Mercury in the brain (tumor tissues) and in markers (hair and blood) of exposure in Western Amazonia patients

BACKGROUND

Central nervous system tumors (CNSTs) represent the second most frequent form of malignant tumors in childhood and the second leading cause of death associated with neurological diseases, affecting individuals of all age groups. In adults, CNSTs are the sixth most common cause of death in patients with malignant tumors. Additionally, the brain is the most sensitive and studied organ for mercury (Hg) toxicity.

METHOD

We studied total Hg (THg) in tissue samples (of benign and malignant CNSTs) and explored its associations with THg in exposure markers (hair and blood) from 65 patients (40 females and 25 males) who underwent surgical treatment.

RESULTS

No statistically significant differences were found in THg concentrations in brain tumors or in blood and hair from these patients (classified as malignant/benign or glioma/non-glioma); also, there were no statistically significant differences between males and females. However, statistically significant correlations were found between THg in CNSTs and in hair (r_s = 0.4967; p = 0.0001) and in blood (r_s = 0.4702; p = 0.0058); but no significant correlations were found between THg in hair and blood (r_s = 0.1229; p = 0.5332). In the Western Amazon, with endemic exposure to fish-methylmercury, these urban patients were low to moderate fish consumers; THg concentrations in blood (median: 0.645 µg.L^-1; range: 8.01-21.02 µg.L^-1; n = 56) and hair (median: 0.686 µg.g-¹; range: 0.01-10.02 µg.g^-1; n = 65) were relatively low, whereas THg levels in brain tumors (median: 8.194 ng.g^-1; range: <0.10-69.16 ng.g^-1; n = 65) were within range of published studies in brain autopsies. Additionally, no statistically significant correlations (p = 0.4828) were observed between frequency of fish consumption and THg in the brain.

CONCLUSION

Although no significant THg concentrations in the type of brain tumors (benign versus malignant) were found, the significantly positive correlation between markers of THg exposure (hair and blood) and THg in the brain tissues indicates its usefulness as a marker/proxy for brain-THg load. These findings confirm the value of using hair and blood as constructs of THg in the brain of exposed populations.

Methylmercury exposure during prenatal and postnatal neurodevelopment promotes oxidative stress associated with motor and cognitive damages in rats: an environmental-experimental toxicology study

The environmental contamination by methylmercury (MeHg) is a major concern for public health. The effects of MeHg in the central nervous system (CNS) of adult animals have been extensively investigated; however, little is known about the effects of MeHg exposure during intrauterine and lactation periods on motor and cognitive functions of adolescent rats. Therefore, this study aimed to investigate the effect of MeHg exposure during intrauterine life and lactation on both motor and cognitive functions of offspring rats. Ten female Wistar rats were exposed to 40 μg/kg/day of MeHg through cookie treats from the first day of pregnancy until the last day of breastfeeding. Both motor and cognitive functions of offspring male rats were assessed by open field, rotarod, and step-down inhibitory avoidance tests. Forty-one days after birth, the hippocampus and cerebellum were collected to determine total Hg content, antioxidant capacity against peroxyl radicals (ACAP), reduced glutathione (GSH) levels, lipid peroxidation (LPO), and nitrite levels. MeHg exposure during CNS development increased Hg levels in both hippocampal and cerebellar parenchymas, triggered oxidative stress throughout ACAP and GSH decrease, increased LPO and nitrite levels. These alterations resulted in reduced spontaneous and stimulated locomotion and short- and long-term memory deficits. Therefore, damages triggered by MeHg exposure during intrauterine life and lactation had detrimental effects on oxidative biochemistry and motor and cognitive functions of offspring rats.

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The MeHg exposure during CNS development increased mercury levels in hippocampal and cerebellar parenchyma.

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The MeHg intoxication during pregnancy and lactation impairs the redox status of hippocampus and cerebellum of the offspring.

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MeHg exposure causes behavioral effects in motor ability and cognition of offspring rats.

Levels of Mercury in Fish-Eating Children, With and Without Amalgam Restoration

Background:

Mercury is a naturally occurring metal that exists in three forms: elemental (metallic), inorganic, and organic mercury. Amalgam, which is an alloy of inorganic mercury, is used as a restorative material in dentistry. Organic mercury gets ingested in the body mainly by the consumption of seafood. Mercury is also stated to cause various adverse health effects such as gastrointestinal disturbances, dermatitis, muscle weakness, and neurological disorders. In recent years, the use of amalgam has become a controversy stating the various adverse effects of mercury. Hence, the study was conducted to determine and compare the variation in levels of organic and inorganic mercury in fish-eating children before and after placement of amalgam restoration.

Materials and Methods:

Seventy-five subjects, 42 males (56%) and 35 females (44%) of age group ranging 7–13 years, living in South Canara district of Karnataka, India, were selected as a part of the study. Hair and urine samples were collected for estimation of organic and inorganic levels of mercury, respectively. Informed consent was collected from all the participating subjects.

Results:

On comparison between organic and inorganic mercury levels during the study period, the concentration of organic mercury in hair samples was greater irrespective of amalgam restorations present (1.172 and 0.085, respectively; P < 0.001).

Conclusion:

Thus inorganic levels of mercury do not seem to pose a threat as much as the organic levels observed in hair, which remain fairly constant for a longer period of time. Hence in a coastal region where this study was undertaken and fish being a staple food, the risk could probably be attributed to more of an organic toxicity than an inorganic one. Thus amalgam is relatively safe to be practiced and the controversy against it should be reevaluated.

Rethinking the Dental Amalgam Dilemma: An Integrated Toxicological Approach

Mercury (Hg) has been identified as one of the most toxic nonradioactive materials known to man. Although mercury is a naturally occurring element, anthropogenic mercury is now a major worldwide concern and is an international priority toxic pollutant. It also comprises one of the primary constituents of dental amalgam fillings. Even though dental mercury amalgams have been used for almost two centuries, its safety has never been tested or proven in the United States by any regulatory agency. There has been an ongoing debate regarding the safety of its use since 1845, and many studies conclude that its use exposes patients to troublesome toxicity. In this review, we present in an objective way the danger of dental amalgam to human health based on current knowledge. This dilemma is addressed in terms of an integrated toxicological approach by focusing on four mayor issues to show how these interrelate to create the whole picture: (1) the irrefutable constant release of mercury vapor from dental amalgams which is responsible for individual chronic exposure, (2) the evidence of organic mercury formation from dental amalgam in the oral cavity, (3) the effect of mercury exposure on gene regulation in human cells which supports the intrinsic genetic susceptibility to toxicant and, finally, (4) the availability of recent epidemiological data supporting the link of dental amalgams to diseases such as Alzheimer’s and Parkinson.

Mercury concentration in maternal serum, cord blood, and placenta in patients with amalgam dental fillings: effects on fetal biometric measurements

AIM

We aimed to determine the extent to which mercury is transmitted from the mother to fetus via the umbilical cord in patients with amalgam dental fillings, and its effect on fetal biometric measurements.

METHODS

Twenty-eight patients as the study group with amalgam fillings, and 32 of them as the control group were included in this prospective case-control study. The mercury levels were measured in the maternal and cord venous sera, and the placental samples. Two groups were compared in terms of these and the fetal/neonatal biometric measurements.

RESULTS

In the study group, the maternal and umbilical cord mercury levels were found to be significantly higher than those from the control group (p = 0.006 and p = 0.010, respectively). These high levels did not affect the fetal biometric measurements.

CONCLUSIONS

The presence of high serum mercury levels in pregnant women with amalgam fillings is important, and warrants further long-term studies in order to investigate the fetal neurological effects as well.