites has caused great potential risks to human health. Up to now, few relevant studies concerned the spatiotemporal variation of risks exposure to multi-pollutants in groundwater using probabilistic methods. In our study, the spatiotemporal characteristics of organics contamination and corresponding health risks in the groundwater of a closed pesticide site were systematically assessed. A total of 152 pollutants were targeted for monitoring over a time span up to five years (i.e., June 2016-June 2020). BTEX, phenols, chlorinated aliphatic hydrocarbons, and chlorinated aromatic hydrocarbons were the main contaminants. The metadata was subjected to health risk assessments using the deterministic and probabilistic methods for four age groups, and the results showed that the risks were highly unacceptable. Both methods showed that children (0-5 years old) and adults (19-70 years old) were the age groups with the highest carcinogenic and non-carcinogenic risks, respectively. Compared with inhalation and dermal contact, oral ingestion was the predominant exposure pathway that contributed 98.41%-99.69% of overall health risks. Spatiotemporal analysis further revealed that the overall risks first increased then decreased within five years. The risk contributions of different pollutants were also found to vary substantially with time, indicating that dynamic risk assessment is necessary. Compared with the probabilistic method, the deterministic approach relatively overestimated the true risks of OPs. The results provide a scientific basis and practical experience for scientific management and governance of abandoned pesticide sites.

Application of homemade portable gas chromatography coupled to photoionization detector for the detection of volatile organic compounds in an industrial park

Traditional offline detection of volatile organic compounds (VOCs) requires complex and time-consuming pre-treatments including gas sampling in containers, pre-concentrations, and thermal desorption, which hinders its application in rapid VOCs monitoring. Developing a cost-effective instrument is of great importance for online measurement of VOCs. Recently, photoionization detectors (PID) are received great attention due to their fast response time and high sensitivity. This study a portable gas chromatography coupled to PID (pGC-PID) was developed and optimized experimental parameters for the application in online monitoring of VOCs at an industrial site. The sampling time, oven temperature and carrier gas flow rate were optimized as 80 s, 50 °C and 60 ml·min^-1, respectively. The sampling method is direct injection. Poly tetra fluoroethylene (PTFE) filter membranes were selected to remove particulate matter from interfering with PID. The reproducibility and peak separation were good with relative standard deviations (RSD) ≤ 7%. Good linearities of 27 VOCs standard curves were achieved with R² ≥ 0.99, and the detection limits were ≤10 ppb with the lowest being 2 ppb for 1,1,2-Trichloroethane. Finally, the pGC-PID is successfully applied in online VOCs monitoring at an industrial site. A total of 17 VOCs species was detected and their diurnal variations were well obtained, indicating pGC-PID is well suited for online analysis in field campaign.

Human health risk assessment for exposure to BTEXN in an urban aquifer using deterministic and probabilistic methods: A case study of Chennai city, India

The aquifer in Tondiarpet, Chennai, had been severely contaminated with petroleum fuels due to an underground pipeline leakage. Groundwater samples were analyzed quarterly for priority pollutants such as benzene, toluene, ethylbenzene, xylenes, and naphthalene (BTEXN) using purge and trap gas chromatography and mass spectrometer from 2016 to 2018. The maximum concentrations of BTEXN in groundwater at the site were found to be greater than the permissible limits significantly. Among the five sampling locations (MW1, MW2, MW3, MW4, and MW5), mean BTEXN levels were found to be higher near MW2, confirming the source location of petroleum leakage. Human health risk assessment was carried out using deterministic and probabilistic methods for exposure to BTEXN by oral and dermal exposure pathways. Risk analysis indicated that mean cancer and non-cancer risks were many times higher than the allowable limits of 1E-06 and 1 respectively in all age groups (children, teens, and adults), implying the adverse health effects. Oral exposure is predominately contributing (60-80%) to the total health risk in comparison to the dermal exposure route. Variability and uncertainty were addressed using the Monte Carlo simulations and the resultant minimum, maximum, 5th, 95th^, and mean percentile risks were predicted. Under the random exposure conditions to BTEXN, it was estimated that the risk would become unacceptable for >98.7% of the exposed population. Based on the sensitivity analysis, exposure duration, and ingestion rate are the crucial variables contributing significantly to the health risk. As part of the risk management, preliminary remediation goals for the study site were estimated, which require >99% removal of the BTEXN contamination for risk-free exposures. It is suggested that the residents of Tondiarpet shouldn't utilize the contaminated groundwater mainly for oral ingestion to lower the cancer incidence related to exposure to BTEXN.

Levels and enantiomeric signatures of organochlorine pesticides in Chinese forest soils: Implications for sources and environmental behavior

We investigated the levels and distributions of organochlorine pesticides (OCPs) in 159 background soil samples collected from 30 forested mountain sites across China. The sum of DDT was the most abundant OCP, with the concentrations of 0.197-207 ng/g and 0.033-122 ng/g in the O-horizon and A-horizon, respectively. High concentrations of OCPs usually occur near agricultural regions or high consumption areas. The spatial distribution was mainly influenced by the emission sources and soil total organic contents (TOC). The chiral compounds were generally nonracemic in the soils and showed preferential degradation of (-) o,p'- dichlorodiphenyltrichloroethane, (+) trans-chlordane, and (-) cis-chlordane in both the O- and A-horizons. The enantiomeric fraction (EF) distributions of chiral OCPs displayed no differences across the forest sites in the O-horizon or the A-horizon. Comparing the deviation of EFs from racemic (DEVrac = absolute value of 0.500 - EF) with environmental parameters, we found that DEVrac of cis-chlordane demonstrated a strong positive correlation with TOC (p < 0.05) and the C/N ratio (p < 0.01). This relationship suggests that these factors could affect the microbial activity and significantly impact the extent of enantioselective degradation of chiral compounds in the soils. Fresh and historical applications of DDT and historical chlordane and endosulfan uses may be prominent sources of OCP accumulation in Chinese forest soils.

Exosomes derived from normal human bronchial epithelial cells down-regulate proliferation and migration of hydroquinone-transformed malignant recipient cells via up-regulating PTEN expression

The gene encoding the tumor suppressor, phosphatase and tensin homolog (PTEN), located on chromosome 10, is frequently expressed at low levels in various tumors, resulting in the stimulation of cell proliferation and migration. However, the role of exosomal PTEN in cell-cell communication during the progress of benzene-induced carcinogenesis remains unclear. The goal of this study was to explore whether exosomes derived from normal human bronchial epithelial cells (16HBE) could transmit PTEN to hydroquinone-transformed malignant recipient cells (16HBE-t) and its possible effects on cell proliferation and migration. Consistent with PTEN expression being down-regulated in transformed cells, we found that its expression was significantly decreased in 16HBE-t relative to 16HBE cells and that purified exosomes secreted by 16HBE, up-regulated PTEN levels in recipient 16HBE-t cells. Thus, down-regulating their proliferation and migration. Further, when exosomes derived from 16HBE cells that had been treated with the PTEN inhibitor SF1670, were incubated with recipient 16HBE-t cells, they exhibited decreased PTEN levels, with a corresponding increase in their proliferation and migration. In conclusion, our study demonstrates that exosomes derived from 16HBE cells can down-regulate proliferation and migration of recipient 16HBE-t cells via transferring PTEN.

Benzene homologues contaminants in a former herbicide factory site: distribution, attenuation, risk, and remediation implication

Benzene homologues often used as organic raw materials or as detergents in chemical industry are prone to accidental release into the environment which can cause serious long-term soil pollutions. In a large former herbicide factory site, we investigated 43 locations for benzene homologues contaminations in soil, soil gas, and groundwater and studied the hydrogeological conditions. An inverse distance weighted interpolation method was employed to determine the pollutants three-dimensional spatial distribution in the soils. Results showed that benzene homologues residues were mainly originated from the herbicide production workshop and that the pollution had horizontally expanded at the deeper soil layer. Contaminants had already migrated 15 m downward from ground surface. Contaminant phase distribution study showed that NAPL was the primary phase (> 99%) for the pollutants accumulated in the unsaturated zone, while it had not migrated to groundwater. The primary mechanism for contaminant transport and attenuation included dissolution of "occluded" NAPL into pore water and pollutant volatilization into soil pore space. Risk assessment revealed that the pollutants brought unacceptable high carcinogenic and non-carcinogenic risks to public health. In order to convert this former chemical processing factory site into a residential area, a remediation to the polluted production workshop sites is urgently required.

Soil toxicants that potentially affect children's health

Soil pollution is a global phenomenon, and children are uniquely susceptible to the wide range of toxicants that persist in topsoil. Given their increased exposure through mouthing activities, increased body surface area, likelihood of breathing air closer to soil, and immature immune and elimination systems, it is essential to understand the mechanisms of children's exposure and the potential health effects of toxicants found in soil. Here we describe the sources and toxicological profiles of a range of inorganic and organic soil contaminants, including arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), benzene, toluene, ethylbenzene and xylenes, chlorinated dibenzo-p-dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), per and polyfluoroalkyl substances (PFAS), as well as agricultural and domestic sources of pollution. The aim of this article is to increase awareness regarding the risks and health impacts of contaminated soil, and to encourage further research and efforts aimed at mitigating children's exposure.

Fluorescence and photophysical properties of xylene isomers in water: with experimental and theoretical approaches

A thorough analysis of the photophysical properties involved in electronic transitions in excitation-emission spectra of xylene isomers has been carried out using the time-dependent density functional theory (PBEPBE/6-31 + G(d,p)) method. For the first time a structural and spectroscopic investigation to distinguish isomers of xylene, a widespread priority pollutant, was conducted experimentally and theoretically. The fluorescence properties of xylene isomers (sole and mixture (binary and ternary)) in water were studied. The fluorescence peak intensities of xylenes were linearly correlated to concentration, in the order of p-xylene > o-xylene > m-xylene at an excitation/emission wavelength (ex/em) of 260 nm/285 nm for o-, m-xylene and ex/em 265 nm/290 nm for p-xylene at the same concentration. The theoretical excitation/emission wavelengths were at ex/em 247 nm/267 nm, 248 nm/269 nm and 251 nm/307 nm for o-, m- and p-xylene, respectively. The vertical excitation and emission state energies of p-xylene (ex/em 4.94 eV/4.03 eV) were lower and the internal conversion energy difference (0.90 eV) was higher than those of m-xylene (ex/em 5.00 eV/4.60 eV) (0.4 eV) and o-xylene (ex/em 5.02 eV/4.64 eV) (0.377 eV). The order of theoretical emission and oscillator strength (0.0187 > 0.0175 > 0.0339) for p-xylene > o-xylene > m-xylene was observed to be in agreement with the experimental fluorescence intensities. These findings provide a novel fast method to distinguish isomers based on their photophysical properties.

Aromatic hydrocarbons in a controlled ecological life support system during a 4-person-180-day integrated experiment

Indoor air quality is vital to the health and comfort of people who live inside a controlled ecological life support system (CELSS) built for long-term space explorations. Here we measured aromatic hydrocarbons to assess their sources and health risks during a 4-person-180-day integrated experiment inside a CELSS with four cabins for growing crops, vegetables and fruits and other two cabins for working, accommodations and resources management. During the experiment, the average concentrations of benzene, ethylbenzene, m,p-xylenes and o-xylene were found to decrease exponentially from 7.91±3.72, 37.2±35.2, 100.8±111.7 and 46.8±44.1μg/m³ to 0.39±0.34, 1.4±0.5, 2.8±0.7 and 2.1±0.9μg/m³, with half-lives of 25.3, 44.8, 44.7 and 69.3days, respectively. Toluene to benzene ratios indicated emission from construction materials or furniture to be a dominant source for toluene, and concentrations of toluene fluctuated during the experiment largely due to the changing sorption by growing plants. The cancer and no-cancer risks based on exposure pattern of the crews were insignificant in the end of the experiment. This study also suggested that using low-emitting materials/furniture, growing plants and purifying air actively would all help to lower hazardous air pollutants inside CELSS. Broadly, the results would benefit not only the development of safe and comfort life support systems for space exploration but also the understanding of interactions between human and the total environment in closed systems.

Urine Methyl Hippuric Acid Levels in Acute Pesticide Poisoning: Estimation of Ingested Xylene Volume and Association with Clinical Outcome Parameters

To determine the relationship between the oral ingestion volume of xylene and methyl hippuric acid (MHA) in urine, we measured MHA in 11 patients whose ingested xylene volume was identified. The best-fit equation between urine MHA and ingested amount of xylene was as follows: y (ingested amount of xylene, mL/kg) = -0.052x² + 0.756x (x = MHA in urine in g/g creatinine). From this equation, we estimated the ingested xylene volume in 194 patients who had ingested pesticide of which the formulation was not available. Our results demonstrated that oxadiazole, dinitroaniline, chloroacetamide, organophosphate, and pyrethroid were xylene-containing pesticide classes, while the paraquat, glyphosate, glufosinate, synthetic auxin, fungicide, neonicotinoid, and carbamate classes were xylene-free pesticides. Sub-group univariate analysis showed a significant association between MHA levels in urine and ventilator necessity in the pyrethroid group. However, this association was not observed in the organophosphate group. Our results suggest that MHA in urine is a surrogate marker for xylene ingestion, and high urine MHA levels may be a risk factor for poor clinical outcome with some pesticide poisoning.

DNA damage and cytotoxicity in pathology laboratory technicians exposed to organic solvents

The aim of this study was to evaluate potential DNA damage and cytotoxicity in pathology laboratory technicians exposed to organic solvents, mainly xylene. Peripheral blood and buccal cells samples were collected from 18 technicians occupationally exposed to organic solvents and 11 non-exposed individuals. The technicians were sampled at two moments: Monday and Friday. DNA damage and cytotoxicity were evaluated using the Comet Assay and the Buccal Micronucleus Cytome assay. Fifteen subjects (83.5%) of the exposed group to solvents complained about some symptom probably related to contact with vapours of organic solvents. DNA damage in the exposed group to solvents was nearly 2-fold higher on Friday than on Monday, and in both moments the individuals of this group showed higher levels of DNA damage in relation to controls. No statistical difference was detected in buccal cell micronucleus frequency between the laboratory technicians and the control group. However, in the analysis performed on Friday, technicians presented higher frequency (about 3-fold) of karyolytic and apoptotic-like cells (karyorrhectic and pyknotic) in relation to control group. Considering the damage frequency and the working time, a positive correlation was found in the exposed group to solvents (r=0.468; p=0.05). The results suggest that pathology laboratory workers inappropriately exposed to organic solvents have increased levels of DNA damage.