Reactive oxygen species alteration of immune cells in local residents at an electronic waste recycling site in northern China

The association of organochlorine pesticides and polychlorinated biphenyls exposure with dyslipidemia and blood lipids: The mediating effect of white blood cell counts

Epidemiological evidence regarding the associations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) with lipid metabolism and its potential biological mechanisms remain largely unknown. We intended to explore the associations of OCPs and PCBs with dyslipidemia and blood lipid levels, and further evaluate the mediating role of total and differential white blood cell (WBC) counts. We measured the blood lipid levels, the concentration of OCPs/PCBs and WBC counts in serum among 2036 adults in Wuhan city, China. In the multiple-pollutant models, the results showed that β-hexachlorocyclohexane (HCH), p,p'-dichlorodiphenyldichloroethylene (DDE), and PCB-153 were positively correlated with increased odds of dyslipidemia. p,p'-DDE and PCB-153 were correlated with elevated triglyceride (TG) and lowered high-density lipoprotein cholesterol (HDL-c). A positive relationship was observed between p,p'-DDE and total cholesterol (TC) as well. Meanwhile, weighted quantile sum (WQS) regression analyses revealed that PCB and OCP mixtures were positively related to dyslipidemia risk and TG and negatively associated with HDL-c, to which p,p'-DDE was the major contributor. BMI, gender and age might modify the associations of OCPs and PCBs with dyslipidemia and TG. Furthermore, we found that WBC counts were significantly associated with dyslipidemia and blood lipid levels, and a positive correlation was also found between p,p'-DDE and lymphocyte count. Mediation analysis further indicated that lymphocyte count might mediate the associations of p,p'-DDE with dyslipidemia, TG, and TC. Accordingly, our results showed that OCPs and PCBs were related to abnormal lipid metabolism, which was partially mediated by WBC counts.

E-waste: mechanisms of toxicity and safety testing

Currently, information on the toxicity profile of the majority of the identified e-waste chemicals, while extensive and growing, is admittedly fragmentary, particularly at the cellular and molecular levels. Furthermore, the toxicity of the chemical mixtures likely to be encountered by humans during and after informal e-waste recycling, as well as their underlying mechanisms of action, is largely unknown. This review paper summarizes state-of-the-art knowledge of the potential underlying toxicity mechanisms associated with e-waste exposures, with a focus on toxic responses connected to specific organs, organ systems, and overall effects on the organism. To overcome the complexities associated with assessing the possible adverse outcomes from exposure to chemicals, a growing number of new approach methodologies have emerged in recent years, with the long-term objective of providing a human-based and animal-free system that is scientifically superior to animal testing, more effective, and acceptable. This encompasses a variety of techniques, typically regarded as alternative approaches for determining chemical-induced toxicities and holds greater promise for a better understanding of key events in the metabolic pathways that mediate known adverse health outcomes in e-waste exposure scenarios. This is crucial to establishing accurate scientific knowledge on mixed e-waste chemical exposures in shorter time frames and with greater efficacy, as well as supporting the need for safe management of hazardous chemicals. The present review paper discusses important gaps in knowledge and shows promising directions for mechanistically anchored effect-based monitoring strategies that will contribute to the advancement of the methods currently used in characterizing and monitoring e-waste-impacted ecosystems.

Persistent immune injury induced by short-term decabromodiphenyl ether (BDE-209) exposure to female middle-aged Balb/c mice

Decabromodiphenyl ether (BDE-209), widely used in various industries for its excellent flame-retardant performance, could be enriched in humans and is closely associated with immune impairment. In addition, immune system is gradually declined and becoming more sensitive to environmental pollutants in the ageing process. Therefore, the immunotoxicity of BDE-209 (4, 40, and 400 mg/kg/day) to middle-aged mice and its recovery and susceptibility was first to be comprehensively investigated in this study. The results showed that BDE-209 exposure could lead to oxidative injury to immune organs (spleen, thymus, and liver), impair humoral (immunoglobulins), cellular (lymphopoiesis), and non-specific immunity, and disturb the expressions of the genes related to Th1/Th2 balance (T helper cells) in the middle-aged mice. In addition, Integrated Biomarker Response (IBR) indicated that BDE-209-induced immune impairment was challenging to self-regulated, and even exacerbated after 21 days of recovery and oxidative injury in immune organs could be the main reason. Furthermore, factorial analysis showed that middle-aged mice exposed to BDE-209 suffered from greater immune impairment than adult mice, and the immune impairment in aged mice is more difficult to be self-repaired than that in adult mice. It can be seen that the aged tend to suffer from BDE-209-induced persistent immune impairment and health threats.

Environmentally relevant concentrations of fenvalerate induces immunotoxicity and reduces pathogen resistance in Chinese rare minnow (Gobiocypris rarus)

Fenvalerate is a broadly used type II pyrethroid with a potential toxic effect in fish. However, information on the immunotoxicity of fenvalerate in fish is scarce. Here, to discover the immunotoxicity of fenvalerate and its underlying mechanism in fish, adult Chinese rare minnow was exposed to fenvalerate at 0, 0.3, 1, and 3 μg/L for 28 days and then subjected to Pseudomonas fluorescens (P. fluorescens) challenge. Fenvalerate induced significant pathological changes, with disintegration of cell boundaries in the intestine, epithelial hyperplasia in gills, and vacuolation of hepatocytes at 3 μg/L treatment. Additionally, the pathological characteristics were more serious during P. fluorescens infection after fenvalerate exposure. A significant increase in neutrophil counts was observed after 3 μg/L fenvalerate exposure for 28 days (p < 0.05), whereas significantly increased monocyte and neutrophil counts and greatly decreased lymphocyte counts were detected at 24 h post-injection (hpi) with P. fluorescens (p < 0.05). Furthermore, obvious decreases in LYS, IgM, ALP, and C3 levels were detected in plasma after 3 μg/L fenvalerate exposure for 28 days, which was consistent with the results at 24 and 48 hpi. Notably, fish exposed to fenvalerate suppressed the transcription of TLR-NF-κB signaling pathway-relevant genes in response to P. fluorescens, accompanied by high mortalities and bacterial loads. Therefore, our results demonstrate that fenvalerate at environmentally relevant concentrations caused immunotoxicity in fish. This study highlights the importance of considering the combined effects of chemicals and pathogens to refine our ability to predict the effects of environmental contaminants on aquatic organisms.

Human developmental toxicity mechanism of polybrominated biphenyl exposure and health risk regulation strategy for special populations

Polybrominated biphenyls (PBBs) can bioaccumulate in nature and are toxic to humans. Long-time exposure to PBBs in pregnant women can lead to the birth of an infant with abnormal conditions. Hence, in this study, we used molecular docking, molecular dynamics, Taguchi experimental design, and fractional factorial experimental design to identify the developmental toxicity characteristics of 10 typical developmental toxic pollutants such as PBBs to which humans are frequently exposed. Furthermore, the correlation and sensitivity analyses of molecular developmental toxicity and structural parameters were performed. The molecular key structural parameters of the pollutants affecting human development were screened. Moreover, the supplementary food factors that could alleviate the developmental toxicity of pollutants were screened to develop supplementary food schemes to prevent or alleviate human developmental toxicity in the special population (e.g., pregnant women, infants) exposed to the pollutants. The results showed that the developmental toxicity was controlled by the main effects of the 10 pollutants. Among the 10 pollutants with developmental toxicity, the most significant pollutant with the main effects was PBB-153 (37.06%). In addition, the correlation and sensitivity analyses of the molecular developmental toxicity of the pollutants and structural parameters showed that the total energy value and infrared C-H vibration frequency of the pollutants were significantly correlated with human developmental toxicity. Accordingly, 15 supplementary food cofactors were selected for the Taguchi experiment design, among which the top seven cofactors were designed by fractional factorial analysis. The most significant cofactor that alleviated the developmental toxicity of PBB-153 exposure was the combination of carotene and docosahexaenoic acid (DHA), with an improvement of 17.28%. The combination of carotene and DHA significantly alleviated the effects of toxicity caused by most of the other pollutants, indicating that the selected supplementary food has certain universality. In this study, we developed a method to identify the characteristics of the developmental toxicity of pollutant exposure and developmental toxicity alleviation. Our study provided theoretical support for the regulation strategy of developmental toxicity caused by pollutants such as PBBs.

Pb and Cd exposure linked with Il-10 and Il-13 gene polymorphisms in asthma risk relevant immunomodulation in children

Genetic variants and environmental factor of heavy metal exposure accelerate the risk of immune-mediated respiratory diseases, including asthma in children. This study aims to investigate the effects and interaction of Pb, Cd exposure from e-waste and interleukin (IL)-10, IL-13 gene polymorphisms on interleukin expressions in children. Pb, Cd levels, Il-10 (rs1800871, rs1800872, rs1800896) and Il-13 (rs20541, rs1800925) polymorphisms were determined in blood or urine of 155 children (75 from e-waste-exposed area, Guiyu and 80 from reference area, Haojiang). Blood Pb and urine Cd levels of e-waste-exposed children were both higher (mean: 5.89 vs. 3.35 μg/dL; 6.04 vs. 1.82 μg/g, both P < 0.05). Exposed children had a larger proportion of high blood Pb level (> 5.00 μg/dL) (66.67% vs. 4.11%, P < 0.001), but they had no statistically different proportion of high urine Cd level (> 1.00 μg/g creatinine). Median levels of IL-13 decreased (3.674 vs. 4.410 ng/L, P < 0.01), but of IL-10 did not vary in serum of exposed children. The analyses revealed no significant associations of Pb or Cd with Il-10 or Il-13 gene polymorphisms. The high blood Pb and urine Cd level were respectively associated with the low IL-13 ( < 3.696 ng/L) and low IL-10 ( < 0.361 ng/L) level, after adjustment for children's age, gender, and BMI (both P ≤ 0.05). Children homozygous carrying major allele for Il-13 (rs20541 and rs1800925) had additive interactions with high blood Pb level on low IL-13 expression (OR = 5.37, 95% CI: 1.96, 14.73 and OR = 8.45, 95% CI: 2.61, 27.32; both P ≤ 0.001). In contrast, no interaction was observed amongst Pb or Cd with Il-10 gene polymorphisms on its expression. Our findings suggest that Pb exposure interacting with Il-13 gene polymorphisms negatively regulates IL-13 expression, which may pose a risk to abnormal asthma-relevant immunomodulation in preschool children.

Health consequences of exposure to e-waste: an updated systematic review

Electronic waste (e-waste) contains numerous chemicals harmful to human and ecological health. To update a 2013 review assessing adverse human health consequences of exposure to e-waste, we systematically reviewed studies reporting effects on humans related to e-waste exposure. We searched EMBASE, PsycNET, Web of Science, CINAHL, and PubMed for articles published between Dec 18, 2012, and Jan 28, 2020, restricting our search to publications in English. Of the 5645 records identified, we included 70 studies that met the preset criteria. People living in e-waste exposed regions had significantly elevated levels of heavy metals and persistent organic pollutants. Children and pregnant women were especially susceptible during the critical periods of exposure that detrimentally affect diverse biological systems and organs. Elevated toxic chemicals negatively impact on neonatal growth indices and hormone level alterations in e-waste exposed populations. We recorded possible connections between chronic exposure to e-waste and DNA lesions, telomere attrition, inhibited vaccine responsiveness, elevated oxidative stress, and altered immune function. The existence of various toxic chemicals in e-waste recycling areas impose plausible adverse health outcomes. Novel cost-effective methods for safe recycling operations need to be employed in e-waste sites to ensure the health and safety of vulnerable populations.

E-Waste in Africa: A Serious Threat to the Health of Children

Waste electronic and electrical equipment (e-waste) consists of used and discarded electrical and electronic items ranging from refrigerators to cell phones and printed circuit boards. It is frequently moved from developed countries to developing countries where it is dismantled for valuable metals in informal settings, resulting in significant human exposure to toxic substances. E-waste is a major concern in Africa, with large sites in Ghana and Nigeria where imported e-waste is dismantled under unsafe conditions. However, as in many developing countries, used electronic and electrical devices are imported in large quantities because they are in great demand and are less expensive than new ones. Many of these used products are irreparable and are discarded with other solid waste to local landfills. These items are then often scavenged for the purpose of extracting valuable metals by heating and burning, incubating in acids and other methods. These activities pose significant health risks to workers and residents in communities near recycling sites. E-waste burning and dismantling activities are frequently undertaken at e-waste sites, often in or near homes. As a result, children and people living in the surrounding areas are exposed, even if they are not directly involved in the recycling. While toxic substances are dangerous to individuals at any age, children are more vulnerable as they are going through important developmental processes, and some adverse health impacts may have long-term impacts. We review the e-waste situation in Africa with a focus on threats to children's health.

Micronucleus Evaluation in Exfoliated Human Buccal Epithelium Cells among E-Waste Workers in Payatas, the Philippines

BACKGROUND

The improper recycling of electronic waste (e-waste) by informal recyclers often leads to contamination of the environment. E-waste contains organic and inorganic compounds along with heavy metals and trace elements. These pollutants can have a negative effect on humans. Biomonitoring can provide information on the sources, amount, geographical distribution, and adverse health effects of contaminants.

OBJECTIVES

The present study aimed to assess risks to the health of informal e-waste recyclers in Payatas, the Philippines due to their exposure to e-waste toxicity by examining the presence of micronuclei in buccal epithelium cells.

METHODOLOGY

Frequencies of binucleated cells (BNc) and abnormal cells were obtained from the buccal epithelium of the study population composed of e-waste exposed recyclers (n=40) and a control group (n=52). Descriptive statistics and regression analysis were employed for the data analysis.

RESULTS

Participants' gender, occupation, smoking status, alcohol consumption, and the number of karyolitic cells of both groups were significantly associated. Only occupation in e-waste recycling and length of e-waste exposure were significantly associated in terms of the number of abnormal cells and micronuclei. Similar trends were found in the linear regression analysis drawn from participants' length of e-waste exposure with a significance of R2= 7346, indicating that as the length of e-waste exposure increased, the number of micronuclei found in the participants' buccal epithelium cells increased as well.

CONCLUSIONS

Longer exposure to e-waste materials may induce genotoxic damage in human cells which is a serious concern, leading to adverse effects to human health.

COMPETING INTERESTS

The authors declare no competing financial interests.

Contaminant-related oxidative distress in common kingfisher (Alcedo atthis) breeding at an e-waste site in South China

The crude electronic waste (e-waste) recycling has caused severe contamination of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the local environment, begging the question of whether wildlife like birds living at e-waste sites are suffering from adverse effects. We examined several oxidative status markers and their relationships with hepatic concentrations of PCBs and PBDEs in common kingfisher (Alcedo atthis) that inhabit an e-waste site in South China. The results showed that the mean concentrations of ∑PCBs (19100 ng/g) and ∑PBDEs (507 ng/g) in kingfishers from e-waste site were several orders of magnitude higher than those in the species from a reference site. Correspondingly, hepatic concentrations of malondialdehyde (MDA) and reactive oxygen species (ROS) in kingfishers from the e-waste site were significantly higher than those detected in the reference population, suggesting oxidative distress in the birds breeding at the e-waste site. The activities of superoxide dismutase (SOD) and catalase (CAT) in the liver from the exposed group were significantly lower compared with the reference group, while the opposite trend was observed for glutathione peroxidase (GPx). Significantly positive correlations were observed between PCB or PBDE concentrations and the levels of MDA and ROS; while negative correlations were found for enzymatic activities of SOD and CAT. Overall, our results may suggest a potential linkage between exposure to e-waste-derived pollutants and elevated oxidative stress, thereby indicating a potential oxidative stress-related health effects in common kingfisher breeding at the e-waste site.

Genomic instability in adult men involved in processing electronic waste in Northern China

BACKGROUND

Managing and recycling electronic waste (e-waste), while useful and necessary, has resulted in significant contamination of several environments in China. The area around Tianjin, China has become one of the world's largest e-waste disposal centers, where electronics are processed by manually disassembly or burning, which can result in serious exposure of workers to a multitude of toxicants.

OBJECTIVE

The present study assessed potential genomic damage in workers involved in recycling e-waste.

METHODS

To detect cytogenetic and DNA damage, chromosomal aberrations (CA), cytokinesis blocking micronucleus (CBMN) and the comet assay were performed. Concentrations of some trace elements, markers of oxidative stress and polychlorinated biphenyls (PCBs) in whole blood or serum were measured, and relationships among the markers described above, age, and duration of exposure were analyzed. The profiles of expression of genes in lymphocytes in peripheral blood were assessed to determine the status of the regulation of genes involved in genome stability.

RESULTS

Concentrations of 28 PCB congeners in the whole blood of the exposed group were significantly (P<0.001) greater than those in the control individuals. Frequency of CA (8.01%) and CBMN (26.3‰) in lymphocytes and the level of DNA damage in the lymphocytes and spermatozoa of the exposed men were also significantly (P<0.0001) greater than those of the controls. There were significant relationships between CA, CBMN, DNA damage and duration of exposure. Concentrations of malondialdehyde (MDA) and lead (Pb) in the blood serum were significantly greater, but activities of superoxide dismutase (SOD), glutathione (GSH) and concentrations of calcium (Ca) and magnesium (Mg) were lower in the serum of the exposed men. MDA, Pb, Ca and Mg were associated with the duration of exposure to handling e-waste. In males involved in handling of e-waste, there were 13 genes - ATM, ATR, ABL1, CHEK1, CHEK2, GADD45A, CDK7, GTSE1, OGG1, DDB1, PRKDC, XRCC1 and CCNH - for which expression of mRNA was up-regulated and 7 genes - BRCA1, GTF2H1, SEMA4A, MRE11A, MUTYH, PNKP and RAD50 - for which the expression of mRNA was down-regulated.

CONCLUSIONS

A strong correlation between indicators of damage of DNA, which could result in instability of the genome, and duration of processing e-waste was observed. If proper procedures are not followed, there are significant risks to the health of the individuals involved in such activities.

Acute exposure to chlorpyrifos induces reversible changes in health parameters of Nile tilapia (Oreochromis niloticus)

Chlorpyrifos (CPF) is one of the most common insecticides found in freshwater ecosystems, and has been detected in agricultural and fishery products worldwide. This study focused on comprehensive panel of hematological, immunotoxic and pathology changes in Nile tilapia (Oreochromis niloticus) during and after exposure to CPF at 15 μg/L (0.043 μM) (1/10 LC₅₀, group CPF1), or 75 μg/L (0.21 μM) (1/2 LC₅₀, group CPF2) for 14 days, followed by 2 weeks recovery. Different endpoints were used to determine effects of CPF on fish health: hematological parameters; antioxidant levels in liver and gills; innate immune parameters; expression levels of pro-inflammatory cytokine genes at mRNA level in anterior kidney and spleen; and histopathological assessment of gills, liver, and kidney tissues. RBCs were significantly decreased in CPF1 group compared to other groups only at day 3. Blood packed cell volume (PCV) and mean corpuscular volume (MCV) showed significant increase at day 3 and 14 of CPF exposure. TLC (Total Leukocytic Counts), neutrophil counts were significantly increased in CPF exposed groups at days 3, 7, 14 compared to the control. While, lymphocytes counts were significantly increased at CPF1 group compared to other groups at day 14. Antioxidant enzyme activity in liver and gills showed significant increase of Malondialdehyde (MDA) and glutathione (GSH), and significant decrease in (catalase/CAT/, glutathione S-transferase/GST/, and superoxide dismutase/SOD/); in CPF exposed groups. Serum bactericidal and lysozyme activity was nominally and significantly decreased, respectively, and whole blood respiratory burst was significantly increased in CPF2 group. The cytokine expression levels showed complex changes in expression patterns. In kidney, cytokine interleukin-8 (IL-8) was significantly upregulated at day 1 in both exposed group. Interleukin-1β (IL-1β) and Tumor necrosis factor-α (TNFα) were significantly upregulated at day 1 in CPF1 group, and then IL-8 and TNFα downregulated at day 3 in same group. At day 7, only TNFα was up and downregulated in CPF1 and CPF2, respectively compared to control. All gene expression levels in spleen were upregulated on day 7 of exposure in the high exposed group. Histopathology showed dose-dependent changes in CPF treated groups, indicating gill, liver, and posterior kidney changes associated with oxidative stress damages. Following recovery period, all measured parameters showed varying degrees in their reversibility to the control level. These findings provide important insights about the acute toxic effects of CPF on fish and show potential to be used as biomarkers in further toxicological evaluation studies.

Decreased vaccine antibody titers following exposure to multiple metals and metalloids in e-waste-exposed preschool children

We explored acquired immunity resulting from vaccination in 3 to 7-year-old children, chronically exposed to multiple heavy metals and metalloids, in an e-waste recycling area (Guiyu, China). Child blood levels of ten heavy metals and metalloids, including lead (Pb), arsenic (As), mercury (Hg), chromium (Cr), cadmium (Cd), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn) and selenium (Se), and seven vaccine antibodies (diphtheria, pertussis, tetanus, hepatitis B, Japanese encephalitis, polio, measles) were measured. The exposed group had higher levels of blood Pb, Mn, Cu, Zn and Cr compared to the reference group (P < 0.05). Levels of all vaccine antibodies in the exposed group were significantly lower than in the reference group (P < 0.01). All vaccine antibodies negatively correlated with blood concentrations of Cu, Zn and Pb, based on spearman rank correlation analysis. Multiple logistic regression and univariate analyses identified the location of residence (Guiyu), high blood Pb (>10 μg/dL) and high blood Cu and Zn (upper median value of each group) to be inversely associated with seven antibody titers. Antibody titers increased with age, BMI, high blood Mn (>15 μg/L), and high blood Cd and Ni (upper median value of each group). Results suggest multiple heavy metal and metalloid exposure, especially to Pb, Zn and Cu, may be a risk factor inhibiting the development of child immunity, resulting in decreased child antibody levels against vaccines.

Elevated lead levels and adverse effects on natural killer cells in children from an electronic waste recycling area

Lead (Pb) has been proved to exert immunotoxicity to influence immune homeostasis in humans. To monitor the internal Pb level and evaluate its effect on natural killer (NK) cells and cytokine/chemokine concentrations, we recruited 285 preschool children from Guiyu, one of the largest electronic waste (e-waste) destinations and recycling areas in the world, and known to have high concentrations of Pb in the air, soil, water, sediment and plants. A total of 126 preschool children were selected from Haojiang as a reference group. Results showed that children in Guiyu, the exposed area, had higher blood Pb levels and lower percentages of NK cells than children from the reference area. A significantly negative association was found between the percentage of NK cells and increasing Pb levels. Moreover, children in Guiyu area had higher platelet counts and IL-1β concentrations, and lower levels of IL-2, IL-27, MIP-1α and MIP-1β were observed in the exposed children. These changes might not be conducive to the development and differentiation of NK cells. Taken together, the elevated Pb levels result in the lower percentages of NK cells, but also alter the levels of platelets, IL-1β and IL-27, which might be unconducive to the activity and function of NK cells.

Urinary Metabolites of Polycyclic Aromatic Hydrocarbons and the Association with Lipid Peroxidation: A Biomarker-Based Study between Los Angeles and Beijing

Air pollution is among the top threats to human health in China. As air toxicants, polycyclic aromatic hydrocarbons (PAHs) could bring significant risks to population; however, the exposure to PAHs in China and its health impact are not fully understood. In 2012, a summer exchange program allowed 10 students to travel from Los Angeles to Beijing and stay there for 10 weeks. Based on the program, this study investigated the difference in urinary concentration of 12 hydroxylated-PAHs (Σ12OH-PAHs) and malondialdehyde (MDA) between the two cities. The median concentration of Σ12OH-PAHs in Beijing (14.1 μg g(-1) creatinine) was significantly higher than that in Los Angeles (5.78 μg g(-1) creatinine), indicating a higher exposure in Beijing. The ratios of homogeneous OH-PAHs (e.g., 1-/2-OH-NAP) changed significantly between the two cities (p < 0.01), which might suggest a potential alteration in metabolism subsequent to exposure. A significant association between Σ12OH-PAHs and MDA (p < 0.01) was observed, with the association varying between the two cities. This study suggests that exposure to PAHs might be linked to metabolism alteration and calls for future studies to investigate the role this possible alteration played in the health effects of PAHs exposure.

Estimation of the Unregistered Inflow of Electrical and Electronic Equipment to a Domestic Market: A Case Study on Televisions in Vietnam

Waste electrical and electronic equipment (WEEE) constitutes one of the most problematic waste streams worldwide, and accurately estimating the scale of WEEE can assist in tackling its associated issues. However, obtaining an accurate estimation of WEEE remains a challenge because a share of the waste is difficult to calculate. This share stems from the administratively unregistered (so-called "invisible") inflow of electrical and electronic equipment (EEE) into the domestic market. As a first attempt to qualitatively and quantitatively investigate this invisible inflow, this study discusses the nature of this flow in detail and proposes a calculation pathway for quantifying its magnitude. The size of the invisible inflow to a domestic market (assumed equal to invisible sales) is calculated by subtracting the registered, also called "visible", sales from the total sales. The total sales are modeled, whereas the visible sales are derived from statistical data. The method is illustrated by a case study on televisions (TVs) in Vietnam. The results show that from 2002 to 2013, the invisible TV inflow contributed, on average, 15% to the total TV sales (coefficient of variation: 0.21). This average share would increase by approximately 1.0% when the maximum number of TVs used per household increased by 1.0%. However, it would decrease by 1.7% when the visible sales increased by 1.0%. Additionally, the average share of the invisible TV inflow would change from 15% to 27% when an unadjusted constant instead of an adjusted time-varying lifespan is employed. This first estimation of the invisible EEE inflow to the domestic market can be improved with additional knowledge and data in the future.

Effects of PCBs and PBDEs on thyroid hormone, lymphocyte proliferation, hematology and kidney injury markers in residents of an e-waste dismantling area in Zhejiang, China

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two typical categories of contaminants released from e-waste dismantling environments. In China, the body burdens of PCBs and PBDEs are associated with abnormal thyroid hormones in populations from e-waste dismantling sites, but the results are limited and contradictory. In this study, we measured the serum levels of PCBs and PBDEs and the thyroid hormone free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in 40 residents in an e-waste dismantling area and in 15 residents in a control area. Additionally, we also measured some lymphocyte proliferation indexes, hematologic parameters and kidney injury markers, including white blood cells, neutrophils, monocytes, lymphocytes, hemoglobin, platelets, serum creatinine and beta 2-microglobulin (β2-MG). The results indicated that the mean level of ΣPCBs in the exposure group was significantly higher than that in the control group (964.39 and 67.98 ng g(-1), p<0.0001), but the mean level of ΣPBDEs in the exposure group was not significantly higher than that in the controls (139.32 vs. 75.74 ng g(-1), p>0.05). We determined that serum levels of FT3, FT4, monocytes and lymphocytes were significantly lower, whereas the levels of neutrophils, hemoglobin, platelets and serum creatinine were significantly higher in the exposed group (p<0.05). The mean level of ΣPCBs was negatively correlated with levels of FT3, FT4, monocytes and lymphocytes (p<0.05) and positively correlated with levels of neutrophils, hemoglobin, serum creatinine and β2-MG (p<0.05). Additionally, the mean level of ΣPBDEs was positively correlated with levels of white blood cells, hemoglobin and platelets (p<0.05). Our data suggest that exposure to an e-waste dismantling environment may increase the body burdens of PCBs and the specific PBDEs congeners in native residents and that the contaminants released from e-waste may contribute to abnormal changes in body levels of thyroid hormone, hematology and kidney injury markers.

A rapid in vivo zebrafish model to elucidate oxidative stress-mediated PCB126-induced apoptosis and developmental toxicity

Dioxin-like 3,3',4,4',5-pentachlorobiphenyl (PCB126) is one of the most potent and widespread environmental pollutants. Although PCB126-induced toxicity is related to the aryl hydrocarbon receptor pathway, there is still no study that has constructed an in vivo visual model to clarify the role of the Nrf2/ARE signaling pathway in the oxidative stress mechanism of PCB126-induced toxicity. In the present study, an in vivo zebrafish model of nrf2a fused to enhanced green fluorescent protein (nrf2a-eGFP) was constructed. The zebrafish embryos microinjected with nrf2a-eGFP (72h postfertilization) were exposed to various concentrations of PCB126 (0, 25, 50, 100, 200μg/L) or 30mMN-acetylcysteine (NAC)+200μg/L PCB126. After 72h exposure, PCB126 significantly increased the malformation rates and induced eGFP expression in a dose-dependent manner in several zebrafish tissue types. The distribution of eGFP fluorescence coincided with developmental deformity sites. NAC pretreatment effectively counteracted PCB126-induced developmental toxicity including heart rate, pericardial edema, and body length. The highest PCB126 dose, 200μg/L, produced marked apoptosis in the eye, gill, and trunk detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. At 48 and 72h exposure, 200μg/L PCB126 affected glutathione metabolism as evidenced by decreased glutathione and increased glutathione disulfide concentrations, indicative of oxidative stress. These effects were also counteracted by NAC pretreatment. Furthermore, the Nrf2-regulated genes gclc, gpx, gstp1, and hmox1 were significantly induced at 24, 48, and 72h at the highest PCB126 exposures but not in the NAC-pretreated group. In addition, a significant increase in ROS generation was detected in zebrafish larvae at 72h PCB126 exposure, which might offer a link for future mechanistic studies. Collectively, these data suggest that PCB126-induced developmental toxicity and apoptosis in the nrf2a-eGFP-injected zebrafish model are due to oxidative stress mediated by disruption to glutathione metabolism and changes in Nrf2-regulated gene expression.

E-waste environmental contamination and harm to public health in China

The adverse effects of electronic waste (e-waste) on the human body have stirred up concern in recent years. China is one of the countries that confront serious pollution and human exposure of e-waste, and the majority of the population is exposed to potentially hazardous substances that are derived from informal e-waste recycling processes. This study reviews recent reports on human exposure to e-waste in China, with particular focus on exposure routes (e.g., inhalation and ingestion) and several toxicities of human (e.g., endocrine system, respiratory system, reproductive system, developmental toxicity, neurotoxicity, and genetic toxicity). Pieces of evidence that associate e-waste exposure with human health effects in China are assessed. The role of toxic heavy metals (e.g., lead, cadmium, chromium, mercury, and nickel) and organic pollutants (e.g., polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), polybrominated biphenyls (PBBs), polyhalogenated aromatic hydrocarbons (PHAHs), bisphenol A (BPA)) on human health is also briefly discussed.

Associations of cadmium, bisphenol A and polychlorinated biphenyl co-exposure in utero with placental gene expression and neonatal outcomes

In utero co-exposure to endocrine disrupting compounds can perturb fetal development. However, the effect of co-exposure on pivotal regulatory genes has seldom been investigated. We explored the effects of in utero co-exposure to cadmium (Cd), bisphenol A (BPA) and polychlorinated biphenyls (PCBs) on master regulator genes. We recruited 284 healthy pregnant women, of whom 262 provided both cord blood and placenta samples, and 200 had all measurements taken. Placental Cd, cord blood BPA and total PCBs in the exposed group were higher than a reference group. KISS1 expression level in placental tissue was threefold higher in the exposed group than in the reference, and was positively associated with all toxicants. Leptin and leptin receptor expression were also significantly higher, but were only associated with BPA. From our findings, we conclude that lower birth weight is correlated with Cd and PCBs, and may result from the increased KISS1 mRNA expression.

Significant accumulation of persistent organic pollutants and dysregulation in multiple DNA damage repair pathways in the electronic-waste-exposed populations

Electronic waste (e-waste) has created a worldwide environmental and health problem, by generating a diverse group of hazardous compounds such as persistent organic pollutants (POPs). Our previous studies demonstrated that populations from e-waste exposed region have a significantly higher level of chromosomal aberrancy and incidence of DNA damage. In this study, we further demonstrated that various POPs persisted at a significantly higher concentration in the exposed group than those in the unexposed group. The level of reactive oxygen species and micronucleus rate were also significantly elevated in the exposed group. RNA sequencing analysis revealed 31 genes in DNA damage responses and repair pathways that were differentially expressed between the two groups (Log2 ratio >1 or <-1). Our data demonstrated that both females and males of the exposed group have activated a series of DNA damage response genes; however many important DNA repair pathways have been dysregulated. Expressions of NEIL1/3 and RPA3, which are critical in initiating base pair and nucleotide excision repairs respectively, have been downregulated in both females and males of the exposed group. In contrast, expression of RNF8, an E3 ligase involved in an error prone non-homologous end joining repair for DNA double strand break, was upregulated in both genders of the exposed group. The other genes appeared to be differentially expressed only when the males or females of the two groups were compared respectively. Importantly, the expression of cell cycle regulatory gene CDC25A that has been implicated in multiple kinds of malignant transformation was significantly upregulated among the exposed males while downregulated among the exposed females. In conclusion, our studies have demonstrated significant correlations between e-waste disposing and POPs accumulation, DNA lesions and dysregulation of multiple DNA damage repair mechanisms in the residents of the e-waste exposed region.

Polycyclic aromatic hydrocarbon (PAH) exposure and oxidative stress for a rural population from the North China Plain

Polycyclic aromatic hydrocarbons (PAHs) belong to a class of ubiquitous pollutants and are possibly associated with adverse health effects. In this study, we aimed to assess PAH exposure by measuring the hydroxylated metabolites (hydroxy-PAHs) in urine samples of a rural population from the North China Plain and to explore the possible associations between PAH exposure and oxidative stress indicated by urinary malondialdehyde (MDA) and 8-hydroxy-2′-deoxyguanosine (8-OHdG). High levels of urinary hydroxy-PAHs were observed, with the geometric mean concentrations of 0.57, 2.2, 5.0, 7.0, and 16.6 μg g−1 creatinine for 1-hydroxypyrene, hydroxyphenanthrenes, hydroxyfluorenes, hydroxybiphenyls, and hydroxynaphthalenes, respectively. Particularly in the winter season, the exposures were 2.3–6.0-fold of those in the spring. Corresponding to PAH exposure, levels of urinary MDA were positively associated with hydroxy-PAHs after controlling for confounders in the linear regression models (p < 0.05). An estimation indicated 21.3–39.3 % increment of urinary MDA per one-fold increase of hydroxy-PAHs. In contrast, no significant correlation was found between urinary 8-OHdG and hydroxy-PAHs; alternatively, living at the e-waste recycling site was found a significant factor on this oxidative DNA damage. These results provide evidence on high PAH exposure and the induction of oxidative stress on lipid peroxidation for this rural population.

A multi-biomarker risk assessment of the impact of brominated flame retardant-decabromodiphenyl ether (BDE209) on the antioxidant system of earthworm Eisenia fetida

Decabromodiphenyl ether (BDE209) is the major contaminant at e-waste recycling sites (EWRSs), and its potential toxicological effects on terrestrial organisms have received extensive attention. However, the impacts of BDE209 on the antioxidant defense system in terrestrial organisms remain vague. Therefore, indoor incubation tests were performed systematically on control and contaminated soil samples to determine the effects of BDE209 on the antioxidant system of earthworm Eisenia fetida. The results showed that compared to the controls, superoxide dismutase (SOD) activities in all treated groups were elevated significantly after 21 and 28 days exposure; catalase (CAT) activities were much higher in all tests during the entire exposure period; peroxidase (POD) and glutathione-s-transferase (GST) activities generally decreased and indicated contrary response trend; the total antioxidant capacity (T-AOC) after exposure to low level of BDE209 (1 mg kg(-1)) was induced, whereas at 10 and 100 mg kg(-1) concentrations it showed suppression status; electron paramagnetic resonance (EPR) spectra suggested that hydroxyl radicals (OH) in earthworms were significantly induced by BDE209; the changes in malondialdehyde (MDA) contents suggested that reactive oxygen species (ROS) might lead to cellular lipid peroxidation in earthworms. The results of these observations suggested that severe oxidative stress occurred in E. fetida, and it may play an important role in inducing the BDE209 toxicity to earthworms.

Tracking the global generation and exports of e-waste. Do existing estimates add up?

The transport of discarded electronic and electrical appliances (e-waste) to developing regions has received considerable attention, but it is difficult to assess the significance of this issue without a quantitative understanding of the amounts involved. The main objective of this study is to track the global transport of e-wastes by compiling and constraining existing estimates of the amount of e-waste generated domestically in each country MGEN, exported from countries belonging to the Organization for Economic Cooperation and Development (OECD) MEXP, and imported in countries outside of the OECD MIMP. Reference year is 2005 and all estimates are given with an uncertainty range. Estimates of MGEN obtained by apportioning a global total of ∼ 35,000 kt (range 20,000-50,000 kt) based on a nation's gross domestic product agree well with independent estimates of MGEN for individual countries. Import estimates MIMP to the countries believed to be the major recipients of e-waste exports from the OECD globally (China, India, and five West African countries) suggests that ∼ 5,000 kt (3,600 kt-7,300 kt) may have been imported annually to these non-OECD countries alone, which represents ∼ 23% (17%-34%) of the amounts of e-waste generated domestically within the OECD. MEXP for each OECD country is then estimated by applying this fraction of 23% to its MGEN. By allocating each country's MGEN, MIMP, MEXP and MNET = MGEN + MIMP - MEXP, we can map the global generation and flows of e-waste from OECD to non-OECD countries. While significant uncertainties remain, we note that estimated import into seven non-OECD countries alone are often at the higher end of estimates of exports from OECD countries.

Polybromobenzene pollutants in the atmosphere of North China: levels, distribution, and sources

Brominated flame retardants (BFRs) are important persistent organic pollutants. Analysis of BFRs in atmospheric samples in a previous study led us to suspect the presence of unidentified organic bromides, other than polybrominated diphenyl ethers (PBDEs), in the atmosphere. In this study, we identified and quantified polybromobenzenes, a group of organic bromides, in air samples collected through passive sampling in gridded observations in North China. We investigated their concentrations and spatial distribution, and estimated the proportion due to different sources. We detected seven species of polybromobenzenes, including hexabromobenzene (HBB), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), pentabromobenzene (PeBB), tetrabromobenzenes (TeBBs), and tribromotoluene (TrBT), in all or most of the field samples, indicating widespread occurrence of this class of pollutants. The median concentrations of each pollutant ranged from 20.0 to 144 pg/sample (or from 0.07 to 1.16 pg/m(3)), with relatively high concentrations found near e-waste recycling sites, BFR manufacturing sites, and areas of high population density. Positive matrix factorization (PMF) analysis revealed that ∼70% of HBB, PBT, PBEB, and PeBB was from commercial products, while ∼80% of 1,2,3,5-TeBB, 1,2,4,5-TeBB, and 2,4,5-TrBT was linked with BFR manufacturing. This study provides essential information on widespread polybromobenzene pollutants in the atmosphere, particularly TeBBs and TrBT, for which this is the first report of their presence as atmospheric pollutants.

Spatial distribution of polychlorinated naphthalenes in the atmosphere across North China based on gridded field observations

Polychlorinated naphthalenes (PCNs) belong to a group of dioxin-like pollutants; however little information is available on PCNs in North China. In this study, gridded field observations by passive air sampling at 90 sites were undertaken to determine the levels, spatial distributions, and sources of PCNs in the atmosphere of North China. A median concentration of 48 pg m(-3) (range: 10-2460 pg m(-3)) for ∑29PCNs indicated heavy PCN pollution. The compositional profile indicated that nearly 90% of PCNs observed were from thermal processes rather than from commercial mixtures. Regarding the source type, a quantitative apportionment suggested that local non-point emissions contributed two-thirds of the total PCNs observed in the study, whereas a point source of electronic-waste recycling site contributed a quarter of total PCNs. The estimated toxic equivalent quantity for dioxin-like PCNs ranged from 0.97 to 687 fg TEQ m(-3), with the electronic-waste recycling site with the highest risk.

Gridded field observations of polybrominated diphenyl ethers and decabromodiphenyl ethane in the atmosphere of north China

Brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) are important pollutants, yet few data on ambient BFRs levels have been available for North China, one of the most developed regions of the country. In this study, we investigated levels and spatial distributions of BFRs based on gridded field observations coupled with passive air sampling in the aforementioned region. A model incorporating both point and nonpoint sources was developed to simulate the spatial distribution and to achieve source apportionment. Although high concentration was observed at an electronic-waste (e-waste) recycling site, the median level of the sum of tri-, tetra-, hepta-, hexa-, and hepta-PBDEs (∑10PBDEs) was 0.56 ng/sample, which was lower than those observed previously in mainland China. Source apportionment revealed that nonpoint emissions contributed nearly 78% of ∑10PBDEs observed in this study. In contrast, high levels of BDE-209 and DBDPE were observed, with median concentrations of 4.0 and 10.2 ng/sample, respectively. Point sources located in the region around Laizhou Bay, Shandong Province were the major sources, which contributed 31% of BDE-209 and 70% of DBDPE observed in this study, indicating that this manufacturing base was the most important source region for atmospheric deca-BFRs in North China. To our knowledge, this is the first study to report source apportionment of atmospheric BFRs based on gridded field observations.

Cotransport of titanium dioxide and fullerene nanoparticles in saturated porous media

This study investigated the cotransport of titanium dioxide nanoparticles (nTiO2) and fullerene nanoparticles (nC60), two of the most widely utilized nanoparticles, in saturated quartz sand under a series of ionic strengths in NaCl solutions (0.1-10 mM) at both pH 5 and 7. Under all examined ionic strengths at pH 5, both breakthrough curves and retained profiles of nTiO2 in the copresence of nC60 were similar to those without nC60, indicating that nC60 nanoparticles copresent in suspensions did not significantly affect the transport and retention of nTiO2 in quartz sand at pH 5. In contrast, under all examined ionic strengths at pH 7, the breakthrough curves of nTiO2 in the copresence of nC60 in suspensions were higher and the retained profiles were lower than those without nC60, which demonstrated that the presence of nC60 in suspensions increased the rate of transport (decreased retention) of nTiO2 in quartz sand at pH 7. Competition of deposition sites on quartz sand surfaces by the copresence of nC60 was found to contribute to the increased nTiO2 transport at pH 7. Under all examined ionic strength conditions at both pH 5 and 7, the breakthrough curves of nC60 were reduced in the copresence of nTiO2, and the corresponding retained profiles were higher than those without nTiO2, indicating that the presence of nTiO2 decreased the transport of nC60 in quartz sand. Co-deposition of nC60 with nTiO2 in the form of nTiO2-nC60 clusters as well as the deposition of nC60 onto previously deposited nTiO2 were responsible for the increased nC60 deposition in the presence of nTiO2 at pH 5, whereas deposition of nC60 onto surfaces of predeposited nTiO2 was found to be responsible for the increased nC60 deposition at pH 7.