Human exposure to mercury: a critical assessment of the evidence of adverse health effects

Mercury and selenium in oysters Saccostrea palmula and Crassostrea corteziensis from coastal lagoons of the southeastern Gulf of California: molar ratio and risk assessment on human health

Total mercury (Hg) and selenium (Se) contents were determined in oysters Saccostrea palmula and Crassostrea corteziensis soft tissues from four coastal lagoons of the southeastern Gulf of California. The annual Hg mean concentrations for S. palmula (0.09 ± 0.04 µg g- 1, wet weight) and C. corteziensis (0.08 ± 0.04 µg g- 1) were similar (p ˃ 0.05) among the lagoons and did not exceed the limit established by the Norma Oficial Mexicana and World Health Organization (< 1.0 µg g- 1 Hg). On the other hand, the annual mean concentrations of Se for S. palmula (3.34 ± 0.96 µg g- 1) and C. corteziensis (2.79 ± 0.89 µg g- 1) were higher (p < 0.05) in El Colorado lagoon. The Se/Hg molar ratios were above 1; the positive selenium health benefit value index suggested that Se load in oysters could reduce the Hg potential toxic effect. The hazard quotient for Hg in both species was below 1. Therefore, the consumption of oysters does not represent a risk due to Hg ingestion.

Pocket Mercury-Vapour Detection System Employing a Preconcentrator Based on Au-TiO2 Nanomaterials

In environments polluted by mercury vapors that are potentially harmful to human health, there is a need to perform rapid surveys in order to promptly identify the sources of emission. With this aim, in this work, a low cost, pocket-sized portable mercury measurement system, with a fast response signal is presented. It consists of a preconcentrator, able to adsorb and subsequently release the mercury vapour detected by a quartz crystal microbalance (QCM) sensor. The preconcentrator is based on an adsorbing layer of titania/gold nanoparticles (TiO₂NP/AuNPs), deposited on a micro-heater that acts as mercury thermal desorption. For the detection of the released mercury vapour, gold electrodes QCM (20 MHz) have been used. The experimental results, performed in simulated polluted mercury-vapour environments, showed a detection capability with a prompt response. In particular, frequency shifts (-118 Hz ± 2 Hz and -30 Hz ± 2 Hz) were detected at concentrations of 65 µg/m³ Hg⁰ and 30 µg/m³ Hg⁰, with sampling times of 60 min and 30 min, respectively. A system limit of detection (LOD) of 5 µg/m³ was evaluated for the 30 min sampling time.

Total mercury concentrations in invasive lionfish (Pterois volitans/miles) from the Atlantic coast of Florida

Invasive lionfish (Pterois volitans/miles) pose a serious threat to marine ecosystems throughout the western Atlantic Ocean and Caribbean Sea. The development of a fishery for lionfish has been proposed as a strategy for controlling populations; however, there is concern about consumption of this species by humans due to its high trophic position and potential for bioaccumulation of mercury. We analyzed total mercury (THg) in tissues of lionfish from two locations on the east coast of Florida. THg in lionfish increased with size and differed by location and sex. THg was highest in muscle tissue and was strongly positively correlated among tissues. THg in lionfish was lower than other commonly consumed marine fishes, and falls into Florida’s least restrictive advisory level. Consumption of lionfish poses a low risk and concerns over mercury bioaccumulation should not present a significant barrier to lionfish harvest.

Mercury Exposure among E-Waste Recycling Workers in Colombia: Perceptions of Safety, Risk, and Access to Health Information

Exposures to the toxic element mercury (Hg) are exceptionally high among recycling workers globally. Recycling is a growing sector in Colombia, yet workers who directly handle e-waste are often unaware of the risks of exposure to mercury from post-consumer lighting products (e.g., fluorescent lamps). This qualitative study aimed to understand how recycling workers perceive their own risks from mercury exposure and how they find information about these risks, through interviews (n = 35) at the three largest formal recycling facilities in Colombia. Workers' risk perception was generally disconnected from their likely actual exposure to mercury, instead often seen juxtaposed to co-workers who worked more directly with hazardous waste. Recycling workers, who were predominantly men from lower-income socioeconomic backgrounds, had limited knowledge of health risks due to mercury exposure and were more likely to receive health-related information from informal sources. Over a third of interviewees had searched online for information about occupational health risks of mercury, but these searches were perceived as unsatisfactory due to information being difficult to find, not available in Spanish, or related to mercury exposure via seafood or mining rather than recycling. Workers expressed (over)confidence in personal protective equipment and concern about frequent employee turnover. This study points to weaknesses in environmental health literacy and public health communication around toxic exposures to mercury in the workplace. Stronger regulation and enforcement are needed to prevent toxic exposures and promote worker health equity.

Potential Health Risk Assessment of Different Heavy Metals in Wheat Products

In the present work, health risk of heavy metals such as As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn in Iranian urban and rural samples including wheat, wheat flour, bread, pasta and sweets were assessed. The real amount of heavy metals in target samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS). Wet ashing and hydride generation techniques were used in sample preparation step. Results demonstrated that heavy metal contaminations in cereal samples were significant. The average concentrations of heavy metals in wheat products were between 0.01 mg kg-1 to 46 mg kg-1. Finally, the health risk assessment results showed that heavy metal contents in rural samples were higher than those in urban samples. The risk of Cu and Zn was significant in two areas and risk of Cr and Cd was not significant.

Mercury Levels in Women and Children from Interior Villages in Suriname, South America

Natural sources of mercury, historical gold mining, and contemporary artisanal and small-scale gold mining (ASGM) activities have led to mercury contamination in Suriname. Our primary objective was to evaluate mercury levels in hair of women and children from interior villages in Suriname where mercury levels in fish are elevated. We also estimated blood levels of mercury using an established mathematical conversion to facilitate comparison with other biomonitoring programs in the United States. Estimated levels of mercury in the blood of participants from Suriname were significantly higher than those in women from a heavy marine fish-consuming population in southeast Louisiana and estimates of the US national average. This includes women from Surinamese villages well upstream of ASGM activities. Since residents in these areas rely heavily on local fish, this is likely the source of their exposure to mercury. The levels in hair are similar to those seen in women from longitudinal studies finding neurological impairments in children exposed pre- and postnatally. Additional biomonitoring and neurodevelopmental assessments are warranted in these areas, as well as other areas of the Suriname. Mercury levels in hair (Suriname) and blood (southeast LA USA) were determined using cold vapor atomic absorption spectroscopy (CVAAS).

Effects of environmental levels of cadmium, lead and mercury on human renal function evaluated by structural equation modeling

A relationship between exposure to heavy metals, including lead and cadmium, and renal dysfunction has long been suggested. However, modeling of the potential additive, or synergistic, impact of metals on renal dysfunction has proven to be challenging. In these studies, we used structural equation modeling (SEM), to investigate the relationship between heavy metal burden (serum and urine levels of lead, cadmium and mercury) and renal function using data from the NHANES database. We were able to generate a model with goodness of fit indices consistent with a well-fitting model. This model demonstrated that lead and cadmium had a negative relationship with renal function, while mercury did not contribute to renal dysfunction. Interestingly, a linear relationship between lead and loss of renal function was observed, while the maximal impact of cadmium occurred at or above serum cadmium levels of 0.8 μg/L. The interaction of lead and cadmium in loss of renal function was also observed in the model. These data highlight the use of SEM to model interaction between environmental contaminants and pathophysiology, which has important implications in mechanistic and regulatory toxicology.

Effect of thimerosal, methylmercury, and mercuric chloride in Jurkat T Cell Line

Mercury is a ubiquitous environmental toxicant that causes a wide range of adverse health effects in humans. Three forms of mercury exist: elemental, inorganic and organic. Each of them has its own profile of toxicity. The aim of the present study was to determine the effect of thimerosal, a topical antiseptic and preservative in vaccines routinely given to children, methyl mercury, and mercuric chloride on cellular viability measured by MTT in Jurkat T cells, a human T leukemia cell line. The treatment of Jurkat T cells with thimerosal caused a significant decrease in cellular viability at 1 μM (25%, p<0.05; IC50: 10 μM). Methyl mercury exhibited a significant decrease in cellular viability at 50 μM (33%, p<0.01; IC50: 65 μM). Mercuric chloride (HgCl₂) did not show any significant change in cellular survival. Our findings showed that contrary to thimerosal and methyl mercury, mercuric chloride did not modify Jurkat T cell viability.

A Prospective Clinical Study on Blood Mercury Levels Following Endodontic Root-end Surgery with Amalgam

INTRODUCTION

The purpose of this clinical study was to compare the blood mercury levels before and after endodontic surgery using amalgam as a root-end filling material.

MATERIALS AND METHODS

Fourteen patients requiring periradicular surgery participated in this prospective clinical study. A zinc-free amalgam was employed as root-end filling material. Blood samples were collected at three intervals: immediately before, immediately after and one week postoperatively. Mercury content of the blood was determined using gold amalgamation cold-vapor atomic absorption spectrometry. Obtained data were analyzed using analysis of variance for repeated measures and paired t-test.

RESULTS

The mean (SD) of blood mercury levels was 2.20 (0.24) ng/mL immediately before surgery, 2.24 (0.28) ng/mL immediately after surgery and 2.44 (0.17) ng/mL one week after the periradicular surgery. The blood mercury level one week post-operative was significantly higher than both blood mercury levels immediately before (P<0.001) and immediately after (P=0.005) the surgery.

CONCLUSION

Placement of an amalgam retroseal during endodontic surgery can increase blood mercury levels after one week. The mercury levels however, are still lower than the toxic mercury levels. We suggest using more suitable and biocompatible root-end filling materials.

Mercuric compounds induce pancreatic islets dysfunction and apoptosis in vivo

Mercury is a toxic heavy metal that is an environmental and industrial pollutant throughout the world. Mercury exposure leads to many physiopathological injuries in mammals. However, the precise toxicological effects of mercury on pancreatic islets in vivo are still unclear. Here, we investigated whether mercuric compounds can induce dysfunction and damage in the pancreatic islets of mice, as well as the possible mechanisms involved in this process. Mice were treated with methyl mercuric chloride (MeHgCl, 2 mg/kg) and mercuric chloride (HgCl₂, 5 mg/kg) for more than 2 consecutive weeks. Our results showed that the blood glucose levels increased and plasma insulin secretions decreased in the mice as a consequence of their exposure. A significant number of TUNEL-positive cells were revealed in the islets of mice that were treated with mercury for 2 consecutive weeks, which was accompanied by changes in the expression of the mRNA of anti-apoptotic (Bcl-2, Mcl-1, and Mdm-2) and apoptotic (p53, caspase-3, and caspase-7) genes. Moreover, plasma malondialdehyde (MDA) levels increased significantly in the mice after treatment with mercuric compounds for 2 consecutive weeks, and the generation of reactive oxygen species (ROS) in the pancreatic islets also markedly increased. In addition, the mRNA expression of genes related to antioxidation, including Nrf2, GPx, and NQO1, were also significantly reduced in these islets. These results indicate that oxidative stress injuries that are induced by mercuric compounds can cause pancreatic islets dysfunction and apoptosis in vivo.

Heavy metal concentrations in hair of newly imported China-origin rhesus macaques (Macaca mulatta)

Macaque monkeys are good sentinel to humans for environmental pollutions because their similarities in genetic and physiological characteristics. So, their reference values about exposures to heavy metals are required for proper data interpretation. Here, we report several heavy metals concentrations in the hair of rhesus monkeys which are widely used in biomedical research. The hair of 28 imported rhesus monkeys from an animal farm in southwest China were examined for the presence of eight heavy metals (Arsenic, Beryllium, Cadmium, Chromium, Iron, Lead, Mercury, and Selenium). The analyzed data in parts per million (ppm) for hair concentrations of heavy metals in rhesus monkeys were as follow: As (0.654±0.331), Be (0.005±0.003), Cd (0.034±0.022), Cr (11.329±4.259), Fe (87.106±30.114), Pb (0.656±0.613), Hg (0.916±0.619), and Se (3.200±0.735). The concentrations of Be, Cr, and As showed significant higher in females than in males (P<0.05). We present here the reference values of several heavy metals in healthy China-origin rhesus monkeys. These data may provide valuable information for veterinarians and investigators using rhesus monkeys in experimental studies.

Toxic elements in tobacco and in cigarette smoke: inflammation and sensitization

Biochemically and pathologically, there is strong evidence for both atopic and nonatopic airway sensitization, hyperresponsiveness, and inflammation as a consequence of exposure to tobacco mainstream or sidestream smoke particulate. There is growing evidence for the relation between exposure to mainstream and sidestream smoke and diseases resulting from reactive oxidant challenge and inflammation directly as a consequence of the combined activity of neutrophils, macrophages, dendritic cells, eosinophils, basophils, as a humoral immunological consequence of sensitization, and that the metal components of the particulate play a role in adjuvant effects. As an end consequence, carcinogenicity is a known outcome of chronic inflammation. Smokeless tobacco has been evaluated by the IARC as a group 1 carcinogen. Of the many harmful constituents in smokeless tobacco, oral tissue metallothionein gradients suggest that metals contribute to the toxicity from smokeless tobacco use and possibly sensitization. This work reviews and examines work on probable contributions of toxic metals from tobacco and smoke to pathology observed as a consequence of smoking and the use of smokeless tobacco.

Synanthropic primates in Asia: potential sentinels for environmental toxins

Macaques are similar to humans both physiologically and behaviorally. In South and Southeast Asia they are also synanthropic, ecologically associated with humans. Synanthropy with humans raises the possibility that macaques come into contact with anthropogenic toxicants, such as lead and mercury, and might be appropriate sentinels for human exposures to certain toxic materials. We measured lead (Pb) and mercury (Hg) levels and characterized the stable isotopic compositions of delta(15)N and delta(13)C in hair from three groups of free-ranging macaques at the Swoyambhu temple in Kathmandhu, Nepal, an urban population that has abundant contact with humans. Hair lead levels were significantly higher among young macaques and differed among the three groups of macaques that were sampled. Hair Hg levels were low. No statistical association was found between stable isotopic compositions (delta(15)N and delta(13)C) and Pb and Hg levels. Our data did not find evidence that lead levels were associated with diet. We conclude that, in this population of macaques, behavioral and/or physiologic factors may play a significant role in determining exposure to lead. Chemical analysis of hair is a promising, noninvasive technique for determining exposure to toxic elements in free-ranging nonhuman primates.

Methylmercury induced toxicogenomic response in C57 and SWV mouse embryos undergoing neural tube closure

Methylmercury (MeHg) is a developmental neurotoxicant and teratogen and is hypothesized to perturb a wide range of biological processes, like other metals including arsenic (As) and cadmium (Cd). Common inbred mouse strains including C57 (sensitive) and SWV (resistant) display differences in sensitivity to metals such as As and Cd when exposed during neurulation. In this study, we investigated the impact of MeHg on neurulation, assessing for potential differences in sensitivity and associated toxicogenomic response in C57 and SWV mouse embryos. Parallel with morphological assessments of neural tube closure, we evaluated quantitative differences in MeHg-induced alterations in expression between strains at the gene level and within gene-enriched biological processes. Specifically, we observed differing sensitivities to MeHg-induced impacts on neural tube closure between C57 and SWV embryos in a time-dependent manner. These observations correlated with greater impact on the expression of genes associated with development and environmental stress-related pathways in the C57 compared to the SWV. Additional developmental parameters (e.g. mortality, growth effects) evaluated showed mixed significant effects across the two strains and did not support observations of differential sensitivity to MeHg. This study provides potential insights into MeHg-induced mechanisms of developmental toxicity, alterations associated with increased MeHg sensitivity and common biological processes affected by metals in embryos undergoing neurulation.