Yes Or No? These two recently published studies (D. Gonzalez-Ramirez, et al., 1995 and D. Echeverria, et al., 1995) present a singular dilemma to the dental profession, which has steadfastly claimed that patients could not possibly be harmed by amalgam mercury since dental personnel suffer no adverse mercury effects. A number of previous studies had already presented evidence of neurologic damage in dental personnel. Shapiro and associates [Shapiro, IM; et al.

Neurophysiological and neuropsychological function in mercury-exposed dentists. Lancet, 1(8282):1147-1150, 1982.] and Uzzell and associates [Uzzell, BP; et al. Chronic low-level mercury exposure and neuropsychological functioning. J Clin Exp Neuropsych. 8(5): 581-593, 1986.] had already demonstrated reduced nerve conduction velocities in dentists exposed to mercury, as determined by X-ray fluorescence of mercury in the wrist and head.

In 1992, Ngim and associates evaluated 98 dentists and 54 controls who were not dentists [Ngim, CH; et al. Chronic neurobehavioral effects of elemental mercury in dentists. Br J Ind Med. 49(11):782-790, 1992]. Dentists exposed to air concentrations of 16.6 ug Hg/m3 were found to have poorer performance in mood, motor speed (finger tapping), visual scanning (trail making), visuomotor coordination and concentration (symbol-digit), digit span, logical memory, and visual reproduction. The dentists also had a higher aggression score than the controls.

It is interesting to note that the Echeverria team found a significant effect in dentists for behavioral parameters, including poor mental concentration, emotional lability, somatosensory irritation, and total mood scores. It is also notable that the Echeverria group stated that "urinary Hg levels provide a more reliable estimate of recent exposure/dose" than do air mercury concentrations (used in the Ngim, et al. study).

As far back as the 1960's, mercury toxicology experts had determined that levels of mercury in urine (and blood) were not valid indicators of body burden or toxic effects of mercury. This has been repeatedly confirmed through the years [NIOSH-1973, USEPA-1984, WHO-1991]. It has even been formally acknowledged by the American Dental Association and the National Institute of Dental Research [NIDR/ADA. Workshop: Biocompatibility of metals in dentistry. JADA, 109:469-471, 1984].

The Gonzalez-Ramirez, et al. study investigated the correlation of neurobehavioral effects to urine mercury levels before and after administration of DMPS, a mercury chelating agent. They found that the adverse neurobehavioral effects of complex attention, a psychomotor task, mood and symptoms correlated to urine mercury levels after administration of DMPS, but not before. The findings in the Echeverria study might have been even more dramatic had the DMPS-challenge technique been utilized.

Consideration of the previous knowledge of the urine mercury levels might have been interesting in yet another context. It is quite possible that the control group of dentists may have had considerably higher body burdens of mercury than the levels revealed by simple urine measurement, without the benefit of DMPS-challenge. If so, then the utilization of a control group in the Echeverria study that did not include dentists, as was performed in the Ngim study, may have revealed even more dramatic effects in dentists.

One thing is certain, the Gonzalez-Ramirez and the Echeverria studies present data that demonstrate adverse neurobehavioral effects on dental personnel, a development in the amalgam controversy that is certainly uncomfortable for the dental profession. There are other published studies that have demonstrated non-neurological adverse effects to mercury in dental personnel. These studies primarily addressed adverse reproductive effects and have been well publicized in a number of review documents. Why then, does the dental profession continue to declare that dental personnel suffer no adverse effects from dental mercury and what defense is offered to counter the extensive documentation to the contrary? The position of organized dentistry has been based on two factors; the American Dental Association's (ADA) Morbidity/Mortality reports, published in the ADA Journal (JADA), and the 1985 study by Brodsky and associates, also published in JADA [Brodsky JG, et al. Occupational exposure to mercury in dentistry and pregnancy outcome. JADA, 111:779-780, 1985].

Review of the ADA Morbidity/Mortality reports quickly reveals that all dentists were compared to the general population. Neither group was divided into those who did and did not have dental amalgams. Since dentists are, or should be, more attuned to prevention of dental problems and also have a greater capability to have gold restorations, it is probable that the average number of amalgam fillings possessed by dentists is significantly less than that of the general population. Moreover, dentists who use amalgam in their practice were not separated from those who do not, such as certain groups of specialists. It is obvious that these Morbidity/Mortality reports have no relationship whatsoever to the issue of the safety of dental amalgam, either in the mouths of subjects or the practice of dentistry.

The 1985 Brodsky study is also very interesting. The expressed goal of the study was to "examine the relationship of mercury exposure and pregnancy outcome among dental professionals and their spouses." A questionnaire survey was mailed to 29,514 male dentists and 30,272 female dental assistants. Respondents were asked to report occurrences of spontaneous abortions or congenital abnormalities. More than 70% (21,634) of the dentists and dental assistants (21,202) completed and returned the questionnaire.

The subjects were originally divided into three mercury exposure groups, one of which was a "no exposure" group. This was subsequently revised into two groups; one of dental personnel and their wives where 40 or less amalgams/week were placed (low direct and indirect exposure groups), and one of dental personnel and their wives where more than 40 amalgams/week were placed (high direct and indirect exposure groups). As no data was provided, the low and high exposure groups may well have averaged 39 and 40 amalgams placed per week, hardly a scientifically valid comparison.

In view of the weakness of the position of the dental profession in the face of mounting contrary documentation and the absolute reliance of the practicing dentist on its leadership, one must wonder what response will occur when the dental practitioners learn that they have possibly been place at personal risk as a result of the use of dental amalgam.

ATSDR "MINIMAL RISK LEVEL" FOR MERCURY VAPOR INHALATION! The Agency for Toxic Substances and Disease Registry (ATSDR) of the U.S. Public Health Service recently published its "Toxicological Profile for Mercury (Update)" [ATSDR. TP-93/10]. Public Law 99-499 extended and amended the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or "Superfund") by directing the ATSDR to prepare toxicological profiles for hazardous substances most commonly found on the CERCLA National Priorities List that pose the most significant potential threat to human health, as determined by ATSDR and EPA. The list of the 275 most hazardous substances (ED: which includes mercury) was published in the Federal Register [57 FR 48801, 28 Oct 1992]. "The ATSDR toxicological profile is intended to succinctly characterize the toxicological and adverse health effects information for the hazardous substance being described. Each profile identifies and reviews the key literature (that has been peer-reviewed) that describes a hazardous substance's toxicological properties. Other pertinent literature is also presented, but described in less detail than the key studies."

"This profile reflects our assessment of all relevant toxicological testing and information that has been peer reviewed. It has been reviewed by scientists from ATSDR, the Centers for Disease Control and Prevention (CDC), and other federal agencies. It has also been reviewed by a panel of nongovernmental peer reviewers and was made available for public review." "The principal audiences for the toxicological profiles are health professionals at the federal, state, and local levels, interested private sector organizations and groups, and members of the public." [Forward: Pages v-vi.]

The ATSDR has established "Minimal Risk Levels (MRL's)" for the various forms of mercury related to their route of exposure. The MRL's for inhalation of mercury vapor are contained in Section 2.4, entitled "Relevance to Public Health," pages 125-128 ("Inhalation MRL's"). The ATSDR MRL for acute inhalation exposure to metallic mercury vapor is 2x10-5 mg Hg/m3 (0.02 mcg Hg/m3) and the MRL for chronic inhalation exposure to metallic mercury vapor is 1.4x10-5 mg Hg/m3 (0.014 mcg Hg/m3). These standards are both well below (by more than 200 times) exposure levels to mercury vapor that have been well documented to emanate from amalgam dental fillings, even in the absence of stimulation.

Studies of office exposure to dental personnel and exposure to in vivo dental amalgam fillings are referenced in the ATSDR document. Humans with dental amalgam fillings are identified as having potentially high exposures to mercury (page 233) and the unborn (prenatal) and newborn are identified as being unusually susceptible to the effects of mercury exposure (page 179). As a recent human autopsy study and three previous animal studies have established the transfer of amalgam mercury from the fillings of pregnant females into the tissues of unborn babies, special consideration should be directed to this concern.

In the preceding issue of the Bio-Probe Newsletter [Vol 11(1):3, Jan 1995] various United States government standards for mercury exposure for the general population were presented. For inhalation of mercury vapor, the USEPA "Reference Dose" is 0.3 mcg Hg/m3, considerably higher than the ATSDR MRL of 0.014 mcg Hg/m3 for chronic inhalation of mercury vapor. In view of the statements presented in the forward of the ATSDR document, there is NO EXCUSE for health professionals (dental or otherwise) or government officials to continue relating mercury vapor exposure from amalgam dental fillings to the OSHA TLV-TWA of 50 mcg Hg/m3, which is specifically limited to medically monitored otherwise healthy workers with no more than 40 hours per week of exposure!

Source: BioProbe Newsletter

Also make sure to read these books: Poison in Your Teeth: Mercury Amalgam (Silver) Fillings...Hazardous to Your Health! and Mercury Detoxification by Tom McGuire