Toenail Metal Research Articles

Toenail Metal Exposures in Fishermen from Bodo City, Nigeria.

We conducted exposure assessment using toenails from 20 fishermen living in Bodo City, a community of the Niger delta region in Nigeria. This community has been affected by over 4000 oil spills and environmental disasters. Fishing is the primary source of food and income for individuals in this community. Previous research in Bodo City found elevated metal levels in fish. Toenails were used as a biomarker to investigate the feasibility for use in risk assessment studies in developing countries. The toenails collected had significantly higher manganese levels (median 5.8µg/g) and lead levels (median 0.98µg/g) than those reported in more developed countries, comparable levels to those from other low-middle incomes countries. These exposure levels are likely a direct result of exposures from the environmental disasters the community has experienced and would be related to increased risks for many diseases previously associated with heavy metal exposures.

Infant toenail metal concentrations associated with gut microbial diversity and specific taxa abundance

Infant toenail metal concentrations associated with gut microbial diversity and specific taxa abundance

Validity of Retrospective Occupational Exposure Estimates of Lead and Manganese in a Case-Control Study

TPS 792: Occupational health 2, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Background: The validity of surrogate measures of retrospective occupational exposure in population-based epidemiological studies has rarely been evaluated. Using toenail samples as indicators of biologic exposure, we assessed whether work tasks and expert assessments of occupational metal exposure obtained from personal interviews were associated with lead and manganese concentrations. Methods: We selected 609 controls from a case-control study of bladder cancer in New England who had held a job for ≥1 year 8-24 months prior to toenail collection. We evaluated associations between toenail metal concentrations and five tasks extracted from occupational questionnaires (grinding, painting, soldering, welding, working near engines) using linear regression models. For 139 subjects, we also evaluated associations between the toenail concentrations and exposure estimates from three experts. Results: We observed a 1.9-fold increase (95% confidence interval (CI) 1.4-2.5) in toenail lead concentrations with painting and 1.4-fold increase (95%CI 1.1-1.7) in manganese concentrations with working around engines and handling fuel. We observed significant trends with increasing frequency of both activities. For lead, significant trends were observed with the ratings from all three experts. Their average ratings showed the strongest association, with subjects rated as possibly or probably exposed to lead having concentrations that were 2.0 and 2.5 times higher, respectively, than in unexposed subjects (Ptrend<0.001). Expert estimates were only weakly associated with manganese toenail concentrations. Conclusions: Our findings support the validity of surrogate measures to assess occupational exposure in epidemiologic studies. The stronger associations with task frequency and expert assessments support using refined exposure characterization whenever possible.

Validity of retrospective occupational exposure estimates of lead and manganese in a case–control study

ObjectivesThe validity of surrogate measures of retrospective occupational exposure in population-based epidemiological studies has rarely been evaluated. Using toenail samples as bioindicators of exposure, we assessed whether work tasks and...

Correlation over time of toenail metals among participants in the VA normative aging study from 1992 to 2014.

BackgroundScientists use biomarkers to evaluate metal exposures. One biomarker, toenails, is easily obtained and minimally invasive, but less commonly used as a biomarker of exposure. Their utility will depend on understanding characteristics of their variation in a population over time. The objective of our study is to describe the correlation of toenail metal levels many years apart among participants in the VA Normative Aging Study (NAS).MethodsToenail clippings from 825 participants of the NAS from year 1992 to 2014 were analyzed for lead (Pb), Arsenic (As), Cadmium (Cd), Manganese (Mn), and Mercury (Hg). We utilized linear mixed models to assess correlation between toenail metal concentrations in multiple toenail samples from the same subject collected years apart and identified the optimal covariance pattern by likelihood ratio tests and Akaike’s information criterion (AIC). Correlations among different metals were described using Spearman correlations.ResultsThe average number of times toenail samples were collected from each subject ranged from 1.63 (Hg) to 2.04 (As). The average number of years between toenails collected per subject ranged from 4.73 (SD=2.44) (Mn) to 5.35 (SD=2.69) (Hg). Metal concentrations had slightly different correlation patterns over time, although for all metals correlations decreased with increasing time between samples. Estimated correlations over a 3-year span were highest for toenail Pb (0.68) and Hg (0.67), while As, Cd, and Mn had lower correlations of 0.49, 0.44, and 0.47, respectively. Even across a six-year span, the lowest correlation was 0.35 (Cd).ConclusionOur results suggest that Pb, As, Cd, Mn, and Hg levels from toenail clippings can reasonably reflect exposures over several years in elderly men in the NAS. Even across six years, toenail metal levels were generally well correlated among NAS participants. As such, they may be useful as biomarkers of exposure in epidemiological studies of similar populations.

Evaluation of Respiratory Symptoms, Spirometric Lung Patterns and Metal Fume Concentrations among Welders in Indoor Air-Conditioned Building at Malaysia

Welding is one of the fundamental processes for metal joining in automotive industries and there is an increasing concern over occupational lung disease among welder due to exposure towards welding fumes. A lung disease questionnaire (ATS-DLD-78) was used to record the presence of respiratory symptoms among welders and in assessing lung function assessment, FEV1, FVC and FEV1/FVC are considered for identifying the lung condition; normal, obstructive or restrictive. The data were tabulated and subjected to logistic and multivariate analyses. Meanwhile, in order to trace metal in welders’ body, this study utilized a non-invasive approach of toenail as a biomarker. Lung functions decrement was established in linear regression for FEV1 and FEV1/FVC respectively although not statistically significant. Analysis conducted revealed the presence of the following trace elements concentration in ascending sequence: As < Al < Cu < Mn < Cr < Ni < Co < Fe (in the toenail) and Co < Al < Cu < Ni < As < Cr < Fe < Mn (in the cassette), respectively. The results validated the postulation that toenail metals composition shared a similar route of exposure with an anthropogenic source of activity. It is suggested a longer follow-up study is required to assess individual effects on lung function systems and the incidence of respiratory diseases among welders and this study indicates that toenail is a reliable biomarker of metal-workplace pollution and suitable for acquiring chronological information of welding fumes exposure.

Heavy Metals Analysis in Human Body (Toenail, Fingernail and Hair Samples) and Drinking Waters of Santa Fe Region, Argentina

This study provides an insight into a province of Santa Fe region of a developing country, namely San Cristobal and Huanqueros, Argentina and a possible link between arsenic, copper and iron concentration in toenail, fingernail and hair in the population. A multivariate statistical tool, known as Principal Component Analysis (PCA) was applied to explain the behaviour of the elements in toenails, fingernails, drinking waters and hair using multi- base 2013 excel add- ins. Correlation test, error bars, and a 2-factor ANOVA test were employed. Results from one hundred and twenty- nine (n=129) samples of tap well water (n=23), rainwater (n=20), bottled water (n=6) and treated well water (n=80) and each of toenail, fingernail and hair (n=129) samples from the subjects were determined and the results compared with the previous works. Mean, standard deviation, covariance and maximum and minimum for each variable were reported. The hypothesis is to understand if there is a correlation between fingernail and toenail metals levels and make a comparison with previous researches. Results show that a positive correlation exists between fingernail and toenail metals concentrations. Also, the study reveals higher concentrations of arsenic, copper and iron in the samples tissues compared with the values available in the previous works. The elevated levels of these metals may be attributed to the drinking water sources. Since this study highlighted elevated levels of these metals, consumptions of contaminated drinking water should be constantly monitored. Finally, the application of multivariate statistical techniques can provide powerful information on heavy metals bioaccumulation analysis in human and environment.

Correlation over Time of Toenail Metals among Participants in the VA Normative Aging Study from 1992 to 2014

Scientists use biomarkers to evaluate metal exposures. One biomarker, toenails, is easily obtained and minimally invasive, but less commonly used as a biomarker of exposure. Their utility will depend on understanding characteristics of their variation in a population over time. The objective of our study is to describe the correlation of toenail metal levels many years apart among participants in the VA Normative Aging Study (NAS). Toenail clippings from 825 participants of the NAS from year 1992 to 2014 were analyzed for lead (Pb), Arsenic (As), Cadmium (Cd), Manganese (Mn), and Mercury (Hg). We utilized linear mixed models to assess correlation between toenail metal concentrations in multiple toenail samples from the same subject collected years apart and identified the optimal covariance pattern by likelihood ratio tests and Akaike’s information criterion (AIC). Correlations among different metals were described using Spearman correlations. The average number of times toenail samples were collected from each subject ranged from 1.63 (Hg) to 2.04 (As). The average number of years between toenails collected per subject ranged from 4.73 (SD = 2.44) (Mn) to 5.35 (SD = 2.69) (Hg). Metal concentrations had slightly different correlation patterns over time, although for all metals correlations decreased with increasing time between samples. Estimated correlations over a 3-year span were highest for toenail Pb (0.68) and Hg (0.67), while As, Cd, and Mn had lower correlations of 0.49, 0.44, and 0.47, respectively. Even across a 6-year span, the lowest correlation was 0.35 (Cd). Our results suggest that Pb, As, Cd, Mn, and Hg levels from toenail clippings can reasonably reflect exposures over several years in elderly men in the NAS. Even across 6 years, toenail metal levels were generally well correlated among NAS participants. As such, they may be useful as biomarkers of exposure in epidemiological studies of similar populations.

Validation of x-ray fluorescence measurements of metals in toenail clippings against inductively coupled plasma mass spectrometry in a Nigerian population**https://www.hsph.harvard.edu/aaron-specht/,††https://scholar.google.ca/citations?user=fZRqIKkAAAAJ&hl=en

Objective: Metal exposures have been linked with many adverse health outcomes affecting nearly every system in the body. Exposure to metals has been tracked primarily using blood. Blood metal concentrations have drawbacks as biomarkers stemming from the metals’ short biologic half-lives, shipping and storage requirements, and invasive collection procedures. Toenails, which capture a longer exposure period, can be collected non-invasively and stored at room temperature, and can be more feasible and cost-effective for large-scale population studies. Approach: Inductively coupled plasma mass spectrometry (ICP-MS) has been used for analysis of toenail metal concentrations, but x-ray fluorescence (XRF) has many advantages in versatility and cost effectiveness over these analyses. This study compared toenail concentrations of manganese (Mn) and lead (Pb) measured with XRF against ICP-MS, in samples collected from 20 adults in Nigeria. To do this we developed a novel calibration method that corrects XRF measurements for toenail weight and thickness to reduce the variability in XRF measurements of toenail clippings. Main results: We found a high correlation (R = 0.91) between toenail manganese metal measurements made with XRF and ICP-MS and a correlation of (R = 0.32) between toenail lead XRF and ICP-MS with over half of the lead results below the detection limit of the instrumentation. Significance: XRF can be used effectively to quantify metals at the part per million level or lower depending on the XRF equipment used in the measurements.

Variations in Blood and Toenail Metal Concentrations by Hemochromatosis (HFE) Genotype

Variations in Blood and Toenail Metal Concentrations by Hemochromatosis (HFE) Genotype

Investigating relationships between biomarkers of exposure and environmental copper and manganese levels in house dusts from a Portuguese industrial city.

This study reports on data obtained from a pilot survey focusing on house dust and toenail metal(loids) concentrations in residents living in the industrial city of Estarreja. The study design hereby described aims at investigating relationships between human toenails and both copper and manganese levels in settledhouse dusts. A total of 21 households and 30 individuals were recruited for the pilot study: 19 households corresponding to 27 residents living near the industrial complex, forming the exposed group, plus 2 households and 3 residents from residential areas with no anticipated environmental contaminants that were used for comparison. Factorial analysis was used for source identification purposes. Investigation on the potential influence of environmental factors over copper and manganese levels in the toenails was carried out via questionnaire data and multiple correspondence analysis. The results show that copper concentrations are more elevated in the indoor dusts, while manganese concentrations are more elevated in the outdoor dust samples. The geometrical relationships in the datasets suggest that the backyard soil is a probable source of manganese to the indoor dust. Copper and manganese contents in the toenail clippings are more elevated in children than in adults, but the difference between the two age groups is not statistically significant (p>0.05). Investigation of environmental factors influencing the exposure-biomarker association indicates a probable relationship between manganese contents in indoor dust and manganese levels in toenail clippings, a result that is partially supported by the bioaccessibility estimates. However, for copper, no relationship was found between indoor dusts and the biomarkers of exposure.

Toenail Metal Concentration as a Biomarker of Occupational Welding Fume Exposure

In populations exposed to heavy metals, there are few biomarkers that capture intermediate exposure windows. We sought to determine the correlation between toenail metal concentrations and prior 12-month work activity in welders with variable, metal-rich, welding fume exposures. Forty-eight participants, recruited through a local union, provided 69 sets of toenail clippings. Union-supplied and worker-verified personal work histories were used to quantify hours welded and respirator use. Toenail samples were digested and analyzed for lead (Pb), manganese (Mn), cadmium (Cd), nickel (Ni), and arsenic (As) using ICP-MS. Spearman correlation coefficients were used to examine the correlation between toenail metal concentrations. Using mixed models to account for multiple participation times, we divided hours welded into three-month intervals and examined how weld hours correlated with log-transformed toenail Pb, Mn, Cd, Ni, and As concentrations. Highest concentrations were found for Ni, followed by Mn, Pb and As, and Cd. All the metals were significantly correlated with one another (rho range = 0.28–0.51), with the exception of Ni and As (rho = 0.20, p = 0.17). Using mixed models adjusted for age, respirator use, smoking status, and BMI, we found that Mn was associated with weld hours 7–9 months prior to clipping (p = 0.003), Pb was associated with weld hours 10–12 months prior to clipping (p = 0.03) and over the entire year (p = 0.04). Cd was associated with weld hours 10–12 months prior to clipping (p = 0.05), and also with the previous year's total hours welded (p = 0.02). The association between Ni and weld hours 7–9 months prior to clipping approached significance (p = 0.06). Toenail metal concentrations were not associated with the long-term exposure metric, years as a welder. Results suggest Mn, Pb, and Cd may have particular windows of relevant exposure that reflect work activity. In a population with variable exposure, toenails may serve as useful biomarkers for occupational metal fume exposures to Mn, Pb, and Cd during distinct periods over the year prior to sample collection.

Toenail metals as a biomarker for metal exposures in welders

Background and aims: Toenail metal concentrations may capture exposure to welding fume components. We sought to identify the association between toenail metal and previous work activity, including specific exposure time periods of interest for individual metals. Methods: Forty-eight participants recruited through a welding school provided 69 toenail samples. Union-supplied personal work histories were confirmed by each subject. Toenails were analyzed for lead (Pb), manganese (Mn), cadmium (Cd), nickel (Ni) and arsenic (As) using ICP-MS. Spearman correlation coefficients were used to examine the correlation between toenail metals. Using mixed models to account for multiple participation times, we investigated whether hours welded—a simplified occupational exposure measurement broken into three month intervals—correlated with log-transformed toenail concentrations of Pb, Mn, Cd, Ni and As. Results: Highest concentrations were found for Ni, followed by Mn, Pb and As, and Cd. All metals were significantly correlated with one another (rho range=0.28-0.51), with the exception of Ni and As. After adjusting for age, smoking and BMI, toenail Pb was associated with hours welded over the entire year (p=0.01). Cd was associated with hours welded over the previous 7-9 months (p = 0.03), and also the entire year (p=0.02). Lastly, toenail Mn levels were associated with hours welded 7-9 months prior to clipping (p=0.003). Conclusions: Results suggest toenail Mn, Pb and Cd may reflect work activity across particular time intervals. Overall, toenails may serve as useful biomarkers for occupational metal fume exposures to Mn, Pb and Cd during distinct periods over the year prior to sample collection.

Environmental and toenail metals concentrations in copper mining and non mining communities in Zambia

Copper mining contributes to increased concentrations of metals in the environment, thereby increasing the risk of metals exposure to populations living in and around mining areas. This study investigated environmental and toenail metals concentrations of non-occupational human exposure to metals in 39 copper-mining town residents and 47 non-mining town residents in Zambia. Elevated environmental concentrations were found in samples collected from the mining town residents. Toenail concentrations of cobalt (GM 1.39 mg/kg), copper (GM 132 mg/kg), lead (21.41 mg/kg) selenium (GM 0.38 mg/kg) and zinc (GM 113 mg/kg) were significantly higher in the mining area and these metals have previously been associated with copper mining. Residence in the mining area, drinking water, dust and soil metals concentrations were the most important contributors to toenail metals concentrations. Further work is required to establish the specific pathways of exposure and the health risks of elevated metals concentrations in the copper mining area.

EXPOSURE TO METALS AND GENE-SPECIFIC METHYLATION IN COMMUNITY-DWELLING ELDERLY MEN

Background and Aims: Methylation changes in promoter regions of genes have been linked to gene expression changes and subsequent human disease. Heavy metals are known to trigger oxidative stress, changes in immune response, and inflammation throughout the body. DNA methylation is a potential pathway through which heavy metals exert their toxicity. We aimed to evaluate the association between exposure to arsenic, cadmium, mercury, manganese and lead and DNA methylation in nine different genes related to inflammation, immune response, and endothelial function in a population of environmentally exposed elderly men. Methods: Our study population was 773 participants from the Normative Aging Study cohort in Boston, USA, with repeated visits between 1999 and 2009. Our associations of interest were explored in a minimum of 423 and a maximum of 611 participants depending on the availability of the exposure and outcome measurements. We measured the concentration of metals in toenails (in mcg/gr) while DNA methylation (in % of 5methyl cytosine) in promoter regions of the IL6, IFN-gamma, iNOS, ICAM, CRAT, OGG, TLR2, F3 and GCR genes was measured in blood leukocytes. The toenail metal concentrations were natural logarithm-transformed. We used multivariable linear mixed effects models to evaluate the associations of interest. Results: Toenail arsenic and manganese concentrations were negatively associated with the iNOS gene methylation [b=-0.2, 95%CI: -0.3 to -0.1 for ten percent increase in toenail arsenic; b= -0.1, 95%CI: -0.1 to -0.01 for ten percent increase in toenail manganese). We did not find any statistically significant associations between the other metals and gene-specific methylation. Conclusions: Both arsenic and manganese concentrations were associated with decreased iNOS methylation which can potentially lead to increased iNOS gene function and subsequent increased nitrogen oxide production, a process involved in inflammation. Our results indicate that heavy metal exposures may exert their effects through epigenetic mechanisms.

Associations of Toenail Arsenic, Cadmium, Mercury, Manganese, and Lead with Blood Pressure in the Normative Aging Study

Background: Arsenic, cadmium, mercury, and lead are associated with cardiovascular disease in epidemiologic research. These associations may be mediated by direct effects of the metals on blood pressure (BP) elevation. Manganese is associated with cardiovascular dysfunction and hypotension in occupational cohorts.Objectives: We hypothesized that chronic arsenic, cadmium, mercury, and lead exposures elevate BP and that manganese lowers BP.Methods: We conducted a cross-sectional analysis of associations between toenail metals and BP among older men from the Normative Aging Study (n = 639), using linear regression and adjusting for potential confounders.Results: An interquartile range increase in toenail arsenic was associated with higher systolic BP [0.93 mmHg; 95% confidence interval (CI): 0.25, 1.62] and pulse pressure (0.76 mmHg; 95% CI: 0.22, 1.30). Positive associations between arsenic and BP and negative associations between manganese and BP were strengthened in models adjusted for other toenail metals.Conclusions: Our findings suggest associations between BP and arsenic and manganese. This may be of public health importance because of prevalence of both metal exposure and cardiovascular disease. Results should be interpreted cautiously given potential limitations of toenails as biomarkers of metal exposure.