Arsenic Poisoning

Arsenic is a heavy metal that exists in 3 metallic forms, alpha or yellow, beta or black and gamma or grey. It also exists in compounds that may be inorganic or organic. It has been used in medicines, as a pigment, a pesticide, and as a weapon of murder. It shares many toxic features with the other heavy metals like mercury and lead. It is used in the production of glass and semiconductors. It is found in some water supplies and seafood.

Arsenic poisoning occurs through industrial pollution, from water supplies, from contaminated wine or illicit spirits, or from criminal intent. Heavy metal contamination can occur in herbal preparations and nutritional supplements.

The most deadly form of arsenic is arsine. It is a gas with the formula AsH₃. It has been suggested as a possible weapon to be used by terrorists. Organic arsenic compounds are often called arsines. The simplest is triphenylarsine with a formula As(C₆H₅)₃. Arsine is used in the manufacture of semiconductors and the manufacture of organic arsines.

In Victorian times arsenic was commonly used for murder but nowadays it is used much less as it is more difficult to acquire. Health and safety at work has also improved so that in this country, both acute and chronic arsenic poisoning is rare. The situation in developing countries is different and in the late 1990s contamination of water supplies in Bangladesh caused the largest outbreak of arsenic poisoning ever.

Men are more likely to experience industrial arsenic exposure than women.

Sources of arsenic include:

• Pesticides
• Herbicides
• Fungicides
• Wood preservatives
• Ceramic enamels
• Paints
• Tobacco (there may be as much as 6 micrograms per pack)
• Burning of fossil fuels as arsenic is a contaminant
• From the diet, as organic arsenic from fish and seafood
• In the USA, illicit whiskey (moonshine) is a possible source of arsenic poisoning.¹

Occupational exposure can occur in:

• The smelting industry (arsenic is a by-product of ores containing lead, gold, zinc, cobalt and nickel)
• The microelectronics industry (as gallium arsenide)
• Coal power plants
• Jobs involving the manufacturing of glass and fireworks
• Jobs with contact with pesticides
• Jobs with contact with wood treated with arsenic as a preservative

Symptoms and signs

• Arsenic exposure is usually occupational but can result from deliberate poisoning.
• Take a work history when a patient presents with painful peripheral neuropathy.
• Exposure to arsine gas is usually the result of an industrial accident and the worker presents rapidly with the fact.
• Unusual cases require a careful history regarding dietary and nutritional habits, hobbies, and alcohol abuse.

Acute Poisoning

• Within 30 minutes of exposure there is a metallic taste in the mouth and slight odour of garlic in the breath along with dry mouth and dysphagia.
• This is followed abruptly by severe nausea and vomiting, colicky abdominal pain and profuse diarrhoea, sometimes bloody with rice water stools.
• If a large amount has been ingested, cyanosis, cold clammy extremities, hypoxic encephalopathy, convulsions and acute tubular necrosis may occur following shock. Hyperpyrexia, pulmonary oedema and acute haemolysis may also occur.
• With a smaller amount the patient will have severe headache, vertigo, periorbital oedema, skeletal muscle cramping and evidence of renal damage manifested as oliguria, proteinuria, and haematuria.
• If death does not occur in the first few hours from shock, the patient may die a few days later from acute liver failure or renal failure.
• Cardiac manifestations include acute cardiomyopathy, subendocardial haemorrhages, and ECG changes of prolonged QT interval and non-specific ST and T wave changes. There is risk of ventricular fibrillation.
• If the patient survives, then 2 to 4 weeks after ingestion there is hair loss, Mee's lines that are white transverse lines seen on the nail plate up to a year after arsenic ingestion, sensorimotor peripheral neuropathy that is usually seen 2 to 8 weeks after exposure, skin changes as in chronic poisoning and possibly chronic renal failure.
• Arsine gas causes acute haemolytic anaemia and marked chills. Haemoglobinuria makes the urine black.

Chronic exposure:

This is much more insidious and difficult to diagnose.

• The earliest skin lesions are persistent erythematous flushing. Hyperkeratosis follows with desquamation of the palms and soles, pigmentation changes, brittle nails with Mee's lines, patchy or diffuse alopecia and oedema of the face, periorbital region or ankles.
• Bowen's disease is a long-term complication of chronic arsenic poisoning and is pre-malignant.
• Neuropathy is characteristic. It is usually a symmetrical sensori-motor polyneuropathy with paraesthesia, numbness, and pain, particularly of the soles of the feet. Eventually, muscular atrophy and ataxia are seen.
• Encephalopathy may occasionally occur, with severe headache, personality disturbance, convulsions or coma.
• Other features of chronic arsenic poisoning are nausea, vomiting, diarrhoea and irritability.
• There can be hepatic and renal damage.

Other forms of poisoning like lead, mercury and botulism, gastroenteritis and haemolytic uraemic syndrome. The skin lesions look like other forms of dermatitis.

• FBC will reveal a hypochromic, microcytic anaemia as with all heavy metal poisoning although interference with folate metabolism can produce a megaloblastic picture. Arsine produces haemolytic anaemia.
• Urea, creatinine and electrolytes to assess renal function.
• Liver function tests.
• Blood levels of arsenic should be less than 50 micrograms per litre. In poisoning the figure is often several hundreds to several thousands.
• A urine spot test for arsenic may be helpful but a 24-hours collection for total arsenic excretion can be diagnostic and useful following therapy. A clearance of more than 50 micrograms per litre is unusual. Shellfish can raise this if consumed in the last 3 days but the arsenic is organic and not dangerous.
• Nerve conduction studies may confirm peripheral neuropathy.
• In acute poisoning an ECG can reveal arrhythmias.
• Plain abdominal x-ray may show opacities in the stomach as arsenic is a heavy metal.
• 2 to 4 weeks after ingestion arsenic is bound to keratin in skin, nails and hair. Analysis of hair² is often used. 4 weeks after ingestion it is in bones. Analysis of hair can diagnose arsenic poisoning many years after death.

Malnutrition³ and Hepatitis B seem to make the individual more susceptible to the toxic effects of arsenic.

Arsenic poisoning has been classified into 4 stages, 7 grades and 20 subgrades⁴ but this is not common practice.

Non-Drug

• Once arsenic is in the tissues treatment may be to no avail, so efforts should be made to remove arsenic from the body before it reaches the tissues. Gastric lavage is used.
• Haemodialysis at an early stage can clear a substantial amount of arsenic.
• In arsine exposure, severe haemolysis can be life threatening despite chelation therapy. Multiple transfusions and even exchange transfusion may be necessary.
• In the acute condition, blood and fluid loss will need replacement. Chelation therapy and haemodialysis should be implemented as soon as possible.

Drugs

• Dimercaprol is the first-line agent for treating arsenic poisoning. Other chelating agents are sometimes used.
• The results of treatment with vitamin E and selenium are unimpressive.⁵
• Pain may require strong analgesics.

Chronic exposure increases the risk of cancer of lung⁶, skin, liver, kidney, colon and bladder as well as diabetes.

• After acute ingestion peripheral neuritis may not present for 2 or 3 weeks.
• Unless there is industrial exposure, check other members of the family as they may also have been exposed. Children do not seem to be more susceptible.⁷

Arsenic was used medicinally in "Fowler's Solution" (1% arsenite) and prolonged use led to chronic skin effects. This was noted by Hutchinson in 1888.

Bangladesh was proud that 97% of its population had access to piped water. This was free of bacterial contamination that caused so much disease but it later transpired that much of the piped water was high in arsenic. It is estimated that 29-77 million Bangladeshis i.e. 23 - 62 % of the 125 million population are at risk of arsenic poisoning. According to some estimates, arsenic in drinking water will cause 5 million deaths in Bangladesh. The World Health Organisation (WHO) has called it the "largest mass poisoning of a population in history". Other countries including the USA, Mexico, China and Chile have discovered arsenic in their water supplies. Chronic arsenic poisoning is likely to become an international health issue and requires research and awareness worldwide. Exactly how arsenic gets into water-soluble form in groundwater remains controversial but some plants have the ability to remove arsenic from the environment.⁸