Associations between mercury exposure with blood pressure and lipid levels: A cross-sectional study of dental professionals.

Mercury (Hg) exposure is a public health problem worldwide that is now being addressed through the Minamata Convention on Mercury. Fish containing methylmercury and dental amalgam containing elemental Hg are the major sources of exposure for most populations. There is some evidence that methylmercury impacts cardiovascular and metabolic health, primarily in populations with high exposure levels. Studies of elemental Hg and these outcomes are relatively rare. We aimed to examine associations between Hg exposure (both elemental and methylmercury) and blood pressure, as well as cholesterol and triglyceride levels. In 2012, we recruited dental professionals attending the Health Screening Program at the American Dental Association (ADA) Annual Session in California. Total Hg levels in hair and blood samples were analyzed as indicators of methylmercury exposure and in urine as an indicator of primarily elemental Hg exposure (n = 386; mean ± sd age 55 ± 11 years). We measured blood pressure (systolic and diastolic) and lipid profiles (total cholesterol, high-density lipoprotein cholesterol [HDL], low-density lipoprotein cholesterol [LDL] and triglycerides). The geometric means (geometric standard deviations) for blood, hair, and urine Hg were 3.64 (2.39) µg/L, 0.60 (2.91) µg/g, and 1.30 (2.44) µg/L, respectively. For every one µg/L increase in specific gravity-adjusted urine Hg, LDL increased by 2.31 mg/dL (95% CI = 0.09, 4.54), in linear regression adjusting for BMI, race, sex, polyunsaturated fatty acid intake from fish consumption, smoking status, and use of cholesterol-lowering medication. No significant associations between Hg biomarkers and blood pressure or hair or blood Hg with lipid levels were observed. Results suggest that elemental Hg exposure may influence LDL concentrations in adults with low-level exposure, and this relationship merits further study in other populations.

Rates and predictors of exposure to Legionella pneumophila in the United States among dental practitioners: 2002 through 2012.

BACKGROUND: In this study, the authors compared the odds of exposure to Legionella pneumophila among currently active dental practitioners with that of nonpractitioners and evaluated demographic and clinical practice predictors of exposure. METHODS: The authors obtained demographic characteristics and dental practice behaviors from participants in the annual American Dental Association Health Screening Program survey administered from 2002 through 2012. The authors assayed serum samples obtained from participants for L pneumophila antibodies. The authors used an adjusted logit model to evaluate predictors of positive results. RESULTS: Among 5,431 participants, approximately 10% were positive for L pneumophila, with no significant differences between dental practitioners and nonpractitioners. Geographic location was the only significant predictor of seropositivity, with no increased risk of being exposed to L pneumophila associated with age, race, sex, years in practice, hours of practice per week, use of barrier protection, or infection control practices. CONCLUSIONS: Prevalence of L pneumophila antibodies was 10.4% among dental and nondental personnel. US Census division was the only significant predictor of seropositivity. The authors conclude that provision of dental care did not increase the risk of being exposed to Legionella. PRACTICAL IMPLICATIONS: Dentists should be aware of the prevalence of Legionella species in their practice areas to understand their personal risk of developing an infection.

Exposures of dental professionals to elemental mercury and methylmercury.

Mercury (Hg) exposure, a worldwide public health concern, predominantly takes two forms--methylmercury from fish consumption and elemental Hg from dental amalgam restorations. We recruited 630 dental professionals from an American Dental Association meeting to assess Hg body burden and primary sources of exposure in a dually exposed population. Participants described occupational practices and fish consumption patterns via questionnaire. Hg levels in biomarkers of elemental Hg (urine) and methylmercury (hair and blood) were measured with a Direct Mercury Analyzer-80 and were higher than the general US population. Geometric means (95% CI) were 1.28 (1.19-1.37) µg/l in urine, 0.60 (0.54-0.67) µg/g in hair and 3.67 (3.38-3.98) µg/l in blood. In multivariable linear regression, personal amalgams predicted urine Hg levels along with total years in dentistry, amalgams handled, working hours and sex. Fish consumption patterns predicted hair and blood Hg levels, which were higher among Asians compared with Caucasians. Five species contributed the majority of the estimated Hg intake from fish--swordfish, fresh tuna, white canned tuna, whitefish and king mackerel. When studying populations with occupational exposure to Hg, it is important to assess environmental exposures to both elemental Hg and methylmercury as these constitute a large proportion of total exposure.

Genetic polymorphisms are associated with hair, blood, and urine mercury levels in the American Dental Association (ADA) study participants.

BACKGROUND/AIMS: Mercury (Hg) is a potent toxicant of concern to the general public. Recent studies suggest that several genes that mediate Hg metabolism are polymorphic. We hypothesize that single nucleotide polymorphisms (SNPs) in such genes may underline inter-individual differences in exposure biomarker concentrations. METHODS: Dental professionals were recruited during the American Dental Association (ADA) 2012 Annual Meeting. Samples of hair, blood, and urine were collected for quantifying Hg levels and genotyping (88 SNPs in classes relevant to Hg toxicokinetics including glutathione metabolism, selenoproteins, metallothioneins, and xenobiotic transporters). Questionnaires were administrated to obtain information on demographics and sources of Hg exposure (e.g., fish consumption and use of dental amalgam). Here, we report results for 380 participants with complete genotype and Hg biomarker datasets. ANOVA and linear regressions were used for statistical analysis. RESULTS: Mean (geometric) Hg levels in hair (hHg), blood (bHg), urine (uHg), and the average estimated Hg intake from fish were 0.62µg/g, 3.75µg/L, 1.32µg/L, and 0.12µg/kg body weight/day, respectively. Out of 88 SNPs successfully genotyped, Hg biomarker levels differed by genotype for 25 SNPs, one of which remained significant following Bonferroni correction in ANOVA. When the associations between sources of Hg exposure and SNPs were analyzed with respect to Hg biomarker concentrations, 38 SNPs had significant main effects and/or gene-Hg exposure source interactions. Twenty-five, 23, and four SNPs showed significant main effects and/or interactions for hHg, bHg, and uHg levels, respectively (p<0.05), and six SNPs (in GCLC, MT1M, MT4, ATP7B, and BDNF) remained significant following Bonferroni correction. CONCLUSION: The findings suggest that polymorphisms in environmentally-responsive genes can influence Hg biomarker levels. Hence, consideration of such gene-environment factors may improve the ability to assess the health risks of Hg more precisely.

Occupational mercury exposure in association with prevalence of multiple sclerosis and tremor among US dentists.

BACKGROUND: The effects of chronic occupational exposure to elemental mercury (Hg(0)) are largely unknown. The objective was to evaluate the association of occupational Hg(0) exposure with multiple sclerosis (MS) and tremor. METHODS: The study included 13,906 dentists who attended the American Dental Association's annual meeting over 24 years (1986-2007 and 2011-2012). Participants reported MS and tremor and provided urine specimens for Hg(0) analysis. The authors estimated mean Hg(0) exposures over time and used logistic regression to estimate the associations of 3 Hg(0) exposure measures with MS or tremor. RESULTS: Among participants, 0.18% reported MS and 1.24% reported tremor. Hg(0) exposure was not associated with MS (odds ratio [OR] per 191 micrograms per liter in cumulative Hg(0) exposure, 0.85; 95% confidence interval [CI], 0.39-1.85). Increased prevalent risk of tremor was found with exposure to both urinary Hg(0) exposure (OR, 1.10 [95% CI, 1.00-1.22]) and cumulative Hg(0) exposure among younger dentists (< 51 years; OR, 1.13 [95% CI, 1.05-1.22]). CONCLUSIONS: Occupational Hg(0) exposure in US dentists decreased over time and now is approaching that of the general population. Our results suggest a positive association between Hg(0) exposure and tremor. PRACTICAL IMPLICATIONS: Studies with more sophisticated outcome and exposure measures, and including more retired dentists, would provide critical information toward understanding the relation of Hg(0) exposures to MS and tremor risk.

Low-level mercury exposure and peripheral nerve function.

BACKGROUND: Mercury is known to be neurotoxic at high levels. There have been few studies of potential peripheral neurotoxicity among persons with exposure to elemental mercury at or near background levels. OBJECTIVES: The present study sought to examine the association between urinary mercury concentration and peripheral nerve function as assessed by sensory nerve conduction studies in a large group of dental professionals. METHODS: From 1997 through 2006 urine mercury measurements and sensory nerve conduction of the median and ulnar nerves in the dominant hand were performed, and questionnaires were completed, on the same day in a convenience sample of dental professionals who attended annual conventions of the American Dental Association. Linear regression models, including repeated measures models, were used to assess the association of urine mercury with measured nerve function. RESULTS: 3594 observations from 2656 subjects were available for analyses. Urine mercury levels in our study population were higher than, but substantially overlap with, the general population. The only stable significant positive association involved median (not ulnar) sensory peak latency, and only for the model that was based on initial observations and exclusion of subjects with imputed BMI. The present study found no significant association between median or ulnar amplitudes and urine mercury concentration. CONCLUSIONS: At levels of urine mercury that overlap with the general population we found no consistent effect of urine mercury concentration on objectively measured sensory nerve function.

Latex allergy and filaggrin null mutations.

OBJECTIVES: Natural rubber latex (NRL) contains over 200 proteins of which 13 have been identified as allergens and the cause of type I latex allergy. Health care workers share a high occupational risk for developing latex allergy. Filaggrin null mutations increase the risk of type I sensitizations to aeroallergens and it is possible that filaggrin null mutations also increase the risk of latex allergy. The aim of this paper was to examine the association between filaggrin null mutations and type I latex allergy. METHODS: Twenty latex allergic and 24 non-latex allergic dentists and dental assistants, occupationally exposed to latex, were genotyped for filaggrin null mutations R501X and 2282del4. Latex allergy was determined by a positive reaction or a historical positive reaction to a skin prick test with NRL. RESULTS: 41 individuals were successfully genotyped. Three individuals were filaggrin mutation carriers. One (2.4%) was a 2282del4 heterozygote and two (4.9%) were R501X heterozygote. No homozygote or compound heterozygote carriers were detected. No association between filaggrin null mutations and type I latex allergy was found (p=0.24). Patients with type I latex allergy more often reported contact dermatitis. CONCLUSIONS: This is the first study to examine a highly plausible association between filaggrin null mutations and type I latex allergy. The study subjects were occupationally exposed to latex but no association between latex allergy and filaggrin mutations were detected. Sensitization to latex in the cases in this study may not have occurred through direct skin contact but through the respiratory organs via latex proteins that are absorbed in glove powder and aerosolized.

The immuno cross-reactivity of gutta percha points.

OBJECTIVE: The purpose of this study is to test the postulated immuno cross-reactivity between proteins derived from raw gutta percha (RGP), gutta percha point (GPP) and natural rubber latex (NRL). METHODS: Antigenicity and cross-reactivity of proteins were determined by the FITkit (FITBiotech, Finland) and ELISA inhibition assays. RESULTS: Antigenicity of proteins derived from RGP or GPP was not demonstrated. Except for NRL glove extracts, neither extracts from RGP or GPP were reactive in ELISA inhibition assay. SIGNIFICANCE: There is no immunologic cross-reactivity in vitro between proteins derived from RGP or GPP, and from NRL gloves. Thus, therapeutic use of GPP is unlikely to initiate adverse immuno-reactivity in individuals previously sensitized to NRL proteins.