Co-exposure levels of volatile organic compounds and metals/metalloids in children: Implications for E-waste recycling activity prediction

1-Bromopropane induces mitochondrial damage and lipid metabolism imbalance in respiratory epithelial cells through the PGC-1α/PPARα pathway

1-Bromopropane (1-BP) has become a new air pollutant in occupational and living environments due to its advantages in industrial applications and as a representative compound of volatile organic compounds (VOCs). As an irritant, its damaging effects on respiratory epithelium are worthy of further study. This study aimed to explore the damage effects of 1-BP on respiratory epithelial cells and reveal its underlying mechanisms. We found that exposure to 1-BP markedly reduced the viability of respiratory epithelial cells in a dose-dependent manner, and induced oxidative stress and vacuolation changes in respiratory epithelial cells. Subsequently, through RNA-seq analysis, we identified that the 1-BP-induced damage of respiratory epithelial cells was related to the mitochondrial function pathway and further verified that 1-BP caused mitochondrial damage of respiratory epithelial cells, which was manifested as ultrastructural damage, decreased membrane potential, ATP, and MFN2 levels. These damages were associated with cellular oxidative stress responses. Pretreating cells with the agonists of PGC-1α and PPARα, we revealed that 1-BP affected the expression of PGC-1α and interfered with its coactivator PPARα levels, causing an increase in the expression of lipid-producing genes and a decrease in the expression of lipid-decomposing genes, thus leading to a lipid accumulation in respiratory epithelial cells. Meanwhile, the imbalance of lipid metabolism in respiratory epithelial cells induced by 1-BP further caused mitochondrial damage, and the effect was bidirectional. These findings suggested that 1-BP has a potential role in inducing respiratory epithelial cell damage and is associated with the PGC-1α/PPARα signaling pathway.

Meet-in-metabonomics: Insights into associations between hair heavy metal and adverse child growth in e-waste recycling area

Heavy metal pollution from informal e-waste recycling may adversely affect child growth. However, the potential toxic mechanisms from a population perspective remain unknown. Herein, 18 hair heavy metals, urinary metabolomics, and three child growth indices [i.e., weight-for-age Z-score (WAZ), height-for-age Z-score (HAZ), and BMI Z-score (BMIZ)] were measured in children from e-waste recycling (ER, N = 426) and control areas (CR, N = 247). We examined longitudinal changes in heavy metal exposure and child growth after e-waste control to further elucidate causal relationships. Results showed that children in regulated ER site were still exposed to higher levels of several heavy metals and experienced poorer growth compared to those in control areas. Elevated exposure to heavy metals like tin, antimony, lead, cadmium, and cobalt correlated with poor child growth, particularly affecting girls and younger children. Tin, rather than traditionally concerning heavy metals, exhibited the most crucial role in driving the adverse effects of metal mixtures on child growth. Reducing heavy metal exposure through e-waste control could notably improve child growth, confirming the causal relationship between heavy metal exposure and poor child growth and underscoring the health benefits of e-waste regulation. Our research identified the roles of steroid biosynthesis, folate biosynthesis, amino acid metabolism, and purine metabolism in mediating the effects of metal exposure on child growth. Testosterone glucuronide, riboflavin, folic acid, xanthosine, and xanthine emerged as key mediators, potentially serving as metabolic signatures of heavy metal exposure. These findings illuminate the toxic mechanisms underlying poor child growth resulted from heavy metal exposure, offering important insights from a population-based perspective. In addition to lead and cadmium, monitoring and regulating tin and antimony are crucial to mitigate their negative impact on child growth in e-waste recycling areas.

Revealing the links between hair metal(loids) and alterations in blood pressure among children in e-waste recycling areas through urinary metabolomics

Hypertension is prevalent in e-waste recycling areas, and elevated blood pressure in children significantly increases the risk of hypertension in adulthood. However, the associations and toxic pathways between chronic exposure to metal(loids) and elevated blood pressure are rarely investigated. In this study, we measured the levels of 29 hair metal(loids) (chronic exposure biomarkers) and blood pressure in 667 susceptible children from an e-waste recycling area to explore their relationships. Paired urine metabolomics analysis was also performed to interpret potential mechanistic pathways. Results showed that the hypertension prevalence in our recruited children (13.0 %) exceeded the average rate (9.5 %) for Chinese children aged 6-17 years. The top five abundant metal(loids), including lead, strontium, barium, and zinc, demonstrated the most profound associations with elevated systolic blood pressure. Quantile g-computation, weighted quantile sum, and Bayesian kernel machine regression analysis jointly demonstrated a significant association between chronic exposure to metal(loids) mixture and systolic blood pressure. Interestingly, selenium showed significant antagonistic interactions with these four metals, suggesting that supplementing selenium may help children resist the elevated blood pressure induced by metal(loids) exposure. Increased metal(loids) and blood pressure levels were significantly linked to changes in urine metabolomics. Structural equation model indicated that androsterone glucuronide and N-Acetyl-1-aspartylglutamic acid were the significant mediators of the associations between metal(loids) and blood pressure, with mediation effects of 77.4 % and 29.0 %, respectively, suggesting that androsterone glucuronide and N-Acetyl-1-aspartylglutamic acid may be involved in the development of metal-induced blood pressure elevating effect. Girls were more vulnerable to metal(loids)-induced hormonal imbalance, especially androsterone glucuronide, than boys. Chronic exposure to metal(loids) at e-waste recycling sites may contribute to elevated blood pressure in children through disrupting various metabolism pathways, particularly hormonal balance. Our study provides new insights into potential mechanistic pathways of metal(loids)-induced changes in children's blood pressure.

Associations between volatile organic compounds exposure and multiple oxidative damage biomarkers: Method development, human exposure, and application for e-waste pollution prediction

Atmospheric monitoring studies reveal substantial health risks from exposure to volatile organic compounds (VOCs) for workers and nearby children in e-waste recycling areas (ERA), yet internal exposure risks are seldom examined. To address this, we developed a method to simultaneously analyze 12 urinary VOC metabolites (mVOCs) and oxidative damage biomarkers (ODBs) in workers and children from ERA and general adults from control areas using ultrahigh performance liquid chromatography coupled with quadrupole/orbitrap high-resolution mass spectrometry (UPLC-Orbitrap-HRMS). The results showed that e-waste workers exhibited significantly higher levels of VOC exposure and ODBs than e-waste children and control adults. Exceeding 91.1 %, 69.1 %, 20.8 %, 19.7 %, and 3.26 % of e-waste workers faced non-carcinogenic risk from exposure to acrolein, acrylonitrile, acrylamide, 1,3-butadiene, and 1,2-dichloroethane, respectively. The weighted quantile sum, quantile g-computation, and Bayesian kernel machine regression models consistently indicated significant positive associations between these VOC mixtures and cholesterol ODB levels (i.e., glycocholic acid, cholic acid, and glycochenodeoxycholic acid), highlighting the necessity for improved protective measures for occupational workers. Interestingly, cholesterol ODBs significantly mediated the association between VOCs exposure and nucleic acid ODBs, accounting for 12.0-26.0 % of the association with 8-hydroxy-2'-deoxyguanosine (an oxidative DNA damage biomarker) and 25.4-53.4 % with 8-hydroxyguanosine (an oxidative RNA damage biomarker). This suggests that cholesterol ODBs potentially serve as better indicators of health risks from VOC exposure than nucleic acid ODBs. Additionally, the combination of mVOCs and ODBs (Mean AUC: 0.906, ACC: 0.821) as exposure fingerprints outperformed either mVOCs (Mean AUC: 0.878, ACC: 0.802) or ODBs (Mean AUC: 0.843, ACC: 0.768) alone in predicting the presence of e-waste pollution, underscoring the importance of integrating exposure and effect biomarker fingerprints to accurately capture e-waste pollution characteristic. Our findings offer a novel approach for screening e-waste pollution in unknow e-waste recycling sites and provide a foundation for developing high-precision prediction models for other polluting industries.

Synthesis and characterization of the trans- and cis-isomers of N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine and their attempted detection in human urine

1,3-Butadiene (BD) is a carcinogenic air pollutant. N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine (MHBMA3 or 4HBeMA), an urinary BD metabolite with unspecified configuration, is considered the most sensitive BD biomarker and has been used in routine biomonitoring since 2012. However, two issues remain unaddressed: why its concentrations are unusually high relative to other urinary BD biomarkers and why some authors reported no detection of the biomarker whereas other authors readily quantitated it. To address the issues, we synthesized and structurally characterized the authentic trans- and cis-isomers of MHBMA3 (designated NE and NZ, respectively), developed an isotope-dilution LC-MS/MS method for their quantification, and examined 67 urine samples from barbecue restaurant personnel (n = 47) and hotel administrative staff (n = 20). The restaurant personnel were exposed to barbecue fumes, which contain relatively high concentrations of BD. The results showed that NE and NZ had highly similar NMR spectra, and were difficult to be well separated chromatographically. The NMR data showed that the MHBMA3 isomer investigated in most previous studies was NE. We did not detect NE and NZ in any samples; however, an interfering peak with varying heights was observed in most samples. Notably, under the chromatographic conditions used in the literature, the peak exhibited indistinguishable retention time from that of NE. Thus, it is highly likely that the interfering peak has been mis-identified as NE in previous studies, providing a reasonable explanation for the high MHBMA3 concentration in urine. The contradiction in the presence of MHBMA3 in urine was also caused by the mis-identification, because the researchers who reported the absence of MHBMA3 were actually detecting NZ. Thus, we clarified the confusion on MHBMA3 in previous studies through correctly identifying the two MHBMA3 isomers. The presence of NE and NZ in human urine warrants further investigations.

Exposure to manganese during sertoli cell formation and proliferation disturbs early testicular development in rats

Manganese (Mn) is a metal and important micronutrient. However, exposure to supraphysiological levels of Mn, which occur through fungicides, atmospheric emissions, drainages, and spills, has been related to health risks, including morphometric changes in the male reproductive organs and impairment on gametogenesis and sperm quality, impacting the fertile ability of adult animals. Despite the relevance of the fetal/perinatal period for toxicological studies on Mn, previous data only deal with the physical and neurological development of the offspring, without mentioning their reproductive development. The present study investigated whether exposure to Mn during fetal/perinatal phase, specifically during the period of formation and proliferation of Sertoli cells, impairs the reproductive development of male offspring in early postnatal life. Therefore, pregnant Wistar rats were randomly distributed into 3 experimental groups: Ctl (received saline solution), Mn-9 (received 9 mg/kg of MnCl2), and Mn-90 (received 90 mg/kg of MnCl2). The female rats received the experimental treatment by gavage from gestational day 13 to lactational day 15, i.e., postnatal day (PND) 15 of the pups. Oxidative damage to the genetic material of germ and Sertoli cells, together with a decrease in connexin 43 immunolabeling were observed in the testis of male pups evaluated at PND 15. In addition, an increase in the seminiferous tubules presenting slight epithelium vacuolization and cells with eosinophilic cytoplasm were observed, without apparent epididymal changes. In conclusion, it was demonstrated that Mn perturbed the initial testicular development by altering Sertoli cell integrity through oxidative insult, which may compromise the spermatogenesis in the long-term.

Construction of Models To Predict the Effectiveness of E-Waste Control through Capture of Volatile Organic Compounds and Metals/Metalloids Exposure Fingerprints: A Six-Year Longitudinal Study

The significant health implications of e-waste toxicants have triggered the global tightening of regulation on informal e-waste recycling sites (ER) but with disparate governance that requires effective monitoring. Taking advantage of the opportunity to implement e-waste control in the Guiyu ER since 2015, we investigated the temporal variations in levels of oxidative DNA damage, 25 volatile organic compound metabolites (VOCs), and 16 metals/metalloids (MeTs) in urine in 918 children between 2016 and 2021 to demonstrate the effectiveness of e-waste control in reducing population exposure risks. The hazard quotients of most MeTs and levels of 8-hydroxy-2'-deoxyguanosine in children decreased significantly during this time, indicating that e-waste control effectively reduces the noncarcinogenic risks of MeT exposure and levels of oxidative DNA damage. Using mVOC-derived indexes as a feature, a bagging-support vector machine algorithm-based machine learning model was constructed to predict the extent of e-waste pollution (EWP). The model exhibited excellent performance with accuracies >97.0% in differentiating between slight and severe EWP. Five simple functions established using mVOC-derived indexes also had high accuracy in predicting the presence of EWP. These models and functions provide a novel human exposure monitoring-based approach for assessing e-waste governance or the presence of EWP in other ERs.

Concepts of circular economy for sustainable management of electronic wastes: challenges and management options

The electronic and electrical industrial sector is exponentially growing throughout the globe, and sometimes, these wastes are being disposed of and discarded with a faster rate in comparison to the past era due to technology advancements. As the application of electronic devices is increasing due to the digitalization of the world (IT sector, medical, domestic, etc.), a heap of discarded e-waste is also being generated. Per-capita e-waste generation is very high in developed countries as compared to developing countries. Expansion of the global population and advancement of technologies are mainly responsible to increase the e-waste volume in our surroundings. E-waste is responsible for environmental threats as it may contain dangerous and toxic substances like metals which may have harmful effects on the biodiversity and environment. Furthermore, the life span and types of e-waste determine their harmful effects on nature, and unscientific practices of their disposal may elevate the level of threats as observed in most developing countries like India, Nigeria, Pakistan, and China. In the present review paper, many possible approaches have been discussed for effective e-waste management, such as recycling, recovery of precious metals, adopting the concepts of circular economy, formulating relevant policies, and use of advance computational techniques. On the other hand, it may also provide potential secondary resources valuable/critical materials whose primary sources are at significant supply risk. Furthermore, the use of machine learning approaches can also be useful in the monitoring and treatment/processing of e-wastes. HIGHLIGHTS: In 2019, ~ 53.6 million tons of e-wastes generated worldwide. Discarded e-wastes may be hazardous in nature due to presence of heavy metal compositions. Precious metals like gold, silver, and copper can also be procured from e-wastes. Advance tools like artificial intelligence/machine learning can be useful in the management of e-wastes.