Inorganic: the other mercury.
Mercury is a metallic element that occurs naturally in the earth's crust and exists in the environment as the result of both natural and anthropogenic processes. The various chemical forms of mercury can be divided into three primary categories: 1) metallic mercury (also called liquid or elemental mercury); 2) inorganic mercury, including common compounds formed from the monovalent and divalent cations (e.g., mercurous chloride, mercuric chloride, mercuric acetate, and mercuric sulfide); and 3) alkyl, dialkyl, and aryl organic mercury compounds (e.g., methylmercuric chloride, dimethyl mercury, and phenylmercuric acetate, respectively) (Agency for Toxic Substances and Disease Registry [ATSDR], 1999; Clarkson, 2002).
Elemental, or metallic, mercury ([Hg.sup.0]) is the primary form of mercury released into the air by natural processes, such as volcanic activity. When bound to other chemicals, mercury may have valence states of either +1 ([Hg.sup.+], or mercurous mercury) or +2 ([Hg.sup.++], or mercuric mercury). Many compounds of mercury can be formed from the monovalent and divalent cation forms (ATSDR, 1999). In the environment, elemental mercury can combine with chlorine, sulfur, phosphorous, and other elements to form inorganic compounds. In water, inorganic mercury can be combined with carbon to form organic mercury compounds through the action of aquatic microorganisms (ATSDR, 1999; U.S. Environmental Protection Agency [U.S. EPA], 1997), but organic forms of mercury are not the focus of this paper and will not be discussed further.
Sources of Exposure
There are many sources of non-occupational exposure to inorganic forms of mercury (Table 1). Metallic mercury in liquid form has been available in homes, schools, offices, and health care facilities for many decades. Its shiny, silvery appearance, its physical ability to form small beads when disturbed, and its ability to make old silver-colored coins look like new make it particularly attractive to children of all ages. Some traditional uses of this form of mercury, as well as accidental spills, have been found to result in a variety of health effects, ranging in severity from relatively benign to lethal (Kanluen & Gottlieb, 1991). Exposure to elemental mercury occurs primarily through the inhalation of mercury vapors (Table 2). Infants and young children, with breathing zones closest to the floor, are at greater risk of significant exposure following spills of elemental mercury, since mercury vapor is heavy and tends to form layers close to the floor (Clarkson, Magos, & Myers, 2003).
Inadvertent exposure to mercury vapor is a recurring source of intake of this metal into the body. In some cases, exposure is completely unknown and is only discovered because of the onset of symptoms. Such cases often involve moving into a previously contaminated residence or structure without knowledge of the mercury contamination (Orloff et al., 1997; Sasso et al., 1996; Yeates & Mortensen, 1994). In other instances, the unapproved removal of mercury from schools, warehouses, or abandoned industrial facilities has resulted in significant exposure, typically of children (Baker & Eshenaur, 2005; George et al., 1996; Malecki & Hopkins, 1995; Risher, Nickle, & Amler, 2003; Sexton et al., 1976). A recent source of inadvertent exposure was the replacement of mercury-containing gas regulators in homes, with subsequent exposure resulting from spillage of elemental mercury in the process (Hryhorczuk et al., 2006).
Dental amalgam also constitutes a source of exposure to elemental mercury for some individuals. Amalgam, or "silver," fillings consist of approximately 50 percent elemental mercury, 35 percent silver, and a mixture of other metals. If such a filling were accidentally broken and swallowed, it would pass through the gastrointestinal tract intact and be eliminated in the feces. Some very slight volatilization occurs through normal chewing processes, however, resulting in some absorption of the metal through the lungs. The World Health Organization (WHO, 1991) estimates that dental-amalgam fillings contribute approximately 4 to 19 micrograms ([micro]g) of mercury per day to humans who have a significant number of dental-amalgam fillings. It is important to note that although dental-amalgam fillings are the major source of mercury exposure for most people, there is no credible evidence to suggest that mercury amalgams represent a health risk. Furthermore, recent studies have found no association between mercury amalgam exposure and neurologic or renal dysfunction in children (Bellinger et al., 2006; DeRouen et al., 2006; Kingman, Albers, Arezzo, Garabrant, & Michalek, 2005), considered to be the most sensitive human sub-population.
A lesser known, yet well-documented, use of metallic mercury among the general population is its use in ethnic or folk medical practices. The oral use of mercury to treat indigestion, or empacho, in some Hispanic populations is also a source of exposure. Some Caribbean religions, such as Vodou, Santeria, Obeah, and Espiritismo, sometimes use mercury ceremonially for a variety of purposes (Wendroff, 2005; Kew, Morris, Aihie, Fysh, Jones, & Books, 1993). Such uses may include the sprinkling of metallic mercury around the home and automobile to ward off "evil spirits." In some practices, mercury is sprinkled in baths or burned on devotional candles. All of these uses can result in exposure to users and family members. Another use of elemental mercury is its subcutaneous injection to ward off evil and protect against infection/disease, an apparently common practice in several Central and South American countries (Prasad, 2004). Intravenous injection of elemental mercury in a number of suicide attempts also has been reported (Kayias, Drosos, Hapsas, & Anafnostopoulou, 2003).
The JSI Center for Environmental Health Studies (2003) reported a study conducted in Massachusetts, in which 898 people, predominantly of Latino or Caribbean background, were surveyed. In this study, 494 individuals, or 55 percent of the study population, indicated that they used mercury in their homes. Of these, 91 individuals admitted swallowing a drink containing mercury, 143 applied mercury to their skin, 152 burned mercury in candles, and 108 sprinkled mercury around their homes. The use of mercury in traditional Chinese medicine can result in the ingestion of up to 1.2 grams (probably as mercury sulfide) daily (Espinoza, Mann, & Bleadsdel, 1996).
The Oregon Environmental and Occupational Epidemiology Web site contains a warning about mercury-containing necklaces worn by some school children (Oregon Health Services, 2006). These necklaces contain metallic mercury in a glass pendant attached to a chain, cord, or leather strap. The pendants are sometimes filled with brightly colored liquids together with the mercury, and may come in a variety of shapes. Breakage of pendants has resulted in mercury spills.
Breast milk is also a potential source of exposure to inorganic mercury, whether the initial source of the mercury is maternal exposure to elemental mercury vapor or methylmercury-contaminated fish (Bjornberg, Vahter, Berglund, Niklasson, Blennow, & Sandborgh-Englund, 2005; Oskarsson, Schutz, Skerfving, Hallen, Ohlin, & Lagerkvist, 1996).
Health Effects of Exposure to Mercury
Mercury exposure can result in wide variety of effects, some of which vary with different mercury species and some of which are universal across the spectrum of mercurials. The effects of all forms of mercury vary with the magnitude and duration of exposure, and with the age and overall health status of the exposed individual or individuals.
The nervous system is the primary target for elemental mercury. Neurological and behavioral disorders in humans have been observed following inhalation of metallic mercury vapor and organic mercury compounds; ingestion or dermal application of inorganic mercury-containing medicinal products such as teething powders, ointments, and laxatives; and ingestion or dermal exposure to organic mercury-containing pesticides or ingestion of contaminated seafood. A broad range of symptoms have been reported, and these symptoms are qualitatively similar, irrespective of the mercury compound to which one has been exposed. Specific neurotoxic symptoms include tremors (initially affecting the hands and sometimes spreading to other parts of the body); emotional lability (characterized by irritability, excessive shyness, confidence loss, and nervousness); insomnia; memory loss; neuromuscular changes (weakness, muscle atrophy, and muscle twitching); headaches; polyneuropathy (paresthesias, stocking-glove sensory loss, hyperactive tendon reflexes, and slowed sensory and motor nerve conduction velocities); and performance deficits in tests of cognitive and motor function. Although improvement has been observed upon removal of persons from the source of exposure, some changes may be irreversible. Autopsy findings of degenerative changes in the brains of poisoned patients exposed to mercury support the functional changes observed (Davis, Wands, Weiss, Price, & Girling, 1974). Extensive distribution of mercury throughout the brain has also been observed following exposure of mice to elemental mercury vapor (Warfvinge, 1995).
Tremors, decrements in nerve function, and cognitive difficulties are sensitive end points for chronic low-level exposure to metallic mercury vapor (Fawer, de Ribaupierre, Guillemin, Berode, & Lob, 1983; Ngim & Davathason, 1989; Ngim, Foo, Boey, & Jeyaratnam, 1992; Urban, Lukas, Nerudova, Cabelkova, & Cikrt, 1999). Photophobia has been reported in children with acrodynia (Fagala & Wigg 1992; Warkany & Hubbard, 1953). Long-term, low-level occupational exposures have been demonstrated to result in decrements in nerve conduction velocity and visual evoked potentials (Urban et al.). Some neurologic effects may be reversible, while others persist for some time after cessation of exposure (Mathiesen, Ellingsen, & Kjuus, 1999).
Exposure to biologically significant levels of elemental mercury can also result in respiratory, renal, immunologic, dermatologi1, and a variety of other effects. While in most cases neurologic effects are the most prominent feature of excessive exposure to mercury vapors, respiratory distress, which may herald the onset of severe lung damage, can also result from extreme exposures, such as the intensive heating of gold-mercury or silver-mercury amalgams (Rowens, Guerrero-Betancourt, Gottlieb, Boyes, & Eichenhorn, 1991). Long-term exposure to both high and low amounts of inorganic mercury can cause renal damage (ATSDR, 1999). Autoimmune effects have been reported in laboratory animals (Bagenstose, Salgame, & Monestier, 1999; Kosuda, Whalen, Greiner, & Bigazzi, 1998; Nielsen & Hultman, 2002; Warfvinge, Hansson, & Hultman, 1995) and humans (Bigazzi, 1999; Silva et al., 2004) following prolonged exposure to inorganic mercury The preponderance of reproductive studies examined by WHO (2003) revealed the absence of such effects resulting from elemental mercury exposure.
A diversity of dermatologic effects has been reported. These effects range from mild rashes and eczema to total body rash or acrodynia (ATSDR, 1999; Bonhomme & Gladyszaczak-Kholer, 1996; Muhlendahl, 1990; Risher et al., 2003; Schwartz, Snider, & Montiel, 1992; Yeates & Mortensen, 1994). The severity of dermal effects depends both on the magnitude and on the duration of exposure, as well as on individual sensitivity to mercury.
Examples of Unintentional Exposures
In addition to the accidental or unintentional types of exposure already mentioned, the following case studies further demonstrate the variability in sources of exposure and the potential health impact for the exposed individual(s).
Rennie, McGregor-Schuerman, Dale, Robinson, and McWilliam (2006) reported the case of a nine-year-old boy who was inadvertently poisoned by leakage of mercury from a hospital sphygmomanometer that had been loaned to the family At initial examination, the boy had presented to a hospital with a three-week history of abdominal pain, constipation, lethargy, limb pain, and unsteadiness. Physical examination revealed mild facial weakness, areflexia, ataxia, impaired sensation, and constant restlessness. Mercury poisoning was confirmed by a serum mercury concentration of 1,000 nmol/L (equivalent to ~200 [micro]g/L). Following treatment with DMPS for 18 days, the serum mercury level dropped by approximately 75 percent and was down to 83 nmol/L (equivalent to ~16.6 [micro]g/L) at day 29. The boy made what was described as a slow neurological recovery, with a period of six months elapsing before his return to his premorbid state. The actual air mercury concentration to which the boy had been exposed was not identified, but the authors reported that "high" atmospheric mercury concentrations were found in the boy's bedroom, particularly around the carpet, prior to remediation.
The case of two half-siblings who were unintentionally exposed to concentrated mercury vapor for three months was reported by Yeates and Mortensen (1994). The poisoning occurred after their family moved into an apartment in which a large jar of elemental mercury had been spilled and improperly cleaned. At the time of first measurement, air mercury levels were found to range from 50 to 400 [micro]g/[m.sup.3]. Both children were treated with DMSA. Pre-chelation 24-hour urine mercury levels were 1,314 [micro]g/L and 624 [micro]g/L for a 15-year-old male and a 13-year-old female, respectively. Admission symptoms and clinical signs experienced by the male included irritability, depression, behavioral problems, tremor, rash, hypertension, cold intolerance, diaphoresis, headache, sleep disturbance, paresthesias, and anorexia. Neurological symptoms and clinical signs experienced by the female were irritability, social withdrawal, emotional lability, tremor, rash, anorexia, paresthesias, and acrodynia. Some neuropsychological deficits persisted one year following treatment.
While there is a wealth of information regarding the effects of methylmercury on fetal development, there are extremely few reports of elemental exposure during pregnancy and of the effects on the developing fetus. Thorp, Boyette, Watson, and Cefalo (1992) reported the case of a 29-year-old woman who had been inadvertently exposed to metallic mercury vapor after moving into a new home in which the previous owner had spilled several containers of mercury onto the carpet. Seventeen weeks into her pregnancy, she sought medical help for her son, who presented to a local university hospital with hypersalivation, tremor, myalgias, irritability, insomnia, and anorexia. A 24-hour urine sample revealed a urine mercury level of 360 [micro]g/L for the child. At that time, the mother's urine mercury level was determined to be 230 [micro]g/L. The woman was reported to be asymptomatic, and neurologic examination was normal. Results from analysis of the air in the home ranged from 20 to 60 [micro]g Hg per cubic meter of air. The woman's urine mercury level declined to 7.5 [micro]g/L at 24 weeks of pregnancy and to 2.7 [micro]g/L at 33 weeks, and was not detectable at 36 weeks. At two years of age, the child had grown appropriately and met all developmental milestones. The authors concluded that elemental mercury appears to pose less of a reproductive threat than the well-known hazards of organic mercurials. Further studies are needed to resolve this apparent difference between inorganic and organic mercurials.
The use of metallic mercury to form an amalgam with gold can also result in significant exposure to humans (Counter, 2003; de Camara, 1997; Hacon et al., 2000; Rojas, Drake, & Roberts, 2001; Silva et al., 2004). De Camara found differences of up to 102.4 [micro]g/L between populations exposed to atmospheric mercury through gold-mining activities and a control population from an agricultural community in Brazil. In some instances, the gold is amalgamated with mercury and taken into the home, where the mercury is melted off, leaving just the gold (Risher et al., 2003). A similar incident, in which the authors became involved, occurred in the state of Nevada in November of 2004. In this case, a 48-year-old male melted the mercury from a mercury-gold amalgamated "rock" over his kitchen stove to free the gold. The heating continued for several hours and resulted in the man experiencing respiratory distress and chest pains within a few hours. The following day, he was taken to the emergency room in a local hospital and placed in the intensive care unit. His urine mercury level at that time was 284 [micro]g/L. He was chelated with succimer (dimercaptosuccinic acid, or DMSA), but chelation was discontinued because of an adverse dermatologic response. At the time of release from the hospital, his urine mercury level remained high (260 [micro]g/L). As a result of this exposure, the man's pulmonary function was degraded by 40 percent, and he continued to suffer from headaches and body pains after a weeklong stay in the hospital. Approximately 3 tablespoons of mercury was subsequently collected from the stovetop where the mercury had been heated.
Examples of Intentional Exposures and Suicide Attempts
Wright, Yeoman, and Carter (1980) reported the intentional exposure of a 17-year-old male who ingested approximately 204 grams of mercury two hours before admission to a hospital. On admission, he was symptom-free, and physical examination and blood analysis were normal. Within three weeks, all mercury had been passed in the feces. During that period, daily urine mercury levels were reported to be normal (all <15 [micro]g/L). The authors concluded that there was no significant absorption of mercury from the GI tract in this patient.
The case of intentional ingestion of approximately 40 grams of mercuric oxide by a 31-year-old was reported by Ly, Williams, and Clark (2002). Soon after ingestion, the man experienced nausea, vomiting, and abdominal cramping. Following administration of activated charcoal and whole-bowel irrigation with polyethylene glycol for 24 hours and 15 days of subsequent chelation, blood chemistry and urine mercury levels were normal. He had an uncomplicated hospital course and remained asymptomatic six months afterward.
The use of mercury in some South American countries in an attempt to enhance athletic performance has been well documented (Ramdial, Jogessar, & Dada, 1999; Smith, Jaffe, & Skinner, 1997; Soo, Wong, Griffith, & Chan, 2003.) The case of a 21-year-old soccer player who deliberately self-administered subcutaneous and intramuscular injections of elemental mercury in an attempt to improve his sporting performance was reported by Ramdial and co-authors (1999). These injections resulted in membranous fat necrosis in the subcutaneous layer. Subcutaneous self-injection of elemental mercury also was reported in the case of a 41-year-old woman with a history of schizophrenia (Soo et al., 2003). Three days following the injections, erythema, swelling, induration, and tenderness were present around the injection sites. Necrotic tissue and mercury were surgically removed, and the patient was chelated with dimercaprol and DMSA.
Attempts at suicide by injection of elemental mercury have been well documented. Intravenous injection has resulted in widespread distribution of elemental mercury throughout the body, including the lungs and brain (Deschamps, Strady, Deslee, Menciere-Faroy, & Deschamps, 2002; Giombetti, Rosen, Kuczmierczyk, & Marsh, 1988; Shareeff, Bhat, Adabala, & Raoof, 2000). Other attempts have involved the subcutaneous injection of elemental mercury, which typically results in skin lesions, tissue necrosis, and a variety of neuropsychologic and other effects, including lethality (Fichte, Ritzau, & Assmann, 1984; Givica-Perez, Santana-Montesdeoca, Diaz-Sanchez, Martinez-Lagares, & Casteneda, 2001; Isik, Guler, Ozturk, & Selmanpakoglu, 1997; Souza, Cintra, Melo, Vieira, De Capitani, & Zambrone, 2000; Zillmer, Lucci, Barth, Peake, & Spyker, 1986).
Medical Uses of Inorganic Mercury
In addition to the long-standing use of elemental mercury in oral thermometers and sphygmomanometers, mercury has been used for medicinal purposes for at least 100 years in the Western world and possibly for centuries or even millennia in Asia. Some of its more significant uses are given in Table 1. In all cases, mercury or its inorganic compounds were used as antimicrobial or antifungal agents in Europe, North America, Australia, and other countries (Al-Saleh & Al-Doush, 1997; Barr, Reese, Cordy, Kungu, Woodger, & Cameron, 1972; Dyall-Smith & Scurry, 1972; Kang-Yum & Oransky, 1992; Millar, 1916; Tunnessen, McMahon, & Baser, 1987; Warkany & Hubbard, 1953; Williams & Bridge, 1958).
Inorganic mercurials have been used topically for treatment of impetigo, syphilis, and psoriasis; as laxatives; and for treatment of other maladies (Bourgeois, Dooms-Goossens, Knockaert, Sprengers, Van Bovens, & Van Titteboom, 1986; Bowman & Rand, 1980; Goodman & Gilman, 2001; O'Shea, 1990; Wands, Weiss, Yardley, & Maddrey, 1974).
Mercurochrome (merbromin-mercuric) also enjoyed widespread usage throughout the 20th century as an effective antiseptic ointment for scrapes and cuts. Mercurous sulfide has been used historically as an effective antibiotic in eardrops. While these mercurials have been employed safely and effectively, prolonged usage or the application of doses above label recommendations may result in untoward effects.
Another currently widespread use of mercury is as a cosmetic or skin-lightening cream (Department of Health and Mental Hygiene [DOHMH], 2005; Flood, McRill, Boer, Ortega, & Roe, 1998; Barr, Woodger, & Rees, 1974). In such preparations, mercurous sulfide or mercurous chloride is typically used. The pharmacologic activity of the skin-light-eners occurs as the mercury blocks the production of melanin pigment in the epithelial melanocytes, thus lightening the skin over time. Because of the continual replacement of epidermal cells, however, this preparation has to be chronically applied, resulting in a potential buildup of mercury in the body, possibly to harmful levels. DOHMH (2005) reported the case of mercury poisoning in a 22-year-old woman who used a skin-lightening cream containing ammoniated mercury. This product, Recetas de la Farmacia Normal--Crema Blanqueadora, which had been brought to the United States from the Dominican Republic, contained 6,190 ppm mercury. Flood and co-authors (1998) reported the use of beauty cream containing mercurous chloride among women in Arizona. Of 89 women submitting urine samples, 66 had urine mercury levels exceeding 20 [micro]g/L, with a mean urine mercury concentration of 170 [micro]g/L. Psychiatric symptoms (not otherwise specified) were reported to be significantly associated with exposure. Approximately 139 days (mean) following termination of the use of the cream, the mean urine mercury level had declined to 32 [micro]g/L, which is consistent with a half-life of about two months.
Mercury also has rather widespread use in some parts of Asia as a traditional folk remedy. Ngim and Devathasin (1989) reported the use of mercury preparations in Singapore for a variety of disorders, including digestive problems, coughing (cough drops or other preparations), sore throat, wound or injury healing, sleep disorders, rheumatism, and hemorrhoids, or as a hypnotic, sedative, or general health aid or "brain tonic." Marcus and Grollman (2002) reported that many herbal products contain undisclosed heavy metals. Of Asian patent medicines sold in the state of California in 1998, 10 to 15 percent contained mercury, lead, or arsenic (Ko, 1998). In another study, it was found that approximately 10 percent of 500 Chinese patent medicines contained undeclared drugs or toxic levels of metals (Au, Ko, Boo, Hsu, Perez, & Yang, 2000).
Montoya-Cabrera, Rubio-Rodriguez, Velazques-Gonzalez, & Avila-Montoya (1991) reported an incident in which an infant with diaper dermatitis and mild respiratory and unspecified enteral infection was treated with a homeopathic mercurial medicine (cinnabar). Following application, the infant became seriously ill, with sequalae including exacerbated and disseminated dermatitis, irritability, and albuminuria. Mercury urine levels obtained post-treatment reached 60 [micro]g/L.
Another source of mercury exposure related to medical practices is the presence of mercury in Ayurvedic herbal-medicine products. Ayurveda is the ancient Indian art of medicine and prolonging life. Its popularity in this country has been increasing over the last 20 years, and Ayurvedic herbal supplements are available over the Internet and through some retail stores. Saper and co-authors (2004) examined a number of retail stores in the Boston, Massachusetts, area to determine the heavy metal content of herbal-medicine products sold in those stores. It was found that six products contained a median mercury concentration of 20,225 [micro]g/g (or 20 parts per thousand), with a range of 28 to 104,000 [micro]g/g.
Biological Markers of Exposure to Mercury
There are multiple biomarkers of mercury exposure, but not all are equally appropriate for individual species of mercury. In the cases of inorganic mercury exposure, including both metallic mercury and inorganic mercury compounds, urine is typically the most appropriate bodily fluid for examination. Inorganic forms of mercury are filtered from the blood in the kidneys in the divalent cationic form and eliminated in the urine. Comparison values for determination of whether the urine mercury level is above or within background levels for the unexposed human population are provided in Table 3. Merely exceeding background values is not, however, an indicator of toxicity. The determination of toxicity cannot be made without a patient examination that includes clinical examination, determination of subjective symptoms, an exposure history, or a combination of these (Risher & Amler, 2005). It is also important that the urine sample be collected in an acid-washed container, and that it be collected before the administration of a chelating agent in the form of a so-called provocative challenge. A 24-hour urine sample is preferred, but a morning first-void may also be considered. Blood may be a useful indicator if the sample is collected within 24 to 48 hours of exposure or in the case of continuing exposure. Since, however, the half-life of inorganic mercury in blood is only ~3 days, blood ceases to be a valuable biomarker a few days after exposure is terminated in most cases (Risher & Amler, 2005).
In summary, there is a broad array of sources from which humans may be exposed to inorganic forms of mercury. The route of exposure, the extent of absorption, the pharmacokinetics, and the effects all vary with the form of mercury and the magnitude and duration of exposure. If exposure is suspected, tissue analyses can be conducted to confirm exposure or to determine whether any exposure might be expected to be biologically significant. In the case of inorganic mercury exposure, including exposure to elemental mercury, urine is the preferred biological medium, with blood normally being of value only if exposure is ongoing. Although treatments are available to help rid the body of inorganic forms of mercury in cases of extreme exposure, prevention of exposure will make such treatments unnecessary. Knowing the sources of mercury and avoiding unnecessary exposure are the prudent ways of preventing mercury intoxication. Finally, it must be kept in mind that while not all exposures will result in adverse health consequences, the elimination of the source of exposure should always be a primary consideration of public health officials.
Corresponding Author: John F. Risher, Senior Science Advisor, ATSDR, Applied Toxicology Branch, Division of Toxicology and Environmental Medicine, F-32, 1600 Clifton Road, Atlanta, GA 30333. E-mail: email@example.com.
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John F. Risher, M.S., Ph.D.
Christopher T. De Rosa, M.S., Ph.D.
TABLE 1 Sources of Nonoccupational Exposure to Mercury* Home/Office/Schools** Medicinal Ethnic or Folk Broken thermometers Dental amalgams ([Hg.sup.0]) Santeria Barometers Skin-lightening creams Espiritismo School science labs ([Hg.sup.+]) Voodoo Sphygmomanometers Ear drops Palo Mayombe Gas regulators Teething powders Chinese folk uses Thermostats Diuretics Mexican folk uses Fluorescent bulbs Laxatives (calomel [Hg.sub.2] Wall light switches [cl.sub.2]) Paints Other cosmetics Tatoo inks Merbromin-mercuric Camera batteries (mercurochrome) * Source: ATSDR (1999). ** Mercury-free versions of many of these items are now available. TABLE 2 Absorption Versus Routes of Exposure* Route of Exposure Elemental Mercury Inorganic Salts Oral Less than <0.01% ~10% Dermal Virtually none absorbed Virtually none absorbed Inhalation ~80% Only as dusts in some occupational scenarios *Source: ATSDR (1999). TABLE 3 Biomarkers and Comparison Values for Inorganic Mercury Biomarker Reason Comparison Value* Urine Primary route of excretion 5 [micro]g Hg per liter of urine for both elemental-mercury 3.27 [micro]g Hg per gram of and inorganic-mercury creatinine compounds Blood Reliable indicator for only 7.1 [micro]g Hg per liter of very recent or ongoing blood exposure; half-life in blood ~ 3 days * Values listed represent 95th-percentile values from NHANES 1999 (CDC, 1999, 2003). These values do not represent threshold values for toxicity, but rather represent the results of data collected from over 1,700 U.S. females not known to be previously exposed to mercury.
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|Author:||Risher, John F.; De Rosa, Christopher T.|
|Publication:||Journal of Environmental Health|
|Article Type:||Author abstract|
|Date:||Nov 1, 2007|
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