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[Neurotoxic effect of exposure to low doses of mercury]

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Abstract

To assess early effects on the Central Nervous System due to occupational exposure to low levels of inorganic mercury (Hg) in a multicenter nationwide cross-sectional study, including workers from chloro-alkali plants, chemical industry, thermometer and fluorescent lamp manufacturing. The contribution of non-occupational exposure to inorganic Hg from dental amalgams and to organic Hg from fish consumption was also considered. Neuropsychological and neuroendocrine functions were examined in a population of 122 workers occupationally exposed to Hg, and 196 control subjects, not occupationally exposed to Hg. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine functions were examined with the measurement of prolactin secretion. The target population was also characterized by the surface of dental amalgams and sea fish consumption. In the exposed workers the mean urinary Hg (HgU) was 10.4 +/- 6.9 (median 8.3, geometric mean 8.3, range 0.2-35.2) micrograms/g creatinine, whereas in the control group the mean HgU was 1.9 +/- 2.8 (median 1.2, geometric mean 1.2, range 0.1-33.2) micrograms/g creatinine. The results indicated homogeneous distribution of most neurobehavioral parameters among exposed and controls. On the contrary, finger tapping (p < 0.01) and the BAMT (Branches Alternate Movement Task) coordination test (p = 0.05) were associated with occupational exposure, indicating an impairment in the exposed subjects. Prolactin levels resulted significantly decreased among the exposed workers, and inversely related to HgU on an individual basis (p < 0.05). An inverse association was also observed between most neuropsychological symptoms and sea fish consumption, indicating a "beneficial effect" from eating sea fish. On the contrary, no effects were observed as a function of dental amalgams. In conclusion, this study supports the finding of early alterations of motor function and neuroendocrine secretion at very low exposure levels of inorganic Hg, below the current ACGIH BEI and below the most recent exposure levels reported in the literature.
... To date, no studies describing relationships between PRL and Hg have been conducted on wildlife. The only few human studies describing such relationships were aimed at studying neurotoxicity of Hg, and baseline PRL was used to ascertain possible interference of Hg with neurotransmitters (Barregård et al 1994;Lucchini et al. 2002Lucchini et al. , 2003Carta et al. 2003 (Faro et al. 1997(Faro et al. , 2000(Faro et al. , 2002(Faro et al. , 2003(Faro et al. , 2007Minnema et al. 1989) but also in wild larvae of a fish species (Fundulus heteroclitus; Zhou et al. 1999) and in wild American minks ...
... Indeed, studies focusing on the relationships between contaminants and PRL are scare and only one study (Verreault et al. 2008) has reported a negative relationship between PRL secretion and blood persistent organic pollutant levels in an Arctic seabird, the Glaucous Gull (Larus hyperboreus). Some human studies have focused on Hg neurotoxicity, and have explored the relationships between Hg and PRL as a proxy of neuroendocrine functions (Barregård et al. 1994Lucchini et al. 2002Carta et al. 2003). These latter studies have reported increased, decreased or unchanged serum PRL with increased organic Hg (Barregård et al. 1994Lucchini et al. 2002Carta et al. 2003). ...
... Some human studies have focused on Hg neurotoxicity, and have explored the relationships between Hg and PRL as a proxy of neuroendocrine functions (Barregård et al. 1994Lucchini et al. 2002Carta et al. 2003). These latter studies have reported increased, decreased or unchanged serum PRL with increased organic Hg (Barregård et al. 1994Lucchini et al. 2002Carta et al. 2003). Regarding birds, Hg-PRL relationships deserve investigation because this heavy metal seems to be associated with the quality of parental cares (Nocera and Taylor, 1998) and to be tightly linked to the secretion of another pituitary hormone (luteinizing hormone, . ...
Thesis
In order to maximise fitness, individuals will have to take several decisions that shall match with environmental conditions (whether to breed or not, when to breed, what level of parental investment). These decisions are mediated by hormones: such as luteinizing hormone (LH), a pituitary hormone involved in the onset of breeding, stress hormones (corticosterone, CORT) and prolactin (PRL) a pituitary hormone involved in the expression of parental care. Environmental contaminants are present world-wide, and also in Polar Regions. Since many contaminants are endocrine disruptors, they may impair breeding decisions, but evidences are scarce for wildlife. The aim of this thesis was to assess the relationships between some legacy persistent organic pollutants (POPs: PCBs, organochlorine pesticides), mercury (Hg) and hormones (LH, CORT, PRL) in different Arctic and Antarctic seabird species. Results show that POPs and Hg clearly interact with LH, CORT and PRL secretion. These contaminants appear to target different hormones: increasing Hg was related to decreasing pituitary hormone secretion (LH and PRL); whereas increasing PCBs were linked to an exacerbated CORT response to an acute stress. Hg disrupted LH secretion by probably suppressing GnRH input to the pituitary; PCBs seem to act at the adrenal level by probably stimulating ACTH receptors. Legacy POPs and Hg are therefore able to disrupt reproductive decisions and to impact fitness: elevated Hg levels were linked to skipped reproduction and poor incubation behavior; elevated PCB levels may make individuals more susceptible to environmental perturbations. The long-term consequences of contaminant exposure for seabirds are discussed in the context of the environmental challenges affecting polar regions.
... Graeme et al. considered that a blood level above 15 g/l indicated mercury toxicity [6] , while Dantzig found that a level as low as 6 g/l or less may be toxic [7] . Hence, symptoms may be present at low levels of exposure [8,9] . Secondly, there are no defined criteria for the diagnosis of mercury poisoning since there is no clear correlation between clinical symptoms of intoxication and the level of mercury in the body [3,8,9] . ...
... Hence, symptoms may be present at low levels of exposure [8,9] . Secondly, there are no defined criteria for the diagnosis of mercury poisoning since there is no clear correlation between clinical symptoms of intoxication and the level of mercury in the body [3,8,9] . ...
Article
Full-text available
Background: Mercury is a highly toxic environmental metal that exists in three different forms: elemental, inorganic and organic. Intoxication occurs in either occupational or non-occupational settings, mainly after the inhalation of vapour and fumes in work places, laboratories or homes. Chronic mercury toxicity ranges from mild and insignificant to severe and life-threatening. We describe the case of a young male patient who presented with multiple organ dysfunction after chronic mercury exposure. Case presentation: We report the case of 28-year-old male artisanal gold miner who was admitted to hospital for severe neurological impairment associated with inflammatory bowel disease-like symptoms and a skin rash after mercury exposure. Symptomatic treatment and corticosteroid administration assured rapid clinical improvement. Chronic mercury poisoning can masquerade as an autoimmune or systemic inflammatory disease. Conclusion: Physicians should be aware that low exposure to mercury, even from artisanal gold mining, may be harmful to health. Management can be simple without the need for aggressive or invasive therapeutic measures. Larger case series are required in order to establish a clear management plan.
... Neurotoxic effects of exposure to mercury happen even with low levels of urine mercury (mean: 10.4, range: 0.32-35.2 g/g creatinine) and include early alterations of motor function and neuroendocrine secretion; and have been reported in chloralkali workers [13]. Thus, monitoring mercury in workers' blood, urine, hair and air can provide valuable information for risk assessment [14]. ...
Article
Background: Mercury is one of the most well-known toxic metals for humans. Chloralkali workers are exposed to mercury vapours extensively, which may be associated with neurotoxicity. Objective: The aim of this study was to determine the associations between mercury concentration in blood and air samples, and mercury's neuropsychological effects among chloralkali workers. Methods: This study was conducted on 50 chloralkali workers as the exposed group and 50 non-industrial office workers as the unexposed group. All subjects were assessed using the Hamilton Depression Rating Scale, Piper Chronic Fatigue Scale and Essential Tremor Rating Scale. Mercury concentration was measured in blood and air samples using cold vapour atomic absorption spectrometry. Results: There were significant correlations between severity of fatigue, depression and tremor in the exposed group compared with the unexposed group. The mean concentration of blood mercury in the exposed group was 22.59±12.5μgL-1 which was significantly higher than the unexposed group (1.28±1.05μg L-1). Based on multiple linear regression, shift work, smoking, fatigue, depression and tremor were predictor variables for blood mercury concentration. Conclusions: This study indicated that this sample of chloralkali workers suffered from neuropsychological problems such as fatigue, depression and tremor, which is probably related to mercury exposure.
... Die neurologischen Tests zeigten, bis auf kleine Effekte von subklinischer Bedeutung, keine adversen Veränderungen bei den Arbeitern. Lucchini et al. (2002Lucchini et al. ( , 2003 verglichen 122 Arbeiter, die im Durchschnitt 14,6 Jahre gegenüber Quecksilber exponiert waren, mit 196 Kontrollpersonen. Die mittleren aktuellen Quecksilberkonzentrationen im Urin lagen bei den exponierten Arbeitern bei 10 ± 6,9 Vg/g Kreatinin (12,5 ± 8,3 Vg/L) (95. ...
Chapter
Veröffentlicht in der Reihe Biologische Arbeitsstoff-Toleranz-Werte (BAT-Werte), Expositionsäquivalente für krebserzeugende Arbeitsstoffe (EKA) und Biologische Leitwerte (BLW), 13. Lieferung, Ausgabe 2006
... The CATSYS Tremor Pen [9] is a portable lightweight microaccelerometer that has been used in several studies for evaluation of tremor among groups of workers with occupational exposure to mercury vapour [10][11][12][13] and manganese [14][15][16][17][18][19][20][21][22]. The equipment has been validated and standardized [23,24]. ...
Article
Full-text available
Objective: The CATSYS Tremor Pen has been used in several studies for measurement of tremor among workers with occupational exposure to neurotoxins like mercury and manganese. The main purpose of this study was to investigate whether recording time has an impact on the measured tremor characteristics. Other aims were to investigate whether there are interactions between recording time and age, and between recording time and (selfreported) nicotine use, respectively; to assess the test-retest repeatability of the instrument; to investigate a possible practice effect when performing the test repeatedly; and to evaluate agreement with another tremor test. Methods: The participants (n=44) consisted of former shipyard workers (mean age 67 years, range 59–76 years). Postural hand tremor was evaluated using the CATSYS Tremor Pen. Five tremor recordings were made; the first lasted 16.4 s, the next three lasted 8.2 s each and the fifth lasted 65.6 s. Results: There was a significant association between recording time and harmonic index; longer recording time produced higher harmonic index. There was no effect of nicotine use or age that was consistent over all recording times, and no practice effect was seen. The agreement with another tremor test was moderate to good, as was the test-retest reliability. Conclusion: Some of the tremor characteristics are affected by length of recording time and hence care should be taken when comparing results across studies or with follow-up. The results indicate that the use of a recording time longer than 16.4 s seems to be of doubtful value.
... In exposed industrial workers, researchers have reported cognitive deficits in information-processing speed, attention, motor speed, verbal memory, abstract thinking, and verbal comprehension. 37,[38][39][40][41][42][43] The current study's participants are different from the populations in other studies of Hg toxicity. They are a community-based sample, albeit a comparatively elite group of well-educated participants who either had corporate benefits that covered or the financial ability to pay for an all-day, comprehensive physical evaluation. ...
... Traces of mercury exposure may occur from food and amalgam fillings; however occupational exposure to mercury typically occurs in higher dosage and workers are exposed to mercury through both inhalation and oral routes (World Health Organization International Agency for Research on Cancer, 1997). The majority of reported fine tremor cases related to mercury have been observed in elemental mercury (Hg 0 ) exposure only (Lucchini et al., 2002;Iwata et al., 2007;Liu et al., 2011). Elemental mercury is also a major source of occupationally related exposure (EPA, 1993). ...
Chapter
Lead, mercury, solvents, and pesticide exposures are common in certain occupations and may cause nervous system dysfunction. Tremors may be the herald manifestation among a constellation of acute toxicity signs and symptoms. However, since tremors may also be the only sign on clinical presentation and since tremors also occur in other diseases, relating tremors to a specific occupational exposure can be challenging. Diagnosis of tremor etiology must be based on other findings on physical exam, laboratory results, and/or imaging. Discerning whether the tremor resulted from the occupational environment versus other etiologies requires knowledge of potential exposure sources, additional detail in history taking, and support of other health and industrial professionals. Reduction or removal from the exposure source remains the key first step in treating patients suffering from tremor that had resulted from occupational exposure toxicity.
... Traces of mercury exposure may occur from food and amalgam fillings; however occupational exposure to mercury typically occurs in higher dosage and workers are exposed to mercury through both inhalation and oral routes (World Health Organization International Agency for Research on Cancer, 1997). The majority of reported fine tremor cases related to mercury have been observed in elemental mercury (Hg 0 ) exposure only (Lucchini et al., 2002;Iwata et al., 2007;Liu et al., 2011). Elemental mercury is also a major source of occupationally related exposure (EPA, 1993). ...
Chapter
Lead, mercury, solvents, and pesticide exposures are common in certain occupations and may cause nervous system dysfunction. Tremors may be the herald manifestation among a constellation of acute toxicity signs and symptoms. However, since tremors may also be the only sign on clinical presentation and since tremors also occur in other diseases, relating tremors to a specific occupational exposure can be challenging. Diagnosis of tremor etiology must be based on other findings on physical exam, laboratory results, and/or imaging. Discerning whether the tremor resulted from the occupational environment versus other etiologies requires knowledge of potential exposure sources, additional detail in history taking, and support of other health and industrial professionals. Reduction or removal from the exposure source remains the key first step in treating patients suffering from tremor that had resulted from occupational exposure toxicity.
... This reflects the present or recent exposure level, not the mercury body burden. Some studies have reported meaningful toxicity symptoms at 50 microgram/L or lower concentrations [37,38]. According to Kazantzis, it has been impossible to establish the mercury concentration level in blood or urine that manifests mercury-related physical symptoms [39]. ...
Article
Full-text available
Mercury occurs in various chemical forms, and it is different to health effects according to chemical forms. In consideration of the point, the evaluation of the mercury exposure to human distinguished from occupational and environmental exposure. With strict to manage occupational exposure in factory, it is declined mercury intoxication cases by metallic and inorganic mercury inhalation to occupational exposure. It is increasing to importance in environmental exposure and public health. The focus on the health impact of exposure to mercury is more on chronic, low or moderate grade exposure—albeit a topic of great controversy—, not high concentration exposure by methylmercury, which caused Minamata disease. Recently, the issue of mercury toxicity according to the mercury exposure level, health effects as well as the determination of what mercury levels affect health are in the spotlight and under active discussion. Evaluating the health effects and Biomarker of mercury exposure and establishing diagnosis and treatment standards are very difficult. It can implement that evaluating mercury exposure level for diagnosis by a provocation test uses chelating agent and conducting to appropriate therapy according to the result. but, indications for the therapy of chelating agents with mercury exposure have not yet been fully established. The therapy to symptomatic patients with mercury poisoning is chelating agents, combination therapy with chelating agents, plasma exchange, hemodialysis, plasmapheresis. But the further evaluations are necessary for the effects and side effects with each therapy.
Chapter
Unlike many other pollutants that are released into the environment and degraded, toxic metals such as mercury, arsenic and lead are stable and retain a degree of toxicity. There is clear evidence that even in non toxic amounts these pollutants can affect our health.
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