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Between September and March, up to 23,000 dolphins will be harvested in Japan, and most sold as ‘whale meat’ for human consumption. Ric O’Barry, an environmental activist, has recently premiered a documentary, “The Cove”,  he filmed about the annual slaughter of dolphins in the Japanese fishing port of Taiji. He hopes to raise awareness about the plight of these marine mammals and sever the sister-city relationship between Taiji and Broome. The Age produced an article here. However, it may not be economic or environmental debate that saves the dolphins from slaughter – it may be human health and safety. The documentary reveals that some of the dolphin meat tested had mercury contamination of up to 2000 ppm. Mercury poisoning causes serious birth defects, brain and kidney damage, sensory impariment and lack of co-ordination. Mercury contamination may prevent the consumption of dolphin meat – will it prevent the slaughter of these animals? And how does mercury effect the health of these intelligent creatures?

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What is the difference between bioaccumulation and biomagnification? Read an interesting article from the Scientific American – “Bald eagles succumb to poisin in rat eradication on Alaskan island” . Is this an example of bioaccumulation or biomagnification?

Local examples of bioaccumulation from the Australian government department of environment, water, heritage and the arts – uranium in freshwater mussles and fish in the Northern Territory. Bioaccumulation of copper and tungsten in northern Queensland. What types of toxins are most likely to bioaccumulate and biomagnify?

“Almost all mercury compounds are toxic and can be dangerous at very low levels in both aquatic and terrestrial ecosystems. Because mercury is a persistent substance, it can build up, or bioaccumulate, in living organisms, inflicting increasing levels of harm on higher order species such as predatory fish and fish eating birds and mammals through a process known as “biomagnification”. Although the long-term effects of mercury on whole ecosystems are unclear, the survival of some affected populations and overall biodiversity are at risk.” from Mercury and the Environment. Another resource about mercury in our environment here: “Methylmercury Contamination in Fish and Shellfish.” Health effects of mercury here: “Mercury in the body and health effects“.

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Over the two week study break and before you return to school on Monday 13th July, you need to have read Chapters 1 and 2 from the “Issues of Sustainability” textbook. This is an introduction to human health and the environmental effects of pollution in the air, water and soil. Try this worksheet to match various terms with their definitions: environmental-pollutants-worksheet.

Use the following to write notes about mercury, sulphur dioxide and fluoride: unit-4-pollutants-table

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There is a good chance you will get a question about this heavy metal on the exam. Mercury and sulphur dioxide (as well as one other pollutant that you have done a case study on) are pollutants that you will have to know about in a good deal of detail – their sources (point and/or diffuse and/or fugitive), transport mechanisms and sinks. Also, what are the human and environmental effects of exposure to these toxic chemcials? Are they likely to cause acute or chronic toxicity and at what levels? How can the efects of these pollutants be minimised to reduce harmful human and environmental health risks?

Article in the Melbourne Age about disposal of mercury in fluorescent light tubes.

“The nervous system is very sensitive to all forms of mercury. Exposure to high levels of any types of mercury can permanently damage the brain, kidneys, and developing foetus. Effects on brain functions may result in irritability, shyness, tremors, changes in vision or hearing and memory problems. High exposures of mercury vapour may cause chest pain, shortness of breath, and a build up of fluids in the lungs (pulmonary oedema) that can be fatal. Methyl mercury and mercury metal vapours are especially harmful, because more mercury reaches the brain. Long term exposures may cloud the eye. Contact with mercuric chloride can cause burns to the skin and permanent damage to the eyes. Mercury also accumulates in the body.

Mercury and mercury containing products will enter the body if we breathe in contaminated air, drink contaminated water, eat contaminated food, or have our skin come into contact with it. Mercury may be absorbed through the skin. Mercury released into the environment is converted into methyl mercury by bacteria. The methyl mercury will then build up in the tissues of fish and shellfish. Humans (and other animals) may also be poisoned by eating these fish or shellfish.”

National Pollutant Inventory – Mercury Fact sheet

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Mercury is a metal which bioaccumulates – which means it can build up in tissues. It is a potent toxin that affects the nervous system of mammals and is especially harmful to developing fetuses. It can cause sensory loss, tremors, loss of muscular coordination, speech, hearing, and visual problems, as well as increased risk of heart attack.

Mercury gets into the environment when toxic waste is burned and the mercury molecules fall from the smoke onto the ground and into water. It moves up the food chain when herbivores eat contaminated plants and drink contaminated water; these animals in turn are consumed by predators, which have a higher concentration of mercury in their flesh.

Californian scientists have found that the mercury in fish is found as a compound with carbon and sulphur, not as methyl-mercury chloride as previously assumed. Further research needs to be done, but it may mean that the mercury in fish is not as toxic as previously thought.

Find out more at: 

• Catalyst;
• National Pollutant Inventory
• Australian Government Food Standards on Mercury

A comparative Life Cycle Analysis of Incandescent and Compact Flourescent Light (CFL) Bulbs took place on the 7.30 Report that aired on ABC 1 on July 1st, 2008. The discussion analysed the potential harm of the mercury in CFL bulbs when they go to landfill. This discussion is therefore also interesting from the perspective of our study of mercury as a pollutant. The transcript and 6 minute video item can be viewed at http://www.abc.net.au/7.30/content/2008/s2291366.htm

More information at:

Australian Conservation Foundation: The truth about CFL globes and mercury

National Pollution Inventory: Mercury and compunds fact sheet

How Stuff Works: Are fluorescent bulbs really more efficient than normal light globes?

Sustainability Victoria: Types of Lighting.

CHOICE: Compact fluorescent light globes