Mercury
For most Australians, the main source of mercury is fish, and the benefits of fish outweigh the risks if you choose well. The bigger worries are a few big predatory fish in pregnancy and imported skin-lightening creams.
Fish: what to eat
- Pregnancy, planning pregnancy and children under 6: 2–3 serves a week of most fish and seafood.
- Orange roughy (sea perch) or catfish: no more than 1 serve a week, and no other fish that week.
- Shark (flake) or billfish (swordfish, broadbill, marlin): no more than 1 serve a fortnight, and no other fish that fortnight.
- Everyone else: 2–3 serves a week of most fish; shark or billfish no more than once a week.
- Low-mercury picks: salmon, canned tuna, prawns, lobster and oysters.
- A serve is 150 g for adults and 75 g for young children.
Other sources
- Skin-lightening creams and soaps bought online or overseas: some contain mercury and can damage the kidneys and nerves. Avoid unregistered products.
- Broken thermometers and old devices: liquid mercury gives off vapour. Ventilate, don’t vacuum it, and follow your council’s clean-up advice.
- Some imported traditional medicines and work exposure (such as gold mining or some industries).
- Dental amalgam fillings release tiny amounts. Removing sound fillings isn’t recommended, because drilling them out releases more.
Symptoms
- Methylmercury (fish): numbness and tingling, poor coordination, vision and hearing problems. In pregnancy, it can affect the baby’s developing brain.
- Mercury vapour: tremor, mood changes, irritability, insomnia and gum problems.
- Skin creams: kidney damage (swelling, frothy urine), rash, numbness and anxiety.
Testing
- Blood mercury reflects recent fish (methylmercury) exposure. Urine mercury suits vapour or skin cream exposure.
- Testing is only useful if there’s a real exposure. Random “toxic metal” panels and hair tests aren’t reliable (see heavy metal testing).
See your GP if
- You use imported skin-lightening products and have swelling, frothy urine, numbness or rash
- You eat shark, swordfish or marlin often and are pregnant or planning pregnancy
- You were exposed to mercury vapour at work or from a large spill
Weird history
- “Mad as a hatter”: 19th-century felt hat makers used mercury, and many developed tremors and mood changes.
- In Minamata, Japan, factory waste contaminated fish with methylmercury in the 1950s, causing severe nerve damage and birth defects. The global Minamata Convention on mercury is named after it.
Common questions
Which fish are high in mercury?
Shark (flake), billfish such as swordfish, broadbill and marlin, orange roughy (sea perch) and catfish. Most other fish, including salmon, canned tuna and prawns, are low.
How much fish can I eat when pregnant?
Two to three serves a week of most fish and seafood. Limit orange roughy or catfish to one serve a week, and shark or billfish to one serve a fortnight, with no other fish that week or fortnight.
Should I have my amalgam fillings removed?
Not if they’re intact. Removing them releases more mercury vapour than leaving them in place. Discuss any concerns with your dentist.
Can skin-lightening creams contain mercury?
Yes, some imported or online products do, and they can damage the kidneys and nerves. Use only products registered in Australia.
What should I do if a mercury thermometer breaks?
Keep people and pets away, ventilate the room, don’t vacuum or sweep, and follow your local council or EPA clean-up advice.
Helpful resources
- Food Standards Australia New Zealand: Mercury in fishOfficial fish advice for pregnancy and children. Free.
- Poisons Information Centre: 13 11 2624/7 advice on poisoning anywhere in Australia. Free.
Evidence and more information
- Better Health Channel: Mercury in fish
- FSANZ: Mercury in fish brochure (2020)
- US FDA: Skin products containing mercury
maladywise.com/mercury/