Drinking water heavy metal toxicity and chronic kidney diseases: a systematic review

Confined within a sugarcane monoculture: A participatory assessment of water pollution and potential health risks in the community of El Tiple, Colombia

Communities neighboring monoculture plantations are vulnerable to different forms of pollution associated with agro-industrial operations. Herein, we examine the case of El Tiple, a rural Afro descendant community embedded within one of the largest sugarcane plantations in the Americas. We implemented a participatory approach to assess water pollution, exposure via water ingestion, and non-carcinogenic health risks associated with the use of local water sources available to the community. We conducted household surveys to unveil demographic characteristics and family dynamics linked to water consumption. Additionally, we measured water quality parameters and assessed the concentration glyphosate, its major metabolite (aminomethylphosphonic acid) and metals and metalloids. Drinking water El Tiple households is sourced from three primary sources: the local aqueduct system, water delivery trucks, and private deep wells. Tests on water samples from both the local aqueduct and delivery trucks showed no traces of pesticides, metals, or metalloids surpassing regulatory limits set by Colombian or EPA standards. However, we found concentration of contaminants of primary concern, including mercury (up to 0.0052 ppm) and lead (up to 0.0375 ppm) that exceed the permissible regulatory thresholds in water from groundwater wells. Residents of the peripheric subdivisions of El Tiple are four times more reliant on well water extraction than residents of the central area of the town due to lack of access to public drinking water and sanitation infrastructure. Finally, adult women and school-age children have a higher health risk associated with exposure to local pollutants than adult men due to their constant presence in the town. We conclude that expanding the coverage of clean water and sanitation infrastructure to include all households of the community would be the most recommended measure to minimize exposure and risk via ingestion of water pollutants.

Association of urinary and blood lead concentrations with all-cause mortality in US adults with chronic kidney disease: a prospective cohort study

Epidemiological evidence on the relationship between lead exposure and mortality in specific chronic kidney disease (CKD) populations is limited. We aimed to examine the relationship between urinary lead and blood lead concentrations and all-cause mortality in US patients with CKD. This cohort study included 2320 participants with CKD from the National Health and Nutrition Examination Survey (2005-2018), with follow-up until December 31, 2019. All-cause mortality was ascertained by matching US National Death Index records. Hazard ratios (HRs) and 95% confidence intervals (CI) for urinary lead and blood lead concentrations in relation to all-cause mortality were estimated using a weighted Cox regression model. During a median follow-up period of 79 months, a total of 625 participants with CKD succumbed to mortality. Compared to the lowest quartile, the highest quartile of urine and blood lead concentrations was associated with an increased risk of all-cause mortality, with HRs and corresponding 95% CIs of 1.77 (1.05-2.99) and 2.65 (1.38-5.10), respectively. Furthermore, each additional unit increase in urinary and blood lead concentrations was associated with HRs for all-cause mortality of 1.21 (95% CI 1.06-1.38) and 1.09 (95% CI 1.01-1.19), respectively. Kaplan-Meier survival curve analysis and restricted cubic regression spline curve analysis demonstrated significant positive associations between elevated blood lead levels, elevated urinary lead levels, and all-cause mortality risk (P < 0.05). A nonlinear concentration-response relationship was observed between blood lead level and all-cause mortality risk (PNonlinear < 0.05), with an inflection point at a concentration of 1.613 µg/dL. Subgroup analysis as well as sensitivity analysis yielded consistent findings. Our findings demonstrate that elevated levels of lead in urine and blood are associated with a significantly increased mortality risk among patients with CKD, underscoring the importance of reducing lead exposure to mitigate mortality risk in individuals at high risk for CKD.

Uric acid mediates the relationship between mixed heavy metal exposure and renal function in older adult people

Background

Population aging is a pivotal trend observed globally, and the exposure to heavy metals can exacerbate the aging process and lead to kidney damage. However, the impact of combined heavy metal exposure on renal function among older individuals remains elusive. Our study employs machine learning techniques to delve into the effects and underlying mechanisms of mixed exposure to heavy metals on the renal function of the aging population.

Methods

This study extracted comprehensive data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2015 and 2020. A total of 3,175 participants aged 60 years and above, with complete information on six metals - lead, cadmium, manganese, cobalt, mercury, and selenium, along with relevant covariates, were included in the study. To assess the impact of single or mixed metal exposure on the renal function of older adult individuals, various statistical techniques were employed: multiple logistic regression, weighted quantitative sum (WQS) regression, Bayesian kernel machine regression (BKMR), and mediation effects analysis.

Results

Multiple logistic regression revealed that selenium and manganese were protective factors for chronic kidney disease (CKD). Cobalt was a risk factor for CKD. High concentrations of lead, cadmium, and cobalt were risk factors for urinary albumin creatinine ratio (ACR). WQS analyses revealed that mixed metal exposure was positively correlated with estimated glomerular filtration rate (eGFR) but negatively correlated with CKD. Selenium and manganese can neutralize the effects of other metals on eGFR. Mixed metal exposure was positively correlated with ACR, with lead and cadmium having a substantial effect. Mediation analysis showed that uric acid (UA) had a mediating effect of 9.7% and -19.7% in the association between mixed metals exposure and proteinuria and CKD, respectively.

Conclusion

The impact of heavy metals on renal function in the older adult differs from that of adolescents and adults. This study suggests that elevated levels of mixed metals exposure are linked to proteinuria and CKD, with UA serving as a mediating factor.

Improvement of hybrid polyvinyl chloride/dapsone membrane using synthesized silver nanoparticles for the efficient removal of heavy metals, microorganisms, and phosphate and nitrate compounds from polluted water

Heavy metals exist in different water resources and can threaten human health, inducing several chronic illnesses such as cancer and renal diseases. Therefore, this work dealt with the fabrication of highly efficient nanomembranes based on silver nanoparticle (Ag NP)-doped hybrid polyvinyl chloride (PVC) by dapsone (DAP) using an in situ method. Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis were used to confirm the hybridization of PVC as well as the crystalline structure of hybrid PVC nanocomposites. Three varying proportions of Ag NPs (i.e., 0.1, 0.2, and 0.3%) were used to fabricate hybrid PVC-DAP nanomembranes. The Brunauer-Emmet-Teller (BET) method was used to estimate membrane surface area, porosity and distribution of pore volume. The mechanical strength and antibacterial properties of the cased films notably improved when Ag NPs were added depending on the NP ratio inside the matrix. Results obtained from adsorption experiments of PVC-DAP nanomembranes at 35 °C revealed that the optimum nanomembrane was achieved at 0.2% NPs and its percentage of removal effectiveness ranged from 71 to 95% depending on the ion type. The surface morphology of the PVC-DAP-0.2 Ag NPs before and after the adsorption process of the metal ions was analyzed using SEM-EDX. Moreover, the impact of other parameters such as the initial concentrations, pH media, temperature, and contacting time, on the adsorption efficiency of PVC-DAP-0.2 Ag NPs was also investigated. Furthermore, kinetic and adsorption isotherm models were suggested to describe the adsorption efficiency of the PVC-DAP-0.2 Ag NP membrane, and the uptake mechanism of metal ion removal was studied. The obtained outcomes for these fabricated nanomembranes demonstrated that they could be potential candidates for water purification and other potential purposes including biomedical areas.

Relationship between heavy metal concentrations and Chronic kidney disease in population of Hoveyzeh cohort study: A cross-sectional study in Iran

BACKGROUND

Chronic kidney disease (CKD) is a multifactorial disease whose prevalence is increasing worldwide. CKD affects 700 million to 1 billion people worldwide, with a prevalence of 9.1% to 13.4%. In Iran, the reported prevalence of CKD is 15.14%, even higher than the global prevalence. Some studies introduced heavy metals as possible risk factors of CKD. We conducted the first study in Iran to examine the relationship between 10 selected urinary heavy metals and CKD in the Hovayzeh cohort study population.

METHODS

In this cross-sectional study, urine samples were collected from two groups of ca ses (suffering from CKD) and controls (without CKD) with equal size (47 people each). Analysis of the 10 sellected heavy metals in the samples was conducted using inductively coupled plasma emission spectroscopy. Basic Information was obtained from the Howayizeh Cohort Study Center. The data was analyzed using SPSS-26 and Excel-2016 software.

RESULTS

There were no significant differences between urinary heavy metal concentrations of case and control groups (P < 0.05). While, the concentration of As, Cr, Cu, Mn, and Ni exceeded the reference limits of Germany, Canada, England, and Belgium. Se and Cd also surpassed the reference limits of England. After adjusting for confounding variables for each μg/l increase in urinary Cd, Ni, Pb, and Se the OR of CKD increased by 20.2%, 4.8%, 3.1%, and 2.6%, respectively. Although, these relationships were not statistically significant. In addition, two groups of heavy metals had a positive and significant correlation: (1) Se, Zn, As, Cu, and Cr; (2) Pb, Cd, and As; and (3) Cd and Ni.

CONCLUSION

we found no significant relationship between urinary heavy metal and CKD. However, there was significant positive correlation in some of urinary heavy metals may indicate their shared resources. Furthermore, the concentration of most heavy metals in the urine of the participants was higher than the reference limits of these metals in the urine of healthy people from other countries. Thus, the elevated levels of these metals could still pose a risk to human health. Therefore, it is necessary to conduct prospective studies with a larger sample size in this area.

Study on the mechanism of arsenic-induced renal injury based on SWATH proteomics technology

BACKGROUND

Arsenic (As) poisoning is a worldwide endemic disease affecting thousands of people. As is excreted mainly through the renal system, and arsenic has toxic effects on the kidneys, but the mechanism has not been elucidated. In this study, the molecular basis of arsenic's nephrotoxicity was studied by using a high-throughput proteomics technique.

METHODS

Eight SD (Sprague-Dawley) rats, half male and half female, were fed an As diet containing 50 mg/kg NaAsO2. Age- and sex-matched rats fed with regular chow were used as controls. At the end of the experiment (90 days), kidney tissue samples were collected and assessed for pathological changes using hematoxylin-eosin staining. Proteomic methods were used to identify alterations in protein expression levels in kidney tissues, and bioinformatic analyses of differentially expressed proteins between arsenic-treated and control groups were performed. The expression of some representative proteins was validated by Western blot analysis.

RESULTS

NaAsO2 could induce renal injury. Compared with the control group, 112 proteins were up-regulated, and 46 proteins were down-regulated in the arsenic-treated group. These proteins were associated with the electron transport chain, oxidative phosphorylation, mitochondrial membrane, apoptosis, and proximal tubules, suggesting that the mechanisms associated with them were related to arsenic-induced kidney injury and nephrotoxicity. The expressions of Atp6v1f, Cycs and Ndufs1 were verified, consistent with the results of omics.

CONCLUSION

These results provide important evidence for arsenic-induced kidney injury and provide new insights into the molecular mechanism of arsenic-induced kidney injury.

Quantitative risk analysis of sediment heavy metals using the positive matrix factorization-based ecological risk index method: a case of the Kuye River, China

Identifying the sources of heavy metals (HMs) in river sediments is crucial to effectively mitigate sediment HM pollution and control its associated ecological risks in coal-mining areas. In this study, ecological risks resulting from different pollution sources were evaluated using an integrated method combining the positive matrix factorization (PMF) and the potential ecological risk index (RI) model. A total of 59 sediment samples were collected from the Kuye River and analyzed for eight HMs (Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg). The obtained results showed that the sediment HM contents were higher than the corresponding soil background values in Shaanxi Province. The average sediment Hg content was 3.42 times higher than the corresponding background value. The PMF results indicated that HMs in the sediments were mainly derived from industrial, traffic, agricultural, and coal-mining sources. The RI values ranged from 26.15 to 483.70. Hg was the major contributor (75%) to the ecological risk in the vicinity of the Yanjiata Industrial Park. According to the PMF-based RI model, coal-mining activities exhibited the strongest impact on the river ecosystem (48.79%), followed, respectively, by traffic (34.41%), industrial (12.70%), and agricultural (4.10%) activities. These results indicated that the major anthropogenic sources contributing to the HM contents in the sediments are not necessarily those posing the greatest ecological risks. The proposed integrated approach in this study was useful in evaluating the ecological risks associated with different anthropogenic sources in the Kuye River, providing valuable suggestions for reducing sediment HM pollution and effectively protecting river ecosystems.

Capturing time-dependent activation of genes and stress-response pathways using transcriptomics in iPSC-derived renal proximal tubule cells

Transcriptomic analysis is a powerful method in the utilization of New Approach Methods (NAMs) for identifying mechanisms of toxicity and application to hazard characterization. With this regard, mapping toxicological events to time of exposure would be helpful to characterize early events. Here, we investigated time-dependent changes in gene expression levels in iPSC-derived renal proximal tubular-like cells (PTL) treated with five diverse compounds using TempO-Seq transcriptomics with the aims to evaluate the application of PTL for toxicity prediction and to report on temporal effects for the activation of cellular stress response pathways. PTL were treated with either 50 μM amiodarone, 10 μM sodium arsenate, 5 nM rotenone, or 300 nM tunicamycin over a temporal time course between 1 and 24 h. The TGFβ-type I receptor kinase inhibitor GW788388 (1 μM) was used as a negative control. Pathway analysis revealed the induction of key stress-response pathways, including Nrf2 oxidative stress response, unfolding protein response, and metal stress response. Early response genes per pathway were identified much earlier than 24 h and included HMOX1, ATF3, DDIT3, and several MT1 isotypes. GW788388 did not induce any genes within the stress response pathways above, but showed deregulation of genes involved in TGFβ inhibition, including downregulation of CYP24A1 and SERPINE1 and upregulation of WT1. This study highlights the application of iPSC-derived renal cells for prediction of cellular toxicity and sheds new light on the temporal and early effects of key genes that are involved in cellular stress response pathways.

Plasmonic nanoparticle's anti-aggregation application in sensor development for water and wastewater analysis

Colorimetric sensors have emerged as a powerful tool in the detection of water pollutants. Plasmonic nanoparticles use localized surface plasmon resonance (LSPR)-based colorimetric sensing. LSPR-based sensing can be accomplished through different strategies such as etching, growth, aggregation, and anti-aggregation. Based on these strategies, various sensors have been developed. This review focuses on the newly developed anti-aggregation-based strategy of plasmonic nanoparticles. Sensors based on this strategy have attracted increasing interest because of their exciting properties of high sensitivity, selectivity, and applicability. This review highlights LSPR-based anti-aggregation sensors, their classification, and role of plasmonic nanoparticles in these sensors for the detection of water pollutants. The anti-aggregation based sensing of major water pollutants such as heavy metal ions, anions, and small organic molecules has been summarized herein. This review also provides some personal insights into current challenges associated with anti-aggregation strategy of LSPR-based colorimetric sensors and proposes future research directions.

Revisiting the Role of NAG across the Continuum of Kidney Disease

Acute and chronic kidney diseases are an evolving continuum for which reliable biomarkers of early disease are lacking. The potential use of glycosidases, enzymes involved in carbohydrate metabolism, in kidney disease detection has been under investigation since the 1960s. N-acetyl-beta-D-glucosaminidase (NAG) is a glycosidase commonly found in proximal tubule epithelial cells (PTECs). Due to its large molecular weight, plasma-soluble NAG cannot pass the glomerular filtration barrier; thus, increased urinary concentration of NAG (uNAG) may suggest injury to the proximal tubule. As the PTECs are the workhorses of the kidney that perform much of the filtration and reabsorption, they are a common starting point in acute and chronic kidney disease. NAG has previously been researched, and it is widely used as a valuable biomarker in both acute and chronic kidney disease, as well as in patients suffering from diabetes mellitus, heart failure, and other chronic diseases leading to kidney failure. Here, we present an overview of the research pertaining to uNAG’s biomarker potential across the spectrum of kidney disease, with an additional emphasis on environmental nephrotoxic substance exposure. In spite of a large body of evidence strongly suggesting connections between uNAG levels and multiple kidney pathologies, focused clinical validation tests and knowledge on underlining molecular mechanisms are largely lacking.

Nephrotoxic Biomarkers with Specific Indications for Metallic Pollutants: Implications for Environmental Health

Environmental and occupational exposure to heavy metals and metalloids is a major global health risk. The kidney is often a site of early damage. Nephrotoxicity is both a major consequence of heavy metal exposure and potentially an early warning of greater damage. A paradigm shift occurred at the beginning of the 21st century in the field of renal medicine. The medical model of kidney failure and treatment began to give way to a social model of risk factors and prevention with important implications for environmental health. This development threw into focus the need for better biomarkers: markers of exposure to known nephrotoxins; markers of early damage for diagnosis and prevention; markers of disease development for intervention and choice of therapy. Constituents of electronic waste, e-waste or e-pollution, such as cadmium (Cd), lead (Pb), mercury (HG), arsenic (As) and silica (SiO₂) are all potential nephrotoxins; they target the renal proximal tubules through distinct pathways. Different nephrotoxic biomarkers offer the possibility of identifying exposure to individual pollutants. In this review, a selection of prominent urinary markers of tubule damage is considered as potential tools for identifying environmental exposure to some key metallic pollutants.

A Bibliometric Analysis and Review of Resource Management in Internet of Water Things: The Use of Game Theory

To understand the current state of research and to also reveal the challenges and opportunities for future research in the field of internet of water things for water quality monitoring, in this study, we conduct a bibliometric analysis and a comprehensive review of the published research from 2012 to 2022 on internet of water things for water quality monitoring. The bibliometric analysis method was used to analyze the collected published papers from the Scopus database. This helped to determine the majority of research topics in the internet of water things for water quality monitoring research field. Subsequently, an in depth comprehensive review of the relevant literature was conducted to provide insight into recent advances in internet of water things for water quality monitoring, and to also determine the research gaps in the field. Based on the comprehensive review of literature, we identified that reviews of the research topic of resource management in internet of water things for water quality monitoring is less common. Hence, this study aimed to fill this research gap in the field of internet of water things for water quality monitoring. To address the resource management challenges associated with the internet of water things designed for water quality monitoring applications, this paper is focused on the use of game theory methods. Game theory methods are embedded with powerful mathematical techniques that may be used to model and analyze the behaviors of various individual, or any group, of water quality sensors. Additionally, various open research issues are pointed out as future research directions.

Interaction between Single Nucleotide Polymorphisms (SNP) of Tumor Necrosis Factor-Alpha (TNF-α) Gene and Plasma Arsenic and the Effect on Estimated Glomerular Filtration Rate (eGFR)

When poisons enter the human body, tumor necrosis factor (TNF-α) will increase and cause damage to tissues through oxidative stress or inflammatory reaction. In previous studies, arsenic (As) has known to cause many health problems. Some studies have shown that As exposure is negatively correlated with estimated glomerular filtration rate (eGFR), or with the prevalence of proteinuria. At present, there are few studies focusing on the effects of As exposure and TNF-α single nucleotide polymorphism (SNP) to eGFR; thus, this study was intended to explore the interactions between TNF-α SNPs and plasma As and their effects on eGFR. A cohort of 500 adults, aged 30 to 70 years, was randomly selected from Taiwan Biobank (TWB). We used the gene chip to screen out seven SNPs of the TNF-α gene and used the results, combined with questionnaires, biochemical tests, and stored plasma samples from the TWB, for the analysis of As by inductively coupled plasma mass spectrometry (ICP-MS). After adjustments for BMI, hypertension, hyperlipidemia, kidney stones, and smoking habits, multiple regression statistics were performed to explore the interaction between SNPs and plasma As with eGFR. In this sample of the general population, plasma As had a significant association with the decline of eGFR (β (SE) = −7.92 (1.70), p < 0.0001). TNF-α gene SNP rs1800629 had the property of regulating TNF-α, which interacts with plasma As; individuals with the AG type had a significantly lower eGFR than those with the GG type, by 9.59 mL/min/1.73 m2 (p < 0.05), which, regarding the dominant model, could infer that the A allele is a risk allele. SNP rs769177 had no interaction with plasma As; however, participants with the TT or TC type had significantly higher eGFR levels than the CC carriers, by 4.02 mL/min/1.73 m2 (p < 0.05). While rs769176 interacted with plasma As, if a person with the TC type had a higher plasma As concentration, that would sustain higher eGFR. This study found that certain SNPs of the TNF-α gene would be robust to the decline of eGFR caused by As exposure. Still, we need further research to confirm the protective regulation mechanism of these SNPs.

Unstable Housing and Kidney Disease: A Primer

Stable housing is essential for health. Over 580,000 Americans experienced homelessness during one night in 2020, and over 37 million households spend over 30% of their income on housing. Unstable housing has been associated with mortality, acute care utilization, communicable and non-communicable diseases, a higher risk of kidney disease, and kidney disease progression. In this review, we define various forms of unstable housing, provide an overview of the interaction between unstable housing and health, and discuss existing evidence associating housing and kidney disease. We provide historical context for unstable housing in the United States, and detail policy, community, and individual-level factors that contribute to the risk of unstable housing. Unstable housing likely affects kidney health via a complex interplay of individual and structural factors. Various screening tools are available for use by providers. Special considerations should be made when working with individuals experiencing unstable housing to meet their unique needs, facilitate health care engagement, and optimize outcomes. Housing interventions have been shown to improve outcomes and should be examined for their role in kidney disease.

Comprehensive Groundwater Quality Analysis in Chronic Kidney Disease of Unknown Etiology (CKDu) Prevalence Areas of Sri Lanka to Investigate the Responsible Culprit

Chronic kidney disease of unknown etiology (CKDu) is a serious health problem in Sri Lanka especially among agricultural communities in dry zone since 19th century. In the present study, several water quality parameters were studied in well water samples and only four parameters, namely, hardness, cadmium level, fluoride level, and strontium level have shown a relationship with the CKDu prevalence. Higher percentage of well water samples collected from CKDu prevalent area in both pre and postmonsoon seasons have exceeded the WHO recommended levels of hardness. Further, water samples collected in postmonsoon seasons had significantly higher hardness than the well water samples collected in premonsoon season ( $P<0.05$ ). This may be due to the dissolution of calcium carbonate by water recharge. Moreover, cadmium and fluoride contents have exceeded the recommended levels in high-risk area during the premonsoon period. Furthermore, according to principal component analysis (PCA), four clusters were identified depending on the different levels of fluoride, cadmium, hardness, and strontium contents. The control area (Am) fell in to separate cluster with low contents of fluoride, cadmium, hardness, and strontium than in CKDu prevalent area. Since it has been found that the above species are directly involved in renal damage, it can be concluded that a synergetic effect of cadmium, fluoride, hardness, and strontium in well water may be a main cause for CKDu in Sri Lanka.

Combined Exposure to Metals in Drinking Water Alters the Dopamine System in Mouse Striatum

Environmental exposure to arsenic (As), lead (Pb), and cadmium (Cd) frequently occurs; however, data on the specific effects of combined exposure on neurotransmission, specifically dopaminergic neurotransmission, are lacking. In this study, motor coordination and dopamine content, along with the expression of tyrosine hydroxylase (TH), dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors (DRs), were examined in the striatum of adult male mice following exposure to drinking water containing As, Pb, and/or Cd. We found that exposure to a metal mixture impaired motor coordination. After 4 weeks of treatment, a significant decrease in dopamine content and expression of TH, DAT, and VMAT2 was observed in the striatum of metal-mixture-treated mice, compared to the controls or single-metal-exposed groups. However, DRD1 and DRD2 expression did not significantly change with metal treatment. These results suggest that altered dopaminergic neurotransmission by the collective action of metals may contribute to metal-mixture-induced neurobehavioral disorders.

Determination of prohibited lead and cadmium traces in hair dyes and henna samples using ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry

In this study ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry was developed to determine prohibited lead and cadmium traces in hair dye and henna samples. For this purpose, deep eutectic solvent, prepared from choline chloride and phenol, was used as an extraction solvent, dithizone was used as a complexing agent, and THF was used as an aprotic solvent. All parameters that affect extraction efficiency, such as pH, the DES volume and composition, the extraction time, the amount of dithizone, were optimized. Under the optimal conditions, for Pb(ii) and Cd(ii), enhancement factors of 92 and 57, LODs of 2.5 μg L^-1 and 0.75 μg L^-1, LOQs of 7.8 μg L^-1 and 2.5 μg L^-1, linear working ranges of 10-250 μg L^-1 and 2.5-50 μg L^-1, were obtained, respectively. Relative standard deviation (n = 10) was calculated to be 2.7 for 100 μg L^-1 of Pb(ii) and 2.1 for 25 μg L^-1 of Cd(ii). The matrix effect was investigated by comparing the solvent-based calibration curve with the matrix-matched calibration curve. The determination of lead and cadmium in hair dye and henna samples without being affected by the sample matrix was successfully performed. The lead content was between 1.3 and 6.5 μg g^-1, and the cadmium content was between 0.028 and 0.54 μg g^-1 for the selected hair dye and henna samples.