Exposure to total and methylmercury among pregnant women in Suriname: sources and public health implications.
ABSTRACT: Previous research has found that women and children living in rural, interior communities in Suriname have high concentrations of mercury in hair. Freshwater fish from these areas also have high concentrations of mercury. Artisanal and small-scale gold mining operations in parts of the country use elemental mercury to extract gold from soils and sediments. Total mercury and methylmercury concentrations have been determined in hair and blood from pregnant women across the country. Pregnant women from interior communities have significantly higher concentrations of both total and methylmercury in hair (median total mercury in hair 3.64?µg/g) compared with pregnant women from two urban coastal cities, Paramaribo (0.63?µg/g) and Nickerie (0.74?µg/g). Total and methylmercury concentrations in blood and hair are highly correlated (r?=?0.986, r?=?0.974) with methylmercury making up 86% of the total in blood and 97% of the total in hair. Most women in the interior regions rely heavily on local fish as part of their regular diet, and many live outsides of areas with active ASGM operations. This study demonstrates that diet and fish consumption largely govern mercury exposures in pregnant women in Suriname.
Project description:PURPOSE:The Caribbean Consortium for Research in Environmental and Occupational Health prospective environmental epidemiologic cohort study addresses the impact of chemical and non-chemical environmental exposures on mother/child dyads in Suriname. The study determines associations between levels of environmental elements and toxicants in pregnant women, and birth outcomes and neurodevelopment in their children. PARTICIPANTS:Pregnant women (N=1143) were enrolled from December 2016 to July 2019 from three regions of Suriname: Paramaribo (N=738), Nickerie (N=204) and the tropical rainforest interior (N=201). Infants (N=992) were enrolled at birth. Follow-up will take place until children are 48 months old. FINDINGS TO DATE:Biospecimens and questionnaire data on physiological and psychosocial health in pregnant women have been analysed. 39.1% had hair mercury (Hg) levels exceeding values considered safe by international standards. Median hair Hg concentrations in women from Paramaribo (N=522) were 0.64 µg/g hair (IQRs 0.36-1.09; range 0.00-7.12), from Nickerie (N=176) 0.73 µg/g (IQR 0.45-1.05; range 0.00-5.79) and the interior (N=178) 3.48 µg/g (IQR 1.92-7.39; range 0.38-18.20). 96.1% of women ate fish, respective consumption of the three most consumed carnivorous species, Hoplias aimara, Serrasalmus rhombeus and Cichla ocellaris, known to have high Hg levels, was 44.4%, 19.3% and 26.3%, respectively, and was greater among the interior subcohort. 89% frequently consumed the vegetable tannia, samples of which showed presence of worldwide banned pesticides. 24.9% of pregnant women had Edinburgh Depression Scale scores indicative of probable depression. FUTURE PLANS:Fish consumption advisories are in development, especially relevant to interior women for whom fish consumption is likely to be the primary source of Hg exposure. Effects of potentially beneficial neuroprotective factors in fish that may counter neurotoxic effects of Hg are being examined. A pesticide literacy assessment in pregnant women is in progress. Neurodevelopmental assessments and telomere length measurements of the children to evaluate long-term effects of prenatal exposures to toxicant mixtures are ongoing.
Project description:The mechanisms by which gut microbiota contribute to methylmercury metabolism remain unclear. Among a cohort of pregnant mothers, the objectives of our pilot study were to determine (1) associations between gut microbiota and mercury concentrations in biomarkers (stool, hair and cord blood) and (2) the contributions of gut microbial mercury methylation/demethylation to stool methylmercury.Pregnant women (36-39 weeks gestation, n=17) donated hair and stool specimens, and cord blood was collected for a subset (n=7). The diversity of gut microbiota was determined using 16S rRNA gene profiling (n=17). For 6 stool samples with highest/lowest methylmercury concentrations, metagenomic whole genome shotgun sequencing was employed to search for the mercury methylation gene (hgcA), and two mer operon genes involved in methylmercury detoxification (merA and merB).Seventeen bacterial genera were significantly correlated (increasing or decreasing) with stool methylmercury, stool inorganic mercury, or hair total mercury; however, aside from one genus, there was no overlap between biomarkers. There were no definitive matches for hgcA or merB, while merA was detected at low concentrations in all six samples.Proportional differences in stool methylmercury were not likely attributed to gut microbiota through methylation/demethylation. Gut microbiota potentially altered methylmercury metabolism using indirect pathways.
Project description:To describe exposure to methylmercury among Cree, focusing on women of childbearing age, we used data from 2 studies. Multiple regression was employed to examine associations between blood and hair mercury concentrations and consumption of locally harvested fish. Approximately 9.9% of non-pregnant women aged 15-44 y and 3.9% of pregnant women required follow-up according to Health Canada's blood mercury guidance value of 40 nmol/L. 8% of hair mercury observations in the non-pregnant women and 2.5% among pregnant women exceeded the equivalent threshold of 10 nmol/g. The geometric mean blood mercury concentration was 12.7 nmol/L in 1,429 persons aged 8 and over, and 17.7 nmol/L in adults aged 18 and older. The proportion of hair mercury concentrations greater than 12.5 nmol/g decreased in all age-sex groups when comparing the 2002-2009 data to published values for 1993-1994. Among women of childbearing age, local fish consumption was associated with increased blood and hair mercury concentrations. While over 90% of women of childbearing age in this population have acceptable levels of mercury, ongoing intake of mercury suggests that their consumption of fish with known high mercury content be minimised. Reducing consumption of fish known to be high in mercury content needs to be balanced with promoting ongoing connection to Cree culture and land-based activities that are also important determinants of health.
Project description:Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies concerning prenatal methylmercury exposure through rice ingestion, yet the health risks are greatest to the developing fetus, and thus should be investigated.Our main objective was to quantify dietary methylmercury intake through rice and fish/shellfish ingestion among pregnant mothers living in southern China, where rice was a staple food and mercury contamination was considered minimal.A total of 398 mothers were recruited at parturition, who donated scalp hair and blood samples. Total mercury and/or methylmercury concentrations were measured in biomarkers, in rice samples from each participant's home, and in fish tissue purchased from local markets. Additional fish/shellfish mercury concentrations were obtained from a literature search. Dietary methylmercury intake during the third trimester was equivalent to the ingestion rate for rice (or fish/shellfish)×the respective methylmercury concentration.Dietary methylmercury intake from both rice and fish/shellfish ingestion averaged 1.2±1.8µg/day (median=0.79µg/day, range=0-22µg/day), including on average 71% from rice ingestion (median: 87%, range: 0-100%), and 29% from fish/shellfish consumption (median 13%, range: 0-100%). Median concentrations of hair total mercury, hair methylmercury, and blood total mercury were 0.40µg/g (range: 0.08-1.7µg/g), 0.28µg/g (range: 0.01-1.4µg/g), and 1.2µg/L (range: 0.29-8.6µg/L), respectively, and all three biomarkers were positively correlated with dietary methylmercury intake through rice ingestion (Spearman's rho=0.18-0.21, p?0.0005), although the correlations were weak. In contrast, biomarkers were not correlated with fish/shellfish methylmercury intake (Spearman's rho=0.04-0.08, p=0.11-0.46).Among pregnant mothers living in rural inland China, rice ingestion contributed to prenatal methylmercury exposure, more so than fish/shellfish ingestion.
Project description:Immune dysregulation associated with mercury has been suggested, although data in the general population are lacking. Chronic exposure to low levels of methylmercury (organic) and inorganic mercury is common, such as through fish consumption and dental amalgams.We examined associations between mercury biomarkers and antinuclear antibody (ANA) positivity and titer strength.Among females 16-49 years of age (n = 1,352) from the National Health and Nutrition Examination Survey (NHANES) 1999-2004, we examined cross-sectional associations between mercury and ANAs (indirect immunofluorescence; cutoff ? 1:80). Three biomarkers of mercury exposure were used: hair (available 1999-2000) and total blood (1999-2004) predominantly represented methylmercury, and urine (1999-2002) represented inorganic mercury. Survey statistics were used. Multivariable modeling adjusted for several covariates, including age and omega-3 fatty acids.Sixteen percent of females were ANA positive; 96% of ANA positives had a nuclear speckled staining pattern. Geometric mean (geometric SD) mercury concentrations were 0.22 (0.03) ppm in hair, 0.92 (0.05) ?g/L blood, and 0.62 (0.04) ?g/L urine. Hair and blood, but not urinary, mercury were associated with ANA positivity (sample sizes 452, 1,352, and 804, respectively), after adjusting for confounders: for hair, odds ratio (OR) = 4.10 (95% CI: 1.66, 10.13); for blood, OR = 2.32 (95% CI: 1.07, 5.03) comparing highest versus lowest quantiles. Magnitudes of association were strongest for high-titer (? 1:1,280) ANA: hair, OR = 11.41 (95% CI: 1.60, 81.23); blood, OR = 5.93 (95% CI: 1.57, 22.47).Methylmercury, at low levels generally considered safe, was associated with subclinical autoimmunity among reproductive-age females. Autoantibodies may predate clinical disease by years; thus, methylmercury exposure may be relevant to future autoimmune disease risk.
Project description:<h4>Background</h4>Some clinical studies have suggested that ingestion of n-3 polyunsaturated fatty acids (PUFA) has neuroprotective effects on peripheral nerve function. However, few epidemiological studies have examined the effect of dietary n-3 PUFA intake from fish consumption on peripheral nerve function, and none have controlled for co-occurrence of methylmercury exposure from fish consumption.<h4>Objectives</h4>We evaluated the effect of estimated dietary n-3 PUFA intake on peripheral nerve function after adjusting for biomarkers of methylmercury and elemental mercury in a convenience sample of 515 dental professionals.<h4>Methods</h4>We measured sensory nerve conduction (peak latency and amplitude) of the median, ulnar and sural nerves and total mercury concentrations in hair and urine samples. We estimated daily intake (mg/day) of the total n-3 PUFA, n-3 docosahexaenoic acid (DHA), and n-3 eicosapentaenoic acid (EPA) based on a self-administrated fish consumption frequency questionnaire. We also collected information on mercury exposure, demographics and other covariates.<h4>Results</h4>The estimated median intakes of total n-3 PUFA, n-3 EPA, and n-3 DHA were 447, 105, and 179 mg/day, respectively. The mean mercury concentrations in urine (1.05 ?g/L) and hair (0.49 ?g/g) were not significantly different from the US general population. We found no consistent association between n-3 PUFA intake and sensory nerve conduction after adjusting for mercury concentrations in hair and urine although some positive associations were observed with the sural nerve.<h4>Conclusions</h4>In a convenience sample of dental professionals, we found little evidence suggesting that dietary intake of n-3 PUFAs from fish has any impact on peripheral nerve function after adjustment for methylmercury exposure from fish and elemental mercury exposure from dental amalgam.
Project description:Human hair is frequently used as a bioindicator of mercury exposure. We have used X-ray absorption spectroscopy to examine the chemical forms of mercury in human hair samples taken from individuals with high fish consumption and concomitant exposure to methylmercury. The mercury is found to be predominantly methylmercury-cysteine or closely related species, comprising approximately 80% of the total mercury, with the remainder an inorganic thiolate-coordinated mercuric species. No appreciable role was found for selenium in coordinating mercury in hair.
Project description:Mercury is a global contaminant of concern though little is known about exposures in México.To characterize mercury levels in pregnant women, children, and commonly consumed seafood samples.Use resources of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohorts to measure total mercury levels in archived samples from 348 pregnant women (blood from three trimesters and cord blood), 825 offspring (blood, hair, and urine) and their mothers (hair), and 91 seafood and canned tuna samples from Mexico City.Maternal blood mercury levels correlated across three trimesters and averaged 3.4 ?g/L. Cord blood mercury averaged 4.7 ?g/L and correlated with maternal blood from trimester 3 (but not trimesters 1 and 2). In children, blood, hair and urine mercury levels correlated and averaged 1.8 ?g/L, 0.6 ?g/g, and 0.9 ?g/L, respectively. Hair mercury was 0.5 ?g/g in mothers and correlated with child's hair. Mean consumption of canned tuna, fresh fish, canned sardine, and shellfish was 3.1, 2.2, 0.5, and 1.0 times per month respectively in pregnant women. Mean mercury content in 7 of 23 seafood species and 5 of 9 canned tuna brands purchased exceeded the U.S. EPA guidance value of 0.3 ?g/g.Mercury exposures in pregnant women and children from Mexico City, via biomarker studies, are generally 3-5 times greater than values reported in population surveys from the U.S., Canada, and elsewhere. In particular, mercury levels in 29-39% of the maternal participants exceeded the biomonitoring guideline associated with the U.S. EPA reference dose for mercury.
Project description:This study examined methylmercury (MeHg) concentrations in fish, the daily MeHg exposure dose, and the risk-benefit of MeHg, ?-3 polyunsaturated fatty acid (?-3 PUFA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) related to fish intake among pregnant and infertile women in Taiwan. The measured MeHg concentrations in fish did not exceed the Codex guideline level of 1 mg/kg. Swordfish (0.28 ± 0.23 mg/kg) and tuna (0.14 ± 0.13 mg/kg) had the highest MeHg concentrations. The MeHg concentration in the hair of infertile women (1.82 ± 0.14 mg/kg) was significantly greater than that of pregnant women (1.24 ± 0.18 mg/kg). In addition, 80% of infertile women and 68% of pregnant women had MeHg concentrations in hair that exceeded the USEPA reference dose (1 mg/kg). The MeHg concentrations in hair were significantly and positively correlated with the estimated daily MeHg exposure dose. Based on the risk-benefit evaluation results, this paper recommends consumption of fish species with a low MeHg concentration and high concentrations of DHA + EPA and ?-3 PUFA (e.g., salmon, mackerel, and greater amberjack).
Project description:Modification of the epigenome may be a mechanism underlying toxicity and disease following chemical exposure. Animal and human data suggest that mercury (Hg) impacts DNA methylation. We hypothesize that methylmercury and inorganic Hg exposures from fish consumption and dental amalgams, respectively, may be associated with altered DNA methylation at global repetitive elements (long interspersed elements, LINE-1) and candidate genes related to epigenetic processes (DNMT1) and protection against Hg toxicity (SEPW1, SEPP1). Dental professionals were recruited at Michigan Dental Association (MDA) meetings in 2009 and 2010. Subjects (n=131) provided survey data (e.g. exposure sources, demographics) and biological samples for Hg measurement and epigenetic analysis. Total Hg was quantified via atomic absorption spectrophotometry in hair and urine, indicative of methylmercury and inorganic Hg exposures, respectively. Global repetitive and candidate gene methylation was quantified via pyrosequencing of bisulfite converted DNA isolated from buccal mucosa. Hair Hg (geometric mean (95% CI): 0.37 (0.31-0.44) µg/g) and urine Hg (0.70 (0.60-0.83) µg/L) were associated with sources of exposure (fish consumption and dental amalgams, respectively). Multivariable linear regression revealed a trend of SEPP1 hypomethylation with increasing hair Hg levels, and this was significant (P<0.05) among males. The trend remained when excluding non-dentists. No significant relationships between urine Hg and DNA methylation were observed. Thus, in a limited cohort, we identified an association between methylmercury exposure and hypomethylation of a potentially labile region of the genome (SEPP1 promoter), and this relationship was gender specific.