Mercury exposure: current concepts, controversies, and a clinic's experience

Relationship between Copper, Zinc, and Copper-to-Zinc Ratio in Hair and Severity of Coronary Artery Disease according to the SYNTAX Score

Coronary artery disease (CAD) continues to be a foremost contributor to global mortality, and the quest for modifiable risk factors could improve prophylactic strategies. Recent studies suggest a significant role of zinc (Zn) and copper (Cu) deficiency in atheromatous plaque formation. Furthermore, hair was previously described as a valuable source of information on elemental burden during the 6-8 week period before sampling. The aim of this study was to investigate the possibility of correlation between the extent of CAD evaluated with the SYNergy Between PCI With TAXUS and the Cardiac Surgery (SYNTAX) score with Cu and Zn content in hair samples, as well as with the Cu/Zn ratio in a cohort of 130 patients. Our findings describe a statistically significant inverse correlation between Cu content and the Cu/Zn ratio in hair samples and the extent of CAD. In contrast, no significant correlation was found between Zn content and the extent of CAD. Considering the scarcity of existing data on the subject, the analysis of hair samples could yield a novel insight into elemental deficiencies and their potential influence on CAD extent.

Failure of chelator-provoked urine testing results to predict heavy metal toxicity in a prospective cohort of patients referred for medical toxicology evaluation

INTRODUCTION

Provoked urine testing (PUT), involving chelating agent administration prior to measuring urine metal excretion levels, is used by some alternative health care practitioners to diagnose patients with heavy metal poisoning. Multiple medical societies have advised against this practice due to its presumed unreliability, expense, and lack of validation. However, no prospective study of the predictive value of PUT for heavy metal poisoning has been undertaken.

METHODS

This study utilized the Toxicology Consortium's prospective case registry to evaluate the reliability of PUT for diagnosing heavy metal poisoning. Inclusion criteria were toxicology clinic patients with PUT results who were subsequently evaluated by a board-certified medical toxicologist and had a determination made regarding whether their signs and symptoms were likely related or unrelated to toxicologic exposures. The primary outcome was the positive predictive value of PUT for heavy metal toxicity as diagnosed by the evaluating medical toxicologist. Patients presenting to participating toxicology clinics without PUT served as a comparison group.

RESULTS

74 of 106 cases presenting with PUT results met inclusion criteria and were analyzed. 15 cases were determined by the examining toxicologist to be likely related to a toxicologic exposure. Only three cases were found to be related to heavy metal exposure, giving a positive predictive value of 4.3%. 20.2% of patients with PUT were found to have signs or symptoms related to any toxicologic exposure, compared to 14.3% of clinic patients without PUT. Demographics of toxicology clinic patients with and without PUT results were not significantly different except for age.

DISCUSSION

Our results provide empiric support that PUT is an inaccurate predictor of a diagnosis of heavy metal poisoning by a board-certified medical toxicologist. Given the inability to properly interpret PUT results along with the increased cost burden and risk of false positives, PUT should not be performed.

Unnecessary Investigations in Environmental Medicine

BACKGROUND

Patients in environmental medicine often want a thorough diagnostic evaluation of nonspecific symptoms. Unconventional testing, as well as conventional testing for indications other than the established ones, can lead to false diagnoses and, in turn, to substantial emotional, social, and financial harm. The goal of this single-center study was to assess inappropriate diagnostic testing among the patients of a specialized university outpatient clinic for environmental medicine.

METHODS

The charts of 653 consecutive outpatients seen in the institute and outpatient clinic of occupational, social, and environmental medicine in Erlangen from 2010 to 2015 were evaluated, and inappropriate diagnostic tests were assessed.

RESULTS

9% of the patients had received at least one inappropriate diagnostic test. The most common one was an inappropriate heavy-metal test (26%), followed by an inappropriately ordered hair analysis (15%) and biomonitoring in the blood or urine with an erroneous choice of the testing matrix or an erroneous interpretation of the findings (15%). Biomonitoring performed by us did not confirm the suspected environmental diagnosis in any case. Laboratory values exceeding the normal limits were rarer among these patients than in the patients for whom we considered biomonitoring to be indicated without any pretesting.

CONCLUSION

An appreciable number of patients in environmental medicine were subjected to inappropriate diagnostic testing. When this happens, proper testing often needs to be done thereafter in order to confirm or refute the findings. This phenomenon should be more thoroughly assessed and quantified.

Quantification of particles of lethal mercury in mouse viscera: high-resolution study of mercury in cells and tissues

To investigate the early visceral distribution of mercury (Hg), we have intraperitoneally injected a lethal dose of HgCl2 that killed BALB/c mice within 2-4 min. Scanning electron microscopy coupled with X-ray microanalysis (SEM-XRM) was used to detect and quantify Hg in situ in different organs. The highest density of Hg was seen in the liver (60.99 ±24.9 Hg particles per mm2 of tissue); this density was three and six times higher than those of renal or splenic Hg, respectively. Hg was scarce in the lungs and absent in the brain. Considering the relative weights of mouse viscera, our quantitative data show that the liver captured 89% of the visceral Hg; the kidneys captured 8.5% and the spleen just 1.7%. SEM-XRM revealed that most of the visceral Hg was associated with resident macrophages, a few Hg dots being detected on the surface of erythrocytes. We conclude that: (i) most intraperitoneally injected Hg was captured by liver Kupffer cells within minutes of injection; (ii) a 10-fold lower density of Hg particles was observed in the kidneys, and a 50-fold lower deposition of Hg was found in the spleen; (iii) SEM-XRM is an adequate method to quantify microparticles of Hg in tissues and cells.

Detection criteria and preventive measures for occupational disease in the mines of Almaden (Spain)

This research focuses on the metallurgy and underground mining job positions in the historic mines of Almaden (Spain). We introduce a preventive methodology for hydrargyrism in work environments known by the name of Methodology for Operational Units Action Levels for Health Indicators (MUONAIS). The methodology allows critical levels to be established using environmental and clinical-biological indicators. The prevention plan concentrated on 15 job positions in the metallurgy department that employed more than 100 workers between the years 1986 and 1997. The development of this preventive methodology managed to keep workers' mercury levels below 60 μg/l in blood and 200 μg/l in urine, values that present no negative effects on human health. MUONAIS has proven very effective in protecting workers' health. During this period, some cases of micro-mercurialism were detected, yet were completely reversible, allowing us to affirm that the terrible disease of hydrargyrism was totally eradicated.

Hair analysis in health assessment

BACKGROUND

Hair analysis is used for estimation of the nutritional status of individuals. In the present work, a systematic review on the relation between the mineral composition of hair and the physical or mental disorders is discussed. Detailed information of examined populations, methods of sample preparations and analytical techniques are presented.

METHODS

A systematic literature search in four electronic databases Scopus, PubMed, Web of Science and Medline (from 1997 to 2012/01/31) for English language articles was performed. In addition, a reference list and manual search was undertaken.

RESULTS

The following number of studies was included: 66. Most of the authors reported that there exists a correlation between deficiency or excess of some elements in hair and occurrence of some diseases, such as: autism, cancer, hypertension, myocardial infarction, kidney disease and diabetes mellitus. However, not all results were consistent.

CONCLUSIONS

Most of the authors concluded that the profile of hair mineral imbalance might be useful as a diagnostic tool for the early diagnosis of many diseases. However, it seems that there is a need to standardize sample preparation procedures, in particular washing and mineralization methods.

Heavy metal chelation in neurotoxic exposures

Metals such as iron and copper are critical to living organisms, whereas other metals such as lead and arsenic have no known biologic role. Any metals in large amounts may cause toxicity. Many metals cause pervasive systemic effects involving the nervous system, which can be subtle in some cases. Although challenging, the diagnosis and treatment of metal poisoning can be made based on history, physical examination, and the proper use of metal testing. This article focuses on the use, and misuse, of chelation in the diagnosis and management of metal intoxication.

The value of ecologic studies: mercury concentration in ambient air and the risk of autism

Ecologic studies of the spatial relationship between disease and sources of environmental contamination can help to ascertain the degree of risk to populations from contamination and to inform legislation to ameliorate the risk. Population risks associated with persistent low-level mercury exposure have recently begun to be of concern and current reports implicate environmental mercury as a potential contributor in the etiology of various developmental and neurodegenerative diseases including autism and Alzheimer's disease. In this demonstration of preliminary findings, we demonstrate for Bexar County Texas and Santa Clara County California, the hypothesis that the spatial structure of the occurrence of autism has a positive co-variation with the spatial structure of the distribution of mercury in ambient air. The relative risk of autism is greater in the geographic areas of higher levels of ambient mercury. We find that the higher levels of ambient mercury are geographically associated with point sources of mercury emission, such as coal-fired power plants and cement plants with coal-fired kilns. Although this does not indicate a cause, these results should not be dismissed, but rather seen as a preliminary step for generating a hypothesis for further investigation.

Cognitive dysfunction associated with elemental mercury ingestion and inhalation: a case study

A 63-year-old man with a history of alcohol dependence ingested elemental mercury as a suicide gesture. Serial abdominal X-rays showed gradual but incomplete clearance of mercury from the colon. Routine chest X-ray showed evidence of punctate radiopaque materials in the lower lobe of the right lung. Blood and urine mercury levels both exceeded thresholds considered to be associated with cognitive dysfunction. Elicited cognitive deficits were most prominent in processing speed, flexibility, and response inhibition. Semantic fluency, visuospatial processing, and recall memory for visual and low-context verbal material were also affected. The deficits may have been attributable primarily to alcohol abuse. Elemental mercury is not readily absorbed from the gastrointestinal tract; however, mercury vapor, which was inhaled inadvertently, readily crosses the blood-brain barrier and is neurotoxic. We argue, therefore, that mercury toxicity is more likely than not to have been a factor contributing to the patient's cognitive dysfunction.

The occurrence and incorporation of copper and zinc in hair and their potential role as bioindicators: a review

This article reviews evidence that suggests Cu and Zn concentrations are not altered significantly by exogenous processes and may be useful in applications of hair analysis. The review attempts to identify what Cu and Zn concentrations may actually indicate biogenically and investigates the mechanisms by which they are incorporated into hair. Associations with specific hair components are proposed and avenues for development as a bioindicator are identified. Areas of research that offer promise in application or confirming the use of Cu and Zn are also indicated. Correlations and relationships with other health disorders are reviewed. Endogenous blood concentrations may also explain alterations in hair structure relating to breast cancer.

Safety considerations with omega-3 fatty acid therapy

It has been suggested that the potential antithrombotic effect of fish oils may theoretically increase the risk for bleeding, which may be a safety concern for individual patients. However, clinical trial evidence has not supported increased bleeding with omega-3 fatty acid intake, even when combined with other agents that might also increase bleeding (such as aspirin and warfarin). Another potential safety concern is the susceptibility of omega-3 fatty acid preparations to undergo oxidation, which contributes to patient intolerance and potential toxicity. Finally, large amounts of fish consumption may result in adverse experiences due to the potential presence of environmental toxins such as mercury, polychlorinated biphenyls, dioxins, and other contaminants. The risks of exposure to environmental toxins and hypervitaminosis with fish consumption are substantially reduced through purification processes used to develop selected concentrated fish oil supplements and prescription preparations. Thus, in choosing which fish oil therapies to recommend, clinicians should be aware of available information to best assess their relative safety, which includes the US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) advisory statement regarding fish consumption, the meaning of certain labeling (such as "verification" through the US Pharmacopeia) and the differences in FDA regulatory requirements between nonprescription fish oil supplements and prescription fish oil preparations, and how all of this is important to the optimal treatment of patients.

Low-level chronic mercury exposure in children and adolescents: meta-analysis

BACKGROUND

Mercury is a well-known neurotoxin. There are three kinds of mercury exposure: elemental mercury poisoning, inorganic mercury poisoning and organomercury poisoning. Organomercury is the most toxic. Twenty-four hour urine for mercury and blood mercury are the gold standards for diagnosis of mercury poisoning, including low-level chronic mercury exposure. Other tests for mercury level are discussed. The purpose of the present paper was to review recent data on the nature, pathophysiology, pharmacokinetics, diagnostic methods, treatment and the linkage to neurodevelopmental disabilities of mercury exposure in children.

METHODS

A literature search was undertaken of MEDLINE (1980-2003), and American Academy of Pediatrics, American Medical Association, American Dental Association, World Health Organization and Center for Disease Control websites. The search string 'mercury' was used in MEDLINE and articles were selected as appropriate by two independent reviewers. All relevant information was reviewed and data were extracted by two independent reviewers.

RESULTS

Based on the meta-analysis of the accuracy of hair mercury, hair mercury levels correlated with mercury level in blood (sample size weighted correlation coefficient, r w = 0.61), with 24 h urine ( r w = 0.46) and with cord blood ( r w = 0.64). However, the correlation for hair mercury level with 24 h urine level and blood level was not high enough to replace them in clinical decision-making of individual patient. Epidemiological evidence has shown that low-level mercury poisoning is not a cause of autism (relative risk = 0.49, 95%CI = 0.36-0.66). The risk of neurodevelopmental disabilities from low-level exposure to methylmercury from the regular consumption of fish is still controversial even after combining results from different epidemiological studies worldwide. There is a lack of data in the literature about the effect of chelation therapy in children with neurodevelopmental disabilities.

CONCLUSION

Mercury poisoning should be diagnosed only with validated methods. There is no evidence to support the association between mercury poisoning and autism.

Sources and trends of environmental mercury emissions in Asia

This paper focuses on environmental mercury emissions in Asia and elaborates its probable trend in the future and associated implications given the anticipated socioeconomic outlook and other macro-environmental factors. Among the various regions, Asia has become the largest contributor of anthropogenic atmospheric Hg, responsible for over half of the global emission. In the next few decades, a significant increase in anthropogenic Hg emissions in Asia is likely owing to rapid economic and industrial development, unless drastic measures are taken. In particular, the dominance of Asia in some Hg-emitting industries, such as coal combustion, steel production and gold mining, provokes a serious environmental concern over their potential contributions of incidental Hg in the region. Moreover, the increasing prevalence of electrical and electronic manufacturing industry as a user and a contributor of Hg in Asia is also worrying. Specifically, disposal of obsolete electrical and electronic wastes represents a phenomenon increasingly encountered in Asia. In addition to escalating anthropogenic Hg emissions in Asia, associated environmental and health implications may also exacerbate in the region for the probable effects of a unique combination of climatic (e.g. subtropical climate), environmental (e.g. acid rain) and socioeconomic factors (e.g. high population density). Hence, much effort is still needed to understand the role of Asia in global Hg cycle and associated environmental and health effects in the region.

Reimbursement profile of a private toxicology practice

This article presents two years of billing and collection data for a bedside toxicology consultation service. The collections rate was 34% or dollars 26.19 per hour of consultative time. There was an inverse correlation between collection rates and patient acuity.

Characteristics of Patients with No Underlying Toxicologic Syndrome Evaluated in a Toxicology Clinic

BACKGROUND

A significant number of patients seek medical evaluation for chronic subjective symptoms they presume to be associated with a single toxic trigger. This report describes our clinic experience with these patients.

CASE SERIES

Twenty patients (of a total of 261 patients) with a mean age of 41 years (median age 42 years; range: 4 to 65 years) were evaluated over an 8 month period. All describe a single past toxic exposure triggering their nonspecific (usually vaguely neurologic) symptoms. Zero of 20 (0%) describe other chemical sensitivities; 2/20 (10%) report ongoing exposure, 18/20 (90%) had a limited exposure dating 1 month to 6 yrs prior to toxicology clinic evaluation; 9/20 (45%) are currently employed; 6/20 (30%) sought alternative medical therapy prior to toxicologist evaluation; 6/20/(30%) have attempted litigation.

CONCLUSION

Despite repeatedly normal toxicologic and medical evaluations, all data refuting an underlying toxic cause are not accepted by this series of patients, and their search for a diagnostic linkage persists. Specific toxin identification or treatment for these patients is unlikely to occur.

Measurement of mercury levels in concentrated over-the-counter fish oil preparations: is fish oil healthier than fish?

CONTEXT

Fish consumption has been associated with a decreased risk of coronary artery disease. Recent studies have illustrated that the high mercury content in cold-water fish may negate the cardiovascular benefits of fish meals. Fish oils have similar antiatherogenic properties to fish, and similar studies should be performed to determine the level of mercury in fish oils.

OBJECTIVE

To determine the concentration of mercury in 5 over-the-counter brands of fish oil.

RESULTS

The levels of mercury in the 5 different brands of fish oil ranged from nondetectable (<6 microg/L) to negligible (10-12 microg/L). The mercury content of fish oil was similar to the basal concentration normally found in human blood.

CONCLUSIONS

Fish are rich in omega-3 fatty acids, and their consumption is recommended to decrease the risk of coronary artery disease. However, fish such as swordfish and shark are also a source of exposure to the heavy metal toxin, mercury. The fish oil brands examined in this manuscript have negligible amounts of mercury and may provide a safer alternative to fish consumption.

Reduced levels of mercury in first baby haircuts of autistic children

Reported rates of autism have increased sharply in the United States and the United Kingdom. One possible factor underlying these increases is increased exposure to mercury through thimerosal-containing vaccines, but vaccine exposures need to be evaluated in the context of cumulative exposures during gestation and early infancy. Differential rates of postnatal mercury elimination may explain why similar gestational and infant exposures produce variable neurological effects. First baby haircut samples were obtained from 94 children diagnosed with autism using Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV) criteria and 45 age- and gender-matched controls. Information on diet, dental amalgam fillings, vaccine history, Rho D immunoglobulin administration, and autism symptom severity was collected through a maternal survey questionnaire and clinical observation. Hair mercury levels in the autistic group were 0.47 ppm versus 3.63 ppm in controls, a significant difference. The mothers in the autistic group had significantly higher levels of mercury exposure through Rho D immunoglobulin injections and amalgam fillings than control mothers. Within the autistic group, hair mercury levels varied significantly across mildly, moderately, and severely autistic children, with mean group levels of 0.79, 0.46, and 0.21 ppm, respectively. Hair mercury levels among controls were significantly correlated with the number of the mothers' amalgam fillings and their fish consumption as well as exposure to mercury through childhood vaccines, correlations that were absent in the autistic group. Hair excretion patterns among autistic infants were significantly reduced relative to control. These data cast doubt on the efficacy of traditional hair analysis as a measure of total mercury exposure in a subset of the population. In light of the biological plausibility of mercury's role in neurodevelopmental disorders, the present study provides further insight into one possible mechanism by which early mercury exposures could increase the risk of autism.