Measurement of Mercury in Saliva - How and Why?

Mercury in its Purest State

Mercury in its Purest State

Does it make sense to measure the mercury levels in saliva?

As a naturally occurring substance, the chemical element, mercury (Hg), is widespread in the earth’s crust and atmosphere. Worldwide, about 30,000 to 150,000 metric tons of Hg are released into the environment from natural sources such as volcanoes, for example. The burning of fossil fuels contributes to environmental pollution at a rate of about 10,000 metric tons of Hg per year. All human beings – particularly in industrialized countries – are contaminated with mercury, with occupational hazards being a significant factor.

Workers in mercury-processing companies are considered to be exposed. By a clear margin, dentists and their personnel receive the second highest level of work-related mercury exposure, and are followed by those in the general public with amalgam fillings. However, the ingestion of mercury through food can also play a significant part in mercury poisoning/contamination.

Presumably, individuals who aren’t exposed to mercury at the workplace and don’t have any caries or dental fillings and who eat food low in mercury content have the lowest levels of mercury contamination. There are a large number of scientific surveys regarding the release of mercury from amalgam fillings in water or saliva; most of these were done in lab experiments.

The release of mercury depends on the type of amalgam, the type of surface finish (polished/unpolished), the age of the amalgam filling, the pH value of the saliva, and the temperature the solubility depends on. Normal ingestion from drinking water and beverages is about 1 mg Hg/day. Saliva tests conducted on people without any amalgam fillings yielded values of less than 2 μg Hg, or levels that barely exceeded this threshold.

According to surveys conducted by Dr. Wirz, the daily release of non-absorbable mercury from amalgam fillings is between 12 and 32 μg on average, while between 5 and 20 μg of absorbable, organically bound mercury is ingested in the form of food every day.

In our own surveys, mercury content in saliva was generally higher in test persons with amalgam fillings than in those without any amalgam fillings. During a ten-minute period of gum chewing, these values increased in test persons with amalgam fillings. There is a weak correlation between the number of fillings or the surface area of the fillings and the mercury concentration in the saliva.

Slightly increased mercury concentrations could only be shown after intensive chewing (of chewing gum) and only for a period of 40 to 60 minutes at most. However, according to assessments by the scientific community, these concentrations are insignificant.

The consumption of alcohol leads to an increase in the release of absorbable mercury vapor and an increased storage of mercury in the liver. Cigarette smokers show higher mercury concentrations in the blood than non-smokers. After chewing chewing gum for ten minutes, mercury measurements in the air exhaled by smokers showed lower values than those of non-smokers. Also, the mercury concentration depends on the time of day that samples were taken and on the share of the organic substances in the saliva.

Authors of earlier surveys had assumed that in terms of mercury release, the chewing of chewing gum mimics typical food chewing. However, in 1990, Berglund found that the chewing of chewing gum leads to an exceptionally high release of mercury (contrary to the chewing process during regular food intake).

Contrary to assumptions, no increase of mercury concentrations in the saliva could be shown after the consumption of hot beverages. Based on his extensive research on the absorption of mercury from amalgam fillings, Berglund concluded that a single examination (regarding the mercury content in saliva or in exhaled air) or a series of samples cannot be used to determine a person’s exposure to mercury from amalgam fillings.

For the purposes of scientific research, a standardized approach is necessary, not just measurements after chewing gum. In order to measure exposure to mercury, bodily fluids such as urine (with regard to creatinine and possibly after administering Dimaval®) and blood are suitable. In terms of the screening test, an analysis of the mercury content in the hair can be employed; however, this area of application is limited to scientific analyses or to incidents of heavy metal poisoning.

Thus, according to the current state of knowledge, there is no need for routine blood or urine analyses in connection with amalgam fillings. If the mercury content in urine is measured for mercury contamination, then measurements should be conducted in 24-hour urine samples.

Values of 200 Hg Hg/1 urine and 50 Hg Hg/1 blood (BAT values) for workers exposed to mercury on the job are considered tolerable in occupational medicine. With special, highly sensitive analytical procedures such as, for example, the ICP atomic emission spectroscopy, the measurement of radioactively labeled mercury, or an X-ray diffractometry, other values may possibly be found as well.

Basically, it’s impossible to differentiate whether the mercury existed as an element or as part of an inorganic or organic compound; however, knowing this would be very important in determining its toxicity.

In summary, one can state that saliva tests should not be viewed as standardized procedure for determining mercury contamination, namely because there is no possibility of standardization (resting saliva/reflex saliva/stimulated saliva).

Furthermore, there is no scientifically well-founded specification of limits, although these are sometimes given by medical laboratory personnel. In principle, data that is collected after provocation or under extreme stress conditions is generally not suitable for evaluation.

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