Brita Palm

Inter-individual variations of human mercury exposure biomarkers: a cross-sectional assessment

BackgroundBiomarkers for mercury (Hg) exposure have frequently been used to assess exposure and risk in various groups of the general population. We have evaluated the most frequently used biomarkers and the physiology on which they are based, to explore the inter-individual variations and their suitability for exposure assessment.MethodsConcentrations of total Hg (THg), inorganic Hg (IHg) and organic Hg (OHg, assumed to be methylmercury; MeHg) were determined in whole blood, red blood cells, plasma, hair and urine from Swedish men and women. An automated multiple injection cold vapour atomic fluorescence spectrophotometry analytical system for Hg analysis was developed, which provided high sensitivity, accuracy, and precision. The distribution of the various mercury forms in the different biological media was explored.ResultsAbout 90% of the mercury found in the red blood cells was in the form of MeHg with small inter-individual variations, and part of the IHg found in the red blood cells could be attributed to demethylated MeHg. THg in plasma was associated with both IHg and MeHg, with large inter-individual variations in the distribution between red blood cells and plasma. THg in hair reflects MeHg exposure at all exposure levels, and not IHg exposure. The small fraction of IHg in hair is most probably emanating from demethylated MeHg. The inter-individual variation in the blood to hair ratio was very large. The variability seemed to decrease with increasing OHg in blood, most probably due to more frequent fish consumption and thereby blood concentrations approaching steady state. THg in urine reflected IHg exposure, also at very low IHg exposure levels.ConclusionThe use of THg concentration in whole blood as a proxy for MeHg exposure will give rise to an overestimation of the MeHg exposure depending on the degree of IHg exposure, why speciation of mercury forms is needed. THg in RBC and hair are suitable proxies for MeHg exposure. Using THg concentration in plasma as a measure of IHg exposure can lead to significant exposure misclassification. THg in urine is a suitable proxy for IHg exposure.

Mercury in human brain, blood, muscle and toenails in relation to exposure: an autopsy study

BackgroundThe main forms of mercury (Hg) exposure in the general population are methylmercury (MeHg) from seafood, inorganic mercury (I-Hg) from food, and mercury vapor (Hg0) from dental amalgam restorations. While the distribution of MeHg in the body is described by a one compartment model, the distribution of I-Hg after exposure to elemental mercury is more complex, and there is no biomarker for I-Hg in the brain. The aim of this study was to elucidate the relationships between on the one hand MeHg and I-Hg in human brain and other tissues, including blood, and on the other Hg exposure via dental amalgam in a fish-eating population. In addition, the use of blood and toenails as biological indicator media for inorganic and organic mercury (MeHg) in the tissues was evaluated.MethodsSamples of blood, brain (occipital lobe cortex), pituitary, thyroid, abdominal muscle and toenails were collected at autopsy of 30 deceased individuals, age from 47 to 91 years of age. Concentrations of total-Hg and I-Hg in blood and brain cortex were determined by cold vapor atomic fluorescence spectrometry and total-Hg in other tissues by sector field inductively coupled plasma-mass spectrometry (ICP-SFMS).ResultsThe median concentrations of MeHg (total-Hg minus I-Hg) and I-Hg in blood were 2.2 and 1.0 μg/L, and in occipital lobe cortex 4 and 5 μg/kg, respectively. There was a significant correlation between MeHg in blood and occipital cortex. Also, total-Hg in toenails correlated with MeHg in both blood and occipital lobe. I-Hg in both blood and occipital cortex, as well as total-Hg in pituitary and thyroid were strongly associated with the number of dental amalgam surfaces at the time of death.ConclusionIn a fish-eating population, intake of MeHg via the diet has a marked impact on the MeHg concentration in the brain, while exposure to dental amalgam restorations increases the I-Hg concentrations in the brain. Discrimination between mercury species is necessary to evaluate the impact on Hg in the brain of various sources of exposure, in particular, dental amalgam exposure.

Exposure determinants of phthalates, parabens, bisphenol A and triclosan in Swedish mothers and their children

Chemicals such as phthalates, parabens, bisphenol A (BPA) and triclosan (TCS), used in a wide variety of consumer products, are suspected endocrine disrupters although their level of toxicity is thought to be low. Combined exposure may occur through ingestion, inhalation and dermal exposure, and their toxic as well as combined effects are poorly understood. The objective of the study was to estimate the exposure to these chemicals in Swedish mothers and their children (6–11 years old) and investigate potential predictors of the exposure. Urine samples from 98 mother–child couples living in either a rural or an urban area were analyzed for the concentrations of four metabolites of di-(2-ethylhexyl) phthalate (DEHP), three metabolites of di-iso-nonyl phthalate (DiNP), mono-ethyl phthalate (MEP), mono-benzyl phthalate (MBzP) and mono-n-butyl phthalate (MnBP), methylparaben (MetP), ethylparaben (EthP), propylparaben (ProP), butylparaben, benzylparaben, BPA, and TCS. Information on sociodemographics, food consumption habits and use of personal care products, obtained via a questionnaire, was used to investigate the associations between the urinary levels of chemicals and potential exposure factors. There were fairly good correlations of biomarker levels between the mothers and their children. The children had generally higher levels of phthalates (geometric mean ΣDEHP 65.5 μg/L; ΣDiNP 37.8 μg/L; MBzP 19.9 μg/L; MnBP 76.9 μg/L) than the mothers (ΣDEHP 38.4 μg/L; ΣDiNP 33.8 μg/L; MBzP 12.8 μg/L; MnBP 63.0 μg/L). Conversely, the mothers levels of parabens (MetP 37.8 μg/L; ProP 13.9 μg/L) and MEP (43.4 μg/L) were higher than the childrens levels of parabens (MetP 6.8 μg/L; ProP 2.1 μg/L) and MEP (28.8 μg/L). The urinary levels of low molecular weight phthalates were higher among mothers and children in the rural area (MBzP p = < 0.001; MnBP p = 0.001–0.002), which is probably due to higher presence of PVC in floorings and wall coverings in this area, whereas the levels of parabens were higher among the children in the urban area (MetP p = 0.003; ProP p = 0.004) than in the rural area. The levels of high molecular weight phthalates were associated with consumption of certain foods (i.e. chocolate and ice cream) whereas the levels of parabens were associated with use of cosmetics and personal care products.

Breast-feeding protects against arsenic exposure in Bangladeshi infants.

Background Chronic arsenic exposure causes a wide range of health effects, but little is known about critical windows of exposure. Arsenic readily crosses the placenta, but the few available data on postnatal exposure to arsenic via breast milk are not conclusive. Aim Our goal was to assess the arsenic exposure through breast milk in Bangladeshi infants, living in an area with high prevalence of arsenic-rich tube-well water. Methods We analyzed metabolites of inorganic arsenic in breast milk and infant urine at 3 months of age and compared them with detailed information on breast-feeding practices and maternal arsenic exposure, as measured by concentrations in blood, urine, and saliva. Results Arsenic concentrations in breast-milk samples were low (median, 1 μg/kg; range, 0.25–19 μg/kg), despite high arsenic exposures via drinking water (10–1,100 μg/L in urine and 2–40 μg/L in red blood cells). Accordingly, the arsenic concentrations in urine of infants whose mothers reported exclusive breast-feeding were low (median, 1.1 μg/L; range, 0.3–29 μg/L), whereas concentrations for those whose mothers reported partial breast-feeding ranged from 0.4 to 1,520 μg/L (median 1.9 μg/L). The major part of arsenic in milk was inorganic. Still, the infants had a high fraction (median, 87%) of the dimethylated arsenic metabolite in urine. Arsenic in breast milk was associated with arsenic in maternal blood, urine, and saliva. Conclusion Very little arsenic is excreted in breast milk, even in women with high exposure from drinking water. Thus, exclusive breast-feeding protects the infant from exposure to arsenic.

High concentrations of essential and toxic elements in infant formula and infant foods – A matter of concern

This study assessed concentrations in and intake of toxic and essential elements from formulas and foods intended for infants during their first 6months of life. Concentrations of the essential elements Ca, Fe, Zn, Mn and Mo were significantly higher in most formulas than in breast milk. Daily intake of Mn from formula varies from ten up to several hundred times the intake of the breast fed infant, levels that may be associated with adverse health effects. One portion of infant food provided significantly more Fe, Mn, Mo, As, Cd, Pb and U than one feeding of breast milk, but less Ca, Cu and Se. Rice-based products in particular contained elevated As concentrations. Drinking water used to mix powdered formula may add significantly to the concentrations in the ready-made products. Evaluation of potentially adverse effects of the elevated element concentrations in infant formulas and foods are warranted.

High-level exposure to lithium, boron, cesium, and arsenic via drinking water in the Andes of Northern Argentina.

Elevated concentrations of arsenic in drinking water are common worldwide, however, little is known about the presence of other potentially toxic elements. We analyzed 31 different elements in drinking water collected in San Antonio de los Cobres and five surrounding Andean villages in Argentina, and in urine of the inhabitants, using ICP-MS. Besides confirmation of elevated arsenic concentrations in the drinking water (up to 210 microg/L), we found remarkably high concentrations of lithium (highest 1000 microg/L), cesium (320 microg/L), rubidium (47 microg/L), and boron (5950 microg/L). Similarly elevated concentrations of arsenic, lithium, cesium, and boron were found in urine of the studied women (N=198): village median values ranged from 26 to 266 microg/L of arsenic, 340 to 4550 microg/L of lithium, 34 to 531 microg/L of cesium, and 2980 to 16,560 microg/L of boron. There is an apparent risk of toxic effects of long-term exposure to several of the elements, and studies on associations with adverse human health effects are warranted, particularly considering the combined, life-long exposure. Because of the observed wide range of concentrations, all water sources used for drinking water should be screened for a large number of elements; obviously, this applies to all drinking water sources globally.

Environmental Exposure to Metals and Children's Growth to Age 5 Years: A Prospective Cohort Study

In this prospective cohort study, based on 1,505 mother-infant pairs in rural Bangladesh, we evaluated the associations between early-life exposure to arsenic, cadmium, and lead, assessed via concentrations in maternal and child urine, and childrens weights and heights up to age 5 years, during the period 2001–2009. Concurrent and prenatal exposures were evaluated using linear regression analysis, while longitudinal exposure was assessed using mixed-effects linear regression. An inverse association was found between childrens weight and height, age-adjusted z scores, and growth velocity at age 5 years and concurrent exposure to cadmium and arsenic. In the longitudinal analysis, multivariable-adjusted attributable differences in childrens weight at age 5 years were −0.33 kg (95% confidence interval (CI): −0.60, −0.06) for high (≥95th percentile) arsenic exposure and −0.57 kg (95% CI: −0.88, −0.26) for high cadmium exposure, in comparison with children with the lowest exposure (≤5th percentile). Multivariable-adjusted attributable differences in height were −0.50 cm (95% CI: −1.20, 0.21) for high arsenic exposure and −1.6 cm (95% CI: −2.4, −0.77) for high cadmium exposure. The associations were apparent primarily among girls. The negative effects on childrens growth at age 5 years attributable to arsenic and cadmium were of similar magnitude to the difference between girls and boys in terms of weight (−0.67 kg, 95% CI: −0.82, −0.53) and height (−1.3 cm, 95% CI: −1.7, −0.89).

Metals and trace element concentrations in breast milk of first time healthy mothers: a biological monitoring study

BackgroundBreast milk is the best source of nutrition for the newborn infant. However, since all infants cannot be breast-fed, there is a need for background data for setting adequate daily intakes. Previously, concentration data on major essential elements and some toxic elements in breast milk, based on different analytical techniques, have been published. There is no recent study on a large number of metals and trace elements in breast milk, using a sensitive analytical method for determination of low element concentrations.MethodsBreast milk concentrations of 32 metals and elements in early lactation (days 14-21) were determined in a random sample of first time Swedish mothers (n = 60) using inductively coupled plasma mass spectrometry (ICPMS).ResultsThere were small inter-individual concentration variations in the macroelements Ca, K, Mg, P and S, and striking similarities across studies and over time, supporting a tight regulation of these elements in breast milk. Large inter-individual and over time differences were detected for Na concentrations, which may reflect an increase in salt consumption in Swedish women. Large inter-individual differences were also detected for the microelements Co, Cr, Mn and Mo, and the toxic metals As, Cd, Pb, Sb and V. Arsenic and B were positively correlated with fish consumption, indicating influence of maternal intake on breast milk concentrations. Observed differences in breast milk element concentrations across studies and over time could be attributed to the timing of sampling and a general decline over time of lactation (Cu, Fe, Mo, Zn), a possible lack of regulation of certain elements in breast milk (As, B, Co, Mn, Se) and time trends in environmental exposure (Pb), or in some cases to differences in analytical performance (Cr, Fe).ConclusionsThis study provides reliable updated information on a number of metals and elements in breast milk, of which some have not previously been reported.

Persistent Exposure to Arsenic via Drinking Water in Rural Bangladesh Despite Major Mitigation Efforts

OBJECTIVES Elevated arsenic levels in tube-well water in Bangladesh have prompted extensive mitigation projects. We evaluated the effectiveness of long-term mitigation efforts by longitudinally measuring arsenic exposure in pregnant women and their children, the most susceptible population groups. METHODS The study was nested in a population-based nutrition intervention in Matlab, Bangladesh. Mother-child pairs (n = 1951) were followed from 2001 to 2003, beginning in early gestation and continuing to 5 years postpartum. We measured arsenic concentrations in urine (U-As) of the 5-year-old children by using high-performance liquid chromatography online with hydride generation and inductively coupled plasma mass spectrometry and compared them with earlier childhood U-As and maternal U-As during pregnancy. RESULTS Children had elevated U-As at 5 years old (median = 51 μg/L, 5th-95th percentiles = 16-355 μg/L), and U-As distribution was similar to that observed in the mothers during gestation. Childrens U-As at 5 years old significantly correlated with their U-As at 1.5 years old and to maternal U-As during early and late gestation. CONCLUSIONS Despite major mitigation efforts, arsenic exposure remains highly elevated in rural Bangladesh. Further mitigation strategies are required and must be rigorously evaluated for long-term efficacy.

Impaired arsenic metabolism in children during weaning.

BACKGROUND Methylation of inorganic arsenic (iAs) via one-carbon metabolism is a susceptibility factor for a range of arsenic-related health effects, but there is no data on the importance of arsenic metabolism for effects on child development. AIM To elucidate the development of arsenic metabolism in early childhood. METHODS We measured iAs, methylarsonic acid (MA) and dimethylarsinic acid (DMA), the metabolites of iAs, in spot urine samples of 2400 children at 18 months of age. The children were born to women participating in a population-based longitudinal study of arsenic effects on pregnancy outcomes and child development, carried out in Matlab, a rural area in Bangladesh with a wide range of arsenic concentrations in drinking water. Arsenic metabolism was evaluated in relation to age, sex, anthropometry, socio-economic status and arsenic exposure. RESULTS Arsenic concentrations in child urine (median 34 microg/L, range 2.4-940 microg/L), adjusted to average specific gravity of 1.009 g/mL, were considerably higher than that measured at 3 months of age, but lower than that in maternal urine. Child urine contained on average 12% iAs, 9.4% MA and 78% DMA, which implies a marked change in metabolite pattern since infancy. In particular, there was a marked increase in urinary %MA, which has been associated with increased risk of health effects. CONCLUSION The arsenic metabolite pattern in urine of children at 18 months of age in rural Bangladesh indicates a marked decrease in arsenic methylation efficiency during weaning.