The effect of occupational exposure to mercury vapour on the fertility of female dental assistants

Mercury, natural fertility and outcomes of assisted reproduction: A systematic review

The primary route of mercury exposure for the general population is through consumption of contaminated seafood. There is a biological basis for an adverse effect of mercury exposure on human fertility. The goal of this review was to evaluate the existing literature on the association between mercury and pregnancy, among men and women attempting to conceive with and without assisted reproductive technology (ART). Systematic searches were performed in PubMed, EMBASE, Scopus and Web of Science for papers published up to March 2023 with no early date restriction, only including studies with a biomarker measurement of mercury exposure. We identified 11 studies examining mercury and natural fertility and 12 studies examining mercury and outcomes of assisted reproduction (implantation or clinical pregnancy). The accumulated evidence provides some support for a null association between bodily mercury concentrations and natural fertility among women, however, a large proportion of studies did not report adjusted estimates or were extremely imprecise. The majority of studies of natural fertility were also cross-sectional in nature. There was no evidence for an inverse or null association between mercury and natural fertility among men, or mercury and ART outcomes among men or women. In spite of biological plausibility, the existing evidence includes studies that are imprecise and often conflicting and does not allow us to make definitive conclusions on the associations of mercury exposure with successful pregnancy. Additional, larger studies are warranted, especially among individuals with high concentrations of mercury exposure as these individuals may be underrepresented in the current literature.

Occupational and environmental mercury exposure and human reproductive health - a review

Mercury is a toxic heavy metal. Humans are exposed to mercury through several sources including environmental, occupational, contaminated food and water and from mercury-containing dental amalgam. Mercury exposure is known to harm the nervous system profoundly, and have a negative impact on digestive and immune systems, and other organs. To review and discuss the effect of mercury exposure through environmental or occupational routes on human reproduction, pregnancy, and its outcome. Published information about the potential toxic effects of mercury on human reproduction were collected and summarized. Literature was identified by systematic search using relevant keywords. Literature review revealed a number of negative impacts of mercury on human reproduction. These included effects on semen quality, including reduced sperm count, motility, and changes in morphology that may reduce fertility potential. There may also be an effect in changing reproductive hormone levels. Mercury exposure might also affect pregnancy but the data concerning mercury effects on female reproduction are limited except for some data about mercury exposure and poor pregnancy outcomes. Available data indicate that mercury exposure may have a toxicity effect on reproductive potential, especially in males. Prenatal mercury exposure may affect pregnancy or its outcome and this appears to be dependent upon dose, duration, and timing of exposure. Nutritional status of exposed individual might also influence the impact of mercury.

Mercury exposure, neopterin profile, and tryptophan degradation in dental technicians

Amalgam has been widely used as a restorative dental material for over 150 years. Most standard dental amalgam formulations contain approximately 50% elemental mercury in a mixture of copper, tin, silver, and zinc. Mercury is a highly volatile metal, which can easily vaporize to a colorless and odorless gas. It has been demonstrated that mercury is released from dental amalgam, which is increased by chewing, eating, brushing, and drinking hot liquids. Besides this, amalgam is the main occupational exposure source of mercury for dental workers. It is known that mercury exposure causes immune modulation in humans. In this study, it was aimed to evaluate the changes in neopterin levels and tryptophan (Trp) degradation in dental technicians. It was observed that low levels of occupational mercury exposure resulted in decreased neopterin, kynurenine (Kyn), and Kyn/Trp levels. Moreover, mercury and neopterin levels had a significant positive correlation in workers. The lower neopterin levels and Kyn/Trp in dental technicians compared to an unexposed group indicates a possible immune suppression with low level of occupational mercury exposure during amalgam preparation. The relationship between urinary mercury levels as an indicator of occupational mercury exposure and neopterin reminded an effect on T-cell-mediated immune response.

Temporal trends of urinary mercury in Chinese people from 1970s to 2010s: A review

Mercury (Hg) is one of the most toxic heavy metals. It can migrate around the globe and magnify through the food chain, ultimately harming human health. Urinary Hg reflects recent exposure of Hg, which reflects the status of environmental contamination by Hg. This review summarized the levels and presented temporal trends of urinary Hg in Chinese people (both the general public and the occupationally exposed people) reported from 1970s to 2010s. It was found that urinary Hg levels in 92.3% of the reported population were less than the reference value (10.0 µg/L) recommended by Chinese health authority, while 76.9% were less than the reference value (4.0 µg/L) recommended by World Health Organization (WHO) in the general public in China. For the temporal trend from 1970s to 2010s, the urinary Hg levels in the general public in China were found to decrease gradually. In the occupationally exposed people, the urinary Hg levels generally exceeded the reference value (10.0 µg/L) for the general public, and about half of them were higher than the occupational exposure limit (35.0 µg/g creatinine) set by Chinese Occupational Health Standard (WS/T 265 - 2006). From 1970s to 2010s, the urinary Hg levels in occupationally exposed population increased first and then decreased slowly. Hg miners in Guizhou were found to have the highest urinary Hg levels, while workers in Anhui, Chongqing, Qinghai and Shanxi also had high levels of urinary Hg. In all, the urinary Hg levels in both the general public and the occupationally exposed people decreased from 1970s to 2010s, especially in recent decades. Attention should be paid to occupationally exposed people since high levels of urinary Hg were found in them. The message provided in this review can help better understand the situation of Hg burden in Chinese people and lay a basis for the coming effectiveness evaluation on the implementation of Minamata Convention on Mercury. Capsule abstract: The urinary Hg levels in both the general public and the occupationally exposed people in China are decreasing.

Effects of Environmental Endocrine-Disrupting Chemicals on Female Reproductive Health

Environmental endocrine-disrupting chemicals (EDCs) are xenobiotic compounds that are frequently contacted in daily life. With the species and quantity of substances created and utilized by human beings significantly surpassing the self-purification capacity of nature, a large number of hazardous substances are enriched in the human body through the respiratory tract, digestive tract, and skin. Some of these compounds cause many problems endangering female reproductive health by simulating/antagonizing endogenous hormones or affecting the synthesis, metabolism, and bioavailability of endogenous hormones, including reproductive disorders, fetal birth defects, fetal developmental abnormalities, endocrine and metabolic disorders, and even gynecological malignancies. Therefore, the study of the relationship between environmental EDCs and female reproductive diseases and related mechanisms is of considerable significance to women, children health care, and improve the quality of the population.

A Systematic Review of Environmental Health Outcomes in Selected American Indian and Alaska Native Populations

BACKGROUND

Economic and social marginalization among American Indians and Alaska Natives (AI/ANs) results in higher chronic disease prevalence. Potential causal associations between toxic environmental exposures and adverse health outcomes within AI/AN communities are not well understood.

OBJECTIVES

This review examines epidemiological literature on exposure to toxicants and associated adverse health outcomes among AI/AN populations.

METHODS

PubMed, Embase, Cochrane, Environment Complete, Web of Science Plus, DART, and ToxLine were searched for English-language articles. The following data were extracted: lead author's last name, publication year, cohort name, study location, AI/AN tribe, study initiation and conclusion, sample size, primary characteristic, environmental exposure, health outcomes, risk estimates, and covariates.

RESULTS

About 31 articles on three types of environmental exposures met inclusion criteria: persistent organic pollutants (POPs), heavy metals, and open dumpsites. Of these, 17 addressed exposure to POPs, 10 heavy metal exposure, 2 exposure to both POPs and heavy metals, and 2 exposure to open dumpsites. Studies on the Mohawk Nation at Akwesasne; Yupik on St. Lawrence Island, Alaska; Navajo Nation; Gila River Indian Community; Cheyenne River Sioux; 197 Alaska Native villages; and 13 tribes in Arizona, Oklahoma, North Dakota, and South Dakota that participated in the Strong Heart Study support associations between toxicant exposure and various chronic conditions including cardiovascular conditions, reproductive abnormalities, cancer, autoimmune disorders, neurological deficits, and diabetes.

DISCUSSION

The complex interplay of environmental and social factors in disease etiology among AI/ANs is a product of externally imposed environmental exposures, systemic discrimination, and modifiable risk behaviors. The connection between environmental health disparities and adverse health outcomes indicates a need for further study.

Mercury affects uterine myogenic activity even without producing any apparent toxicity in rats: Involvement of calcium-signaling cascades

BACKGROUND

Mercury is an established environmental toxicant reported to cause reproductive disorders in women, however, its direct action on myometrial activity is yet to be understood. Earlier we have reported the underlying mechanism of mercury-induced myometrial contractions following in vitro exposure; however, no such information on the effect of mercury on myometrial activity following in vivo exposure is available, therefore, the present study was undertaken.

OBJECTIVE

Present study was designed to evaluate the effect of mercury on myometrial activity following in vivo exposure of rats and unravel the possible underlying mechanism.

METHODS

Female Wistar rats were orally exposed to mercury (5, 50 and 500 μg/L in drinking water) for 28 days to investigate the toxicodynamics of mercuric chloride (HgCl₂)-induced alterations in myometrial activity. Response of the isolated myometrial strips to different spasmogens was recorded using polyphysiograph. Blood and uterine calcium, mercury, iron and zinc levels were estimated by atomic absorption spectrophotometry. Blood biochemicals and serum hormonal profiles (estradiol, progesterone) were also determined.

RESULTS

No systemic toxicity of mercury was observed in any of the treatment groups (5, 50 and 500 μg/L) in terms of alterations in body weight, organ weights, blood biochemical parameters including hormonal profile. Interestingly, mercury at 5 μg/L concentration significantly increased the receptor-dependent (PGF_2α-induced) and receptor-independent (CaCl₂-induced and high K⁺-depolarizing solution-induced) myometrial contractions and it was coupled with corresponding increase in the uterine calcium levels. However, mercury at higher dose levels (50 and 500 μg/L) did not significantly alter the myometrial response.

CONCLUSION

Our results evidently suggest that mercury at low level (5 μg/L) produced detrimental effect on myometrial activity by altering calcium entry into the smooth muscle and/or the release of calcium from intracellular stores without causing any apparent systemic toxicity in rats.

Elevated blood mercury level has a non-linear association with infertility in U.S. women: Data from the NHANES 2013-2016

Mercury is a ubiquitous toxic heavy metal associated with an increased risk of female infertility; however, the evidence supporting this is limited and controversial. We aimed to explore the relationship between the total blood mercury and infertility in 1796 selected participants from the National Health and Nutrition Examination Survey (NHANES) (2013-2016). We found no significant association between mercury and infertility based on a fully-adjusted model (OR 1.04; 95 % CI 0.91, 1.19), and the results remained robust in a series of sensitive analysis. However, a non-linear relationship was detected. By a two-piecewise linear regression model and recursive algorithm, we identified an inflection point of 5.278 μg/L, when blood mercury was >5.278 μg/L, a 1-unit increase in mercury (log2) was associated with 157 % greater adjusted odds of infertility (OR 2.57; 95 % CI 1.12, 5.87). Our findings provide new insights to advance the research of the link between mercury and infertility.

Mercury exposure and its effects on fertility and pregnancy outcome

Mercury (Hg), a highly toxic environmental pollutant, shows harmfulness which still represents a big concern for human health, including hazards to fertility and pregnancy outcome. Research has shown that Hg could induce impairments in the reproductive function, cellular deformation of the Leydig cells and the seminiferous tubules, and testicular degeneration as well as abnormal menstrual cycles. Some studies investigated spontaneous abortion and complicated fertility outcome due to occupational Hg exposure. Moreover, there is a relation between inhaled Hg vapour and reproductive outcome. This MiniReview evaluates the hypothesis that exposure to Hg may increase the risk of reduced fertility, spontaneous abortion and congenital deficits or abnormalities.

Mercury vapor volatilization from particulate generated from dental amalgam removal with a high-speed dental drill - a significant source of exposure

Background

The ubiquitous use of dental amalgam for over 180 years has resulted in the exposure of millions of dental workers to mercury. Dental amalgam contains approximately 50% mercury. Dental workers, including dentists, dental assistants, and dental hygienists, have been shown to have increased levels of mercury and suffer more from health issues related to mercury exposure than the general public. Mercury is known to be absorbed via inhalation or through the skin. There are many routine dental procedures that require the removal of dental amalgam by using the dental high-speed drill, which we suspected generates an occupational mercury exposure that is not sufficiently recognized.

Results

We showed that drilling dental amalgam generates particulate that volatilizes significant amounts of mercury vapor generally for more than an hour after removal. The levels of mercury vapor created by this procedure frequently exceed the safety thresholds of several jurisdictions and agencies.

Conclusions

A significant, underrecognized source of localized exposure to mercury vapor was identified in this study. The vapor was created by microgram levels of particulate generated from dental amalgam removal with a high-speed dental drill, even when all feasible engineering controls were used to reduce mercury exposure. This exposure may explain why dental workers incur health effects when safety thresholds are not breached. The dispersion patterns for the particulate are not known, so the use of effective skin barriers and inhalation protection are required during amalgam removal to protect the dental worker from this form of occupational mercury exposure. Standard methodologies for occupational mercury exposure assessment appear to be inadequate when assessing mercury exposure during amalgam removal.

Exposure to mercury and human reproductive health: A systematic review

BACKGROUND

Evidences from human and animal studies suggest that reproductive function may be affected by mercury. The aim of this review was to explore the mercury influence on human fertility.

METHODS

A systematic search was made in PubMED for papers published between 1975-2017, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Increased mercury levels were associated with infertility or subfertility status. Further, infertile subjects with unexplained infertility showed higher levels of mercury in hair, blood and urine than fertile ones. Mercury exposure induced sperm DNA damage and abnormal sperm morphology and motility. Additionally, mercury levels were related with higher incidence of menstrual and hormonal disorders and increased rates of adverse reproductive outcomes.

CONCLUSIONS

Our review showed that mercury negatively impacts human reproduction, affecting the reproductive and endocrine systems in both male and female. However, the molecular mechanisms underlying the mercury-associated decline on fertility remains unknown.

Urinary Mercury Levels Among Workers in E-waste Shops in Nakhon Si Thammarat Province, Thailand

OBJECTIVES

To determine urinary mercury levels in e-waste workers in Southern Thailand and the airborne mercury levels in the e-waste shops where they worked, to describe the associations between urinary and airborne mercury levels, and to evaluate the prevalence of mercury exposure-related health effects among e-waste workers.

METHODS

A cross-sectional study was conducted by interviewing 79 workers in 25 e-waste shops who lived in Nakhon Si Thammarat Province, Thailand. Information on general and occupational characteristics, personal protective equipment use, and personal hygiene was collected by questionnaire. Urine samples were collected to determine mercury levels using a cold-vapor atomic absorption spectrometer mercury analyzer.

RESULTS

The e-waste workers' urinary mercury levels were 11.60±5.23 μg/g creatinine (range, 2.00 to 26.00 μg/g creatinine) and the mean airborne mercury levels were 17.00±0.50 μg/m³ (range, 3.00 to 29.00 μg/m³). The urinary and airborne mercury levels were significantly correlated (r=0.552, p<0.001). The prevalence of self-reported symptoms was 46.8% for insomnia, 36.7% for muscle atrophy, 24.1% for weakness, and 20.3% for headaches.

CONCLUSIONS

Personal hygiene was found to be an important protective factor, and should therefore be stressed in educational programs. Employers should implement engineering measures to reduce urinary mercury levels and the prevalence of associated health symptoms among e-waste workers.

Urinary Mercury Levels Among Workers in E-waste Shops in Nakhon Si Thammarat Province, Thailand

OBJECTIVES

To determine urinary mercury levels in e-waste workers in Southern Thailand and the airborne mercury levels in the e-waste shops where they worked, to describe the associations between urinary and airborne mercury levels, and to evaluate the prevalence of mercury exposure-related health effects among e-waste workers.

METHODS

A cross-sectional study was conducted by interviewing 79 workers in 25 e-waste shops who lived in Nakhon Si Thammarat Province, Thailand. Information on general and occupational characteristics, personal protective equipment use, and personal hygiene was collected by questionnaire. Urine samples were collected to determine mercury levels using a cold-vapor atomic absorption spectrometer mercury analyzer.

RESULTS

The e-waste workers' urinary mercury levels were 11.60±5.23 μg/g creatinine (range, 2.00 to 26.00 μg/g creatinine) and the mean airborne mercury levels were 17.00±0.50 μg/m³ (range, 3.00 to 29.00 μg/m³). The urinary and airborne mercury levels were significantly correlated (r=0.552, p<0.001). The prevalence of self-reported symptoms was 46.8% for insomnia, 36.7% for muscle atrophy, 24.1% for weakness, and 20.3% for headaches.

CONCLUSIONS

Personal hygiene was found to be an important protective factor, and should therefore be stressed in educational programs. Employers should implement engineering measures to reduce urinary mercury levels and the prevalence of associated health symptoms among e-waste workers.

Physiological Aspects of Female Fertility: Role of the Environment, Modern Lifestyle, and Genetics

Across the Western World there is an increasing trend to postpone childbearing. Consequently, the negative influence of age on oocyte quality may lead to a difficulty in conceiving for many couples. Furthermore, lifestyle factors may exacerbate a couple's difficulty in conceiving due mainly to the metabolic influence of obesity; however, the negative impacts of low peripheral body fat, excessive exercise, the increasing prevalence of sexually transmitted diseases, and smoking all have significant negative effects on fertility. Other factors that impede conception are the perceived increasing prevalence of the polycystic ovary syndrome, which is further exacerbated by obesity, and the presence of uterine fibroids and endometriosis (a progressive pelvic inflammatory disorder) which are more prevalent in older women. A tendency for an earlier sexual debut and to have more sexual partners has led to an increase in sexually transmitted diseases. In addition, there are several genetic influences that may limit the number of oocytes within the ovary; consequently, by postponing attempts at childbearing, a limitation of oocyte number may become evident, whereas in previous generations with earlier conception this potentially reduced reproductive life span did not manifest in infertility. Environmental influences on reproduction are under increasing scrutiny. Although firm evidence is lacking however, dioxin exposure may be linked to endometriosis, phthalate exposure may influence ovarian reserve, and bisphenol A may interfere with oocyte development and maturation. However, chemotherapy or radiotherapy is recognized to lead to ovarian damage and predispose the woman to ovarian failure.

A Review of Mercury Exposure and Health of Dental Personnel

Considerable effort has been made to address the issue of occupational health and environmental exposure to mercury. This review reports on the current literature of mercury exposure and health impacts on dental personnel. Citations were searched using four comprehensive electronic databases for articles published between 2002 and 2015. All original articles that evaluated an association between the use of dental amalgam and occupational mercury exposure in dental personnel were included. Fifteen publications from nine different countries met the selection criteria. The design and quality of the studies showed significant variation, particularly in the choice of biomarkers as an indicator of mercury exposure. In several countries, dental personnel had higher mercury levels in biological fluids and tissues than in control groups; some work practices increased mercury exposure but the exposure levels remained below recommended guidelines. Dental personnel reported more health conditions, often involving the central nervous system, than the control groups. Clinical symptoms reported by dental professionals may be associated with low-level, long-term exposure to occupational mercury, but may also be due to the effects of aging, occupational overuse, and stress. It is important that dental personnel, researchers, and educators continue to encourage and monitor good work practices by dental professionals.

Neurological disease or intellectual disability among sons of female Swedish dental personnel

OBJECTIVE

Prenatal exposure to elemental mercury may be a potential hazard for the offspring of female dental personnel working with dental amalgam. The aim of this study was to investigate whether potential in utero exposure to mercury might have affected the development of nervous system of the sons of Swedish female dental personnel leading to an increased risk of neurological disease or intellectual disability.

MATERIAL AND METHODS

We used national Swedish registers to investigate risks for diseases potentially related to adverse effects on neurodevelopment. Sons of female dentists (n=1690) and dental nurses (n=10,420) were compared with cohorts consisting of sons of other female healthcare personnel. Due to changes in mercury exposure in dentistry during the study period, analyses were stratified by decade of birth. Hazard ratios (HRs) were calculated using Cox proportional hazard models.

RESULTS

We found no elevated risk for neurological disease, epilepsy or intellectual disability among the sons of dental personnel during any of the decades studied. HRs for neurological disease among the dental nurse cohort were even below 1.00 during the 1970s and 1980s. A low number of events resulted in uncertainty regarding results in the dentist cohort.

CONCLUSIONS

We did not find any support for the hypothesis that mercury exposure in Swedish dentistry during the 1960s, 1970s or 1980s had any effect on the incidence of neurological disease or intellectual disability among the sons of female dental personnel. Our results imply that current use of dental amalgam should not represent an elevated risk for neurological disease or intellectual disability among the offspring of dental personnel.

Occupational Metallic Mercury Poisoning in Gilders

Occupational exposure to elemental mercury vapor usually occurs through inhalation during its utilizations. This leads to a variety of adverse health effects. In some Islamic cities, this type of poisoning may occur during gilding of shrines using elemental mercury with gold. Herein, we report on three male patients aged 20-53 years, who were diagnosed with occupational metallic mercury poisoning due to gilding of a shrine. All patients presented with neuro-psychiatric disorders such as anxiety, loss of memory and concentration, and sleep disorders with high urinary mercury concentrations of 326-760 μg/L upon referring, 3-10 days after cessation of elemental mercury exposure. Following chelating therapy, the patients recovered clinically and their mercury concentrations declined to non-toxic level (<25 μg/L). Health, environmental and labor authorities, as well as the gilders should be aware of the toxicity risk of exposure to metalic mercury during gilding in closed environments and act accordingly.

Effect of mercury vapor inhalation on rat ovary: Stereology and histopathology

AIM

Mercury, an environmental contaminant, is a risk factor for health in whole living organisms. In this study, we investigated whether mercury vapor (HgO) inhalation has an effect on rat ovary.

METHODS

Twelve Wistar albino rats were divided equally into experimental (Hg) and control groups (n = 6). Animals in the Hg group were exposed to HgO for 45 days at a dose 1 mg/m(3)/day, after which, histological and stereological assessment were carried out.

RESULTS

Ovaries exposed to HgO had histo-morphometric alterations. HgO inhalation resulted in reduction of the total number of primordial, primary and Graaf follicles. Also, mean volume of ovary, medulla and cortex, corpus luteum (c. luteum) and Graaf follicles was decreased in the Hg group. Moreover, there was a significant increase in total volume of the atretic follicles. On light microscopy, thickening of tunica albuginea, increase of fibrils within the connective tissue, congestion of the capillaries and venous vessels, thinned walls and fibrin deposition in some large blood vessels, and edema were seen. Also, irregular follicle and oocyte borders, and hydropic degeneration in follicular granulosa cells were detected.

CONCLUSION

Structural alterations could be attributed to the toxic influence of HgO on rat ovary. The use of Hg should therefore be more controlled to minimize its toxic effect.

Maternal occupational exposure to ionizing radiation and major structural birth defects

BACKGROUND

Ionizing radiation (IR) is known to be carcinogenic and mutagenic, but little is known about the association between maternal occupational exposure to IR and birth defects.

METHODS

We studied 38,009 mothers who participated in the National Birth Defects Prevention Study and delivered between 1997 and 2009. We assessed odds ratios [ORs] for the association between maternal occupations with potential exposure to IR and 39 birth defects.

RESULTS

We observed significant odds ratios (ORs) for isolated hydrocephaly (adjusted OR [AOR], 2.1; 95% confidence interval [CI], 1.1-4.2), isolated anotia/microtia (AOR, 2.0; 95% CI, 1.0-4.0), isolated colonic atresia (crude OR, 7.5; 95% CI, 2.5-22.3), isolated omphalocele (AOR, 2.3; 95% CI, 1.1-4.6) and isolated anencephaly (crude OR, 0.23; 95% CI, 0.06-0.94). We also observed a nonsignificant OR for birth defects in aggregate (AOR, 2.0; 95% CI, 0.9-4.6) among mothers with potential occupational exposure to fluoroscopy.

CONCLUSION

We assessed 39 birth defects, observing that maternal occupations with potential exposure to IR were associated with a significantly increased risk for 4 birth defects and a significantly protected risk for 1 birth defect. These results should be interpreted cautiously because our measurement of exposure is qualitative, some of these associations may be due to occupational exposures that are correlated with IR and some may be due to chance. However, these findings serve as the first evaluation of these relationships in a large study and may be useful for generating hypotheses for future studies.

Hair mercury concentrations and in vitro fertilization (IVF) outcomes among women from a fertility clinic

Total hair mercury (Hg) was measured among 205 women undergoing in vitro fertilization (IVF) treatment and the association with prospectively collected IVF outcomes (229 IVF cycles) was evaluated. Hair Hg levels (median=0.62ppm, range: 0.03-5.66ppm) correlated with fish intake (r=0.59), and exceeded the recommended EPA reference of 1ppm in 33% of women. Generalized linear mixed models with random intercepts accounting for within-woman correlations across treatment cycles were used to evaluate the association of hair Hg with IVF outcomes adjusted for age, body mass index, race, smoking status, infertility diagnosis, and protocol type. Hair Hg levels were not related to ovarian stimulation outcomes (peak estradiol levels, total and mature oocyte yields) or to fertilization rate, embryo quality, clinical pregnancy rate or live birth rate.

Metals and female reproductive toxicity

Research into occupational exposure of metals and consequences of reproductive systems has made imperative scientific offerings in the preceding few decades. Early research works focused on possible effects on the reproductive functions rather than the complete reproductive health of the woman. Later, it was realized that metals, as reproductive toxins, may also induce hormonal changes affecting other facets of reproductive health such as the menstrual cycle, ovulation, and fertility. Concern is now shifting from considerations for the pregnant woman to the entire spectrum of occupational health threats and thus reproductive health among women.

Mortality among sons of female dental personnel--a national cohort study

AIMS

Dental personnel are exposed to mercury when using dental amalgam. This exposure constitutes a potential hazard to offspring of women working in dentistry. The present study examined increased mortality risk in offspring of mothers working in dentistry.

METHODS

Mortality was compared between sons of dental personnel and sons of nondental health-care personnel. Hazard ratios were calculated for three decades (1960s-1980s), when the magnitude of mercury exposure in dentistry was likely to have varied.

RESULTS

During the 1960s, there was a statistically significant increase in the risk of neonatal mortality for sons of dental nurses when compared with sons of assistant nurses: hazard ratio (HR) 1.82 (95% confidence interval, CI: 1.04-3.22). There was no increased risk in the subsequent decades, but a trend test demonstrated a consistent decrease in the risk over the three decades: HR for trend 0.63 (95% CI: 0.44-0.90). The raised mortality risk was limited to neonatal mortality. The comparison between dentists and physicians had insufficient statistical power.

CONCLUSIONS

There is no increased mortality risk among sons of female dentists after the 1960s. Although the results should be interpreted with caution, they suggest a modestly raised risk of neonatal mortality, during the 1960s, when exposure to mercury was thought to be highest.

Environmental mercury and its toxic effects

Mercury exists naturally and as a man-made contaminant. The release of processed mercury can lead to a progressive increase in the amount of atmospheric mercury, which enters the atmospheric-soil-water distribution cycles where it can remain in circulation for years. Mercury poisoning is the result of exposure to mercury or mercury compounds resulting in various toxic effects depend on its chemical form and route of exposure. The major route of human exposure to methylmercury (MeHg) is largely through eating contaminated fish, seafood, and wildlife which have been exposed to mercury through ingestion of contaminated lower organisms. MeHg toxicity is associated with nervous system damage in adults and impaired neurological development in infants and children. Ingested mercury may undergo bioaccumulation leading to progressive increases in body burdens. This review addresses the systemic pathophysiology of individual organ systems associated with mercury poisoning. Mercury has profound cellular, cardiovascular, hematological, pulmonary, renal, immunological, neurological, endocrine, reproductive, and embryonic toxicological effects.

Mercury vapour exposure during dental student training in amalgam removal

Background

Amalgam that is used for dental fillings contains approximately 50% elemental mercury. During dental student training, amalgam is often removed by drilling without the use of water spray and suction, which are protective measures in preventing mercury aerosol. In this study we measured mercury vapor levels in ambient air during amalgam removal as is typically performed in dental training.

Methods

Mercury vapor levels in ambient air were measured in a dental school laboratory during removal of amalgam fillings from artificial teeth set into a dental jaw simulator. Mercury vapor was measured under three conditions (25 measurements each): with the simultaneous use of water spray and suction, with the use of suction only, and with the use of neither suction nor water spray. These three conditions are all used during dental student training. Results were compared to Alberta occupational exposure limits for mercury vapor in order to assess potential occupational risk to students. Analysis of variance testing was used to compare data obtained under the three conditions.

Results

When water spray and suction were used, mercury vapor levels ranged from 4.0 to 19.0 μg/m³ (arithmetic mean = 8.0 μg/m³); when suction only was used, mercury vapor levels ranged from 14.0 to 999.0 (999.0 μg/m³ represents the high limit detection of the Jerome analyzer) (arithmetic mean = 141.0 μg/m³); when neither suction nor water was used, the vapor levels ranged from 34.0 to 796.0 μg/m³ (arithmetic mean = 214.0 μg/m³).

Conclusions

The Alberta Occupational Health and Safety threshold limit value for mercury vapor over an eight-hour time-weighted period is 25.0 μg/m³. The absolute ceiling for mercury vapor, not to be exceeded at any time, is 125.0 μg/m³. When both water spray and suction were used, mercury vapor levels were consistently below this threshold. When suction without water spray was used, mercury vapor levels exceeded the safety threshold 8% of the time. When neither water spray nor suction was used, 36% of the mercury vapor readings exceeded the absolute ceiling value. To maximize safety, dental schools should train students to remove amalgam only while using water spray and high volume suction. Alternatively, students should use appropriate occupational hygiene personal protective equipment during amalgam removals.

Effect of methyl mercury induced free radical stress on nucleic acids and protein: Implications on cognitive and motor functions

Mercury pollution and acute neurotoxicity of mercury is well known. The recent reports suggest the adverse effect of low dose mercury, though the available literature is still silent on its mechanism. This study was therefore undertaken to probe the effect of low dose methyl mercury induced heavy metal toxicity on free radical stress and its impact on behaviour of male albino rats. Male albino rats were exposed to 1 mg/kg body wt of methylmercury chloride for seven days, on day 8 they were tested for motor and memory functions. They were sacrificed later for biochemical estimations for rate of lipid peroxidation, nucleic acids, proteins in cerebrum, cerebellum and brain stem. There was an increase in the rate of lipid peroxidation showing methyl mercury induced free radical stress. The motor and memory functions demonstrated a clear decline, besides there was a lowering in the levels of nucleic acids and proteins as compared to controls. The results are important in view of recent reports that methyl mercury induced free radical stress results in early ageing and may serve as an initiating factor more specifically for neurodegenerative disorders like Alzeihemer's disease and dementias. The current findings support the notion that incorporating dietary antioxidants like curcumin, ascorbic acid and α-tocopherol in routine diet from early age may help combat the risk of developing such disorders in ensuing years.

The endocrine disruptive effects of mercury

Mercury, identified thousands of years ago is one of the oldest toxicants known. The endocrine disruptive effects of mercury have recently become one of the major public concerns. In this report, the adverse effects of mercury on the hypothalamus, pituitary, thyroid, adrenal gland, and gonads (testis and ovary) in laboratory animals as well as in humans are reviewed. The effects of both environmental and occupational exposures to organic, inorganic, or metallic mercury are explained. There is sufficient evidence from animal studies supporting the disruptive effects of mercurials on the functions of the thyroid, adrenal, ovary, and testis, although several factors make it difficult to extrapolate the animal data to the human situation. However, the human studies performed so far, which focused mainly on serum hormone levels, failed to provide any conclusive data to confirm the findings from the animal studies. Therefore, further well-designed epidemiological studies are urgently needed. The possible mechanisms of the toxic effects are also discussed. The broad enzyme inhibition and the influence on the combining of hormones by their receptors, which seem due to its avid binding to sulphydryl, may account for the primary mechanism. The interference with intracellular calcium metabolism, and peroxidation may also be involved.

Mercury production and use in colonial Andean silver production: emissions and health implications

BACKGROUND

Colonial cinnabar mining and refining began in Huancavelica, Peru, in 1564. With a local source of mercury, the amalgamation process was adopted to refine silver in Potosí, Bolivia, in the early 1570s. As a result, large quantities of mercury were released into the environment.

OBJECTIVES

We used archival, primary, and secondary sources to develop the first estimate of mercury emissions from cinnabar refining in Huancavelica and to revise previous estimates of emissions from silver refining in Potosí during the colonial period (1564-1810).

DISCUSSION

Although other estimates of historical mercury emissions have recognized Potosí as a significant source, Huancavelica has been overlooked. In addition, previous estimates of mercury emissions from silver refining under-estimated emissions because of unrecorded (contra-band) production and volatilization of mercury during processing and recovery. Archival descriptions document behavioral and health issues during the colonial period that are consistent with known effects of mercury intoxication.

CONCLUSIONS

According to our calculations, between 1564 and 1810, an estimated 17,000 metric tons of mercury vapor were emitted from cinnabar smelting in Huancavelica, and an estimated 39,000 metric tons were released as vapor during silver refining operations in Potosí. Huancavelica and Potosí combined contributed > 25% of the 196,000 metric tons of mercury vapor emissions in all of Latin America between 1500 and 1800. The historical record is laden with evidence of mercury intoxication consistent with effects recognized today. Our estimates serve as the foundation of investigations of present-day contamination in Huancavelica and Potosí resulting from historical emissions of mercury.

Mercury pollution in Malaysia

Although several studies have been published on levels of mercury contamination of the environment, and of food and human tissues in Peninsular Malaysia, there is a serious dearth of research that has been performed in East Malaysia (Sabah and Sarawak). Industry is rapidly developing in East Malaysia, and, hence, there is a need for establishing baseline levels of mercury contamination in environmental media in that part of the country by performing monitoring studies. Residues of total mercury and inorganic in food samples have been determined in nearly all previous studies that have been conducted; however, few researchers have analyzed samples for the presence of methlymercury residues. Because methylmercury is the most toxic form of mercury, and because there is a growing public awareness of the risk posed by methylmercury exposure that is associated with fish and seafood consumption, further monitoring studies on methylmercury in food are also essential. From the results of previous studies, it is obvious that the economic development in Malaysia, in recent years, has affected the aquatic environment of the country. Primary areas of environmental concern are centered on the rivers of the west Peninsular Malaysian coast, and the coastal waters of the Straits of Malacca, wherein industrial activities are rapidly expanding. The sources of existing mercury input to both of these areas of Malaysia should be studied and identified. Considering the high levels of mercury that now exists in human tissues, efforts should be continued, and accelerated in the future, if possible, to monitor mercury contamination levels in the coastal states, and particularly along the west Peninsular Malaysian coast. Most studies that have been carried out on mercury residues in environmental samples are dated, having been conducted 20-30 years ago; therefore, the need to collect much more and more current data is urgent. Furthermore, establishing baseline levels of mercury exposure to humans in Malaysia will be useful in establishing the levels at which detrimental effects in both humans and marine life may occur, and therefore the levels at which warning should be raised or limits established. In particular, we believe that two or three monitoring centers should be established in Peninsular Malaysia, and one in East Malaysia for the specific purpose of monitoring for the presence of hazardous environmental chemicals, and particularly monitoring for heavy metals such as mercury that reach food that is subject to consistent human consumption.

Is dental amalgam safe for humans? The opinion of the scientific committee of the European Commission

It was claimed by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)) in a report to the EU-Commission that "....no risks of adverse systemic effects exist and the current use of dental amalgam does not pose a risk of systemic disease..." [1, available from: http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_016.pdf].SCENIHR disregarded the toxicology of mercury and did not include most important scientific studies in their review. But the real scientific data show that:(a) Dental amalgam is by far the main source of human total mercury body burden. This is proven by autopsy studies which found 2-12 times more mercury in body tissues of individuals with dental amalgam. Autopsy studies are the most valuable and most important studies for examining the amalgam-caused mercury body burden.(b) These autopsy studies have shown consistently that many individuals with amalgam have toxic levels of mercury in their brains or kidneys.(c) There is no correlation between mercury levels in blood or urine, and the levels in body tissues or the severity of clinical symptoms. SCENIHR only relied on levels in urine or blood.(d) The half-life of mercury in the brain can last from several years to decades, thus mercury accumulates over time of amalgam exposure in body tissues to toxic levels. However, SCENIHR state that the half-life of mercury in the body is only "20-90 days".(e) Mercury vapor is about ten times more toxic than lead on human neurons and with synergistic toxicity to other metals.(f) Most studies cited by SCENIHR which conclude that amalgam fillings are safe have severe methodical flaws.

Comments on the Article “The Toxicology of Mercury and Its Chemical Compounds” by Clarkson and Magos (2006)

Clarkson and Magos (2006) provide their perspectives on the toxicology of mercury vapor and dental amalgam. As scientists who are involved in preparing a German federal guideline regarding dental amalgam, we welcome additional scientific data on this issue. However, Clarkson and Magos do not present all the relevant studies in their review. The additional data provided here show that: (a) Dental amalgam is the main source of human total mercury body burden, because individuals with amalgam have 2-12 times more mercury in their body tissues compared to individuals without amalgam; (b) there is not necessarily a correlation between mercury levels in blood, urine, or hair and in body tissues, and none of the parameters correlate with severity of symptoms; (c) the half-life of mercury deposits in brain and bone tissues could last from several years to decades, and thus mercury accumulates over time of exposure; (d) mercury, in particular mercury vapor, is known to be the most toxic nonradioactive element, and is toxic even in very low doses, and (e) some studies which conclude that amalgam fillings are safe for human beings have important methodogical flaws. Therefore, they have no value for assessing the safety of amalgam.

Weibliche und männliche Fertilitätsstörungen und Risiken der assistierten Fertilisation

Ca. 10–15% der Paare im reproduktionsfähigen Alter bleiben ungewollt kinderlos. Der Anteil steigt tendentiell durch den zunehmend „späten Kinderwunsch“. Das durchschnittliche Alter der Erstgebärenden hat sich u.a. aus Gründen der Ausbildungszeit und Berufstätigkeit der Frau zwischen 1970 und 2000 vom 24. auf das 30. Lebensjahr verschoben. Eine gewollte Kinderlosigkeit kommt in ca. 10% der Ehen vor.

Maternal dental history, child's birth outcome and early cognitive development

Prenatal exposure to high levels of mercury, radiation and inflammation have been associated with adverse reproductive outcomes such as increases in preterm delivery, low birthweight and delayed neurodevelopment. Few data are available to evaluate the potential effects of prenatal low-level exposure to these factors as may occur during dental care. We evaluated maternal dental history prior to and during pregnancy in relation to birth outcomes and early communicative development among offspring in a large cohort (n = 7375) of British children born in 1991-92. Dental history was assessed by questionnaire. The child's communicative development was assessed using the MacArthur Communicative Development Inventory at 15 months of age. Total mercury was measured in umbilical cord tissue for a subset of the children. Overall, dental care, including amalgam fillings, was not associated with birth outcomes or language development. Having X-rays taken during pregnancy was not associated with birthweight measured continuously (b = 14.7, P = 0.4), but was associated with slightly increased odds of having a term, low-birthweight baby (OR 1.9, [95% confidence interval 1.0, 3.4]). More detailed evaluation of the potential adverse effects of elective dental treatment during pregnancy, particularly dental X-rays, may be warranted.

Environmental factors implicated in the causation of adverse pregnancy outcome

Adverse pregnancy outcome from environmental factors may include congenital anomalies, increased risk for miscarriage, preterm delivery, intrauterine growth restriction, and still birth. Apart from adverse pregnancy outcome, there may be effects on the other reproductive functions, like menstrual disorders and infertility. Environmental factors which have been implicated in adverse pregnancy outcome include smoking, video display terminals, anesthetic gases, antineoplastic drugs, and exposure to lead, selenium, and inorganic mercury. Among these, cigarette smoking during pregnancy has been the leading environmental factor for adverse pregnancy outcome. Cigarette smoking during pregnancy continues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g). Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Similarly, air pollution, pesticide exposure, and stress have also been associated with low birth weight and preterm delivery. This review gives an overview of the importance of environmental factors in adverse pregnancy outcome.

A 30-year follow-up of residual effects on New Zealand School Dental Nurses, from occupational mercury exposure

This paper reports possible residual adverse effects from occupational mercury exposure in dentistry, Thirty years ago, the all-women exposed group worked with both silver and copper amalgam filling material without protective gloves or a ventilation system, resulting in chronic mercury exposure. The aim of the study was to test the null hypothesis in a survey of general and reproductive health, and a battery of nine neurobehavioral tests. The population was the 115 graduates of one school for dental nurses from 1968 to 1971. The sample was 43 mercury-exposed women and 32 matched controls. Statistical comparisons revealed that the two groups were equivalent on cognitive tasks and four of the six mood subscales. Significant between-group differences were found in current health symptom experience and reproductive health, especially early hysterectomy experience. Reporting of Occupational Overuse Syndrome was strongly positively correlated with years of work. In general, the study suggests that acute symptoms from mercury exposure may be reversible, while some residual health effects may be becoming more of a concern with the women's increasing age.

Asian ethnicity is associated with reduced pregnancy outcomes after assisted reproductive technology

OBJECTIVE

To determine whether success rates were similar in Asian and Caucasian women undergoing infertility treatment.

DESIGN

Secondary data analysis and multivariate modeling.

SETTING

Clinics reporting to the national Society for Assisted Reproductive Technology registry and a university-based clinic.

PATIENT(S)

Caucasian and self-identified Asian infertile women undergoing IVF. The study included 25,843 Caucasian and 1,429 Asian patients from the national registry; 370 Caucasian and 197 Asian patients were included from the site-specific clinic.

INTERVENTION(S)

In vitro fertilization.

MAIN OUTCOME MEASURE(S)

Pregnancy rate and live-birth rate.

RESULT(S)

Infertile Asian women differed only minimally from their Caucasian counterparts in baseline characteristics and treatment response. Yet Asian women had a decreased clinical pregnancy rate (odds ratio, 0.71; 95% confidence interval 0.64-0.80) and a decreased live-birth rate (odds ratio, 0.69; 95% confidence interval 0.61-0.77). Subsequent multivariate analysis demonstrated that Asian ethnicity was an independent predictor of poor outcome.

CONCLUSION(S)

After treatment, infertile Asian women have significantly fewer pregnancies than do Caucasian women. Multivariate analysis indicates that this discrepancy cannot be accounted for by differences in baseline characteristics or by response to current therapeutic interventions.

Occupational exposure in dentistry and miscarriage

BACKGROUND

Information on the reproductive effects of chemical exposures in dental work is sparse or inconsistent.

AIM

To investigate whether dental workers exposed to acrylate compounds, mercury amalgam, solvents or disinfectants are at an increased risk of miscarriage.

METHODS

The study was conducted among women dental workers and a comparison group of workers occupationally unexposed to dental restorative materials. Information on pregnancies was obtained from national registers and outpatient units of hospitals. Data on occupational exposure were obtained using postal questionnaires. The final study population included 222 cases of miscarriage and 498 controls (births). An occupational hygienist assessed exposure to acrylate compounds, disinfectants and solvents. Exposure to other agents was assessed on the basis of the questionnaire data. Odds ratios (ORs) and confidence intervals (CIs) were estimated using conditional logistic regression.

RESULTS

The ORs adjusted for confounding factors were increased for moderate-exposure and high-exposure categories of mercury amalgam (OR 2.0, 95% CI 1.0 to 4.1 and OR 1.3, 95% CI 0.6 to 2.5, respectively). The risk was slightly increased for the highest-exposure category of 2-hydroxyethylmethacrylate (OR 1.4, 95% CI 0.7 to 2.6) and polymethylmethacrylate dust (OR 1.4, 95% CI 0.8 to 2.4). A slightly increased risk was also detected for likely exposure to organic solvents (OR 1.4, 95% CI 0.8 to 2.3) and disinfectants (OR 1.5, 95% CI 0.9 to 2.7).

CONCLUSIONS

No strong association or consistent dose-response relationship was observed between exposure to chemical agents in dental work and the risk of miscarriage. A slightly increased risk was found for exposure to mercury amalgam, some acrylate compounds, solvents and disinfectants. These findings indicate that the possibility of a weak association between exposure to these agents and an increased risk of miscarriage cannot be excluded.

Environmental contaminant levels and fecundability among non-smoking couples

OBJECTIVE

To investigate the effects of low level maternal and paternal persistent contaminant exposures on fecundability among couples from the general population.

METHODS

About 41 couples having their first pregnancy completed questionnaires and provided blood samples for analysis of metals, organochlorine pesticides, and polychorinated biphenyls. Associations of personal consumption and contaminant measures for mothers, fathers, and couples overall were analyzed through fecundability odds ratios (fOR, probability of pregnancy per month in more versus less exposed) in multivariable analyses.

FINDINGS

Couples with higher reported caffeine consumption (couple consumption > or =111 drinks/month, fOR 0.25, 95% CI, 0.10, 0.63) and higher mercury concentrations in maternal blood (>1.2 microg/L or 0.24 ppm in hair, fOR 0.22, 95% CI, 0.07, 0.72) had lower fecundability, after adjustment for intercourse frequency.

CONCLUSION

Reduced fecundability at levels below the mercury reference dose warrants further research and prudent reduction in persistent toxic substances exposure among women and men of reproductive age.

Mercury and selenium concentrations in hair samples of women in fertile age from Amazon riverside communities

The aim of the present study was to evaluate mercury and selenium concentrations in hair samples of reproductive age women from riverside communities of the Tapajós River basin. We studied 19 pregnant and 21 non-pregnant women, 13 to 45 years old, living in the region for at least 2 years, and having a diet rich in fish. The analysis of Se and total Hg were performed in the Instituto de Pesquisas Energéticas e Nucleares (IPEN, São Paulo, Brazil) by using a Varian AA220-FS atomic absorption spectrometer with a flow injection system. There were no differences between the two groups - pregnant and non-pregnant -- concerning age (23.80 +/- 6.92 and 26.60 +/- 9.60 years old, respectively) and residential time (20.21 +/- 8.30 and 22.20 +/- 10.90 years, respectively). The geometric means and ranges for total Hg concentration were similar (p > 0.05): 8.25 microg/g (1.51-19.43) in pregnant and 9.39 microg/g (5.25-21.00) in non-pregnant women, respectively. Total Hg concentrations were also similar in different gestational stages. However, there was a significant difference between the two groups (p < 0.05, Student t test) in relation to Se concentration: 0.61 microg/g (0.40-2.33) in pregnant and 2.46 microg/g (0.92-5.74) in non-pregnant women, respectively. We concluded that Hg exposure levels in reproductive age women were only slightly higher than a provisional tolerable weekly intake of MeHg would provide, that Hg concentration in maternal hair samples was independent of gestational age, and that low Se concentration in pregnant women indicates high mineral consumption by fetal organism to satisfy their metabolic requirements raised during pregnancy, including as a protective mechanism for Hg cytotoxic effects.

Low dose mercury toxicity and human health

Post Minamata incident there has been awareness about mercury toxicity even among the general public. Previous researches contributed a vast amount of data regarding acute mercury exposure, but gradually information about the low dose [Ninomiya, T., Ohmori, H., Hashimoto, K., Tsuruta, K., Ekino, S., 1995. Expansion of methylmercury poisoning outside minamata: an epidemiological study on chronic methylmercury poisoninig outside of Minamata. Environ. Res. 70 (1) 47-50; Lebel, J., Mergler, D., Lucotte, M., Amorim, M., Dolbec, J., Miranda, D., Arantes, G., Rheault, I., Pichet, P., 1996. Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels of methylmercury. Neurotoxicology 17 (1) 157-167] of mercury toxicity has been trickling in. With mercury contaminating rain-, ground- and sea-water no one is safe. Polluted water leads to mercury laced fish, meat and vegetable. In aquatic environments, inorganic mercury is microbiologically transformed into lipophilic organic compound 'methylmercury'. This transformation makes mercury more prone to biomagnification in food chains. Consequently, populations with traditionally high dietary intake of food originating from fresh or marine environment have highest dietary exposure to mercury. Extensive research done on locals across the globe have already established this, persons who routinely consume fish or a particular species of fish are at an increased risk of methylmercury poisoning. The easy access of the toxicant to man through multiple pathways air, water, food, cosmetic products and even vaccines increase the exposure. Foetus and children are more susceptible towards mercury toxicity. Mothers consuming diet containing mercury pass the toxicant to foetus and to infants through breast milk. Decreased performance in areas of motor function and memory has been reported among children exposed to presumably safe mercury levels. Similarly, disruption of attention, fine motor function and verbal memory was also found in adults on exposure to low mercury levels. It is an occupational hazard for dental staff, chloralkali factory workers and goldminers, etc. Mercury has been found to be a causative agent of various sorts of disorders, including neurological, nephrological, immunological, cardiac, motor, reproductive and even genetic. Recently heavy metal mediated toxicity has been linked to diseases like Alzeihemer's, Parkinson's, Autism, Lupus, Amyotrophic lateral sclerosis, etc. Besides this, it poses danger to wildlife. Therefore, it becomes imperative to spread the information regarding the threat of mercury exposure amongst the scientists and masses.

Amalgam toxicity--environmental and occupational hazards

OBJECTIVES

To discuss briefly the recent developments in mercury production, consumption and waste handling especially in relation to the use of mercury in dentistry. Furthermore, to discuss the toxicological and reproductive aspects of the mercury body burden of dental personnel.

DATA, SOURCES AND STUDY SELECTION

The data discussed are primarily based on published scientific studies and on publications and reviews from governmental and other official authorities which have been published within the last 10 years, References have been traced manually or by MEDLINE.

CONCLUSIONS

Global production and consumption of mercury is decreasing, as is the production of amalgam fillings in some countries. By proper measures it is possible to further reduce the environmental burden of mercury from dental clinics. In general, the mercury body burden of the dental personnel can be kept below the normally accepted toxicological limits and reproductive effects have not been proven provided a proper mercury hygiene regimen is adopted.

Infertility and environmental pollutants

While it has long been known that female fertility is impaired by oestrogen exposure, it is unclear whether environmental pollutants with weak oestrogenic effects are sufficiently potent and prevalent to have biological effects in humans. Male fertility, or sperm concentration at least, appears to have deteriorated, and there is substantial spatial variation at both national and global level, as well as a genetic component. Sperm morphology and motility are implicated too. There is good evidence for an increase in testicular cancer, and possibly in other conditions that certain spatial characteristics plus evidence on heritability suggest are linked to impaired spermatogenesis. A candidate agent would need to have started increasing in the early 20th century. Weak environmental oestrogens are not responsible. Candidates include agents affecting endogenous maternal oestrogen levels, environmental anti-androgens (although these cannot explain the epidemiological findings), and dioxin and related compounds. Genetic damage should be considered as a unifying hypothesis, possibly focused on the Y-chromosome.

Factors associated with amalgam restorations in Taiwan

OBJECTIVE

This study investigated the prevalence of and factors associated with amalgam restorations of posterior teeth in Taiwan.

METHOD

The authors analyzed the dental data regarding direct restorations of posterior teeth from the National Health Insurance Research Database of 1997, which was the first nationwide data available. The chi-square test and analysis of variance was used to compare the characteristics of the teeth, patients, dentists, and dental treatment settings between amalgam and composite restorations. The multivariate analysis was applied to obtain the Generalized Estimating Equation estimation for associations of multiple factors with amalgam restorations, taking into account the intra-individual correlation of teeth restored.

RESULTS

Amalgam was used in 53.3% of the direct restorations of posterior teeth. When all the important factors were assessed simultaneously, characteristics significantly associated with more amalgam restorations were: dentists aged 43 years and above, patients aged 1-22 years, primary molars, two- or three-surface cavity, regions with higher number of population served per dentist, and dental clinic.

CONCLUSION

Doctors' age, patients' age, type of dental treatment settings, population served per dentist, type of tooth, and number of surfaces restored were significantly associated with amalgam restorations in Taiwan.

Infertility, blood mercury concentrations and dietary seafood consumption: a case-control study

OBJECTIVE

To compare blood mercury concentrations of infertile couples with those of fertile couples in Hong Kong, and to examine the relationship between blood mercury concentrations and seafood consumption.

DESIGN

Case-control study.

SETTING

In vitro fertilisation (IVF) Unit and Antenatal Unit of a university teaching hospital. Sample One hundred fifty-seven infertile couples attending IVF treatment and 26 fertile couples attending antenatal care without known occupational exposure to mercury.

METHODS

Mercury concentrations in whole blood were measured by cold vapour atomic absorption spectrophotometry. A dietitian recorded the quantity of seafood consumption among infertile couples via a food-frequency questionnaire. Blood mercury concentrations and quantity of seafood consumption were compared between infertile and fertile couples.

MAIN OUTCOME MEASURES

Whole blood mercury concentrations, quantity of seafood consumption.

RESULTS

Infertile couples had higher blood mercury concentrations than fertile couples. 'Infertile males with abnormal semen' and 'infertile females with unexplained infertility' also had higher blood mercury concentrations than their fertile counterparts. Blood mercury concentrations were positively correlated with quantity of seafood consumption. Infertile subjects with elevated blood mercury concentrations consumed a larger amount of seafood.

CONCLUSION

Higher blood mercury concentration is associated with male and female infertility. Higher seafood consumption is associated with elevated blood mercury concentrations in our infertile population.