Arsenic poisoning

Arsenic is often found in metal ores

Arsenic is known best as a deadly poison, although in small doses it does have medical benefits. BBC News Online looks at the workings of the chemical infamous for its deadly effects.

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What is arsenic?

Arsenic is a semi-metallic naturally-occurring chemical. It is all around us in the environment and we are all exposed to small doses on a regular basis.It is difficult to detect as it is generally odourless and flavourless, meaning people have little idea when it is around.

What is the risk?

Arsenic can kill humans quickly if consumed in large amounts, although small, long-term exposure can lead to a much slower death or other illness. Studies have linked prolonged exposure to arsenic with cancer, diabetes, thickening of the skin, liver disease and problems with the digestive system. It has also been associated with nervous system disorders - feeling tingling or losing sensation in the limbs - and hearing difficulties.

What happens if you are poisoned?

A person exposed to large amounts of arsenic - either through eating or drinking it - will usually die, and symptoms will appear within 30 minutes of exposure. There is a similar outlook for people who breathe large amounts of it, although the onset of symptoms may be delayed as the concentration is likely to be lower. Physical contact with arsenic can cause, initially, the skin to thicken and, with prolonged contact, blood flow to the heart to become decreased.

What are the symptoms?

The first sensations include a metallic taste in the mouth, excessive saliva production and problems swallowing. The next stage is to suffer vomiting and diarrhoea coupled with garlic-like breath, stomach cramps and excessive sweating. As the poison's effects progress, the patient will suffer seizures and go into shock, dying within a few hours. If death does not occur at this stage, it will happen a few days when the kidney fails.

What is the treatment?

Arsenic poisoning can be treated if it is caught early enough, through a series of injections into muscles. The patient needs 2.5mg to 5mg per kilogram of body weight of a drug called dimercaporal every four hours for the first two days followed by two injections on the third day then one a day for the next five days.

What is the environmental threat?

There is growing concern about levels of arsenic in the environment, both from natural occurrence and from pollution. Forty million people in West Bengal and Bangladesh are thought to be at risk from arsenic-contaminated water supplies, although studies are continuing into what effect the poisoning is having.

The contamination is thought to have occurred naturally, as a result of arsenic being released from rocks into underground water supplies. The US Environmental Protection Agency has an ongoing research programme to look into arsenic in the environment and to establish what constitutes a safe level.

What are the benefits?

Small doses of arsenic have been shown to send some forms of cancer into remission, and it can also help thin blood.Homeopathists have also used undetectable amounts of it to cure stomach cramps.

However, therapies involving the chemical are still in the experimental stages.