Electronic-waste-associated pollution of per- and polyfluoroalkyl substances: Environmental occurrence and human exposure

Leaching profile of per- and polyfluoroalkyl substances from selected e-waste components and potential exposure pathways from discarded components

Improper handling and disposal of Waste Electrical and Electronic Equipment (WEEE) containing PFAS can lead to the release of these substances into the environment. In this study, we have collected and characterized PFAS leaching profiles of selected e-waste components, including keyboards, cables, monitor screens, and circuit boards, and discussed potential PFAS exposure routes during e-waste disposal by landfilling and associated environmental and health risks. The e-waste components were disassembled, separated, sorted, shredded, and grounded, and leaching experiments were conducted for 30 days to elucidate the potential release and distribution of PFAS from the e-waste components into the environment. PFAS were extracted by solid phase extraction and analyzed through liquid chromatography-mass spectrometry (LC-MS/MS) in e-waste leachate samples to investigate their occurrence and composition in the different e-waste components. The leachate from the e-waste components had 21 out of the 40 PFAS analyzed, in which the most predominant and abundant were perfluorobutanoic acid, perfluorohexanoic acid, perfluorooctanoic acid, and perfluorooctanesulfonic acid. The cables had the highest sum of PFAS in the leachate with concentrations up to 465 ng/kg. Mobilization of PFAS from e-waste components deposited in landfills through leachate requires proper management practices to protect the environment and public health.

Towards a Better Understanding of the Human Health Risk of Per- and Polyfluoroalkyl Substances Using Organoid Models

The ubiquitous presence of per- and polyfluoroalkyl substances (PFAS) in the environment has garnered global public concern. Epidemiological studies have proved that exposure to PFAS is associated with human health risks. Although evidence demonstrated the toxic mechanisms of PFAS based on animal models and traditional cell cultures, their limitations in inter-species differences and lack of human-relevant microenvironments hinder the understanding of health risks from PFAS exposure. There is an increasing necessity to explore alternative methodologies that can effectively evaluate human health risks. Human organoids derived from stem cells accurately mimic the sophisticated and multicellular structures of native human organs, providing promising models for toxicology research. Advanced organoids combined with innovative technologies are expected to improve understanding of the breadth and depth of PFAS toxicity.

Recycling PCBs for nanoparticles production with potential applications in cosmetics, cement manufacturing, and CO2 capture

Electronic waste (e-waste) is a global problem, and many countries have established laws and regulations to promote its proper disposal and recycling. E-waste contains a significant content of printed circuit boards (PCBs), composed of metals and other valuable metals that may become scarce in Earth's crust - Copper (Cu), nickel (Ni), gold (Au), silver (Ag), palladium (Pd), and others. The main objective of this review is to explore the potential for producing nanoparticles (NPs) from the metals extracted through PCB recycling, with applications in the cosmetics, cement manufacturing, and carbon dioxide (CO2) capture industries. For this purpose, the recycling methods for PCBs e-waste, using physical processes (gravity, magnetic, electrostatic separation, and flotation), metallurgical processes (pyrometallurgy and hydrometallurgy), and purification techniques to obtain an enriched metal solution for the subsequent nanoparticle synthesis was performed. The production of NPs is a novel approach to obtain value-added products for industry. Therefore, recent research from pre-treatment of PCBs to NPs production is summarized, aligning with the circular economy principles and sustainable development goals. Towards this end, wasted PCBs can be transformed into valuable materials with innovative and potential applications in cosmetics, cement manufacturing, and carbon dioxide capture, contributing to a more sustainable future.

Increased health risk from co-exposure to polycyclic aromatic hydrocarbons, phthalates, and per- and polyfluoroalkyl substances: Epidemiological insight from e-waste workers in Hong Kong

The alarming surge in electronic waste (e-waste) in Hong Kong has heightened concerns regarding occupational exposure to a myriad of pollutants. Among these, polycyclic aromatic hydrocarbons (PAHs), phthalates (PAEs), and per- and polyfluoroalkyl substances (PFASs) are prevalent and known for their harmful effects, including the induction of oxidative stress and DNA damage, thereby contributing to various diseases. This study addresses gaps in knowledge by investigating exposure levels of these pollutants-measured via hydroxylated PAHs (OH-PAHs), phthalate metabolites (mPAEs), and PFASs-in urine from 101 e-waste workers and 100 office workers. E-waste workers exhibited higher concentrations of these substances compared to office workers. Elevated urinary levels of OH-PAHs, mPAEs, and PFASs correlated significantly with increased 8-hydroxy-2-deoxyguanosine (8-OHdG) levels (β = 2.53, 95 % CI: 2.12-3.02). The association between short-chain PFASs (Perfluoropentanoic acid, PFPeA) and DNA damage was discovered for the first time. Despite most participants (95 %) showing hazard index (HI) values below non-carcinogenic risk thresholds for PAHs and PAEs, certain pollutants posed higher risks among e-waste workers, necessitating enhanced protective measures. Moreover, the 95th percentile of carcinogenic risk associated with diethylhexyl phthalate (DEHP) exceeded 10-4 in both groups, highlighting the urgent need for regulatory measures to mitigate DEHP exposure risks in Hong Kong.

Atmospheric concentrations of per- and polyfluoroalkyl substances and their emissions at a waste recycling facility producing refuse-derived paper and plastics densified fuel

To better understand the types and concentrations of per- and polyfluoroalkyl substances (PFAS) emitted into the air from waste recycling facilities that produce refuse-derived paper and plastics densified fuel (RPF) from industrial waste, we conducted an air sampling campaign at a waste recycling facility in Japan. Both passive and active air sampling were conducted, and the samples collected were used to quantify the PFAS emitted into the air during the production of RPF. Overall, few ionic PFAS were detected in the air at the facility; however, high levels of neutral PFAS (8.21-53.4 ng/m3; 20.7-130 pmol/m3) were measured in the air near the heat molding machines. The two neutral PFAS detected at the highest concentrations were 6:2 fluorotelomer alcohol and 6:2 fluorotelomer methacrylate, which are currently unregulated under the Stockholm Convention, suggesting that product manufacturers have shifted away from using regulated PFAS. Small amounts of regulated PFAS such as 8:2 fluorotelomer methacrylate and 8:2 fluorotelomer acrylate were measured in some parts of the facility. Analysis of the concentrations of PFAS in the exhaust gas from the heat molding machines revealed neutral PFAS concentrations (537-2160 ng/m3; 1350-5040 pmol/m3) that were 1-2 orders of magnitude higher than those in the surrounding indoor air. The total emission of neutral PFAS from the facility to the environment was estimated to be 0.066-0.260 g/day (0.168-0.607 mmol/day), depending on whether air volume discharged as exhaust gas or as indoor ventilation was considered. A contribution analysis of the emissions revealed that treating the exhaust gas from the heat molding machines, which constitutes over 94 % of the total emissions, is very effective at reducing PFAS emissions from the facility.

Identification of Emerging Per- and Polyfluoroalkyl Substances (PFAS) in E-waste Recycling Practices and New Precursors for Trifluoroacetic Acid

Electronic waste is an emerging source of per- and polyfluoroalkyl substance (PFAS) emissions to the environment, yet the contribution from hazardous recycling practices in the South Asian region remains unclear. This study detected 41 PFAS in soil samples from e-waste recycling sites in Pakistan and the total concentrations were 7.43-367 ng/g dry weight (dw) (median: 37.7 ng/g dw). Trifluoroacetic acid (TFA) and 6:2 fluorotelomer sulfonic acid emerged as the dominant PFAS, constituting 49% and 13% of the total PFAS concentrations, respectively. Notably, nine CF3-containing emerging PFAS were identified by the high-resolution mass spectrometry (HRMS)-based screening. Specifically, hexafluoroisopropanol and bistriflimide (NTf2) were consistently identified across all the samples, with quantified concentrations reaching up to 854 and 90 ng/g dw, respectively. This suggests their potential association with electronic manufacturing and recycling processes. Furthermore, except for NTf2, all the identified emerging PFAS were confirmed as precursors of TFA with molar yields of 8.87-40.0% by the TOP assay validation in Milli-Q water. Overall, this study reveals significant emission of PFAS from hazardous e-waste recycling practices and emphasizes the identification of emerging sources of TFA from precursor transformation, which are essential for PFAS risk assessment.

Association Between Prenatal Exposure to Per- and Poly-Fluoroalkyl Substances From Electronic Waste Disassembly Areas and Steroid Hormones in Human Milk Samples

Per- and poly-fluoroalkyl substances (PFAS), which are long-lasting environmental contaminants that are released into the environment during the e-waste disassembly process, pose a threat to human health. Human milk is a complex and dynamic mixture of endogenous and exogenous substances, including steroid hormones and PFAS. Therefore, in this study, we aimed to investigate the association between PFAS and steroid hormones in human milk from women living close to an e-waste disassembly area. In 2021, we collected milk samples from 150 mothers within 4 weeks of delivery and analyzed them via liquid chromatography-tandem mass spectrometry to determine the levels of 21 perfluorinated compounds and five steroid hormones (estrone, estriol, testosterone, progesterone, and androstenedione [A-dione]). We also performed multiple linear regression analysis to clarify the association between maternal PFAS exposure and steroid hormone concentrations. Our results indicated that PFOA and PFOS were positively associated with estrone (β, 0.23; 95% CI, 0.08-0.39) and A-dione (β, 0.186; 95% CI, 0.016-0.357) concentrations in human milk, respectively. Further, the average estimated daily intake of PFOA and PFOS were 36.5 ng/kg bw/day (range, 0.52-291.7 ng/kg bw/day) and 5.21 ng/kg bw/day (range, 0.26-32.3 ng/kg bw/day), respectively. Of concern, the PFAS intake of breastfeeding infants in the study area was higher than the recommended threshold. These findings suggested that prenatal exposure to PFAS from the e-waste disassembly process can influence steroid hormones levels in human milk. Increased efforts to mitigate mother and infant exposure to environmental pollutants are also required.

Physicochemical reactions in e-waste recycling

Electronic waste (e-waste) recycling is becoming a global concern owing to its immense quantity, hazardous character and the potential loss of valuable metals. The many processes involved in e-waste recycling stem from a mixture of physicochemical reactions, and understanding the principles of these reactions can lead to more efficient recycling methods. In this Review, we discuss the principles behind photochemistry, thermochemistry, mechanochemistry, electrochemistry and sonochemistry for metal recovery, polymer decomposition and pollutant elimination from e-waste. We also discuss how these processes induce or improve reaction rates, selectivity and controllability of e-waste recycling based on thermodynamics and kinetics, free radicals, chemical bond energy, electrical potential regulation and more. Lastly, key factors, limitations and suggestions for improvements of these physicochemical reactions for e-waste recycling are highlighted, wherein we also indicate possible research directions for the future.

Informal E-waste dismantling activities accelerated the releasing of liquid crystal monomers (LCMs) in Pakistan: Occurrence, distribution, and exposure assessment

Liquid crystal monomers (LCMs) are emerging contaminants characterized by their persistence, bioaccumulation potential, and toxicity. They have been observed in several environmental matrices associated with electronic waste (e-waste) dismantling activities, particularly in China. However, there is currently no information on the pollution caused by LCMs in other developing countries, such as Pakistan. In this study, we collected soil samples (n = 59) from e-waste dismantling areas with different functions in Pakistan for quantification analysis of 52 target LCMs. Thirty out of 52 LCMs were detected in the soil samples, with the concentrations ranging from 2.14 to 191 ng/g (median: 16.3 ng/g), suggesting widespread contamination by these emerging contaminants. Fluorinated LCMs (median: 10.4 ng/g, range: 1.27-116 ng/g) were frequently detected and their levels were significantly (P < 0.05) higher than those of non-fluorinated LCMs (median: 6.11 ng/g, range: not detected (ND)-76.7 ng/g). The concentrations and profiles of the observed LCMs in the soil samples from the four functional areas varied. The informal dismantling of e-waste poses a potential exposure risk to adults and infants, with median estimated daily intake (EDI, ng/kg bw/day) values of 0.0420 and 0.1013, respectively. Calculation of the hazard quotient (HQ) suggested that some LCMs (e.g., ETFMBC (1.374) and EDFPB (1.257)) may pose potential health risks to occupational workers and their families. Considering the widespread contamination and risks associated with LCMs, we strongly recommend enhancing e-waste management and regulation in Pakistan.

Global quantification of emerging and legacy per- and polyfluoroalkyl substances in indoor dust: Levels, profiles and human exposure

This study investigated the occurrence and distribution of per- and polyfluoroalkyl substances (PFASs) in house dust samples from six regions across four continents. PFASs were detected in all indoor dust samples, with total median concentrations ranging from 17.3 to 197 ng/g. Among the thirty-one PFAS analytes, eight compounds, including emerging PFASs, exhibited high detection frequencies in house dust from all six locations. The levels of PFASs varied by region, with higher concentrations found in Adelaide (Australia), Tianjin (China), and Carbondale (United States, U.S.). Moreover, PFAS composition profiles also differed among regions. Dust from Australia and the U.S. contained high levels of 6:2 fluorotelomer phosphate ester (6:2 diPAP), while perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were predominant in other regions. Furthermore, our results indicate that socioeconomic factors impact PFAS levels. The assessment of human exposure through dust ingestion and dermal contact indicates that toddlers may experience higher exposure levels than adults. However, the hazard quotients of PFASs for both toddlers and adults were below one, indicating significant health risks are unlikely. Our study highlights the widespread occurrence of PFASs in global indoor dust and the need for continued monitoring and regulation of these chemicals.

Perfluoroalkyl/Polyfluoroalkyl Substances: Links to Cardiovascular Disease Risk

Conservative estimates by the World Health Organization suggest that at least a quarter of global cardiovascular diseases are attributable to environmental exposures. Associations between air pollution and cardiovascular risk have garnered the most headlines and are strong, but less attention has been paid to other omnipresent toxicants in our ecosystem. Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are man-made chemicals that are extensively used in industrial and consumer products worldwide and in aqueous film-forming foam utilized in firefighting. As such, our exposure to PFAS is essentially ubiquitous. Given the long half-lives of these degradation-resistant chemicals, virtually, all people are carrying a body burden of PFAS. Health concerns related to PFAS are growing such that the National Academies of Sciences, Engineering and Medicine has recommended standards for clinical follow-up of individuals with high PFAS blood levels, including prioritizing screening for dyslipidemia. The link between PFAS and dyslipidemia has been extensively investigated, and evidence for associations is compelling. However, dyslipidemia is not the only cardiovascular risk factor with which PFAS is associated. Here, we review the epidemiological evidence for links between PFAS of concern identified by the National Academies of Sciences, Engineering and Medicine and risk factors for cardiovascular disease, including overweight/obesity, glucose intolerance, hypertension, dyslipidemia, and hyperuricemia. Moreover, we review the potential connections of PFAS with vascular disease and atherosclerosis. While observational data support associations between the National Academies of Sciences, Engineering and Medicine PFAS and selected cardiac risk factors, additional research is needed to establish causation and better understand how exposure to PFAS leads to the development of these conditions.

Aromatic amine antioxidants (AAs) and p-phenylenediamines-quinones (PPD-Qs) in e-waste recycling industry park: Occupational exposure and liver X receptors (LXRs) disruption potential

Recently, evidence of aromatic amine antioxidants (AAs) existence in the dust of the electronic waste (e-waste) dismantling area has been exposed. However, there are limited studies investigating occupational exposure and toxicity associated with AAs and their transformation products (p-phenylenediamines-quinones, i.e., PPD-Qs). In this study, 115 dust and 42 hand wipe samples collected from an e-waste recycling industrial park in central China were analyzed for 19 AAs and 6 PPD-Qs. Notably, the median concentration of ∑6PPD-Qs (1,110 ng/g and 1,970 ng/m2) was significantly higher (p < 0.05, Mann-Whitney U test) than that of ∑6PPDs (147 ng/g and 34.0 ng/m2) in dust and hand wipes. Among the detected analytes, 4-phenylaminodiphenylamine quinone (DPPD-Q) (median: 781 ng/g) and 1,4-Bis(2-naphthylamino) benzene quinone (DNPD-Q) (median: 156 ng/g), were particularly prominent, which were first detected in the e-waste dismantling area. Occupational exposure assessments and nuclear receptor interference ability, conducted through estimated daily intake (EDI) and molecular docking analysis, respectively, indicated significant occupational exposure to PPD-Qs and suggested prioritized Liver X receptors (LXRs) disruption potential of PPDs and PPD-Qs. The study provides the first evidence of considerable levels of AAs and PPD-Qs in the e-waste-related hand wipe samples and underscores the importance of assessing occupational exposure and associated toxicity effects.

The effect of PFAS exposure on glucolipid metabolism in children and adolescents: a meta-analysis

Background

Previous studies showed that per- and polyfluoroalkyl substances (PFAS), which are widely found in the environment, can disrupt endocrine homeostasis when they enter the human body. This meta-analysis aimed to evaluate current human epidemiological evidence on the relationship between PFAS exposure and glucolipid metabolism in childhood and adolescence.

Methods

We searched PubMed, Web of Science, Embase, and Cochrane Library databases, and identified population-based epidemiological studies related to PFAS and glucolipid metabolism indexes that were published before 30 December 2022. The heterogeneity of the included literature was assessed using the I-square (I2) test and statistics Q. Random-effects and fixed-effects models were used to combine the effect size. Subgroup analysis based on age and sex of the study participants was performed. A sensitivity analysis was used to evaluate the robustness and reliability of the combined results. Egger's and Begg's tests were used to analyze publication bias.

Results

A total of 12 studies were included in this analysis. There was a positive association between PFAS and TC (β = 1.110, 95% CI: 0.601, 1.610) and LDL (β = 1.900, 95% CI: 1.030, 2.770), and a negative association between PFAS and HOMA-IR in children and adolescents (β = -0.130, 95% CI: -0. 200, -0.059). PFOS was significant positive associated with TC (β = 8.22, 95% CI: 3.93, 12.51), LDL (β = (12.04, 95% CI: 5.08, 18.99), and HOMA-IR (β = -0.165, 95% CI: -0.292, -0.038). Subgroup analysis showed that exposure to PFAS in the adolescent group was positively associated with TC and LDL levels, and the relationship was stronger in females.

Conclusion

PFAS exposure is associated with glucolipid metabolism in children and adolescents. Among them, PFOS may play an important role. Recognition of environmental PFAS exposure is critical for stabilizing the glycolipid metabolism relationship during the growth and development of children and adolescents.

Combustion of high-calorific industrial waste in conventional brick kilns: An emerging source of PFAS emissions to agricultural soils

The brick kilns in the South Asian region are widely documented to partially combust high-calorific waste components of synthetic-industrial origin, which contain hazardous constituents, including per- and polyfluoroalkyl substances (PFAS). Correspondingly, these establishments are necessarily built on agricultural land to easily acquire clay by excavating soil horizons, thus making cultivation soils vulnerable to PFAS contaminations. In this pioneering study, the occurrence, distribution profile, traceability and human health risk exposure to forty-four legacy and novel PFAS homologues, including two ultrashort-chain (C2-C3) PFAS, were investigated in agricultural soils around thirty-two conventional brick kilns across three districts of Pakistan. ⅀44PFAS concentrations ranged from 14.3 to 465 ng/g (median: 28.2 ng/g), which were 2 to 70 folds higher than those in background soils, and slightly higher than those reported in agricultural soils in the global literature. The highest occurrence was observed for PFAS alternatives, i.e., 6:2 fluorotelomer sulfonate (6:2 FTSA) (40 %) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (4.5 %). A significant positive correlation (p < 0.01) was observed among the concentrations of short-chain perfluoroalkyl acids (C4-C7) and novel PFOS substitutes, implying their origin from common sources. Furthermore, ultrashort-chain and short-chain perfluorocarboxylic acids (PFCA) (89 %) and perfluorosulfonic acids (PFSA) (63 %) dominated over long-chain's PFCA (11 %) and PFSA (37 %), respectively. The estimated daily intake to children exposed in surrounding inhabited communities, at 95th percentile concentrations was found to be approaching the European tolerable daily intake limit of 0.63 ng/kg bw/day. Therefore, the brick manufacturing industry is identified as a novel source of PFAS in the adjacent environment and for residents. This suggests the need for further investigations to elucidate the origin of emerging contaminants in the waste streams of the region to safeguard ecological integrity.

Risk assessment and partitioning behavior of PFASs in environmental matrices from an e-waste recycling area

OBJECTIVE

Perfluoroalkyl and polyfluoroalkyl substance (PFAS) contamination and their human exposure risks are a major concern. However, knowledge of PFAS contamination in environments near e-waste recycling sites and their health risk assessment are scarce.

METHODS

We measured the concentrations of PFASs in soil (n = 12), water (n = 12) and atmospheric samples (n = 26) by LCP-MS/MS, analyzed the source apportionment of PFASs by PCA, and investigated the child health risk assessment from an e-waste recycling area (Guiyu) and a reference area (Haojiang).

RESULTS

We found high concentrations of PFASs in the atmosphere and low concentrations of PFASs in soil. The average concentration of perfluoro-n-heptanoic acid (PFHpA) (9.43 ng/L) was highest among PFASs in water. The concentrations PFASs in the atmosphere and water were higher in the e-waste recycling area than in the reference area (p < 0.05). According to Multi-Linear regression model, we found that daily intake doses for PFASs in air of PFODA [β (95 % CI): -0.217 (-0.332, -0.048), p < 0.05] and PFBS [β (95 % CI): -0.064 (-0.106, -0.006), p < 0.05] were negatively associated with child BMI. PFBA [β (95 % CI: -1.039 (-2.454, -0.010), p < 0.05] was negatively correlated with child head circumference.

CONCLUSION

The concentrations of PFASs in the water and atmosphere are higher in the e-waste recycling site than in the reference area. We found that their intake affected growth and development in children. We need to reduce pollution from PFASs in the e-waste recycling area while maintaining a focus on their impact on child health.