Mercury, health and food

See also: mercury toxicity

The mercury problem

Mercury is one of the heavy metals most feared by consumers, alarmed by the news that is periodically relaunched by the media. The carabinieri of the Anti-Sophistication Unit, for their part, constantly monitor to avoid that foods with significant percentages of mercury arrive on our tables. When large contaminated foodstuffs are intercepted, the news is immediately amplified by the media, triggering the so-called "mercury psychosis". Many of the most health conscious consumers find themselves so disoriented and, it should be said, they no longer know which way to turn. Is it better to increase the consumption of fish products for their content of proteins and omega-3 fatty acids that are good for the heart, or to reduce it to avoid the risk of mercury poisoning?

Mercury in nature and in industry

Mercury is a relatively abundant element throughout the earth's crust. Among all metals it is the only one to be liquid at room temperature and as such, it has a high volatility. In this state, even if ingested, it is not very toxic but especially its vapors are.

In nature, mercury is present in some minerals, the most common of which is cinnabar (HgS) which stands out for its beautiful red color. It is naturally introduced into the environment through spontaneous processes of vaporization (volcanic activities) and erosion of the rocks. Man, for his part, has introduced and still introduces mercury into the environment, albeit to a lesser and more conscious extent. of this metal are in fact exploited in many industrial processes, aimed above all at the production of electrical components, instrumentation and the catalysis of some chemical processes.

Mercury is also used in the manufacture of batteries, particularly in the "button" batteries found in watches and electronic calculators. If they are unconsciously thrown into the environment or into the bins together with other waste, they inevitably end up contaminating the ground and aquifers.

Considering the high toxicity of mercury, numerous campaigns have been promoted aimed at progressively reducing the use of the mineral in the industrial field. Thanks to these interventions, many of the traditional uses, including the old thermometer, have been considerably reduced.

Mercury contamination

It is a short step from industrial waste to our tables. Mercury, released into the environment through vapors or waste liquids, contaminates the soil, passes into the aquifers and from there enters the food chain. The toxicity of the mineral is greatly amplified by the bacteria that populate the aquatic seabed and, to a lesser extent, from the intestinal microflora of many animal species, including fish. These microorganisms transform inorganic mercury into its organic forms, among which the most widespread and dangerous is methylated (methylmercury). The high fat solubility gives these compounds the ability to rise the food chain, accumulating mainly in the nervous tissue of smaller fish, which in turn transmit it to their predators. Thus, in general, the larger the size of the fish, the greater its mercury content.

On the other hand, the existence of microorganisms capable of "detoxifying" methylmercury (some of which of biotechnological derivation) and of industrial plants capable of recycling the metal while minimizing its environmental impact should be emphasized.

Mercury toxicity

The ingestion of metallic mercury, for example following the breaking of a thermometer, has no important toxicological consequences. On the contrary, the vapors taken by inhalation are very harmful. Should such an accident occur, it is advisable to immediately remove pregnant women and children, avoiding to use a vacuum cleaner or broom so as not to contaminate the air. The mercury will instead be separated from the glass with the help of a syringe, scotch tape or by rolling it on a sheet of paper. It will therefore be placed in a well-closed and properly sorted non-metallic container (generally pharmacies are available for this). By lighting the area where the accident occurred with a flashlight, any mercury residues can be identified and removed using the techniques indicated above. Finally, before staying there, it is advisable to ventilate the environment for a long time.

The methylmercury present in food and in particular in fish remains the most dangerous source of contamination. Pregnant women are the most exposed to the problem, as mercury can lead to alterations in the brain development of the fetus. In adults, chronic exposure causes neurological alterations, with the appearance of fears, hallucinations, amnesia, to the point of provoking a symptomatology exactly comparable to multiple sclerosis.

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