Lead induced oxidative DNA damage in battery-recycling child workers from Bangladesh

Exploring urinary biomarkers to assess oxidative DNA damage resulting from BTEX exposure in street children

Children are highly susceptible to environmental contaminants as their physiology and some metabolic pathways differ from adults. The present cross-sectional study aimed to assess whether exposure to benzene, toluene, ethylbenzene, o,p-xylene, and m-xylene (BTEX) affects oxidative DNA damage in street children using a biomonitoring approach. Thirty-five boys (7-13 years of age), exposed by working at a busy intersection, and 25 unexposed boys of similar age and living in the neighborhood near the busy intersection were recruited. Urinary un-metabolized BTEX levels were quantified by a headspace gas chromatography-mass spectrometry (GC-MS). Urinary malonaldehyde (MDA) was measured with spectrophotometry. Sociodemographic and lifestyle conditions information was collected by interviews using administered questionnaires. Exposed subjects provided urine before (BE) and after work exposure (AE), while unexposed boys gave a single morning sample. Urinary BTEX concentrations in BE samples were similar to unexposed. Concentrations in AE samples were 2.36-fold higher than observed in BE samples (p < 0.05) and higher than those in the unexposed group (p < 0.05). In addition, urinary MDA levels in AE samples were 3.2 and 3.07-times higher than in BE samples and in the unexposed group (p < 0.05). Environmental tobacco smoke (ETS) increased urinary BTEX and MDA levels in both groups. Our findings confirm that street children working at busy intersections are significantly exposed to BTEX, which is associated with oxidative stress. Implementing protective measures is crucial to reduce exposure and to improve health outcomes in this group.

The Health Impacts of Hazardous Chemical Exposures among Child Labourers in Low- and Middle-Income Countries

Of 218 million working children worldwide, many are suspected to be exposed to hazardous chemicals. This review aims to synthesize reported evidence over the last two decades on chemical exposure and adverse health consequences in children labourers in low- and middle-income Countries (LMIC). Included studies investigated health outcomes related to chemical exposures among child labourers aged 5-18 in LMIC. Twenty-three papers were selected for review, focusing on pesticides (n = 5), solvents (n = 3), metals (n = 13) and persistent organic pollutants (POPs) (n = 2). Adverse health effects identified among child labourers included abnormal biomarkers, for example elevated blood and urine chemical concentrations, neurobehavioural deficits and neurological symptoms, mental health issues, oxidative stress and DNA damage, poor growth, asthma, and hypothyroidism. Workplace exposure to chemicals has pernicious health effects on child labourers. Large research gaps exist, in particular for long-term health impacts through chronic conditions and diseases with long latencies. A sizeable disease burden in later life is likely to be directly attributable to chemicals exposures. We urge national and international agencies concerned with child labour and occupational health, to prioritize research and interventions aiming to reduce noxious chemical exposures in workplaces where children are likely to be present.

Ferulic acid exerts Nrf2-dependent protection against prenatal lead exposure-induced cognitive impairment in offspring mice

Prenatal and/or early postnatal exposure to lead (Pb) may be associated with deficits in cognitive function in the toddler offspring, and oxidative stress likely play a central role in mediating these adverse effects. Here, we tested the hypothesis that ameliorative effect of ferulic acid (FA) on lead-induced cognitive deficits attributed to its antioxidant properties in a nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-dependent manner in the context of prenatal Pb exposure. To test this hypothesis, Nrf2 knockout and C57BL/6 wild type mouse dams were exposed/unexposed to PbAc (250 ppm) during gestation day 5 to postnatal day 14 via drinking water, and FA (50 mg/kg)/vehicle was administered orally to dams for 31 d. Spatial learning and memory in pups was assessed by Morris water maze. Biochemical assays, real-time PCR, western blot techniques were employed to evaluate oxidative stress and signaling pathways in the brain of pups. We report that lead acetate (PbAc) leads to deficits in cognitive functions in offspring, which were partially attenuated by FA (P<.05). In parallel, pretreatment with FA also significantly inhibited the PbAc-induced oxidative stress, as indicated by a change in NAD+/NADH ratio, glutathione (GSH) and malondialdehyde contents (all P<.05). Interestingly, FA significantly elevated the glutamate cysteine ligase and heme oxygenase 1 at levels of transcription and translation in both mice exposed and unexposed to Pb, increasing de novo synthesis of GSH (all P<.05). Furthermore, maternal FA administration activates extracellular signal-regulated kinases 1 and 2 and promotes more Nrf2 nuclear accumulation by increasing the Nrf2 total protein in brain of offspring mice (all P<.05). Conversely, FA failed to influence Pb-induced both memory deficits and oxidative stress in offspring of Nrf2 knockout mice (all P≥.05), suggesting that Nrf2 is essential in mediating the cognition-enhancing and antioxidant effects of FA. Overall, our results demonstrate that FA protects against Pb-induced offspring's cognitive deficits, suggesting that it is a promising candidate for the treatment of Pb toxicity.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) μg/dl in 2016 to 18.5 (10.5, 27.2) μg/dl in 2017, and to 20.8 (11.3, 31.0) μg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.

Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids

This study investigated the relationship between lead (Pb) speciation determined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy in <10 μm particulate matter (PM₁₀) from mining/smelting impacted Australian soils (PP, BHK5, BHK6, BHK10 and BHK11) and inhalation exposure using two simulated lung fluids [Hatch's solution, pH 7.4 and artificial lysosomal fluid (ALF), pH 4.5]. Additionally, elemental composition of Pb rich regions in PP PM₁₀ and the post-bioaccessibility assay residuals were assessed using a combination of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to provide insights into how extraction using simulated lung fluids may influence Pb speciation in vitro. Correlation between Pb speciation (weighted %) and bioaccessibility (%) was assessed using Pearson r (α = 0.1 and 0.05). Lead concentration in PM₁₀ samples ranged from 782 mg/kg (BHK6) to 7796 mg/kg (PP). Results of EXAFS analysis revealed that PP PM₁₀ was dominated by Pb adsorbed onto clay/oxide, while the four BHK PM₁₀ samples showed variability in the weighted % of Pb adsorbed onto clay/oxide and organic matter bound Pb, Pb phosphate, anglesite and galena. When bioaccessibility was assessed using different in vitro inhalation assays, results varied between samples and between assays, Pb bioaccessibility in Hatch's solution ranged from 24.4 to 48.4%, while in ALF, values were significantly higher (72.9-96.3%; p < 0.05). When using Hatch's solution, bioaccessibility outcomes positively correlated to anglesite (r:0.6246, p:0.0361) and negatively correlated to Pb phosphate (r: -0.9610, p:0.0041), organic bound Pb (r: -0.7079, p: 0.0578), Pb phosphate + galena + plumbojarosite (r: -0.9350, p: 0.0099). No correlation was observed between Pb bioaccessibility (%) using Hatch's solution and weighted % of Pb adsorbed onto clay/oxide and between bioaccessibility (%) using ALF and any Pb species. SEM and EDX analysis revealed that a layer of O-Pb-Ca-P-Si-Al-Fe formed during the in vitro extraction using Hatch's solution.

Dynamics of Lead Bioavailability and Speciation in Indoor Dust and X-ray Spectroscopic Investigation of the Link between Ingestion and Inhalation Pathways

Lead (Pb) exposure from household dust is a major childhood health concern because of its adverse impact on cognitive development. This study investigated the absorption kinetics of Pb from indoor dust following a single dose instillation into C57BL/6 mice. Blood Pb concentration (PbB) was assessed over 24 h, and the dynamics of particles in the lung and gastro-intestinal (GI) tract were visualized using X-ray fluorescence (XRF) microscopy. The influence of mineralogy on Pb absorption and particle retention was investigated using X-ray absorption near-edge structure spectroscopy. A rapid rise in PbB was observed between 0.25 and 4 h after instillation, peaking at 8 h and slowly declining during a period of 24 h. Following clearance from the lungs, Pb particles were detected in the stomach and small intestine at 4 and 8 h, respectively. Analysis of Pb mineralogy in the residual particles in tissues at 8 h showed that mineral-sorbed Pb and Pb-phosphates dominated the lung, while organic-bound Pb and galena were the main phases in the small intestines. This is the first study to visualize Pb dynamics in the lung and GI tract using XRF microscopy and link the inhalation and ingestion pathways for metal exposure assessment from dust.