Mercury exposure and poisoning

About mercury

Mercury is a natural substance present in the earth's crust and is found in 3 forms:

• Elemental mercury – such as mercury in thermometers and dental fillings
• Organic mercury – elemental mercury is converted by bacteria in water to methylmercury, which is ingested or absorbed by fish and enters the food chain
• Inorganic mercury – is naturally present in combination with other elements in mineral ores. Inorganic mercury may be released into the air when coal is burned to generate power. It is also produced as a waste product in various industrial processes.

Most mercury exposure to humans is through methylmercury that has entered the food chain through fish. Typically, larger or older fish have a higher level of mercury.

Inhaling mercury vapour can cause acute mercury poisoning. Preventing or minimising exposure to mercury in your environment is the best way to reduce your risk of mercury poisoning.

Sources of mercury exposure

Common sources of mercury exposure include:

• Larger fish species – if eaten in large quantities can increase the amount of mercury in your body.
• Fluorescent lamps, low-energy light bulbs and batteries – if broken, there is a risk of inhaling mercury vapour and absorbing mercury through skin contact.
• Mercury thermometers – pure mercury (or ‘quicksilver’) from broken thermometers poses some risk to people if they inhale mercury vapour or absorb mercury through skin contact.
• Dental fillings – modern white fillings do not contain mercury. Amalgam fillings contain mercury that when replaced and removed from teeth, increase the risk of mercury exposure from inhaling mercury vapour or swallowing amalgam fragments.

Reduce exposure to mercury

There are precautions that you can take to minimise your exposure to mercury while also reducing the amount of mercury in our environment.

Reduce exposure to mercury from fish

Learn about the types of commercially available fish and recreationally caught fish that are more likely to contain higher levels of mercury.

Most people can still eat fish with higher levels of mercury, however, Food Standards Australia and New Zealand (FSANZ) recommend that they should be eaten less often. This is especially important for pregnant women, women planning pregnancy, children and people with kidney disease. Refer to the FSANZ website for guidance on portion size and number of portions of different types of fish that can be safety consumed in Australia.

Some freshwater species of fish in Victoria can have high levels of mercury due to Victoria’s goldmining history. Goldmining has increased the level of mercury in some riverbeds and sediments. Large brown trout and redfin, in the Upper Goulburn River, Lake Eildon and surrounding rivers, are likely to have high levels of mercury.

Fish oil products and supplements are not a major source of dietary mercury and there is no need to restrict your intake due to mercury content.

Reduce exposure to mercury from fluorescent lamps and low-energy light bulbs

In 2010, new standards were introduced for low-energy bulbs in Australia. The amount of low-energy light bulb use has greatly increased. These light bulbs contain small amounts of mercury and are also known as compact fluorescent lamps (or CFLs). Fluorescent tubes are also a type of lamp that contain mercury.

The amount of mercury in a single bulb or lamp is very small and unlikely to cause harm to people. However, care needs to be taken when a bulb or lamp is broken as this will release the mercury vapour. Refer to the Environment Protection Authority Victoria website for how to clean up mercury spills.

Reduce exposure to mercury from thermometers and other devices

Spirit-containing thermometers are now widely available, but some people still use thermometers containing 'quicksilver' mercury. These are not dangerous when they are intact, but if broken there is the possibility of mercury exposure through inhaling mercury vapour and absorbing mercury through skin contact. These spills should be cleaned up immediately and carefully.

Other devices around the home can contain more than 2 tablespoons of mercury. These include thermostats and some medical equipment (such as a sphygmomanometer which measures blood pressure).

Refer to the Environment Protection Authority Victoria website for how to clean up mercury spills.

Reduce exposure to mercury from dental fillings

The best way to avoid dental fillings is to take good care of your oral health.

Dental fillings are used to treat damaged or worn teeth and can be made of amalgam or alternate materials that are similar in colour to teeth. Amalgam is used because of its strength, especially in the back teeth that are under a lot of pressure during chewing.

Alternate materials for fillings that are similar in colour to teeth are not as strong as amalgam, but they do not contain mercury. However, ‘old’ metal amalgam fillings contain much higher levels of mercury that when removed or replaced can release mercury vapour that a patient can inhale.

When removing these old amalgam fillings, dentists place a protective sheet over the mouth of the patient during the procedure. This catches any amalgam fragments before they can be swallowed. A high-pressure suction unit is used to remove most of the solid amalgam and any mercury vapour.
Some people are advised to avoid getting new amalgam fillings and if possible, avoid having existing amalgam removed or replaced:

• Pregnant women – mercury may cross the placenta and enter the bloodstream of the unborn baby
• Women who are breastfeeding – mercury may be passed to the baby through breastmilk. But, if the nursing mother has limited their mercury intake up to and during pregnancy, the amount transferred in breast milk will be very low. The benefits of breastfeeding far outweigh any risk posed by the small amount of mercury that may be present in human milk.
• Children – levels of mercury may affect the brain and nervous system that are still growing and developing. Children’s teeth are sensitive to the effects of any chemical substance in the environment, including mercury
• People with kidney disease – high levels of mercury exposure can affect the kidneys, so exposure to mercury should be minimised.

People who are most at risk from mercury

The effect of mercury exposure depends on the type of mercury. In general, mercury tends to affect the nervous system. This means that unborn babies and children are at more risk because their nervous systems are developing.
People at higher risk from mercury exposure include:

• unborn babies
• infants
• children up to 6 years of age
• people with kidney disease
• people born before the 1950s who were exposed to mercury in baby products and contracted pink disease
• workers in industrial settings where mercury is used or produced.

Pregnant women should avoid mercury so that it is not transmitted to their unborn baby via the bloodstream. Levels of mercury in breastmilk are normally not high enough to be a risk for babies.

Pink disease and mercury

Until the 1950s, teething powders and other products for babies contained mercury and some babies contracted pink disease.

In this condition, the feet, hands and the tip of the nose are bright pink. Other symptoms included skin problems, diarrhoea and lethargy.

Pink disease is now rare, but adults who had pink disease are more sensitive to mercury and may have other health complaints.

Symptoms of mercury poisoning

Health effects from exposure to mercury depend on the amount and form of mercury, the pathway and duration of exposure and age.

Symptoms of poisoning from elemental mercury

This type of poisoning is most likely to occur if there is a spill of mercury from a thermometer or other mercury-containing device. Mercury poisoning is often caused by inhaled mercury vapour, especially in places where there is poor ventilation.

Symptoms include:

• tremors
• headaches
• difficulty sleeping
• impaired sensations
• muscle weakness and twitching
• emotional changes (mood swings, irritability, nervousness)
• kidney damage
• breathing difficulties
• death.

Symptoms of organic (methylmercury) poisoning from fish

Most people have some methylmercury in their tissues, but these are at a level that does not pose a risk to human health. Excess methylmercury particularly affects the nervous symptom.

Methylmercury poisoning can cause disturbances in:

• peripheral vision
• sensation, especially on the hands, feet and mouth
• coordination and walking
• speech and hearing
• muscle strength.

Symptoms of poisoning from inorganic mercury

This type of poisoning is more likely to be related to industrial exposure. Symptoms of inorganic mercury poisoning include:

• skin conditions (rashes and dermatitis)
• breathing problems
• mood changes
• problems with memory
• mental health issues
• reduction in muscle strength.

Diagnosis of mercury poisoning

Poisoning from methylmercury can take weeks or months to appear. Exposure from a chemical spill of elemental mercury or inorganic mercury might give you symptoms more rapidly.

Mercury poisoning is diagnosed by testing your blood and urine for mercury levels. Urine might be collected over a 24-hour period. Your doctor will ask about the history of your possible exposure.

If mercury poisoning is suspected, treatment might begin before the diagnosis is confirmed. This is because the test results can take some time to come back to the doctor.

Treatment of mercury poisoning

If mercury poisoning is suspected in a person who is very ill, treatment will likely be chelation therapy. This is regardless of the form of mercury that caused the poisoning.

Chelation therapy is made up of compounds that enter your bloodstream and bind to the mercury so that it can be eliminated by your body.

Clean-up, disposal and recycling of mercury

For information on how best to recycle or dispose of fluorescent lamps, low-energy light bulbs and mercury-containing batteries used in your home, contact your local council.

For public lighting and industrial sectors, FluoroCycle is a voluntary national scheme that recycles mercury-containing lamps for industrial and public lighting use.