Nexus - 0208 - New Times Magazine-pages

Page Content (OCR)

vapours of the Ngawha Springs in New Zealand. The fumarole — human tissue. Once inhaled, mercury vapour is rapidly absorbed gasses contained levels of mercury ranging from 13,000 micro- _ by the lungs and transferred to the blood in varying amounts within grams to 270,000 micrograms per cubic meter, together with minor —_ several minutes. The rate of mercury vapour absorption by the amounts of hydrogen sulphide and other gasses. This resulted in _ lungs depends partly upon the dose inhaled. The larger the dose, the mercury content of the air being sufficient to cause mercury to _the less efficient the absorption factor, with smaller doses not infre- condense on the metallic gutters of houses nearby, particularly after © quently exhibiting rates of 80% absorption. This presents another cool nights. The springs themselves which contain concentrations _clear indication that it is naive to base the toxicity potential of mer- of mercury ranging from 26ppb to 29ppb also contain a very high _—_cury solely on the response of the human organism to large doses degree of mineralisation, with high concentrations of of mercury vapour. boron, ammonia and bicarbonate in the brines. Once in the blood, metallic mer- These hot springs are used for balneal purposes for cury passes the blood-brain barrier . A number of subsequent studies rheumatic arthritis and dermatitis. The researchers have now confi rmed that rapidly and after oxidation accumu- conclude their report with the revealing observation: subjects with fillings have lates in the brain.” In spite of the high localised mercury con- substantially higher levels of JRBGmncincum paving centrations no ill effects have been observed mercury in expired air, mercury vapour can enter the body among the inhabitants who frequent to the d with | f orally and can even be absorbed by balneal establishments.» compare wit n amaigamiless the skin. Gastrointestinal absorp- It seems likely that elements co-existing with mer- subjects. tion is not uncommon. cury in Nature may in these instances contribute to Another possible source of mer- either low body absorption or facilitated detoxification. cury poisoning is believed to result from the deterioration of dental The man made contribution of mercury now can be seen to be = amalgam by corrosion. This being so, it follows that mercury ions particularly significant from two aspects. The form of the mercury _could in theory be diffused through the teeth to nerve endings and may be more toxic or more readily assimilated biologically and the _ other tissue membranes in root canals and undemeath the fillings. increased mercury background levels may begin to exceed the lev- els at which individuals can safely detoxify heavy metals. This lat- fore) ter situation undoubtedly corresponds to the reaction which is euphemistically termed "hypersensitivity" to mercury, which is per- oie up oiliedaaes contaminants now found in the 1S THERE A CASE FOR MERCURY POISONING environment contribute significantly to the problem with dental FROM DENTAL AMALGAM? from other sources can sensitise living organisms even to the addi- of giving off deadly fumes of mercury vapour is incon- tional though seemingly trivial quantities found in amalgam fill- testable; what is being resisted by many authorities is first ings. This is a point which seems invariably to be neglected by _the claim that once mixed with alloys and installed in teeth, amal- those who insist on defending the safety of silver and mercury fill- gam actually gives off mercury vapour and second, that if mercury ings on the basis of quantities. To quote from a supplement to the —_ vapour is exuded by dental amalgam, the quantities are too small to amalgam for the simple reason that exposure to sufficient mercury T« the elemental mercury used in dental amalgam is capable Australian Dental Association News Bulletin in August 1984: be harmful. Let us see whether the weight of argument in research In extremely rare cases individuals may develop hyper- terms shows that the use of silver-mercury fillings in dental therapy sensitivity or an allergic reaction to mercury. Symptoms is a health hazard. may vary from a local dermatitis near recently placed In 1979 D.D. Gay and co-workers reported finding significantly amalgam restorations to a generalised erythema over the increased mercury levels in the exhaled air of patients with amal- entire body. gam fillings. After chewing, the amount of mercury collected Symptoms associated with chronic mercury _intoxifica- ranged from 64 to 244 nanograms per ten exhalations.” A number tion may include gingivitis and neurological disturbances of subsequent studies have now confirmed that subjects with fill- such as tremor and personality changes. The levels of ings have substantially higher levels of mercury in expired air, (up mercury found to be released by the amalgam restorations to 50 times in one report) compared with amalgamless subjects. were far below those associated with such symptoms.” Furthermore, after chewing or brushing the level of mercury vapour The point to be stressed is that environmental contaminants in exuded from the fillings increased yet again, often by as much as the form of organic mercury can predispose the living organism to 15 times, with levels of mercury vapour up to 29 micrograms per heightened sensitivity to exposure from inorganic sources. cubic meter being reported. » Within the class of inorganic mercury on finds metallic mercury, In the United States, 50 micrograms/m’ represents the maximum the form used to produce dental amalgam for fillings. Because of permissible industrial level for 8 hours, 5 days a week exposure to its disposition to release toxic mercury vapour when agitated, mercury vapour." However, because some of the effects of chronic metallic mercury is considered to be th most volatile form of the mercury poisoning have been found to occur in workers exposed to element. Metallic mercury vapour can be activated at room tem- _aif-mercury levels below 50 micrograms/m’, the World Health perature merely by being compressed or heated. One reason why Organisation (WHO) has recommended a health-based occupation- absorption of elemental mercury vapour into cell membranes occurs readily is because of its amenability to dissolution or solu- bility in blood lipids or the fats characteristically present in all Continued on page 65 JUNE-JULY 1992 NEXUS¢19 a Another possible source of mer- cury poisoning is believed to result from the deterioration of dental amalgam by corrosion. This being so, it follows that mercury ions could in theory be diffused through the teeth to nerve endings and other tissue membranes in root canals and undemeath the fillings. of giving off deadly fumes of mercury vapour is incon- testable; what is being resisted by many authorities is first the claim that once mixed with alloys and installed in teeth, amal- gam actually gives off mercury vapour and second, that if mercury vapour is exuded by dental amalgam, the quantities are too small to be harmful. Let us see whether the weight of argument in research terms shows that the use of silver-mercury fillings in dental therapy is a health hazard. T« the elemental mercury used in dental amalgam is capable In 1979 D.D. Gay and co-workers reported finding significantly increased mercury levels in the exhaled air of patients with amal- gam fillings. After chewing, the amount of mercury collected ranged from 64 to 244 nanograms per ten exhalations.* A number of subsequent studies have now confirmed that subjects with fill- ings have substantially higher levels of mercury in expired air, (up to 50 times in one report) compared with amalgamless subjects. Furthermore, after chewing or brushing the level of mercury vapour exuded from the fillings increased yet again, often by as much as 15 times, with levels of mercury vapour up to 29 micrograms per cubic meter being reported.» In the United States, 50 micrograms/m’ represents the maximum permissible industrial level for 8 hours, 5 days a week exposure to mercury vapour.” However, because some of the effects of chronic mercury poisoning have been found to occur in workers exposed to air-mercury levels below 50 micrograms/m’, the World Health Organisation (WHO) has recommended a health-based occupation- NEXUS¢19 IS THERE A CASE FOR MERCURY POISONING FROM DENTAL AMALGAM? Continued on page 65