Mercury derived from dental amalgams and neuropsychologic function. (Environmental Medicine).There is widespread concern regarding the safety of silver-mercury amalgam dental restorations, yet little evidence to support their harm or safety. We examined whether mercury dental amalgams dental amalgam Dentistry A filling material that contains up to 50% mercury, silver and other metals. See Alternative dentistry, Fluoridation, Gutta percha, Mercury. are adversely associated with cognitive functioning cognitive function Neurology Any mental process that involves symbolic operations–eg, perception, memory, creation of imagery, and thinking; CFs encompasses awareness and capacity for judgment in a cross-sectional sample of healthy working adults. We studied 550 adults, 30-49 years of age, who were not occupationally exposed to mercury. Participants were representative of employees at a major urban medical center. Each participant underwent a neuropsychologic test battery, a structured questionnaire, a modified dental examination, and collection of blood and urine samples. Mercury exposure was assessed using a) urinary mercury concentration (UHg); b) the total number of amalgam surfaces; and c) the number of occlusal occlusal /oc·clu·sal/ (o-kloo´z'l)
1. pertaining to the masticating surfaces of the premolar and molar teeth.
1. amalgam surfaces. Linear regression Linear regression
A statistical technique for fitting a straight line to a set of data points. analysis was used to estimate associations between each marker of mercury exposure and each neuropsychologic test, adjusting for potential confounding variables. Exposure levels were relatively low. The mean UHg was 1.7 [micro]g/g creatinine creatinine /cre·at·i·nine/ (kre-at´i-nin) an anhydride of creatine, the end product of phosphocreatine metabolism; measurements of its rate of urinary excretion are used as diagnostic indicators of kidney function and muscle mass. (range, 0.09-17.8); the mean total number of amalgam surfaces was 10.6 (range, 0-46) and the mean number of occlusal amalgam surfaces was 6.1 (range, 0-19). No measure of exposure was significantly associated with the scores on any neuropsychologic test in analyses that adjusted for the sampling design and other covariates. In a sample of healthy working adults, mercury exposure derived from dental amalgam restorations was not associated with any detectable deficits in cognitive or fine motor functioning. Key words: attention, cognition, dental amalgams, memory, mercury exposure, neuropsychologic function. Environ Health Perspect 111:719-723 (2003). doi:10.1289/ehp.5879 available via http://dx.doi.org/[Online 13 November 2002]
Despite widespread concern about the safety of silver-mercury amalgam dental restorations (Skare and Engqvist 1994), there is little evidence regarding harm or safety in the general population. Dental amalgams have been used for over 150 years with no overt adverse effects. Nevertheless, a 1991 American Dental Association American Dental Association (ADA),
n.pr a nonprofit professional association whose membership is dental professionals in the United States. Its purpose is to assist its members in providing the highest professional and ethical care to the citizens of the survey of 1,000 adults found that 50% thought amalgam restorations might have adverse effects (Gerbert et al. 1992). A similar survey of dentists found that although 89% of respondents believed that amalgams posed no risk, 52% reported that they would replace such restorations at a patient's request (Gerbert et al. 1992). Reviews in both the scientific and lay literature link amalgam restorations to severe psychiatric, neurologic, and immunologic effects (Anonymous 1991; Fung and Molvar 1992; Hanson and Pleva 1991; Weiner et al. 1990).
Severe chronic occupational exposure to elemental mercury ([Hg.sup.0]) vapor has been associated with a constellation of neuropsychologic symptoms, the "Mad Hatter Syndrome Mad Hatter syndrome
A complex of disorders resulting from chronic mercury poisoning including stomatitis, diarrhea, ataxia, tremor, hyperreflexia, sensorineural impairment, and emotional instability. ." Amalgam restorations are approximately 50% inorganic mercury ([Hg.sup.0]), and systemic absorption of [Hg.sup.0] vapor from amalgams is well demonstrated (Berlin 1969; Berlin et al. 1975; Hurch et al 1980; Newton and Fry 1978; Takahata et al. 1970; Wantanbe 1969). Occupational exposure in dentists is associated with intentional tremor tremor /trem·or/ (trem´er) an involuntary trembling or quivering.
action tremor rhythmic, oscillatory, involuntary movements of the outstretched upper limb; it may also affect the voice and of muscles responsible for fine motor tasks, personality changes, behavioral changes, memory loss, increased excitability excitability
readiness to respond to a stimulus; irritability. , and severe depression (Echeverria et al. 1995; Ngim et al. 1992). No data are available to assess possible neurotoxic neurotoxic
pertaining to or emanating from a neurotoxin.
a case of poisoning by a neurotoxin.
neurotoxic adjective effects related to levels of amalgam-derived exposure found in the general population.
The present report draws on a cross-sectional sample of working adults, 30-49 years of age, that was designed to examine whether amalgam-derived mercury exposure is associated with cognitive functioning, including memory, attention and executive function, and visuomotor visuomotor /vis·uo·mo·tor/ (-mo´ter) pertaining to connections between visual and motor processes.
Of or relating to motor activity dependent on or involving sight. and visuospatial visuospatial /vis·uo·spa·tial/ (-spa´shal) pertaining to the ability to understand visual representations and their spatial relationships.
adj. coordination. Exposure was assessed using the total number of visible amalgam surfaces and the number of visible occlusal amalgam surfaces, and by urinary mercury concentration (UHg).
Materials and Methods
The Columbia-Presbyterian Institutional Review Board approved the protocol and informed consent documents for this study. Between September 1997 and December 1999, we invited a random sample of 1,966 employees at a university health center to participate in a study titled "Dental Health and General Well-Being." We used a stratified stratified /strat·i·fied/ (strat´i-fid) formed or arranged in layers.
Arranged in the form of layers or strata. random sampling of the personnel roster to select a sample with equal numbers in four strata defined by age (30-39 or 40-49 years) and employment status (professional or support staff). Older employees were not studied because, on average, the total number of amalgam surfaces declines after 50 years of age because of the loss of teeth (National Institute of Dental Research 1987). After excluding 229 noneligible persons, 550 (32%) agreed to participate in a 90-min evaluation that included collection of urine and blood samples, a questionnaire, and a neuropsychologic battery. We excluded personnel no longer employed at the medical center, dental personnel, non-English speakers, and pregnant women.
Participants. Compared with nonparticipants, participants were less likely to be professional staff and less likely to be male (Table 1). One hundred nonparticipants agreed to complete a brief telephone interview to obtain basic demographic data (not the full questionnaire). They were similar to participants with regard to Hispanic origin and educational attainment Educational attainment is a term commonly used by statisticans to refer to the highest degree of education an individual has completed.
The US Census Bureau Glossary defines educational attainment as "the highest level of education completed in terms of the , but were slightly more likely to be white and less likely to be Asian.
Data collection. Informed consent was obtained by one of four trained interviewers. Spot urine samples were obtained for the measurement of UHg and creatinine. A specially trained dentist performed a modified oral examination. An interview obtained information on demographic and social characteristics, occupational exposures, lifestyle behaviors (smoking, alcohol consumption, caffeine consumption, and gum-chewing behavior), bruxism Bruxism Definition
Bruxism is the habit of clenching and grinding the teeth. It most often occurs at night during sleep, but it may also occur during the day. It is an unconscious behavior, perhaps performed to release anxiety, aggression, or anger. , and health history. Each subject completed a neuropsychologic battery in the clinical research unit. The neuropsychologic tests were administered in a fixed order.
Laboratory assays. UHg was determined by flow-injection cold vapor atomic absorption spectrometry Absorption spectrometry
A scientific procedure to determine chemical makeup of samples.
Mentioned in: Herbalism, Traditional Chinese (Guo and Baasner 1993) by one technician. The laboratory participated in the quality control program for UHg run by Jean Phillippe Weber of the Centre de Toxicologie du Quebec. Over the full range (i.e., 5-1,000 nmol/L) of standards analyzed, agreement was excellent [intraclass correlation In statistics, the intraclass correlation (or the intraclass correlation coefficient) is a measure of correlation, consistency or conformity for a data set when it has multiple groups. coefficient (ICC ICC
See: International Chamber of Commerce ) = 0.99]. Agreement was also excellent (ICC = 0.99) when data were reanalyzed over the low end of concentration (5-200 nmol/L). All UHgs were adjusted for urinary creatinine and measured using quantitative colorimetric col·or·im·e·ter
1. Any of various instruments used to determine or specify colors, as by comparison with spectroscopic or visual standards.
2. determinations (Sigma Diagnostics Creatinine Kit; Sigma-Aldrich, St. Louis, MO), a modification of the Jaffe reaction Jaffe reaction
a method of creatinine assay based on the orange-red color produced by creatinine reacting with alkaline picrate. (Heinegard and Tiderstrom 1973; Jaffe 1886).
Modified dental examination. Four specially trained dentists performed structured modified oral examinations to assess the number of teeth present and the number and location of all restorations. All examinations required only tongue depressors; teeth were not probed physically. Prior to the study, interobserver reliability was assessed in 49 clinic patients by having each examiner compared with an expert dentist. Overall agreement for amalgam counts, both total and occlusal, was excellent (ICCs from 0.93 to 0.99).
Neuropsychologic battery. Participants were evaluated on a neuropsychologic battery comprising widely used and well-standardized tests. Specific cognitive domains assessed and measures administered were based upon reports of neuropsychologic impairments in occupational studies (Albers et al. 1988; Echeverria et al. 1995; Langolf al. 1978; Ngim et al. 1992; Ritchie et al. 1995; Roels et al. 1982; Smith et al. 1970, 1983). Specifically, verbal memory, nonverbal non·ver·bal
1. Being other than verbal; not involving words: nonverbal communication.
2. Involving little use of language: a nonverbal intelligence test. memory, attention, and fine motor coordination Gross motor coordination addresses the gross motor skills: walking, running, climbing, jumping, crawling, lifting one's head, sitting up, etc.
Fine motor coordination were assessed. We used the Selective Reminding Test (SRT (1) (Source Routing Transparent) An IEEE-standard that provides bridging between Ethernet and Token Ring networks. Ethernet LANs use transparent bridging, and Token Ring LANs use source route bridging (SRB). )-total recall measure (Buschke and Fudd 1974), in which subjects have six trials to learn a 12-word list, to assess verbal memory. To assess nonverbal memory, we used the Benton Visual Retention Test-immediate recall condition (BVRT BVRT Benton Visual Retention Test
BVRT British Vita Racing and Tuning ) (Benton 1974), in which subjects are given a 10-sec exposure to each of 10 designs, with immediate recall by drawing.
The Trail-Making Test trail-making test Reitan's test A two-part test for assessing motor speed and integration, in which multiple dots are connected to form various objects; like the Bender-Gestalt test, the 'Trail-maker' screens for gross organic defects. See Psychological testing. (Reitan 1958) and the digit symbol subtest of the Wechsler Adult Intelligence Scale-Revised Wechsler Adult Intelligence Scale-Revised WAIS-R Psychology A measure of a person's cognitive abilities. See Psychological tests. (WAIS-R WAIS-R Wechsler Adult Intelligence Scale-Revised, see there ) (Wechsler 1981) assessed attention and psychomotor psychomotor /psy·cho·mo·tor/ (si?ko-mo´ter) pertaining to motor effects of cerebral or psychic activity.
1. speed. The Trail-Making Test is given in two parts, and time to complete each task is measured. In part A, the participant is presented with a page of randomly organized numbers and is asked to draw a line connecting them in consecutive order. In part B, the participant is presented with a page containing both numbers and letters and is asked to connect them in order, but alternating between numbers and letters (i.e., 1-A, 2-B, etc.). The digit symbol subtest of the WAIS-R is considered a nonspecific nonspecific /non·spe·cif·ic/ (non?spi-sif´ik)
1. not due to any single known cause.
2. not directed against a particular agent, but rather having a general effect.
1. yet sensitive indicator of subtle brain dysfunction. For successful performance, participants must efficiently integrate attentional, executive, perceptual, and motor skills. The test consists of rows of blank squares, each paired with a random digit from 1 to 9. Above these rows is a printed key pairing each digit to a nonsense symbol. The participant fills in as many as possible blank spaces according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. the key in 90 sec. The raw score represents the number of squares filled in correctly in the allotted al·lot
tr.v. al·lot·ted, al·lot·ting, al·lots
1. To parcel out; distribute or apportion: allotting land to homesteaders; allot blame.
2. time. We used age-corrected scores, with a mean of 10 and a standard deviation In statistics, the average amount a number varies from the average number in a series of numbers.
(statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. of 3, in analyses.
We used the Grooved Pegboard (Klove 1963; Matthews and Klove 1964) to assess fine motor coordination. This task was administered once with the dominant hand and once with the nondominant hand. The test is scored as time to completion of the placement of grooved pegs into a 25-hole board.
Four trained testers, blinded to the results of the UHg assay, administered all neuropsychologic assessments. A random sample of test sessions was observed by an expert neuropsychologist Neuropsychologist
A clinical psychologist who specializes in assessing psychological status caused by a brain disorder.
Mentioned in: Post-Concussion Syndrome to ensure reliability of test administration. To ensure scoring accuracy, two examiners scored all batteries; the correlation measuring agreement was 99%.
Statistical analysis. Associations between each exposure measure (UHg, total number of amalgam restorations, number of occlusal amalgam restorations) and each neuropsychologic test were estimated using linear regression analysis. Analyses were adjusted for known predictors of neuropsychologic performance and demographic characteristics associated with the exposure variables. All analyses were adjusted for sampling stratum stratum /stra·tum/ (strat´um) (stra´tum) pl. stra´ta [L.] a layer or lamina.
stratum basa´le as a four-category indicator variable (support staff 30-39 years of age, support staff 40-49 years of age, professional staff 30-39 years of age, and professional staff 40-49 years of age). Depending on the outcome, we controlled for age, sex, race/ethnicity, first language (English/other), U.S. born (yes/no), job description, and educational level (high school graduate, some college, college graduate, master's degree master's degree
An academic degree conferred by a college or university upon those who complete at least one year of prescribed study beyond the bachelor's degree.
Noun 1. , doctoral degree) in the regression model.
We conducted confirmatory analyses that used number of total or occlusal amalgam restorations excluding restorations that were sized as "pinprick pinprick Neurology A sharply focused stimulation of the skin, often by a needle, used to evaluate the sense of touch ." Analyses were repeated excluding the 43 subjects with more than four missing teeth not attributable to either orthodontic orthodontic (ôr´thdän´tik),
adj reasons or to removal of third molars. We also assumed that these teeth had a range of amalgam restorations. Results were essentially identical to the main analyses and are not presented.
Mercury exposure. Results for the characteristics of mercury exposure are shown in Table 2. The mean UHg was 1.7 [micro]g/g creatinine and ranged between 0.09 and 17.8 [micro]g/g creatinine. Fewer than 5% of participants had UHg > 5 [micro]g/g creatinine. Mean UHg and mean numbers of total and occlusal amalgams varied by sampling strata, with older officers and support staff having higher UHg and more restorations. Approximately 14% of participants had no amalgam restorations. The numbers of total and occlusal amalgams were linearly related to UHg (Figure 1) (r = 0.46, p < 0.0001); mean UHg in those with 0 amalgam surfaces and those with > 15 were 0.75 and 2.9 [micro]g/g creatinine, respectively.
Neuropsychologic tests. Results of the neuropsychologic battery are shown in Table 3. The mean scores of each neuropsychologic test were within the norms for the ages studied, and the scores followed the pattern expected by age. Professional staff performed better than support staff on the entire test battery in both age strata.
Associations between other covariates and neuropsychologic battery. Bivariate bi·var·i·ate
Mathematics Having two variables: bivariate binomial distribution.
Adj. 1. associations between potential confounders and neuropsychologic scores were as expected. Women performed better on tests of verbal and nonverbal memory (Lezak 1995) and on the digit symbol test (Kaufman et al. 1988; Snow and Weinstock 1990). Increasing education was associated with better scores on all tests (Lezak 1995).
Associations between mercury exposure and neuropsychologic scores. UHg was not associated with any measure of neuropsychologic performance (Table 4), either in analyses that adjusted only for sampling strata or in analyses that also adjusted for covariates. The results were essentially the same when UHg was replaced by its logarithmic logarithmic
pertaining to logarithm.
when the logs of two variables plotted against each other create a straight line. transformation.
Mean scores, adjusted for covariates and sampling strata, on the SRT for subjects with UHg above and below the median (1.29 [micro]g/g creatinine) were 53.0 and 52.1, respectively. Adjusted mean scores on the BVRT were 7.5 and 7.7, respectively. No differences were found for the WAIS-R digit symbol (11.4 vs. 11.3), Trail-Making B (68.0 vs. 69.7), and the Grooved Pegboard for the dominant (65.2 vs. 65.3) and nondominant (70.3 vs. 70.6) hands.
Similarly, no associations between counts of either total or occlusal amalgams and neuropsychologic performance were found (Table 4). Adjusted mean scores for subjects with more or less than the median numbers of total amalgams were 52.6 and 52.5, respectively, on the SRT and 7.4 and 7.8, respectively, on the BVRT. In addition, no differences were found for the WAIS-R digit symbol (11.4 vs. 11.3), Trail-Making B (68.6 vs. 69.1), and the Grooved Pegboard for the dominant (66.4 vs. 64.4) and nondominant (71.2 vs. 69.9) hands. Results were similar in parallel analyses of occlusal amalgams.
The results were unchanged in analyses that excluded all pinpoint amalgams, regardless of tooth surface The tooth surface (flank) forms the side of a gear tooth.1
It is convenient to choose one face of the gear as the reference face and to mark it with the letter “I”. The other non-reference face might be termed face “II”. . Results of the sensitivity analyses for the missing teeth also were unchanged.
In our sample of working adults, exposure to mercury from dental amalgams was not associated with cognitive dysfunction. Specifically, performance on tests of verbal and nonverbal memory, attention and psychomotor speed, and fine motor coordination were not associated with UHg. This sample excluded persons with occupational exposure to mercury; thus, our results should not be generalized to this group.
Exposure levels in our sample were low; mean UHg was 1.7 [micro]g/g creatinine. In comparison, UHg in persons occupationally exposed ranges between 2.0 and 60 [micro]g/g creatinine and varies with occupation. Dentists and dental workers have lower UHg (range, 2.0-45 [micro]g/g creatinine) (Bittner et al. 1998; Cianciola et al. 1997; Naleway et al. 1985, 1991; Ritchie et al. 1995; Steinberg et al. 1995; Woods et al. 1993) than workers in chloralkali or other factories that use mercury (range, 50-116 [micro]g/g creatinine) (Bernard et al. 1980; Buchet et al. 1980; Ellingsen et al. 2000, 2001; Hansteen et al. 1993; Lauwerys and Buchet 1973; Roels et al. 1985). Occupational studies that include unexposed employees as controls have found UHg similar to ours (range, 0.9-1.4 [micro]g/g creatinine) (Bernard et al. 1980; Buchet et al. 1980; Ellingsen et al. 2000; Hansteen et al. 1993; Lauwerys and Buchet 1973; Roels et al. 1985). In a healthy male military population with an average age of 53 years, UHg was also comparable (1.8 [micro]g/g creatinine) (Kingman et al. 1998). Some reports suggest that, in a minority of individuals, parafunctional behaviors (chewing and grinding) are associated with increased UHg (Barregard et al. 1995; Mackert 1987; Vimy et al. 1988). Our data do not confirm these reports, perhaps because the prevalence of these behaviors was very low. Nevertheless, our results may not be generalizable gen·er·al·ize
v. gen·er·al·ized, gen·er·al·iz·ing, gen·er·al·iz·es
a. To reduce to a general form, class, or law.
b. To render indefinite or unspecific.
2. to such individuals because their exposure may be closer to that in occupational groups, where associations between exposure to mercury and neuropsychologic performance are reported.
Numbers of amalgam surfaces, total and occlusal, were lower than reported in previous U.S. samples. In the first National Health and Nutrition Examination Survey (NHANES NHANES National Health and Nutrition Examination Survey (US CDC) I) performed between 1971 and 1974, the average numbers of decayed, missing, and filled surfaces were 25.7 and 55.5 in those 30-34 and 45-49 years of age, respectively (Brown and Swango 1993). Similar means were found in the 1985/1986 National Institute of Dental Research survey of employed adults and seniors (National Institute of Dental Research 1987). Our lower numbers likely reflect the increased prevalence of water fluoridation Water fluoridation is the practice of adding fluoride compounds to water with the intended purpose of reducing tooth decay in the general population. Many North American and Australian municipalities fluoridate their water supplies in the belief that this practice will reduce tooth and increased use of fluoride fluoride, a salt of hydrofluoric acid; see hydrogen fluoride. See also fluoridation; fluorine. supplementation. Our results (Figure 1) confirm the previously observed linear association between number of amalgams and UHg (Kingman et al. 1998).
Our data show the expected relationships between several covariates, namely, employment strata, age, sex, and education, and performance on the neuropsychologic tests. These associations enhance our confidence in the data.
Unlike our study, where exposure levels were very low, occupational studies of workers in the thermometer thermometer, instrument for measuring temperature. Galileo and Sanctorius devised thermometers consisting essentially of a bulb with a tubular projection, the open end of which was immersed in a liquid. and chloralkali industries find associations between UHg level and both neurologic and neuropsychologic deficits (Albers et al. 1988; Ehrenberg et al. 1991; Fawer et al. 1983; Herber et al. 1988; Langolf et al. 1978, 1981; Miller et al. 1975; Piikivi and Hanninen 1989; Ritchie et al. 1995; Roels et al. 1982; Smith and Langolf 1981; Smith et al. 1970, 1983). Neurologic deficits include increased intention and resting tremor (Albers et al. 1988; Ehrenberg et al. 1991; Fawer et al. 1983; Langolf et al. 1978, 1981; Roels et al. 1982; Smith et al. 1970), balance (Ehrenberg et al. 1991), and sensory and motor peripheral nerve dysfunction (Albers et al. 1982; Langolfet al. 1978; Levine et al. 1982; Miller et al. 1975; Singer et al. 1987). Current exposure was associated with decreased scores on the WAIS-R digit symbol subtest and the BVRT (Ellingsen et al. 2001). Two studies suggest long-lasting impairment of function 20-35 years after exposure ceased, indicating that cumulative, rather than recent, exposure is important (Fawer et al. 1983; Mathiesen et al. 1999). Studies evaluating neuropsychologic performance find associations between UHg and deficits in nonverbal memory, attention, and psychomotor coordination (Herber et al. 1988; Piikivi and Hanninen 1989; Ritchie et al. 1995; Smith and Langolf 1981; Smith et al. 1983).
Dentists and dental workers, who have exposure levels substantially lower than occupational workers, exhibit deficits in visuospatial skills, verbal and nonverbal memory, attention, logical reasoning The three methods for logical reasoning, deduction, induction and abduction can be explained in the following way: 
Given preconditions α, postconditions β and the rule R1: α ∴ β (α therefore β). , response time and psychomotor coordination, and increases in tremor (Bittner et al. 1998; Ngim et al. 1992; Ritchie et al. 1995). These data suggest that dose-response relationships may begin at UHg levels found in U.S. dentists (4.6-8.1 [micro]g/g creatinine) (Naleway et al. 1991). Echeverria et al. (1998) reported associations between mercury exposure and motor function, cognition, and self-reported symptoms and mood in their study of dental personnel receiving a challenge chelation Chelation
The process by which a molecule encircles and binds to a metal and removes it from tissue.
Mentioned in: Heavy Metal Poisoning
chelation test (which has not been validated as a measure of mercury exposure). Mean UHg in that study was 0.9 [micro]g/L before and 9.1 [micro]g/L after chelation (unadjusted for creatinine, although urine was collected for only 11 hr before and 6 hr after chelation).
Our power calculations indicated excellent power to detect small associations. Using a conservative significance level of 0.01, we had 80% power to detect 0.29 standard deviation units difference in neuropsychologic test score for those above the median exposure levels, and 90% power to detect 0.33 standard deviation units.
We considered the temporal relationship between placement of amalgams and neuropsychologic performance. Although cross-sectional studies are notable to derive temporal precedence, we may safely assume that the placement of amalgams and the resultant exposure to mercury preceded the outcomes. Most amalgams are first placed during the teenage years, and relatively few are placed after the age of 25 years.
We also considered the possibility of confounding confounding
when the effects of two, or more, processes on results cannot be separated, the results are said to be confounded, a cause of bias in disease studies.
confounding factor by social class in childhood, because both dental care and neuropsychologic performance may be related to parental education and occupation. However, no associations between educational attainment and parental occupations up until the participant was 13 years of age and either the number of amalgams or neuropsychologic performance were found in the adult child. We also included these variables in the regression analysis In statistics, a mathematical method of modeling the relationships among three or more variables. It is used to predict the value of one variable given the values of the others. For example, a model might estimate sales based on age and gender. ; in no case did their inclusion (either individually or together) change the regression coefficient Regression coefficient
Term yielded by regression analysis that indicates the sensitivity of the dependent variable to a particular independent variable. See: Parameter.
regression coefficient relating mercury exposure to neuropsychologic test performance.
One limitation of this study is the absence of data on when the amalgams were placed, removed, or replaced. Most amalgam fillings were probably placed 10-20 years ago. Although it was possible to obtain the name of and permission to contact the participants' current family dentists, it was unlikely that participants would remember the name and addresses of all dentists seen over the 20-year period.
Finally, it is well known that exposure to high concentrations of organic mercury (notably methyl mercury) via fish and seafood consumption, such as those found in the Minimata Bay episode, is associated with neuropsychologic deficits in children (Igata 1991). Those findings, however, were not confirmed in more recent studies in the Faroe Islands Faroe Islands
or Faeroe Islands
Group of islands in the Atlantic Ocean that form a self-governing region of Denmark. Area: 540 sq mi (1,399 sq km). Population: (2002 est.) 47,400. (Grandjean et al. 1997) and Seychelles Islands Noun 1. Seychelles islands - a group of about 90 islands in the western Indian Ocean to the north of Madagascar
Republic of Seychelles, Seychelles - a republic on the Seychelles islands; achieved independence from the United Kingdom in 1976 (Palumbo et al. 2000) in the lowest exposure groups (which ate likely to reflect levels found in U.S. children). We obtained data related to usual consumption of fish and other seafood, but we did not measure methyl mercury in the blood for two reasons. First, blood mercury represents relatively recent exposure and would yield little information regarding lifetime exposure history. Second, among participants, seafood consumption was distributed randomly across persons with few of many amalgams (data not shown). Our biological measure of exposure, UHg, also likely includes some organic mercury exposure organic mercury exposure,
n mercury exposure from dietary sources such as seafood. .
The benefits of amalgams over other currently available restorative re·stor·a·tive
1. Of or relating to restoration.
2. Tending or having the power to restore.
A medicine or other agent that helps to restore health, strength, or consciousness. materials have been well described (Dodes 2001). Given the level of concern regarding amalgam safety among the public and dental profession, our results are reassuring in that exposure to amalgam-derived mercury is not associated with detectable subtle neuropsychologic deficits.
Table 1. Characteristics of study participants and nonparticipants. Nonparticipants Without telephone Participants interviews (a) No. of subjects 550 1,087 Professional staff (%) 53 70 Male (%) 38 47 Mean age [+ or -] SD 38.8 [+ or -] 5.8 39.7 [+ or -] 5.8 White (%) 40 -- (b) African American (%) 13 -- Asian (%) 21 -- Other/unknown (%) 26 -- Hispanic origin (c) (%) 21 -- Less than 4-year college degree (%) 26 -- 4-year college degree (%) 12 -- Master's degree (%) 23 -- Doctoral degree (%) 39 -- Nonparticipants Responded to the telephone interview No. of subjects 100 Professional staff (%) 57 Male (%) 45 Mean age [+ or -] SD 39.4 [+ or -] 6.4 White (%) 47 African American (%) 12 Asian (%) 9 Other/unknown (%) 32 Hispanic origin (c) (%) 22 Less than 4-year college degree (%) 24 4-year college degree (%) 22 Master's degree (%) 13 Doctoral degree (%) 38 (a) Nonparticipants were asked to answer a brief 5-min telephone questionnaire, which obtained data only on basic demographic characteristics. (b) Data were not obtained for nonparticipants who refused the telephone interview. (c) Asked independently from race. Table 2. Elemental mercury exposure characteristics of healthy, working, nonoccupationally exposed adults. No. of participants Mean [+ or -] SD UHg ([micro]g/g creatinine) 542 1.7 [+ or -] 1.7 No. of total amalgam surfaces (a) 511 (b) 10.6 [+ or -] 9.0 No. of occlusal amalgam surfaces 511 6.1 [+ or -] 4.5 No. of nonocclusal amalgam surfaces 511 4.5 [+ or -] 5.2 Median Range UHg ([micro]g/g creatinine) 1.3 0.09-17.8 No. of total amalgam surfaces (a) 10 0-46 No. of occlusal amalgam surfaces 6 0-19 No. of nonocclusal amalgam surfaces 3 0-32 (a) Assessed during a noninvasive modified dental examination as described in "Materials and Methods." (b) Dental assessments missing on 39 participants. Table 3. Results (mean [+ or -] SD) of neuropsychologic tests in 550 study participants 30-39 or 40-49 years of age. Overall sample Test (n = 547-549) SRT total recall (no. correct) 52.52 [+ or -] 8.37 BVRT (no. correct) 7.62 [+ or -] 1.84 WAIS digit symbol (age- scaled score) 11.38 [+ or -] 2.63 Trail-Making Test, condition A (time, seconds) 32.17 [+ or -] 13.11 Trail-Making test, condition B (time, seconds) 68.89 [+ or -] 29.60 Grooved Pegboard, dominant hand (time, seconds) 65.26 [+ or -] 13.63 Grooved Pegboard, nondominant hand (time, seconds) 70.46 [+ or -] 15.29 Support staff 30-39 years 40-49 years Test (n = 168-169) (n = 91-92) SRT total recall (no. correct) 52.28 [+ or -] 8.54 48.31 [+ or -] 8.78 BVRT (no. correct) 7.55 [+ or -] 1.78 6.54 [+ or -] 2.15 WAIS digit symbol (age- scaled score) 11.03 [+ or -] 2.92 10.01 [+ or -] 1.98 Trail-Making Test, condition A (time, seconds) 31.86 [+ or -] 12.66 40.84 [+ or -] 17.11 Trail-Making test, condition B (time, seconds) 70.80 [+ or -] 26.23 87.38 [+ or -] 40.96 Grooved Pegboard, dominant hand (time, seconds) 63.05 [+ or -] 11.27 73.38 [+ or -] 20.74 Grooved Pegboard, nondominant hand (time, seconds) 69.97 [+ or -] 14.76 78.12 [+ or -] 21.15 Professional staff 30-39 years 40-49 years Test (n = 157-158) (n = 129-131) SRT total recall (no. correct) 54.90 [+ or -] 6.90 52.89 [+ or -] 8.41 BVRT (no. correct) 8.30 [+ or -] 1.42 7.66 [+ or -] 1.77 WAIS digit symbol (age- scaled score) 11.99 [+ or -] 2.40 12.06 [+ or -] 2.48 Trail-Making Test, condition A (time, seconds) 27.80 [+ or -] 9.85 31.73 [+ or -] 10.90 Trail-Making test, condition B (time, seconds) 58.25 [+ or -] 22.31 66.21 [+ or -] 25.89 Grooved Pegboard, dominant hand (time, seconds) 60.80 [+ or -] 7.97 67.82 [+ or -] 12.61 Grooved Pegboard, nondominant hand (time, seconds) 64.41 [+ or -] 9.52 73.02 [+ or -] 13.76 Table 4. Estimated adjusted regression coefficients of each exposure variable for each neuropsychologic test. UHg ([miro]g/g creatinine) Test [beta] (a), SE([beta]) (b) SRT total recall (no. correct) (e) -0.020 0.194 BVRT recall condition (no. correct) (f) -0.040 0.040 WAIS-R digit symbol (age-adjusted scores) (g) -0.038 0.056 Trail-Making test: A [time to completion (seconds)] (h) 0.120 0.320 Trail-Making test: B [time to completion (seconds)] (i) -0.372 0.703 Grooved Pegboard: dominant hand [time to completion (seconds)] (j) -0.428 0.339 Grooved Pegboard: nondominant hand [time to completion (seconds)] (k) -0.323 0.380 Total number of amalgams [beta] (c) SE([beta]) SRT total recall (no. correct) (e) 0.033 0.041 BVRT recall condition (no. correct) (f) -0.004 0.009 WAIS-R digit symbol (age-adjusted scores) (g) -0.001 0.012 Trail-Making test: A [time to completion (seconds)] (h) -0.004 0.068 Trail-Making test: B [time to completion (seconds)] (i) 0.081 0.143 Grooved Pegboard: dominant hand [time to completion (seconds)] (j) 0.085 0.071 Grooved Pegboard: nondominant hand [time to completion (seconds)] (k) -0.030 0.079 Number of occlusal amalgams [beta] (d) SE ([beta]) SRT total recall (no. correct) (e) 0.049 0.081 BVRT recall condition (no. correct) (f) -0.018 0.017 WAIS-R digit symbol (age-adjusted scores) (g) -0.016 0.023 Trail-Making test: A [time to completion (seconds)] (h) -0.052 0.135 Trail-Making test: B [time to completion (seconds)] (i) 0.323 0.283 Grooved Pegboard: dominant hand [time to completion (seconds)] (j) 0.189 0.140 Grooved Pegboard: nondominant hand [time to completion (seconds)] (k) -0.044 0.155 (a) Estimated adjusted regression coefficient. (b) Change in test score per unit increase in UHg ([micro]g/g creatinine). (c) Change in test score per unit increase in the total number of amalgams. (d) Change in test score per unit increase in the number of occlusal amalgams. (e) Adjusted for age, position (professional, support staff), sex, education, and English as a first language. (f) Adjusted for age, position (professional, support staff), job category (maintenance, facilities, security; clerks, receptionists, secretaries; engineers, research technicians; nurses, physicans' assistants, social workers, managers, attorneys; scientists, educators; physicians, psychologists, dentists), and English as a first language. (g) Adjusted for age, position, sex, education, ethnic group, U.S. born, and job category. (h) Adjusted for age, position, education, ethnic group, and U.S. born. (i) Adjusted for age, position, sex, education, ethnic group, and English as a first language. (j) Adjusted for age, position, sex, education, and ethnic group. (k) Adjusted for age, position, education, and ethnic group.
Albers JW, Cavender GD, Levine SP, Langolf GD. 1982. Asymptomatic sensorimotor polyneuropathy sensorimotor polyneuropathy Neurology A peripheral neuropathy characterized by ↓ movement or sensation, due to nerve damage; SP is a systemic process that damages nerves, with loss of myelin, which slows neural conduction or damages neurons, especially the in workers exposed to elemental mercury. Neurology 32:1168-1174.
Albers JW, Kallenbach LR, Fine LJ, Langolf GD, Wolfe RA, Donofrio PO, et al. 1988. Neurological abnormalities associated with remote occupational mercury exposure. Ann Neurol 24:651-659.
[Anonymous.] 1991. The Mercury in Your Mouth. Consumer Reports (May):316-319.
Barregard L, Sallsten G, Jarvholm B. 1995. People with high mercury uptake from their own dental amalgam fillings. Occup Environ Med 52:124-128.
Benton A. 1974. The Revised Visual Retention Test. 4th ed. New York New York, state, United States
New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of :Psychological Corporation.
Berlin M. 1969. The uptake of mercury in the brains of mammals exposed to mercury vapor and to mercuric mercuric /mer·cur·ic/ (mer-kur´ik) pertaining to mercury as a bivalent element.
Relating to or containing mercury, especially with a valence of 2. salts. Arch Environ Health 18:719-729.
Berlin M, Blomstrand C, Grant CA, Hamberger A, Trofast J. 1975. Tritiated Trit´i`at`ed
a. 1. (Chem.) containing tritium; - of chemical compounds; as, tritiated thymine s>. methylmercury in the brain of squirrel monkeys. Arch Environ Health 30:591-597.
Bernard A, Roels HA, Buchet J-P, Lauwerys RR. 1980. Comparison, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel electrophoresis
Electrophoresis performed in a gel composed of agarose, polyacrylamide, or starch. , of urinary proteins excreted by workers exposed to cadmium cadmium (kăd`mēəm) [from cadmia, Lat. for calamine, with which cadmium is found associated], metallic chemical element; symbol Cd; at. no. 48; at. wt. 112.41; m.p. 321°C;; b.p. 765°C;; sp. gr. 8. , mercury or lead. Toxicol Lett 5:219-222.
Bittner AC, Echeverria D, Woods JS, Aposhian HV, Naleway C, Martin MD, et al. 1998. Behavioral effects of low-level exposure to [Hg.sup.0] among dental professionals: a cross-study evaluation of psychomotor effects. Neurotoxicol Teratol 20:429-439.
Brown LJ, Swango PA. 1993. Trends in caries caries
or tooth decay
Localized disease that causes decay and cavities in teeth. It begins at the tooth's surface and may penetrate the dentin and the pulp cavity. experience in US employed adults from 1971-74 to 1985: cross-sectional comparisons. Adv Dent Res 7:52-60.
Buchet JP, Roels H, Bernard A, Lauwerys R. 1980. Assessment of renal function In medicine (nephrology) renal function is an indication of the state of the kidney and its role in physiology. Indirect markers
Most doctors use the plasma concentrations of creatinine, urea, and electrolytes to determine renal function. of workers exposed to inorganic lead, cadmium or mercury vapor. J Occup Med 22:741-750.
8uschke H, Fudd PA. 1974. Evaluation of storage, retention and retrieval in disordered memory and learning. Neurology 11:1019-1025.
Cianciola ME, Echeverria D, Martin MD, Aposian HV, Woods JS. 1997. Epidemiologic assessment of measures used to indicate low-level exposure to mercury vapor ([Hg.sup.0]). J Toxicol Environ Health 52:19-33.
Dodes JE. 2001. The amalgam controversy. An evidence-based analysis. J Am Dent Assoc 132:348-356.
Echeverria D, Aposhian HV, Woods JS, Heyer NJ, Aposhian MM, Bittner AC, et al. 1998. Neurobehavioral effects from exposure to dental amalgam [Hg.sup.0]: new distinctions between recent exposure and Hg body burden. FASEB FASEB Federation of American Societies for Experimental Biology J 12:971-980.
Echeverria D, Heyer NJ, Martin MO, Naleway CA, Woods JS, 8ittner AC. 1995. Behavioral effects of low-level exposure to [Hg.sup.0] among dentists. Neurotoxicol Teratol 17:161-168.
Ehrenberg RL, Vogt RL, Blair Smith A, Brondum J, Brightwell WS, Hudson PJ, et al. 1991. Effects of elemental mercury exposure at a thermometer plant. Am J Ind Med 19:495-507.
Ellingsen DG, Bast-Pettersen R, Efskind J, Thomassen Y. 2001. Neuropsychological neu·ro·psy·chol·o·gy
The branch of psychology that deals with the relationship between the nervous system, especially the brain, and cerebral or mental functions such as language, memory, and perception. effects of Iow mercury vapor exposure in chloralkali workers. Neurotoxicology 22:249-258.
Ellingsen DG, Efskind J, Haug E, Thomassen Y, Martinsen I, Gaarder PI. 2000. Effects of low mercury vapour exposure on the thyroid function in chloralkali workers. J Appl Toxicol 20:483-489.
Fawer RF, DeRibaupierre Y, Guillemin MP, Berode M, Lob M. 1983. Measurement of hand tremor induced by industrial exposure to metallic mercury. Br J Ind Med 40:204-408.
Fung YK, Molvar MP. 1992. Toxicity of mercury from dental environment and from amalgam restorations. Clin Toxicol 30:49-61.
Gerbert B, Bernzweig J, Bleecker T, Bader J, Miyasaki C. 1992. Risks of the "big three": what dentists and patients believe about dental amalgam, fluoride and HIV HIV (Human Immunodeficiency Virus), either of two closely related retroviruses that invade T-helper lymphocytes and are responsible for AIDS. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of AIDS in the United States. . J Am Dent Assoc 123:82-88.
Grandjean P, Weihe P, White R, Debes F, Araki S, Yokoyama K, et al. 1997. Cognitive deficit Cognitive deficit is an inclusive term to describe any characteristic that acts as a barrier to cognitive performance. The term may describe deficits in global intellectual performance, such as mental retardation, or it may describe specific deficits in cognitive abilities in 7-year-old children with prenatal exposure to methylmercury. Neurotoxicol Teratol 19:417-428.
Guo T, Baasner J. 1993. Determination of mercury in urine by flame injection cold vapor atomic absorption spectrophotometry spectrophotometry
Branch of spectroscopy dealing with measurement of radiant energy transmitted or reflected by a body as a function of wavelength. The measurement is usually compared to that transmitted or reflected by a system that serves as a standard. . Anal Chim 278:189-198.
Hanson M, Pleva J. 1991. The dental amalgam issue. A review. Experientia 47:9-22.
Hansteen I-L, Ellingsen DG, Clausen KO, Kjuus H. 1993. Chromosome aberrations in chloralkali workers previously exposed to mercury vapor. Scand J Work Environ Health 19:375-381.
Heinegard D, Tiderstrom G. 1973. Determination of serum creatinine by a direct colorimetric method. Clin Chim Acta 43:305-310.
Herber RFM RFM Recency, Frequency, Monetary
RFM Rotorcraft Flight Manual
RFM Reform Party
RFM Radio Frequency Module
RFM Radio Free Monterey
RFM Retirement and Financial Management
RFM Reply to Flagged Message
RFM Radio Frequency Monitor
RFM Request for Material , deGee AJ, Wibowo AAE AAE American Association of Endodontists. . 1988. Exposure of dentists and assistants to mercury: mercury levels in urine and hair related to conditions of practice. Community Dent Oral Epidemiol 16:153-158.
Hurch JB, Greenwood MR, Clarkson TW, Allen J, Demuth S. 1980. The effect of ethanol on the fate of mercury vapor inhaled in·hale
v. in·haled, in·hal·ing, in·hales
1. To draw (air or smoke, for example) into the lungs by breathing; inspire.
2. by man. J Pharmacol Exp Ther 214:520--527.
Igata A. 1991. Epidemiological and clinical features of Minamata Disease Minamata disease
Disease first identified in 1956 in Minamata, Japan. A fishing port, Minamata was also the home of Nippon Chisso Hiryo Co., a manufacturer of chemical fertilizer, carbide, and vinyl chloride. . In: Advances in Mercury Toxicology toxicology, study of poisons, or toxins, from the standpoint of detection, isolation, identification, and determination of their effects on the human body. Toxicology may be considered the branch of pharmacology devoted to the study of the poisonous effects of drugs. (Suzuki T, Imura N, Clarkson TW, eds). New York:Plenum Press, 439-458.
Jaffe M. 1886. Uber den Niederschlag, welchem Picrinsaure in normalen Harn erzeugt und uber eine neue Reaction des Kreatinins. Z Physiol Chem 10:391.
Kaufman AS, McLean JE, Reynolds CR. 1988. Sex, race, residence, region, and education differences on the 11 WAIS-R subtests. J Clin Psychol 44:231-248.
Kingman A, Albertini T, Brown LJ. 1998. Mercury concentrations in urine and whole blood associated with amalgam exposure in a US military population. J Dent Res 77:461-471.
Klove H. 1963. Clinical neuropsychology Clinical neuropsychology is a sub-specialty of clinical psychology that specialises in the diagnostic assessment and treatment of patients with brain injury or neurocognitive deficits. . In: The Medica medica (māˑ·dē·k 1 Clinics of North America North America, third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. (Forster FM, ed). New York:Saunders, 1647-1658.
Langolf GD, Chaffin DB, Henderson R, Whittle HP. 1978. Evaluation of workers exposed to elemental mercury using quantitative tests of tremor and neuromuscular neuromuscular /neu·ro·mus·cu·lar/ (-mus´ku-ler) pertaining to nerves and muscles, or to the relationship between them.
1. function. Am Ind Hyg J 39: 976-984.
Langolf GD, Smith PJ, Henderson R, Whittle H. 1981. Measurements of neurological functions in the evaluation of exposure to neurotoxic agents. Ann Occup Hyg 24:293-296.
Lauwerys RR, Buchet JP. 1973. Occupational exposure to mercury vapors and biological action. Arch Environ Health 27:65-68.
Levine SP, Cavender GD, Langolf GD, Albers JW. 1982. Elemental mercury exposure: peripheral neurotoxicity neurotoxicity /neu·ro·tox·ic·i·ty/ (noor?o-tok-sis´it-e) the quality of exerting a destructive or poisonous effect upon nerve tissue. . Br J Ind Med 39:136-139.
Lezak MO. 1995. Neuropsychological Assessment Neuropsychological assessment was traditionally carried out to assess the extent of impairment to a particular skill and to attempt to locate an area of the brain which may have been damaged after brain injury or neurological illness. . 3rd ed. New York:Oxford University Press.
Mackert JR. 1987. Factors affecting estimation of dental amalgam mercury exposure from measurements of mercury vapor levels in intra-oral and expired air. J Dent Res 68:1775-1780.
Mathiesen T, Ellingsen DG, Kjuus H. 1999. Neuropsychological effects associated with exposure to mercury vapor among former chloralkali workers. Scand J Work Environ Health 25:342-350.
Matthews CG, Klove H. 1964. Instruction Manual for the Adult Neuropsychology neuropsychology
Science concerned with the integration of psychological observations on behaviour with neurological observations on the central nervous system (CNS), including the brain. Test Battery. Madison, WI:University of Wisconsin Medical School.
Miller JM, Chaffin DB, Smith RG. 1975. Subclinical subclinical /sub·clin·i·cal/ (sub-klin´i-k'l) without clinical manifestations.
Not manifesting characteristic clinical symptoms. Used of a disease or condition. psychomotor and neuromuscular changes in workers exposed to inorganic mercury. Am Ind Hyg Assoc J 10:725-734.
Naleway C, Chou H-N, Muller T, Dabney J, Roxe D, Farrida S. 1991. On-site screening for urinary Hg concentrations and correlation with glomerular glomerular /glo·mer·u·lar/ (glo-mer´u-ler) pertaining to or of the nature of a glomerulus, especially a renal glomerulus.
adj. and renal tubular function. J Public Health Dent 51:12-17.
Naleway C, Sakaguchi R, Mitchell E, Muller T, Ayer WA, Hofferren JJ. 1985. Urinary mercury levels in US dentists, 1975-1983: review of health assessment program. J Am Dent Assoc 111:37-42.
National Institute of Dental Research. 1987. Oral Health of United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. Adults. The National Survey of Oral Health in US Employed Adults and Seniors: 1985-86. NIH "Not invented here." See digispeak.
NIH - The United States National Institutes of Health. Publication no. 87-2868. Bethesda, MD:U.S. Department of Health and Human Services Noun 1. Department of Health and Human Services - the United States federal department that administers all federal programs dealing with health and welfare; created in 1979
Health and Human Services, HHS .
Newton D, Fry FA. 1978. The retention and distribution of radioactive mercuric oxide following accidental inhalation. Ann Occup Hyg 21:21-32.
Ngim CH, Foo SC, Boey KW, Jeyaratnam J. 1992. Chronic neurobehavioural effects of elemental mercury in dentists. Br J Ind Med 49:782-790.
Palumbo DR, Cox C, Davidson PW, Myers G J, Choi A, Shamlaye C, et al. 2000. Association between prenatal exposure to methyl mercury and cognitive function in Seychellois children: a reanalysis of the McCarthy Scales of Children's Ability from the main cohort study A cohort study is a form of longitudinal study used in medicine and social science. It is one type of study design.
In medicine, it is usually undertaken to obtain evidence to try to refute the existence of a suspected association between cause and disease; failure to refute . Environ Res 84:81-88.
Piikivi L, Hanninen H. 1989. Subjective symptoms and psychological performance of chlorine-alkali workers. Scand J Work Environ Health 15:69-74.
Reitan RM. 1958. Validity of the Trail Making Test as ah indicator of organic brain damage. Percept percept /per·cept/ (per´sept?) the object perceived; the mental image of an object in space perceived by the senses.
1. The object of perception.
2. Motor Skills 8:271-276.
Ritchie KA, Macdonald EB, Hammersley R, 0'Neil JM, McGowan DA, Dale IM, et al. 1995. A pilot study of the effect of low level exposure to mercury on the health of dental surgeons. Occup Environ Med 52:813-817.
Roels H, Gennart J-P, Lauwerys R, 8uchet J-P, Malchaire J, Bernard A. 1985. Surveillance of workers exposed to mercury vapour: validation of a previously proposed biological threshold limit value threshold limit value
n. Abbr. TLV
The maximum concentration of a chemical allowable for repeated exposure without producing adverse health effects. for mercury concentration in urine. Am J Ind Med 7:45-71.
Roels H, Lauwerys R, Buchet JP, Bernard A, Barthels A, Oversteyns M, et al. 1982. Comparison of renal function and psychomotor performance in workers exposed to elemental mercury. Int Arch Occup Environ Health 50:77-93.
Singer R, Valciukas JA, Rosenman KO. 1987. Peripheral neurotoxicity in workers exposed to inorganic mercury compounds. Arch Environ Health 42:181-184.
Skare I, Engqvist A. 1994. Human exposure to mercury and silver released from dental amalgam restorations. Arch Environ Health 49:384-394.
Smith PJ, Langolf GD. 1981. The use of Sternberg's memory scanning paradigm in assessing effects of chemical exposures. Hum Factors 23:701-708.
Smith PJ, Langolf GD, Goldberg J. 1983. Effects of occupational exposure to elemental mercury on short term memory. Br J Ind Med 40:413-419.
Smith RG, Vorwald AJ, Path LS, Mooney TF Jr. 1970. Effects of exposure to mercury in the manufacture of chlorine. Am Ind Hyg Assoc J 31:687-699.
Snow WG, Weinstock J. 1990. Sex differences among non-brain damaged adults on the Wechsler Adult Intelligence Scales Wechsler Adult Intelligence Scale (WAIS): see psychological tests. : a review of the literature. J Clin Exp Neuropsychol 12:873-886.
Steinberg D, Grauer F, Niv Y, Perlyte M, Kopolovic K. 1995. Mercury levels among dental personnel in Israel: a preliminary study. Isr J Med Sci 31:428-432.
Takahata N, Hayashi H, Watanbe B, Anso T. 1970. Accumulation of mercury in the brains of two autopsy cases with chronic inorganic mercury poisoning mercury poisoning, tissue damage resulting from exposure to more than trace amounts of the element mercury or its compounds. Elemental mercury (the silver liquid familiar from thermometers) is the most common occupational source. . Folia fo·li·a
Plural of folium. Psychiatr Neurol Jpn 24:59-69.
Vimy MJ, Luft AF, Lorscheider FL. 1988. Estimation of mercury body burden from dental amalgam: computer simulation of a metabolic compartmental model. J Dent Res 66:1235-1242.
Watanbe S. 1969. Mercury in the body 10 years after long term exposure to mercury [Abstract]. In: Proceedings of Sixteenth International Congress on Occupational Health, 22-27 September 1969, Tokyo, Japan. Tokyo:Japan Organizing Committee of Sixteenth International Con9ress on Occupational Health, 553.
Wechsler D. 1981. WAIS-R Manual. New York:Psychological Corporation.
Weiner JA, Nylander M, Berglund F. 1990. Does mercury from amalgam restorations constitute a health hazard health hazard Occupational safety Any agent or activity posing a potential hazard to health. Cf Physical hazard. ? Sci Total Environ 99:1-22.
Woods JS, Martin MD, Naleway CA, Echeverria D. 1993. Urinary porphyrin profiles as a biomarker of mercury exposure: studies on dentists with occupational exposure to mercury vapor. J Toxicol Environ Health 40:235-246.
Pam Factor-Litvak, (1,2) Gunnar Hasselgren, (3) Diane Jacobs, (4) Melissa Begg, (5) Jennie Kline, (1,4,6) Jamie Geier, (1) Nancy Mervish, (1) Sonia Schoenholtz, (1) and Joseph Graziano (2)
(1) Department of Epidemiology and (2) Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University Columbia University, mainly in New York City; founded 1754 as King's College by grant of King George II; first college in New York City, fifth oldest in the United States; one of the eight Ivy League institutions. , New York, New York, USA; (3) School of Dental and Oral Surgery, Columbia University, New York, New York, USA; (4) Sergievsky Center, Columbia University, New York, New York, USA; (5) Department of Biostatistics biostatistics /bio·sta·tis·tics/ (-stah-tis´tiks) biometry.
The science of statistics applied to the analysis of biological or medical data. , Mailman School of Public Health, Columbia University, New York, New York, USA; (6) Epidemiology of Developmental Brain Disorders Department, New York State Psychiatric Institute The New York State Psychiatric Institute, established in 1895, was one of the first institutions in the United States to integrate teaching, research and therapeutic approaches to the care of patients with mental illnesses. , New York, New York, USA
Address correspondence to P. Factor-Litvak, Department of Epidemiology, Mailman School of Public Health, Columbia University, 622 West 168 St., PH18-107, New York, NY 10032 USA. Telephone: (212) 305-7851. Fax: (212) 305-9413. E-mail: email@example.com
This study was supported by grants RO1 DE 11708 from the National Institute of Dental and Craniofacial Research The National Institute of Dental and Craniofacial Research (NIDCR), is part of the U.S. National Institutes of Health, and as such its function is to the promote the general health of the American people, by improving their oral, dental and craniofacial health. and P30 ES09089 from the National Institute of Environmental Health Sciences The National Institute of Environmental Health Sciences (NIEHS) is one of 27 Institutes and Centers of the National Institutes of Health (NIH),which is a component of the Department of Health and Human Services (DHHS). The Director of the NIEHS is Dr. David A. Schwartz. .
The authors declare they have no conflict of interest. Received 9 July 2002; accepted 13 November 2002.