Urinary Mercury Levels Research Articles

Effects of mercury vapor exposure on neuromotor function in Chinese miners and smelters

Current risk assessment of elemental mercury vapor is based on the tremor toxicity. To clarify the neuromotor effects of occupational exposure to mercury vapor, hand tremor and postural sway were measured in 27 miners and smelters (i.e., exposed workers) and 52 unexposed subjects. Urine samples were collected and total mercury and creatinine concentrations were determined. Data of the tremor and postural sway were analyzed using the fast Fourier transformation. The geometric means of the urinary mercury level (UHg) were 228 (range 22.6-4,577) microg/g creatinine for the exposed workers and 2.6 (1.0-17.4) microg/g creatinine for the unexposed subjects. Total tremor intensity and frequency-specific tremor intensities at 1-6 and 10-14 Hz were significantly larger in the exposed workers than in the unexposed subjects (P < 0.05), but they were not significantly related to the UHg among the exposed workers (P > 0.05). In contrast, there were no significant differences in any postural sway parameters between the above two groups (P > 0.05), but the transversal sway with eyes open was positively related to the UHg among the exposed workers in using multiple regression analysis (P < 0.05). These findings suggest that postural sway, as well as hand tremor, may be affected by elemental mercury vapor exposure, but the former test seems to be less sensitive to mercury than the latter one.

Total mercury levels in hair, toenail, and urine among women free from occupational exposure and their relations to renal tubular function

To investigate the relations among total mercury levels in hair, toenail, and urine, together with potential effects of methylmercury intake on renal tubular function, we determined their levels, and urinary N-acetyl- β- d-glucosaminidase activity (NAG) and α 1-microglobulin (AMG) in 59 women free from occupational exposures, and estimated daily mercury intakes from fish and other seafood using a food frequency questionnaire. Mercury levels ( mean ± SD ) in the women were 1.51 ± 0.91 μ g / g in hair, 0.59 ± 0.32 μ g / g in toenail, and 0.86 ± 0.66 μ g / g creatinine in urine; and, there were positive correlations among them ( P < 0.001 ) . The daily mercury intake of 9.15 ± 7.84 μ g / day was significantly correlated with total mercury levels in hair, toenail, and urine ( r = 0.551 , 0.537, and 0.604, P < 0.001 ). Among the women, the NAG and AMG were positively correlated with both the daily mercury intake and mercury levels in hair, toenail, and urine ( P < 0.01 ) ; and, these relations were almost similar when using multiple regression analysis to adjust for possible confounders such as urinary cadmium ( 0.47 ± 0.28 μ g / g creatinine) and smoking status. In conclusion, mercury resulting from fish consumption can explain total mercury levels in hair, toenail, and urine to some degree (about 30%), partly through the degradation into the inorganic form, and it may confound the renal tubular effect of other nephrotoxic agents. Also, the following equation may be applicable to the population neither with dental amalgam fillings nor with occupational exposures: [hair mercury (μg/g)]=2.44×[toenail mercury (μg/g)].

Potential Confounder: Bernard and de Burbure Respond

We thank Aschner for his positive comments and interesting suggestion regarding a possible influence of manganese on serum prolactin levels. We fully acknowledge that the four elements we studied (de Burbure et al. 2006) are probably not the only determinants of serum prolactin levels, especially because variations in blood or urinary levels explained only a few percent of the total variance. Other factors, including perhaps some other metals, most probably also contribute to modulate dopaminergic function and serum prolactin levels. Because the epidemiologic evidence suggesting a link between manganese and serum prolactin in children is recent, we did not measure this metal in our study. However, if we had measured blood manganese in the children in our study, it is far from certain that this factor would have emerged as a significant determinant, possibly confounding the relationships between neurologic markers and blood or urinary levels of cadmium, mercury, and lead. In the recent study by Wasserman et al. (2006), neurocognitive deficits were indeed not related to blood concentrations of manganese. As to the correlation between blood manganese at birth and cord blood prolactin levels reported by Takser et al. (2004), this association was not adjusted for possible exposure to lead, an indisputable confounder in this sort of study. This being said, we agree of course with Aschner that exposure to manganese should be considered in future studies investigating the developmental effects of heavy metals in the environment.

Mercury in traditional Tibetan medicine-panacea or problem?

Symptoms of mercury toxicity, biochemical changes, and blood/urine mercury levels were evaluated in a small group of patients. Six patients attending Delek Hospital, Dharamsala, India, taking mercury-containing traditional Tibetan medicine (TTM) (Group I), were compared with three patients taking non-mercury containing TTM (Group II) and healthy volunteers(Group II). Quantitative estimation of mercury ingestion based on chemical analysis was compared with US regulatory standards. Group I were significantly older (mean 55 years+/-SE 6.4) range 26-69 years, than Group II (26.7 years+/-SE 5) range 17-34 years and Group III (32.5 years +/-SE 0.5) range 33-34 years (P =0.05). Group I took TTM on average for 51 months and had a mean of 2.5 non-specific, mercury-related symptoms. Group I had higher mean diastolic pressures (85 mmHg) than Group II (73 mmHg) (P=0.06) and more loose teeth. Mean daily mercury intake for Group I was 674 microg, estimated as 10 microg/kg per day. (Established reference dose for chronic oral exposure: 0.3 microg/kg per day.) Blood mercury levels were non-detectable, but mean urinary mercury levels for Group I were 67 microg/L (EPA levels <20 microg/L). Renal and liver function tests were not significantly different between groups and within normal clinical range. Prolonged ingestion of mercury containing TTM is associated with absent blood levels, but relatively high urinary levels. Further studies are needed to evaluate toxicity and therapeutic potential.

Blood and urine levels of Pb, Cd and Hg in the general population of the Czech Republic and proposed reference values

The Human Biological Monitoring (HBM) project was launched in the Czech Republic in 1994 as a part of the nation-wide Environmental Health Monitoring System to assess the exposure of the Czech general population to a broad spectrum of environmental contaminants. Over the years 2001–2003, the concentrations of lead (Pb), cadmium (Cd), and mercury (Hg) were determined in whole blood of 1188 adults (blood donors) and 333 children and in urine of 657 adults and 619 children. In adults, the median blood lead (B-Pb) level was 33 μg/l. Men had higher B-Pb levels than women (medians 37 μg/l vs. 25 μg/l). Significantly higher B-Pb levels were observed in smokers compared to non-smokers (36 μg/l vs. 31 μg/l). In children, no sex-dependent differences were observed (median 31 μg/l). In total, the median blood Cd level (B-Cd) in adults was 0.5 μg/l. Smokers showed a median B-Cd level about 3 times as high as non-smokers (1.3 μg/l vs. 0.40 μg/l). Neither sex- nor age-related differences were observed in B-Cd levels. In 65% of children, B-Cd levels were below the limit of detection (LOD). The overall median urinary cadmium level (U-Cd) in adults was 0.31 μg/g creatinine. Significantly higher U-Cd levels were found in women (median 0.39 μg/g creatinine) compared to men (0.29 μg/g creatinine). No significant differences were found between smokers and non-smokers. In more than 50% of children, the U-Cd level was below the LOD (=0.2 μg/l). The median blood mercury (B-Hg) level in adults was 0.89 μg/l. Significant differences were found between smokers (0.80 μg/l) and non-smokers (0.92 μg/l), and between men and women (0.86 μg/l vs. 0.94 μg/l). The median B-Hg level in children was 0.42 μg/l and no sex-related differences were observed. The median urinary mercury (U-Hg) levels were 0.63 μg/g creatinine in adults and 0.37 μg/g creatinine in children. Significantly higher U-Hg levels were obtained in women and non-smokers compared to men and smokers, respectively. The B-Pb, B-Hg, U-Cd, and U-Hg levels significantly correlated with age. The following reference values were recommended for the period 2001–2003: 80, 65 and 55 μg/l for B-Pb and 3.1, 4.0 and 1.5 μg/l for B-Hg in men, women and children, respectively; 1.1 μg/l and 1.2 μg/g creatinine for B-Cd and U-Cd, respectively, in adult non-smokers; 5.4 and 12.0 μg/g creatinine for U-Hg in men and women, respectively, and 3.7 and 5.5 μg/g creatinine for U-Hg in boys and girls, respectively. The previous reference values for B-Pb and B-Cd needed revision and were reduced.

A Most Irregular Threat: Old Gas Regulators Can Present Mercury Exposure

Residential gas regulators reduce the pressure of gas from main feeder lines to usable levels for household pipes. Gas regulators built before 1961 were commonly located within dwellings and incorporated a component that contained, on average, 136 grams (about 2 teaspoons) of elemental mercury. Newer units do not contain mercury, but as a group of Chicago-area researchers report, careless replacement of the older units can result in potentially hazardous mercury contamination [EHP 114:848–852; Hryhorczuk et al.]. The authors describe how this newly identified source of residential mercury exposure came to light in 2000, when a suburban Chicago family discovered a pool of the silvery element on the floor of their basement workroom six weeks after a gas company contractor removed and replaced their gas regulator and meter. An investigation showed that the air in the house contained elevated levels of mercury vapor, and the father and the 9-year-old son, who spent more time in the basement area than the mother, had blood and urine mercury levels above recommended background limits. Short-term exposure to high levels of metallic mercury vapors can cause lung damage, nausea, vomiting, diarrhea, elevated blood pressure or heart rate, skin rash, and eye irritation. Fortunately, ventilation and remediation of the home brought mercury concentrations in the home’s air down to safe levels, and several weeks after exposure ceased, the father’s and son’s blood and urine mercury levels returned to normal background ranges. Neither ever manifested overt clinical signs of mercury poisoning. This case and a cluster of similar cases quickly caught the attention of area authorities. Ultimately, two area gas companies were required to conduct inspections in 361,000 homes where their employees or subcontractors had replaced old gas regulators. Free urine mercury screenings were offered to concerned residents. Of the 301,000 homes inspected by one of the companies, 1,308 (0.43%) were found to be contaminated, and 1,033 were remediated. Of 60,000 homes screened by the other company, 55 (0.09%) were found to be contaminated and were remediated. The risk was considerably higher in homes where the equipment had been replaced by one particular subcontractor—of 120 homes screened, 20 (16.7%) were found to have been contaminated by mercury. Of the 625 residents who elected to undergo urine mercury screenings, 9 (1.4%) had positive bioassays, defined as a 24-hour urine mercury concentration equal to or higher than 10 micrograms per liter. Although none of the subjects showed overt symptoms of mercury poisoning, as the authors point out, the screenings were not designed to detect subclinical effects of mercury exposure. Interestingly, positive urine mercury in residents was more strongly associated with elevated air mercury concentrations on the first floor of the homes than with elevated basement air levels, even though the air concentrations were considerably higher in basements, where the spills typically occurred. The authors attribute this result to the simple fact that people generally spend less time in their basements than in the living quarters aboveground. The Chicago episode not only revealed a previously unidentified environmental exposure hazard but also provided valuable lessons on how to respond quickly and efficiently. As the authors note, gas companies and their subcontractors, clinicians, public health and environmental officials, and residents all need to be aware of the potential for contamination in older homes or other buildings where mercury-containing gas regulators have been replaced in the past, or where they may still exist.

Neurobehavioral Effects of Dental Amalgam in Children

Dental (silver) amalgam is a widely used restorative material containing 50% elemental mercury that emits small amounts of mercury vapor. No randomized clinical trials have determined whether there are significant health risks associated with this low-level mercury exposure. To assess the safety of dental amalgam restorations in children. A randomized clinical trial in which children requiring dental restorative treatment were randomized to either amalgam for posterior restorations or resin composite instead of amalgam. Enrollment commenced February 1997, with annual follow-up for 7 years concluding in July 2005. A total of 507 children in Lisbon, Portugal, aged 8 to 10 years with at least 1 carious lesion on a permanent tooth, no previous exposure to amalgam, urinary mercury level <10 microg/L, blood lead level <15 microg/dL, Comprehensive Test of Nonverbal Intelligence IQ > or =67, and with no interfering health conditions. Routine, standard-of-care dental treatment, with one group receiving amalgam restorations for posterior lesions (n = 253) and the other group receiving resin composite restorations instead of amalgam (n = 254). Neurobehavioral assessments of memory, attention/concentration, and motor/visuomotor domains, as well as nerve conduction velocities. During the 7-year trial period, children had a mean of 18.7 tooth surfaces (median, 16) restored in the amalgam group and 21.3 (median, 18) restored in the composite group. Baseline mean creatinine-adjusted urinary mercury levels were 1.8 microg/g in the amalgam group and 1.9 microg/g in the composite group, but during follow-up were 1.0 to 1.5 microg/g higher in the amalgam group than in the composite group (P<.001). There were no statistically significant differences in measures of memory, attention, visuomotor function, or nerve conduction velocities (average z scores were very similar, near zero) for the amalgam and composite groups over all 7 years of follow-up, with no statistically significant differences observed at any time point (P values from .29 to .91). Starting at 5 years after initial treatment, the need for additional restorative treatment was approximately 50% higher in the composite group. In this study, children who received dental restorative treatment with amalgam did not, on average, have statistically significant differences in neurobehavioral assessments or in nerve conduction velocity when compared with children who received resin composite materials without amalgam. These findings, combined with the trend of higher treatment need later among those receiving composite, suggest that amalgam should remain a viable dental restorative option for children. clinicaltrials.gov Identifier: NCT00066118.

Neuropsychological and Renal Effects of Dental Amalgam in Children

No randomized trials have been published that address the concern that inhalation of mercury vapor released by amalgam dental restorations causes adverse health effects. To compare the neuropsychological and renal function of children whose dental caries were restored using amalgam or mercury-free materials. The New England Children's Amalgam Trial was a 2-group randomized safety trial involving 5 community health dental clinics in Boston, Mass, and 1 in Farmington, Me, between September 1997 and March 2005. A total of 534 children aged 6 to 10 years at baseline with no prior amalgam restorations and 2 or more posterior teeth with caries were randomly assigned to receive dental restoration of baseline and incident caries during a 5-year follow-up period using either amalgam (n=267) or resin composite (n =267) materials. The primary neuropsychological outcome was 5-year change in full-scale IQ scores. Secondary outcomes included tests of memory and visuomotor ability. Renal glomerular function was measured by creatinine-adjusted albumin in urine. Children had a mean of 15 tooth surfaces (median, 14) restored during the 5-year period (range, 0-55). Assignment to the amalgam group was associated with a significantly higher mean urinary mercury level (0.9 vs 0.6 microg/g of creatinine at year 5, P<.001). After adjusting for randomization stratum and other covariates, no statistically significant differences were found between children in the amalgam and composite groups in 5-year change in full-scale IQ score (3.1 vs 2.1, P = .21). The difference in treatment group change scores was 1.0 (95% confidence interval, -0.6 to 2.5) full-scale IQ score point. No statistically significant differences were found for 4-year change in the general memory index (8.1 vs 7.2, P = .34), 4-year change in visuomotor composite (3.8 vs 3.7, P = .93), or year 5 urinary albumin (median, 7.5 vs 7.4 mg/g of creatinine, P = .61). In this study, there were no statistically significant differences in adverse neuropsychological or renal effects observed over the 5-year period in children whose caries were restored using dental amalgam or composite materials. Although it is possible that very small IQ effects cannot be ruled out, these findings suggest that the health effects of amalgam restorations in children need not be the basis of treatment decisions when choosing restorative dental materials. clinicaltrials.gov Identifier: NCT00065988.

Mercury in Dental Amalgam—A Neurotoxic Risk?

DENTAL AMALGAM, WHICH CONTAINS 50% MERcury by weight, has been used for at least 150 years. Because mercury is an acknowledged neurotoxin, concerns about the health effects of exposure to this chemical are widespread. Consequently, many individuals have submitted to removal of amalgam dental fillings, an uncomfortable, expensive procedure that is not free of hazard. In this issue of JAMA, Bellinger and colleagues and DeRouen and colleagues report the first 2 randomized controlled trials comparing the health effects in children treated with mercury amalgam fillings with those treated with a composite dental restorative material. Mercury is a highly reactive metal that has widely recognized toxic properties at high dose, including parethesias, cerebellar ataxia, dysarthria, and constriction of the visual fields. The significance of lower-level asymptomatic exposures on brain function is less clear, and sound clinical studies are needed to define this risk. Amalgam mercury enters the bloodstream, and a number of investigations suggest that this has toxic consequences. Mercury levels in expired air are correlated with the number of amalgam fillings. Dentists and dental assistants have deficits in motor function and cognitive scores in relation to their number of fillings and to their urinary mercury excretion. Mercury also has been suggested as a risk factor for multiple sclerosis and Alzheimer disease. Sensitivity to mercury toxicity may have a genetic basis. Echeverria et al recently reported that polymorphisms of coproporphyrinogen oxidase (CPOX4), the gene encoding urinary porphyrin excretion, altered the impact of mercury on cognitive and mood scores. Approximately 25% of the US population is polymorphic for this genotype. Although the literature is sparse, other molecular effects of mercury exposure also are receiving attention. For example, in an in vitro study, mercury has been shown to affect heat shock protein levels in human cells and in an animal model, mercury inhibited the binding of guanosine triphosphate (GTP) to tubulin in the rodent brain. With the application of better epidemiological designs and more robust statistical methods to investigate toxicity, the usual consequence is uncovering effects at lower thresholds. The trajectory of discovery of the toxic effects of another metal, lead, has followed this path and may offer insight into the future path that mercury investigations may follow. When childhood lead poisoning was first reported, it was believed to have only 2 outcomes: death or complete recovery with no sequelae. After long-term neurobehavioral deficits were found in survivors of lead poisoning, these effects were thought to occur only in children who had displayed signs of severe encephalopathy. In the 1970s, studies of elevated lead burden in children who had displayed no symptoms revealed dose-dependent deficits in cognitive skills, attention, and behavioral control. In the 1960s, the defined toxic threshold for lead was 60 μg/dL (2.90 μmol/L); however, over the next 30 years, on the basis of newer studies, this threshold was sequentially reduced to 10 μg/dL (0.48 μmol/L). A recent pooled analysis of 7 longitudinal cohort studies demonstrated that blood lead levels below 10 μg/dL (0.48 μmol/L) in children are associated with decrements in IQ scores. These findings are the consequence of larger sample sizes, more sensitive outcome measures, and better multivariate techniques. History is likely to repeat itself with other neurotoxins. The 2 clinical trials reported in this issue of JAMA examine the neuropsychological and renal effects of dental amalgam in children. In their study of 534 New England children aged 6 to 10 years, Bellinger et al found that, at 5 years’ follow-up, children randomly assigned to the amalgam group had higher mean mercury levels than those in the resinbased composite group, but there were no statistically significant differences between the groups in terms of 5-year change in full-scale IQ score, 4-year change in general memory index, or visual motor composite score, or urinary albumin levels. In the report by DeRouen et al, 507 8to 10-year-old children from Lisbon, Portugal, were randomly assigned to receive dental restorations using amalgam or resin composite. At 7 years of follow-up, children in the amalgam group had higher urinary mercury levels, but there were no statistically significant differences be-

A Meta-Analysis of the Neuropsychological Effects of Occupational Exposure to Mercury

ABSTRACT This paper reports a meta-analysis of 36 peer-reviewed published studies of the neuropsychological effects of occupational exposure to mercury, which yielded 43 independent samples. These studies included 2,512 exposed participants and 1,846 controls, for a total sample size of 4,358. Because the independent variables defining mercury exposure varied across studies, effect sizes were calculated for exposed versus non-exposed workers. Dose–response relations were considered for measures of mercury levels in urine (81% of studies reported), blood (42% of studies reported), and air samples (33% of studies reported). Level of exposure was also estimated by reported years of exposure (M = 11.3, SD = 5.6). Cohen's d statistic yielded a statistically significant weighted study-mean effect size of −.23, p < .0001 for occupational mercury exposure. However, an effect this small is typically undetectable when evaluating individuals because it is smaller than the typical 95% confidence interval used for most neuropsychological measures. None of the exposure variables analyzed reached statistical significance. The magnitude of self-reported symptoms (−.30) was slightly larger than that obtained from objective test scores (−.22), though the difference was not statistically significant. Also, the weighted mean effect size for psychomotor skills (−.34) was the largest in magnitude, whereas the weighted mean effect size for verbal comprehension measures had the smallest (−.06). However, an analysis of the differential effects of mercury exposure across cognitive domains found significant differences between verbal comprehension measures and all other domains. None of the other domains were significantly different from one another. The weighted study-mean effect size suggests that the prevalence of neuropsychological deficits due to occupational exposure to mercury is small and difficult to detect on an individual case-by-case basis.

Community mercury levels in the vicinity of peri-urban waste disposal sites and fossil fuel burning operations

IntroductionA study was conducted as a result of concern about mercury absorption amongst residents of a peri-urban area in Cape Town, South Africa, in close proximity to waste disposal sites and an industrial area. Study methodsThe study compared urine mercury concentrations in a random sample of adult residents and children in both the formal and informal housing settlements of the “exposure” area (n=90) and a control area (n=90). A short questionnaire elicited demographic, lifestyle and medical details and possible occupational, household and environmental mercury exposures. ResultsThe two samples were comparable with respect to background and potential confounding variables. The prevalence of urinary mercury levels≥the WHO reference range in the exposure area was also higher than that in the control area (13% vs. 0%). The median urinary mercury concentrations in both study areas were below the World Health Organisation (WHO) reference level of 5.0 μg/g creatinine. The median level in the exposure area was slightly, but statistically significantly, higher than in the control area (1.1 vs. 0.25 μg/g creatinine), and the excess persisted after controlling for known possible mercury exposures. ConclusionsThis is to our knowledge the first study of community inorganic mercury absorption in a developing country setting, and where airborne mercury was the exposure of concern. It was concluded that the health risk associated with the urinary mercury levels of residents in the exposure area was very low. However, low level environmental exposure in the area of concern could not be excluded.

Exposure, health complaints and cognitive performance among employees of an MRI scanners manufacturing department

To assess sensory effects and other health complaints that are reported by system testers working near magnetic resonance imaging (MRI) magnets, realizing that it is believed that exposure up to 8 T is safe for humans. Levels of exposure to static magnetic fields (SMFs), movement speed during exposure, health complaints, and cognitive performance among employees in an MRI-manufacturing department and at a reference department have been analyzed. Mercury concentrations in urine samples were determined to analyze whether they depend on exposure to SMFs. Average exposure of system testers was 25.9 mT/8 hours at a 1.0-T system and 40.4 mT/8 hours at a 1.5-T system. Vertigo, metallic taste, and concentration problems were more reported among workers of MRI-fabrication than in the reference department. Cognitive performance was tested outside the SMF, and no significant changes were detected. This study suggests that any effects on cognitive functions are acute and transient and disappear rapidly after exposure has ended. All complaints, except for headaches, were more frequently reported by "fast movers" than by "slow movers," and depended on field strength and duration of exposure. Mercury-levels in urine were not affected.

The association between a genetic polymorphism of coproporphyrinogen oxidase, dental mercury exposure and neurobehavioral response in humans

We previously described a polymorphism in exon 4 of the gene encoding the heme biosynthetic pathway enzyme, coproporphyrinogen oxidase (CPOX4), which significantly modifies the effect of mercury exposure on urinary porphyrin excretion in humans. Here, we examined potential consequences of this polymorphism (“CPOX4”) on performance within neurobehavioral domains, symptoms, and mood that are known to be affected by elemental mercury (Hg°) exposure in human subjects. A behavioral test battery was administered on the day of urine and buccal cell collections for 194 male dentists (DDs) and 233 female dental assistants (DAs) occupationally exposed to Hg° for an average of 19 and 10 years, respectively. Subjects had no history of health disorders and were employed for a minimum of 5 years in the dental profession. Respective mean urinary mercury (HgU) levels in DDs and DAs were 3.32 (4.87) μg/l and 1.98 (2.29) μg/l. Corresponding indices of chronic occupational Hg° exposure, weighted for historical exposure, were 27.1 (20.6) and 15.2 (12.3). The frequencies of the homogygous common (A/A), heterozygous (A/C), and homozygous polymorphic (C/C) genotypes were 75%, 23% and 2% for DDs and 73%, 25%, and 2% for DAs, respectively. DDs and DAs were evaluated separately. Regression analyses controlled for age, premorbid intelligence, alcohol consumption, and education. Statistically significant associations with HgU ( p < 0.05) were found for nine measures among DDs (BEES Digit Span Forward and Backward, WMS-R Visual Reproduction N Correct, BEES Symbol Digit Rate, BEES Finger Tapping Dom/Non-dom, and Alternate Partialed, Hand Steadiness Factor1, and BEES Tracking), and eight measures among DAs (BEES Digit Span Forward, BEES Symbol Digit Rate, BEES Pattern Discrimination Rate, BEES Trailmaking B, BEES Finger Tapping Dom/Non-dom, and Alternate Partialed, Hand Steadiness Factor1, and Vibration Sensitivity Hits). CPOX4 status was associated with four measures in DDs (BEES Spatial Span Forward, BEES Pattern Memory N Correct, BEES Symbol Digit Rate, and BEES Vigilance Hit) and five measures in DAs (BEES Digit Span Forward, WMS-R Visual Reproductions N Correct, BEES Symbol Digit Rate, BEES Simple and Choice Reaction Time Move. Both groups experienced an additive effect (no interaction term) for HgU and the CPOX4 polymorphisms on the Digit Rate whereas DAs also had additive effects for BEES Digit Span Forward and for Beck's Depression factor ‘Worthlessness’. These exploratory findings suggest that the CPOX4 polymorphism may affect susceptibility for specific neurobehavioral functions associated with mercury exposure in human subjects.

Maternal exposure to arsenic, cadmium, lead, and mercury and neural tube defects in offspring

Arsenic, cadmium, lead, and mercury are neurotoxins, and some studies suggest that these elements might also be teratogens. Using a case–control study design, we investigated the relation between exposure to these heavy metals and neural tube defects (NTDs) in offspring of Mexican–American women living in 1 of the 14 Texas counties bordering Mexico. A total of 184 case-women with NTD-affected pregnancies and 225 control-women with normal live births were interviewed about their environmental and occupational exposures during the periconceptional period. Biologic samples for blood lead and urinary arsenic, cadmium, and mercury were also obtained for a subset of these women. Overall, the median levels of these biomarkers for heavy metal exposure did not differ significantly ( P > 0.05 ) between case- and control-women. However, among women in the highest income group, case-women were nine times more likely (95% confidence interval (CI) 1.4–57) than control-women to have a urinary mercury ⩾5.62 μg/L. Case-women were 4.2 times more likely (95% CI 1.1–16) to report burning treated wood during the periconceptional period than control-women. Elevated odds ratios (ORs) were observed for maternal and paternal occupational exposures to arsenic and mercury, but the 95% CIs were consistent with unity. The 95% CIs of the ORs were also consistent with unity for higher levels of arsenic, cadmium, lead, and mercury in drinking water and among women who lived within 2 miles at the time of conception to industrial facilities with reported emissions of any of these heavy metals. Our findings suggest that maternal exposures to arsenic, cadmium, or lead are probably not significant risk factors for NTDs in offspring. However, the elevated urinary mercury levels found in this population and exposures to the combustion of treated wood may warrant further investigation.

Examination of urinary mercury levels in dentists in Turkey

Mercury (Hg) is a naturally occurring element and its toxicity, especially in certain forms, has been known for many years. Exposure to Hg can occur in occupational and environmental settings. The toxicity of Hg compounds in dentistry has been an issue of increasing concern. Dental personnel are occupationally exposed to Hg vapor in their working environment and this exposure constitutes a potential risk to people in the dental surgery, mainly from the inhalation of Hg vapor and fine particles of amalgam. In this study, the urinary Hg excretion levels of 20 dentists and nine control subjects, matched for age, were determined by cold-vapor atomic absorption spectrometer (CV-AAS). The levels of Hg in the urine samples of the dentists was about three times higher than the control subjects (6.2 +/- 3.5 and 1.97 +/- 0.9 microg/L, respectively) (P <0.001). Some 90% of dentists wore both gloves and masks. Standards of hygiene (use of mask, glove and gown) may contribute to the degree of exposure. Attention to important hygiene measures, such as the avoidance of spills of Hg, cleaning of floors after such spills, ventilation and the installation of ventilation, depending on technology, should be taken into consideration. Age and smoking habits did not influence the urinary Hg excretion. Our results showed that dentists had significant exposure to Hg vapor compared to control subjects and therefore might be subject to possible adverse effects due to Hg toxicity.

Environmental Review: Magico-Religious Mercury Use in Caribbean and Latino Communities: Pollution, Persistence, and Politics

Elemental mercury is put to magico-religious uses, most problematically the sprinkling of mercury on floors of homes in Caribbean and Latino communities. Indoor mercury spills are persistent and release toxic levels of mercury vapor over long periods of time. Surveys in these communities have demonstrated widespread and large-scale mercury sales for ritualistic use, elevated mercury vapor levels in public hallways, increased amounts of mercury in wastewater, and elevated urine mercury levels in Latino children. Yet no clear connection has been drawn between ritualistic mercury use and these elevated levels, nor has any pathology been associated with such use. Social, political, and economic factors have acted to preclude advocacy for these affected communities, whose members are largely unaware of their mercury exposure (frequently secondhand) and of its adverse health effects. Without the political mandate to act, environmental agencies have not allocated the resources necessary for environmental professionals to assess and respond to this latent environmental health disaster. Steps to investigate and respond to this impending public health emergency are suggested, as presently there is no coordinated plan for assessing and remediating the tens of thousands of dwellings around the country likely to be contaminated with actionable levels of mercury vapor.

Urinary mercury concentrations associated with dental restorations in adult women aged 16–49 years: United States, 1999–2000

Background: Mercury amalgam dental restorations have been used by dentists since the mid 19th century and issues on safety continue to be periodically debated within the scientific and public health...

Mercury Levels in Urine and Hair of Children in an Andean Gold-mining Settlement

This field study investigated mercury (Hg) levels in urine and hair of Andean children of indigenous Saraguro and Metizo gold miners in the Nambija, Ecuador gold mining settlement. Spot samples of urine and hair samples were collected concurrently from 80 children each. Urine samples were used to determine the inorganic Hg burden, while hair samples were used as an index of methylmercury (MeHg) exposure from consumption of Hg contaminated fish. The mean level of Hg in urine (HgU) was 10.9 microg/L, and the mean level in hair (HgH) was 6.0 microg/g. Regression analysis showed a significant association (r = 0.404, p = 0.0007) between matched HgU and HgH samples. Mean HgU and HgU levels tended to be higher for children aged 6-14 years than for a younger group. The wide range of Hg levels in the urine and hair of Andean children of gold miners may place them at risk for neurodevelopmental and learning disorders.

Impact of Consumption of Freshwater Fish on Mercury Levels in Hair, Blood, Urine, and Alveolar Air

Human exposure to methylmercury occurs mainly via consumption of fish. The aim of the study was to investigate the influence of freshwater fish consumption on mercury levels in hair, blood, urine, and end-exhaled air. Twenty subjects without dental amalgam fillings were recruited from sport-fishing societies. They ranged in age from 61 to 87 yr. Six individuals ate freshwater fish at least once a week and were categorized as high consumers. Eight individuals were classified as medium consumers and ate freshwater fish at least once a month but less than once a week. Six individuals were categorized as low consumers and had not eaten freshwater fish in the past 3 mo. Among the high consumers, median concentrations of mercury were 8.6 μg/L in blood, 2.4 μg/g in hair, 10 pg/L in end-exhaled air, and 1.1 μg/g creatinine in urine. The relationship between freshwater fish consumption and mercury was significant in all biological media. The high-consumption group had much higher mercury levels in blood (9-fold), hair (7-fold), alveolar air (3-fold), and urine (15-fold) than the low-consumption group. The latter finding may be explained by demethylation of methylmercury in the body. The ratio between mercury concentration in blood and hair was 1:270. This implies that the typical blood–hair ratio of 1:250, specified by the World Health Organization (WHO) in 1990, is valid also for exposure to low amounts of methylmercury.This study was funded by a grant from Sahlgrenska University Hospital, Sweden. Gunnel Garsell and Anna-Karin Arvidsson are acknowledged for skillful technical assistance and Giovanni Ferrari for excellent analytical work. Lars Barregård is gratefully acknowledged for valuable advice and comments on the article.Andrejs Schütz is deceased.

Exposição humana ao mercúrio na Amazônia brasileira: uma perspectiva histórica

The objective of the present article was to present the most important data generated by a multicentric study carried out by Brazilian researchers who, with the support of national and international institutions, worked during the 1990s to describe human exposure to mercury in gold mining areas in the Brazilian Amazon. Three sets of procedures were followed with residents of the Tocantins and Xingu river basins: (1) clinical examination, based on a standardized protocol and performed by a single researcher, in order to identify five basic levels of contamination; (2) determination of mercury levels in blood, hair, and urine, using atomic absorption spectrophotometry (Xingu Project); and (3) investigation of genotoxicity by using four cytogenetic indicators. During the first stage, 41 individuals were studied. Mercury was found in miners and their family members. Contamination was significantly associated with occupation and showed a differential correlation with genotoxicity indicators. After that, the Xingu project, which encompassed 625 individuals, focused on 417 Kayapó natives from the Gorotire and Djudjetiktire villages; 142 miners; and 66 riverine individuals (ribeirinhos). The highest levels of methylmercury in hair and total mercury in blood and urine were found among the Indian population. Contamination with inorganic forms of mercury was also observed in the blood, hair, and urine of Indians. Following a specific recommendation from the World Health Organization, special attention was given to pregnant Gorotire and Djudjetiktire women, who, although not directly exposed to mercury vapors, showed considerable levels of mercury intoxication. Despite this worrisome scenario, a number of social achievements in the 1990s point to new standards of dignity in health care and of social ethics in Brazil that could benefit everyone, including the victims of environmental injury.