Mercury Australia

Mercury (Hg) is a toxic element. It is widely distributed in the environment and is naturally present in aquatic systems, albeit in very low concentrations. The extensive industrial use of pure metal mercury and its compounds, together with widespread agricultural applications in the form of organomercurials, has resulted in serious contamination of surface waters, lakes, rivers and sediments in many locations.

The organic form of mercury accumulates in living organisms as it absorbed by fats, oils and proteins, where it remains trapped. This means that fish, turtles and other aquatic creatures will build up this form of mercury in their tissues, particularly as it moves up the food chain. No form of cooking will remove it, so when people eat mercury laden food, the mercury is transferred to them, in ever increasing concentrations. Further, females may pass on mercury to their children, either through birth or by breast-feeding.

Methylmercury has a high bioaccumulation potential, increasing its concentration in the tissues of organisms at successively as it moves up the food chain. Concentrations in water free from contamination are usually very low (e.g., 50 ng/L), but can be biomagnified to over 300 ng/g in organisms occupying high trophic positions. This represents an mercury concentration increase of 5000 fold from water to the top of the food chain.

An example of a mercury biomagnification in a food web in Lake Murray in Papua New Guinea is provided in the box below:

In Lake Murray, plankton absorb the mercury compounds directly from the water and also from algae. The plankton (with a mercury concentration of 50 ppt) are then eaten by small herbivorous fish, who eat a lot of plankton. All of the mercury from its meals builds up, so it ends up with a mercury concentration of 90 ppt.

Omnivorous fish eats a range of food items, including invertebrates. As invertebrates have higher mercury concentration than algae and plankton, omnivorous fish ends up with a concentration of 500 ppt.

As larger fish eat small fish, the mercury accumulates in them, so they end up with even higher mercury concentrations (1,200 ppt).

The Fish are then eaten by human beings. This creates a high concentration of mercury in the human being that is enough to start causing mercury poisoning.

The Impacts of Mercury Poisoning on Humans

The health impacts of mercury depend its type, the amount absorbed, the age of the recipient (worse for a foetus), and whether it was breathed in, eaten, or absorbed through the skin. Symptoms may include:

– Damage to the nervous, digestive and immune systems.

– Damage to lungs and kidneys.

– Neurological and behavioural disorders (tremors, insomnia, memory loss, neuromuscular effects, headaches and cognitive and motor dysfunction).

– Adverse effect in baby’s growing brain and nervous system (and consequently damage on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills).

– Damage to the skin or eyes.

– Death.