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Mercury in the Environment – Soils, Sludges and Fish

From fluorescent lamps to thermometers and tattoo inks, mercury is a very handy (albeit highly toxic) element used for a wide variety of applications. However useful the alchemical ‘element of spirit’ may be, it has been known since the days of the Roman Empire to negatively impact health and can in the most extreme cases lead to mercury poisoning, permanent brain damage and even death.

So, what makes mercury dangerous to humans and the environment, and how do we minimise the risk?

It’s all in the form!

The toxic effects of mercury are very much dependant on two key factors: the chemical form of mercury and route of exposure. Methylmercury [CH3Hg]+ is the most toxic form, being an organometallic cation that is produced through the action of microbes living in aquatic systems. The inorganic mercury that forms methyl mercury can come from a wide variety of sources, some natural like volcanoes and forest fires, others being anthropogenic, like burning mercury waste and coal.

Due to formation in aquatic systems and not being readily eliminated (half-life of approximately 72 days), methylmercury is biomagnified within the aquatic food chain, from plankton all the way to piscivorous fish. At every step of the food chain, the concentration of methylmercury increases, meaning that humans receive the highest dose through accumulation!

Just like the danger of mercury itself, methylmercury dosage is highly dependent on the species, size, and age of fish! Generally larger fish, especially those predating on other fish, are the most likely to contain a higher concentration of methyl mercury. It is also believed that fish developing in a more acidic body of water have higher levels of methyl mercury.

The health risks for humans

The greatest risk of methylmercury is to foetuses of women who consume a large amount of fish and seafood. This is because within the body methylmercury can complex with free cysteine. These complexes can mimic methionine, an essential amino acid, and can therefore transport freely across the blood-brain-barrier and placenta.

Several studies have linked methylmercury to development deficits in children exposed in utero, including a reduction in mental faculties and reduced performance in terms of language skills, memory function and attention levels. Long term exposure for adults has been linked to an increased risk of cardiovascular disease and may cause autoimmune effects in especially sensitive individuals.

In terms of severe poisoning through contamination of food, several episodes (such as Minimata, Japan during the 1950’s) where many people have been affected have shed light on the various neurological symptoms associated with mercury poisoning.  This includes:

  • Loss of physical coordination
  • Difficulty in speech
  • Paresthesias (abnormal sensation of the skin)
  • Narrowing of the visual field
  • Hearing impairment
  • Blindness
  • Death

It is for these reasons that many governmental agencies across the globe issue guidance for fish consumers to minimise methylmercury exposure, especially focusing on pregnant women to protect develop foetuses.

But how about the environment?

Mercury poisoning can also occur in a wide variety of animals. American alligators studied in the Everglades of Florida, have shown mercury levels approximately 400 times above those found in farm born and raised alligators, attributed to the severe pollution of the region. Methylmercury pollution is also implicated in the near extinction of salamanders in Acadia National Park (Maine, USA).

Environmental pollution with mercury tends to be in the form of atmospheric release and deposition, which as mentioned previously comes through the burning of fossil fuels – most notably coal. Mercury compounds are also often released directly into the air and land through the application of fungicides.

Natural sources of mercury include geologic deposits, volcanoes, and volatilisation from the ocean. Although practically all water, sediments, soils, and rocks contain a small amount of mercury, some thermal springs and mineral occurrences can contain considerably larger amounts.

Keeping track of mercury

It’s clear that mercury can have a severe negative impact on human and environmental health, which is why a wide range of industries, from petrochemicals to environmental testing and food laboratories, frequently test samples.

We at a1-envirosciences offer the state-of-the-art analyser for mercury elemental analysis, the Nippon MA-3000. It was developed to offer customers highly accurate analysis to a ppb (parts per billion) range, without requiring specialist knowledge or wet pre-treatment. Compared to the standard method of mercury analysis (including pre-treatment) the required analysis time can be reduced by up to 86%!

Conclusion

It’s clear that certain steps must be taken to minimise the impact of mercury on both the environment and food chain. The major human-driven contributor is burning fossil fuels, so an increase in green-energy would go a long way to minimising the likelihood of dangerous levels of mercury.

Evidently, it’s also critical that we continue to test products and samples, to make sure that the levels of mercury are safe. Whether the samples are solids, liquids or gases, the MA Mercury Analysers employ heat-vaporisation to ensure high sensitivity and accuracy and are the gold-standard mercury analysers currently available on the market.

If you’re looking for the gold-standard of mercury elemental analysis or would like to find out more about our wide range of elemental analysers, call us on 0845 873 8181 or reach us by email: sales@a1-envirosciences.co.uk