Geochemical insights of arsenic mobilization into the aquifers of Punjab, Pakistan.

It is well known that groundwater arsenic (As) contamination affects million(s) of people throughout the Indus flood plain, Pakistan. In this study, groundwater (n = 96) and drilled borehole samples (n = 87 sediments of 12 boreholes) were collected to investigate geochemical proxy-indicators for As release into groundwater across floodplains of the Indus Basin. The mean dissolved (µg/L) and sedimentary As concentrations (mg/kg) showed significant association in all studied areas viz.; lower reaches of Indus flood plain area (71 and 12.7), upper flood plain areas (33.7 and 7.2), and Thal desert areas (5.3 and 4.7) and are indicative of Basin-scale geogenic As contamination. As contamination in aquifer sediments is dependent on various geochemical factors including particle size (3-4-fold higher As levels in fine clay particles than in fine-coarse sand), sediment types (3-fold higher As in Holocene sediments of floodplain areas vs Pleistocene/Quaternary sediments in the Thal desert) with varying proportion of Al-Fe-Mn oxides/hydroxides. The total organic carbon (TOC) of cored aquifer sediments yielded low TOC content (mean = 0.13 %), which indicates that organic carbon is not a major driver (with a few exceptions) of As mobilization in the Indus Basin. Alkaline pH, high dissolved sulfate and other water quality parameters indicate pH-induced As leaching and the dominance of oxidizing conditions in the aquifers of upper flood plain areas of Punjab, Pakistan while at the lower reaches of the Indus flood plain and alluvial pockets along the rivers with elevated flood-driven dissolved organic carbon (exhibiting high dissolved Mn and Fe and a wide range of redox conditions). Furthermore, we also identified that paired dissolved AsMn values (instead of AsFe) may serve as a geochemical marker of a range of redox conditions throughout Indus flood plains.

Human biomonitoring of trace metals from different altitudinal settings of Pakistan.

Human biomonitoring of toxic trace elements is of critical importance for public health protection. The current study aims to assess the levels of selected trace metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) into paired human nail and hair samples (n = 180 each) from different altitudinal setting along the Indus River, and which were measured by using inductively coupled plasma mass spectrometry (ICP-MS). The human samples (hair and nail) were collected from four different ecological zones of Pakistan which include frozen mountain zone (FMZ), wet mountain zone (WMZ), riverine delta zone (RDZ), and low-lying southern areas (LLZ). Our results showed the following occurrence trends into studied hair samples: higher values (ppm) of Zn (281), Co (0.136), and Mn (5.65) at FMZ; Cr (1.37), Mn (7.83), and Ni (1.22) at WMZ; Co (0.15), Mn (11.89), and Ni (0.99) at RDZ; and Mn (8.99) and Ni (0.90) at LLZ. While in the case of nails, the levels (ppm) of Mn (9.91) at FMZ and Mn (9.38, 24.1, and 12.5), Cr (1.84, 3.87, and 2.33), and Ni (10.69, 8.89, and 12.6) at WMZ, RDZ and LLZ, respectively, showed higher concentration. In general, among the studied trace elements, Mn and Ni in hair/nail samples were consistently higher and exceeded the WHO threshold/published reference values in most of the studied samples (> 50-60%) throughout the Indus basin. Similarly, hair/nail Pb values were also higher in few cases (2-10%) at all studied zones and exceeded the WHO threshold/published reference values. Our area-wise comparisons of studied metals exhibited altitudinal trends for Cd, Cr, Zn, and Mn (p < 0.05), and surprisingly, the values were increasing from south to north (at higher altitudes) and indicative of geogenic sources of the studied toxic elements, except Mn, which was higher at lower floodplain areas. Estimated daily intake (EDI) values showed that food and drinking water had the highest contribution towards Zn, Cu, Mn, and Ni and accumulation at all studied zones. Whereas, dust also acts as the main exposure route for Mn, Co, Cr, and Cd followed by the food, and water.

Toxic trespassers: Uncovering phthalates and organophosphate flame retardants in children's rooms and their health implications.

Organophosphate flame retardants (OPEs) and phthalates have garnered significant attention due to their widespread presence in indoor environments. Many recent investigations have reported extensive contamination of indoor dust, air, children's toys, and other environmental compartments with these chemicals. This research aimed to analyze OPEs and phthalates in air (PM10) and dust samples collected from the bedrooms of children (N = 30) residing in various households in Jeddah, Saudi Arabia. High mean levels (ng/g) of phthalates namely DEHP (1438600) and DnBP (159200) were found in indoor dust while TPhP (5620) was the major OPEs in indoor dust. Similarly, DEHP and DnBP were the predominant phthalates in PM10 samples, exhibiting mean levels of 560 and 680 ng/m3, respectively. However, TCPP was the main OPEs with average levels of 72 ng/m3 in PM10 samples. The majority of individual phthalates and OPEs were detected in 90-100 % of the dust samples, whereas in PM10 samples, their presence ranged from 25 % to 100 %. The concentrations of OPEs were notably greater than those of PBDEs and other BFRs previously reported in these samples, suggesting their broader use than alternative BFRs. The estimated long-term non-carcinogenic risk, hazardous index (HI) and daily exposure via dust for children was above threshold levels for DEHP. On the other hand, the cumulative risk of cancer was below the concerning levels. Further research is required to explore diverse groups of chemicals in indoor microenvironments particularly significant for children, such as kindergartens, primary schools, and their rooms at home.

Influence of the chronic groundwater fluoride consumption on cholinergic enzymes, ACHE and BCHE gene SNPs and pro-inflammatory cytokines: A study with Pakistani population groups.

Fluoride is one of the abundant elements found in the Earth's crust and is a global environmental issue. The present work aimed to find the impact of chronic consumption of fluoride contained groundwater on human subjects. Five hundred and twelve volunteers from different areas of Pakistan were recruited. Cholinergic status, acetylcholinesterase and butyrylcholinesterase gene SNPs and pro-inflammatory cytokines were examined. Association analysis, regression and other standard statistical analyses were performed. Physical examination of the fluoride endemic areas' participants revealed the symptoms of dental and skeletal fluorosis. Cholinergic enzymes (AChE and BChE) were significantly increased among different exposure groups. ACHE gene 3'-UTR variant and BCHE K-variant showed a significant association with risk of fluorosis. Pro-inflammatory cytokines (TNF-α, IL-1ß and IL-6) were found to be increased and have a significant correlation in response to fluoride exposure and cholinergic enzymes. The study concludes that chronic consumption of high fluoride-contained water is a risk factor for developing low-grade systemic inflammation through the cholinergic pathway and the studied cholinergic gene SNPs were identified to be associated with the risk of flurosis.

Profiling of phthalates, brominated, and organophosphate flame retardants in COVID-19 lockdown house dust; implication on the human health.

In this study, brominated flame retardants (BFRs), phthalates, and organophosphate flame retardants (PFRs) were analyzed in indoor household dust collected during the COVID-19 related strict lockdown (April-July 2020) period. Floor dust samples were collected from 40 households in Jeddah, Saudi Arabia. The levels of most of the analyzed chemicals were visibly high and for certain chemicals multifold high in analyzed samples compared to earlier studies on indoor dust from Jeddah. Bis (2-ethylhexyl) phthalate (DEHP) was the primary chemical in these dust samples, with a median concentration of 769,500 ng/g of dust. Tris (2-butoxy ethyl) phosphate (TBEP) and Decabromodiphenyl ether (BDE 209) contributed the highest among PFRs and BFRs with median levels of 5990 and 940 ng/g of dust, respectively. The estimated daily exposure in the worst case scenario (23,700 ng/kg bw/day) for Saudi children was above the reference dose (20,000 ng/kg bw/day) for DEHP, and the hazardous index (HI) was also >1. The long-term carcinogenic risk was above the 1 × 10-5, indicating a risk to the health of Saudi young children from getting exposed to DEHP from indoor dust. This study draws attention to the increased indoor pollution during the lockdown period when all of the daily activities by adults and children were performed indoors, which negatively impacted human health, as suggested by the calculated risk. However, the current study has limitations and warrants more monitoring studies from different parts of the world to understand the phenomenon. At the same time, this study also highlights another side of COVID-19 related to our lives.

Molecularly tracing of children exposure pathways to environmental organic pollutants and the Autism Spectrum Disorder Risk.

Organic pollutants (OPs) including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) have showed neuro-damaging effects, but studies concerning the autism spectrum disorder (ASD) risk are limited. A case-control study with ASD (n = 125) and healthy control (n = 125) children was conducted on the different land use settings across Punjab, Pakistan. Serum concentrations of 26 OCPs, 29 PCB congeners, 11 PBDEs and 32 PAHs were measured. Serum PCB77 (AOR = 2.00; 95% CI: 1.43, 2.18), PCB118 (AOR = 1.49; 95% CI: 1.00, 2.00), PCB128 (AOR = 1.65; 95% CI: 1.01, 1.91), PCB153 (AOR = 1.80; 95% CI: 1.55, 1.93) were significantly higher, but PCB187 (AOR = 0.37; 95% CI: 0.24, 0.49) was significantly lower in the ASD cases when compared to the controls. Serum BDE99 (AOR = 0.48; 95% CI: 0.26, 0.89) was significantly higher in the healthy controls than in the ASD cases. Among the analyzed OCPs, p,p'-DDE (AOR = 1.50; 95% CI: 1.00, 1.85) was significantly elevated in the ASD cases with comparison in the controls. For PAHs, serum dibenzothiophene (AOR = 7.30; 95% CI: 1.49, 35.85) was significantly higher in the ASD, while perylene (AOR = 0.25; 95% CI: 0.06, 1.10) and fluorene (AOR = 0.21; 95% CI: 0.06, 0.72) were significantly higher in the controls. In addition, many of the serum pollutants were significantly associated with GSTT1, GSTM1 (null/present polymorphism) and presented the genotypic variation to respond xenobiotics in children. The children living in proximity to urban and industrial areas had a greater exposure to most of the studied pollutants when compared to the rural children, however children residing in rural areas showed higher exposure to OCPs. This comprehensive study documents an association between environmental exposure risk of several organic pollutants (OPs) from some contaminated environmental settings with ASD risk in children from Pakistan.

Monitoring and prediction of high fluoride concentrations in groundwater in Pakistan.

Concentrations of naturally occurring fluoride in groundwater exceeding the WHO guideline of 1.5 mg/L have been detected in many parts of Pakistan. This may lead to dental or skeletal fluorosis and thereby poses a potential threat to public health. Utilizing a total of 5483 fluoride concentrations, comprising 2160 new measurements as well as those from other sources, we have applied machine learning techniques to predict the probability of fluoride in groundwater in Pakistan exceeding 1.5 mg/L at a 250 m spatial resolution. Climate, soil, lithology, topography, and land cover parameters were identified as effective predictors of high fluoride concentrations in groundwater. Excellent model performance was observed in a random forest model that achieved an Area Under the Curve (AUC) of 0.92 on test data that were not used in modeling. The highest probabilities of high fluoride concentrations in groundwater are predicted in the Thar Desert, Sargodha Division, and scattered along the Sulaiman Mountains. Applying the model predictions to the population density and accounting for groundwater usage in both rural and urban areas, we estimate that about 13 million people may be at risk of fluorosis due to consuming groundwater with fluoride concentrations >1.5 mg/L in Pakistan, which corresponds to ~6% of the total population. Both the fluoride prediction map and the health risk map can be used as important decision-making tools for authorities and water resource managers in the identification and mitigation of groundwater fluoride contamination.

Impact of organochlorine pollutants on semen parameters of infertile men in Pakistan.

Male infertility is a major problem with important socioeconomic consequences. It is associated with several pathological factors, including but not limited to endocrine disruption as a result of environmental pollution and the alarming decline in sperm count over the decades is indicative of involvement of many environmental and lifestyle changes around the globe. Organochlorine pollutants such as dichlorodiphenyltrichlorethanes (DDTs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) disrupt male reproductive system but the exact effect of environmental exposure on semen parameters in human is still not clear. This study was designed to monitor PCBs, DDTs and HCB in hair, urine and serum samples of infertile and healthy fertile men. Solid-phase microextraction gas chromatography-mass spectrometry (SPME/GC-MS) was used to monitor analytes. All tested compounds were detected, indicating recent use/persistent accumulation. Hair samples revealed no significant association with serum/urine concentrations of the analytes, while serum/urine concentrations were significantly correlated positively. Concentrations were higher in serum compared to other samples. The levels of organochlorine pollutants were higher in infertile men compared to controls with few exceptions. Among PCBs, and DDTs, PCB-153 and pp'-DDT were detected in highest concentrations, respectively. op'-DDT and pp'-DDT levels were significantly higher in infertile men compared to controls. HCB was significantly correlated negatively with sperm motility in all samples. Serum concentrations of all compounds were higher in men with defective semen parameters compared to normospermics. Serum was the best biological sample for assessing health outcomes in relation to exposure levels.

Arsenic and lead in the indoor residential settings of different socio-economic status; assessment of human health risk via dust exposure.

In the present study, occurrence of arsenic (As) and lead (Pb) is reported in rural and urban household dust (floor and AC filter dust) of the Kingdom of Saudi Arabia (KSA). Several studies have found concerning concentrations of these toxic metals in indoor dust from different countries, but data from this region is missing. The association between studied toxic metals and different socioeconomic parameters was investigated. Furthermore, health risk associated with these toxic metals via dust exposure was evaluated for the Saudi population. Mean concentration of Pb was several times higher than As in both types of dust samples. AC filter dust was more contaminated with these metals than floor dust. Levels of Pb were up to 775 ppm in AC filter dust from urban areas, while 167 ppm in rural AC filter dust. Different socioeconomic parameters did not influence much on the presence of studied metals in both AC and floor dust. To estimate health risk from contaminated dust hazardous index (HI), hazardous quotient (HQ), and incremental lifetime cancer risk (ILCR) via dust ingestion, inhalation, and dermal contact was calculate using USEPA equations. The ILCR range for both toxic metals was within the tolerable range of reference values of USEPA (1 × 10-5 to 5 × 10-7). Nonetheless, HI was close to 1 for Pb via dust exposure for young urban children, which signifies the risk of non-carcinogenic health problems in studied area. Graphical abstract.

Urinary profiles of selected metals and arsenic and their exposure pathway analysis in four large floodplains of Pakistan.

In context of fragile geological conditions and rapid urbanization, element exposure via dietary (food, water) and non-dietary (dust, soil) routes into human population at different land use settings is a major concern in the Indus floodplains (FPs) of Pakistan. In current study, several important trace elements including arsenic (As), chromium (Cr), manganese (Mn), cobalt (Co), cadmium (Cd), nickel (Ni), copper (Cu) and lead (Pb) were analyzed in the paired human urine, food, water and dust samples collected from main FPs of Pakistan. Daily intake estimation and regression analysis were used to evaluate the relationships between internal exposure, exposure routes of studied trace elements and different land use settings. High concentrations of urinary As, Cr, Cu, Mn, and Cd were detected in the general male population of the studied floodplains (FPs). Moreover, the levels (µg/L) of urinary As increased gradually from FP1 (12.8), FP2 (18), FP3 (61) to FP4 (71). Regression analysis showed that As contaminated water was correlated with elevated urinary As concentrations in FP3 and FP4, and water Cr and Mn was significantly associated with urinary Cr and Mn concentrations in FP2. Moreover, the associations of food Mn and urinary Mn were found in FP1. Over all, cumulative estimated daily intake (EDI) values from water, dust and food from all the flood plains showed that Mn had the highest values (6.6, 9.2, 14.4 µg/kg/day) followed by water As (1.98 µg/kg/day), dust Cu (1.5 µg/kg/day) and Pb (1.7 µg/kg/day). Studied floodplains were moderately to highly polluted in terms of studied trace elements (As, Cr, Cu, Mn, and Cd) contamination especially in FP3 and FP4. The results will contribute to improve the knowledge and information on current exposure of Pakistani male adults to the different contaminants.

Environmental exposure pathway analysis of trace elements and autism risk in Pakistani children population.

The pursuit of industrialization and urbanization in developing countries disrupt the fragile environment, resulting in biogeochemical extra-emission of the trace elements into human inhabitance causing serious health concerns. We aimed to determine the associations between Autism spectrum disorder (ASD) risk and exposure to trace elements (As, Zn, Ni, Pb, Hg, Cu, Cd, and Co), associations between the internal doses and environmental sources of these elements were also assessed. Genetic susceptibility to toxins was assessed through GSTT1 and GSTM1 null polymorphism analysis. Our results showed that lower BMI in children was significantly associated with ASD (p < 0.05, AOR = 0.86; 95% CI: 0.76, 0.98). As was significantly higher in both hair (p < 0.01, AOR = 18.29; 95% CI: 1.98, 169) and urine (p < 0.01, AOR = 1.04; 95% CI: 1.01, 1.06) samples from children with ASD; urinary Hg (p < 0.05, AOR = 2.90; 95% CI: 1.39, 6.07) and Pb (p < 0.05, AOR = 1.95; 95% CI: 1.01, 3.77) were also positively associated with ASD. Regarding the genetic susceptibility, Cu was significantly associated with GSTM1 positive genotype (p < 0.05, AOR = 1.05; 95% CI: 1.00, 1.10). Children inhabiting the urban areas exposed to significantly higher levels of studied trace elements. The Estimated Daily Intake (EDI) values highlighted that the different land use settings resulted in children's source specific exposure to studied trace elements. The exposure pathway analysis showed that the distal factors of land-use settings associated with children increased exposure risk for most of the investigated elements, noticeably As, Pb and Hg associated with ASD prevalence.

Assessment of organochlorine pesticides in the Himalayan riverine ecosystems from Pakistan using passive sampling techniques.

Organochlorine pesticides (OCPs) pose a considerable threat to human and environmental health. Despite most OCPs have been banned, they are still reported to be used in developing countries, including Pakistan. We aimed to identify the distribution, origin, mobility, and potential risks from OCPs in three major environmental compartments, i.e., air, water, and soil, across Azad Jammu and Kashmir valley, Pakistan. The sums of OCPs ranged between 66 and 530 pg/g in soil, 5 and 13 pg/L in surface water, and 14 and 191 pg/m3 in air, respectively. The highest sum of OCPs was observed in the downstream zone of a river that was predominantly influenced by peri-urban and urban areas. The OCP isomers ratios (α-HCH/γ-HCH and o,p'-DDT/p,p'-DDT) indicate use of lindane and technical DDTs mixture as a source of HCH and DDT in the riverine environment. Similarly, the ratios of DDE and DDD/the sum of DDTs, α-endosulfan/ß-endosulfan, and cis-chlordane/trans-chlordane indicate recent use of DDTs, endosulfan, and chlordane in the region. The air-water exchange fugacity ratios indicate net volatilization (fw/fa > 1) of α-endosulfan and trans-chlordane, and net deposition (fw/fa < 1) of ß-endosulfan, α-HCH, γ-HCH p,p'-DDD, p,p'-DDE, and p,p'-DDT. Based on the risk quotient (RQ) method, we consider the acute ecological risks for fish associated with the levels of OCPs as negligible. However, more studies are recommended to evaluate the chronic ecological risks to other riverine-associated aquatic and terrestrial species as well as human health risks to the POPs exposure through food chain transfer in forthcoming years.

Trends of climate change in the upper Indus basin region, Pakistan: implications for cryosphere.

The Indus River, the lifeline of Pakistan's economy and its tributaries, derives most of water flow from the upper Indus basin comprised of Karakorum, Himalaya, and Hindu Kush mountain ranges, thus making this area important in climate change studies. We analyzed the records of climatic variables including temperature, precipitation, and relative humidity (RH) from two weather stations (Gilgit and Skardu) of upper Indus basin region from 1953 to 2006. To observe the trends of climate change, the selected time was divided into two temporal half periods consisting of 27 years each (1953-1979 and 1980-2006). The overall mean temperature (OMT) was decreased by - 0.137 °C in Gilgit, while an increase of 0.63 °C was observed in Skardu during the later period compared to the previous one. The mean minimum temperature (MMT) was found to decrease while mean maximum temperature (MXT) showed non-significant changes during the summer at both locations. However, there was an evidence of spring and winter warming at both locations due to increase in the MXT. The precipitation data showed large interannual variation at both locations. Significant increases in the morning relative humidity (RH) were observed during summer and autumn months at Skardu and throughout the year at Gilgit, while the evening RH increased during the same seasons at both stations. Significant increase in MXT and OMT during spring and winter months at higher elevation (Skardu) may have serious implications for the deposition and melting of seasonal snowpack with impacts on local livelihoods and river flow.

Persistent organic pollutant emission via dust deposition throughout Pakistan: Spatial patterns, regional cycling and their implication for human health risks.

In the current study, Persistent Organic Pollutants (POPs) in outdoor dustfall was monitored for the first time along the Indus river system of Pakistan. Among the studied OCPs (ng/g, dry weight), DDTs (0.16-62) were the predominant contaminants identified in deposited dust followed by HCHs (0.1-10.2), HCB (0.09-7.4) and chlordanes (0.1-2.8). The indicative diagnostic ratio for DDTs and HCHs suggested recent emission of DDTs as well as historical emission of both chemicals in regions where they were used for crop protection and malarial control. The levels of ∑31PCBs (ng/g, dry weight) in dust ranged from 0.95-125, and compositional profiles suggested arochlor-1248, -1254 commercial mixtures as source. A few exceptions were samples from urban areas that reflected the use of aroclor-1260, and-1262 and/or unintentional leakage from several industrial processes. The WHO05-TEQ values for dioxin-like PCBs (with major contributions of PCB-126) were found to be 0.07-34.5 (median; 1.87) pg TEQg-1dw for all the studied samples. Correlation analysis identified that DDTs, HCHs, HCB and PCBs were significantly associated (r=90; p<0.01) with dusts collected in proximity to urban centers with widespread anthropogenic activities in these areas. A few cases where high levels of POPs from remote mountain highlands were detected, point to the potential for long range transport of these chemicals. Human risk assessment analysis of contaminated dust showed that DDTs and PCBs are major constituent chemicals of concern with regard to the development of cancer in children, with ingestion being the main route of exposure of dust-borne DDTs (0.12-1.03×10-6) and PCBs (0.86-12.43×10-6).

Occurrence of selected elements (Ti, Sr, Ba, V, Ga, Sn, Tl, and Sb) in deposited dust and human hair samples: implications for human health in Pakistan.

The current study determined, for the first time, the levels of titanium (Ti), strontium (Sr), barium (Ba), vanadium (V), gallium (Ga), tin (Sn), thallium (Tl), and antinomy (Sb), in deposited dust, and human hair collected from general population of different geographical areas of Pakistan. All the samples were prepared by microwave digestion and measured by ICP-MS. The results showed that on deposited dust samples, the detected elements followed the descending trend as: Ti > Sr > Ba > V > Ga > Sn > Tl > Sb similar to the upper continental crust. The deposited dust samples from low elevation areas exhibited highest levels of all studied elements (except antimony which was higher in soil samples from mountainous areas), followed by rive plains, mountainous areas, and highland valleys. In contrast, on human hair samples, the elements followed the descending trend as: Sr > Ba > Ti > Ga > V > Sn > Sb > Tl respectively. Ba, Ga, and V concentrations were higher in soil samples from lower elevation Indus plain, and Sr, Tl, Sb, and Ti were higher in samples from mountainous areas. The bioaccumulation trend of all studied elements was in descending order as follows: Sb, Ga, Sn, Ba, Sr, Ti, V, Tl, respectively. Principal component analysis (PCA) and correlation matrix evidenced both geological influences and anthropogenic activities as potential sources of these studied elements. On the other hand, the risk estimation (HI > 1) concluded that population were at higher health risk (non-carcinogenic) for Ga and Ti. All other studied rare elements were within safe limit for humans from all zones.

Aerobic degradation of fenvalerate by a Gram-positive bacterium, Bacillus flexus strain XJU-4.

Synthetic pyrethroid-fenvalerate-is one of the most widespread toxic pollutants and has adverse effect on living systems. However, little is known about its biotransformation mechanism in different microorganisms. To elucidate the pathway that might be involved in the catabolism of fenvalerate, we used Bacillus flexus strain XJU-4 (3-nitrobenzoate degrading organism) as an ideal fenvalerate degrading bacterium. Thin layer chromatography, high performance liquid chromatography and gas chromatography-mass spectrometry analysis results revealed that 3-phenoxybenzoate, protocatechuate, and catechol are the three main by-products of fenvalerate metabolism. Additionally, the bacterial cell-free enzymes showed the activities of fenvalerate hydrolyzing esterase, 3-phenoxybenzaldehyde dehydrogenase, 3-phenoxybenzoate dioxygenase, phenol hydroxylase, protocatechuate 2,3-dioxygenase and catechol-2,3-dioxygenase. Thus, in strain XJU-4, protocatechuate and catechol were further metabolized through meta-cleavage pathway. Moreover, laboratory-scale soil experiments results suggest that B. flexus strain XJU-4 is a suitable contender for bioremediation of pyrethroid fenvalerate-contaminated sites.

Extensive arsenic contamination in high-pH unconfined aquifers in the Indus Valley.

Arsenic-contaminated aquifers are currently estimated to affect ~150 million people around the world. However, the full extent of the problem remains elusive. This is also the case in Pakistan, where previous studies focused on isolated areas. Using a new data set of nearly 1200 groundwater quality samples throughout Pakistan, we have created state-of-the-art hazard and risk maps of arsenic-contaminated groundwater for thresholds of 10 and 50 µg/liter. Logistic regression analysis was used with 1000 iterations, where surface slope, geology, and soil parameters were major predictor variables. The hazard model indicates that much of the Indus Plain is likely to have elevated arsenic concentrations, although the rest of the country is mostly safe. Unlike other arsenic-contaminated areas of Asia, the arsenic release process in the arid Indus Plain appears to be dominated by elevated-pH dissolution, resulting from alkaline topsoil and extensive irrigation of unconfined aquifers, although pockets of reductive dissolution are also present. We estimate that approximately 50 million to 60 million people use groundwater within the area at risk, with hot spots around Lahore and Hyderabad. This number is alarmingly high and demonstrates the urgent need for verification and testing of all drinking water wells in the Indus Plain, followed by appropriate mitigation measures.

Infant Exposure to Bisphenol A Can Be Quantitatively Assessed by a Simply Improved High-Performance Liquid Chromatography-Tandem Mass-Spectrometry Method.

To quantitatively measure trace levels of bisphenol A (BPA) in infant urine, a simply improved high-performance liquid chromatography (HPLC)-tandem mass-spectrometry method was developed and validated. In the present work, a ZORBAX SB-C18 column (2.1 × 30 mm, 3.5 µm) was used for trapping and isolating BPA from the HPLC mobile phase. The result showed that the trapping column can provide effective separation from the background BPA to the sample BPA. This method has a limit of detection (LOD) of 0.048 µg/L, spiked recoveries 85.4% (0.50 - 10.0 µg/L), and relative standard deviations of 1.8 - 15.9%. By using its low-LOD advantage, we firstly reported that Chinese infants (n = 48 with age <6 months) have been ubiquitously exposed to BPA (detection frequency of 93%) with an median level of 0.13 µg/L (ranging from below LOD to 5.04 µg/L).

Currently used organophosphate and brominated flame retardants in the environment of China and other developing countries (2000-2016).

This review summarizes the environmental occurrence of new brominated flame retardants (NBFRs) and organophosphate compounds (OPs) in the environment of developing countries since 2000. The ban on the production and use of commercial formulations of polybrominated diphenyl ethers (PBDEs) have paved the way for the high use of NBFRs and OPs in consumer products to fulfill the fire safety regulations. Recent studies have shown that the ever increasing production volumes and extensive use of these chemicals as additive FRs and plasticizers have resulted into their ubiquitous occurrence in all environmental compartments. Although presumed to be safe for use and the environment, recent studies on their occurrence and persistence in the environment have raised questions. Due to the lack of awareness, research interest, and availability of technical facilities, limited scientific data is available on the occurrence of these chemicals in developing countries. In this study, we collected reported data and provide an overview of environmental occurrence of NBFRs and OPs in abiotic and biotic matrices of different developing countries. Finally, research gaps were identified with recommendations for future research work and would be useful towards the environmental management of these toxic chemicals.

Arsenic activates the expression of 3ß-HSD in mouse Leydig cells through repression of histone H3K9 methylation.

Arsenic exposure has been associated with male reproductive dysfunction by disrupting steroidogenesis; however, the roles of epigenetic drivers, especially histone methylation in arsenic-induced steroidogenic toxicity remain not well documented. In this study, we investigated the role of histone H3 lysine 9 (H3K9) methylation in steroidogenesis disturbance in mouse Leydig cells (MLTC-1) due to arsenic exposure. Our results indicated that mRNA and protein expression levels of 3ß-hydroxysteroid dehydrogenase (3ß-HSD) were both significantly up-regulated while the rest of key genes involved in steroidogenesis were down-regulated. Moreover, arsenic exposure significantly decreased the histone H3K9 di- and tri-methylation (H3K9me2/3) levels in MLTC-1 cells. Since H3K9 demethylation leads to gene activation, we further investigated whether the induction of 3ß-HSD expression was ascribed to reduced H3K9 methylation. The results showed that H3K9me2/3 demethylase (JMJD2A) inhibitor, quercetin (Que) significantly attenuated the decrease of H3K9me2/3 and increase of 3ß-HSD expression induced by arsenic. To further elucidate the mechanism for the activation of 3ß-HSD, we determined the histone H3K9 methylation levels in Hsd3b gene promoter, which also showed significant decrease of H3K9me2/3 in the investigated region after arsenic exposure. Considering these results, we conclude that arsenic exposure induced 3ß-HSD up-regulation by suppressing H3K9me2/3 status, which is suggested as a compensatory mechanism for steroidogenic disturbance in MLTC-1 cells.