Arsenic
Arsenic comes in two kinds: the inorganic type, which is toxic and causes cancer, and the organic type in seafood, which passes straight through you. Mixing them up is the most common testing mistake.
Sources of the toxic kind
- Bore and well water in some areas, especially near old mining or naturally high-arsenic rocks. Town water is tested and safe.
- Rice: rice takes up more arsenic than other grains. Brown rice has more than white. Cooking rice in plenty of water and draining it lowers the amount.
- Some imported traditional and Ayurvedic medicines.
- Old treated timber (CCA, the green-tinged pine in older decks and playgrounds): don’t burn it or sand it without protection.
- Work: mining, smelting and some pesticide work.
Symptoms
- Large exposure: vomiting, severe diarrhoea, tummy pain, then numbness and weakness. A medical emergency.
- Long-term exposure: darkened or speckled skin, thick skin on palms and soles, numbness and tingling, and higher risk of skin, bladder and lung cancers.
- Pale lines across the nails (Mees’ lines) can appear weeks after an exposure.
Testing pitfall: seafood
- Fish and shellfish contain arsenobetaine, a harmless organic arsenic that the body clears within 1–2 days.
- It can make a total urine arsenic test look alarmingly high.
- Avoid seafood for 2 days before a urine test, and ask the lab to separate (speciate) toxic inorganic arsenic from harmless forms if the total is high.
See your GP if
- You drink untreated bore water and haven’t had it tested
- You take imported traditional medicines and have skin changes or numbness
- A urine test shows high arsenic: ask about seafood and repeat with speciation
Call 000 for sudden severe vomiting and diarrhoea after a possible poisoning. For advice, call the Poisons Information Centre on 13 11 26.
Weird history
- Arsenic was nicknamed “inheritance powder” in 19th-century Europe, because it was a popular choice for impatient heirs.
- In 1836, chemist James Marsh invented a sensitive test for arsenic, which made it much harder to poison someone undetected.
- Green wallpaper dyed with Scheele’s green, an arsenic pigment, was popular in Victorian homes.
Common questions
Is the arsenic in seafood dangerous?
Mostly not. Seafood contains arsenobetaine, an organic form that isn’t toxic and is passed in urine within a day or two. It can, however, make urine tests look high.
Should I stop eating rice because of arsenic?
No. Eat a variety of grains. Cooking rice in extra water and draining it reduces arsenic. Rice-based drinks are not recommended as the main milk for young children.
What are the symptoms of arsenic poisoning?
Large doses cause vomiting, severe diarrhoea and tummy pain. Long-term exposure causes skin changes, numbness and tingling, and a higher risk of some cancers.
How is arsenic tested?
Usually with a urine test. Avoid seafood for 2 days beforehand, and if the total is high, the lab can separate toxic inorganic arsenic from harmless seafood arsenic.
Helpful resources
- Poisons Information Centre: 13 11 2624/7 advice on poisoning anywhere in Australia. Free.
Evidence and more information
maladywise.com/arsenic/