The bitter-sweet taste of toxic substances
Box 2 | Cyanide and arsenic
People have been poisoning other people for centuries. Sometimes it has been deliberate – Cleopatra, a queen of ancient Egypt, is said to have tested the efficacy of poisons on slaves before using snake venom on herself. And at other times it has been accidental – the ancient Romans systematically poisoned themselves by funnelling their water through lead-based pipes and by using lead to sweeten and store their wine. Cyanide and arsenic have been involved in both deliberate and accidental poisonings.
Cyanide
Cyanide is very popular with crime writers, but it is also used in mining when extracting gold and silver. (This is one reason why gold and silver mining can be controversial – the leakage of cyanide from processing sites can affect the health of humans and other animals.) Cyanide can be absorbed via the lungs, skin and stomach, from where it is distributed throughout the body. It inhibits certain enzymes within cells, preventing oxygen use by the cell and causing cell death. At lethal doses for humans, death can occur within 15 minutes.
Arsenic
Another substance popular with crime writers is arsenic, the twentieth most common element in the Earth's crust. Arsenic occurs in many forms, but is most toxic as an ion because it reacts with sulfur-containing groups on certain enzymes.
Exposure to non-lethal levels of arsenic over a long period of time may result in chronic poisoning and carcinogenic (cancer-causing) effects. For this reason, arsenic remains a work-safety issue in industries where it is still used, such as in the manufacture of weed killers and insecticides, the preservation of wood, and in the extraction of lead and copper ores.
The symptoms of acute arsenic poisoning occur in two forms. In the paralytic form, a severe paralysis develops within 1-2 hours, often accompanied by signs of delirium. In the gastrointestinal form, symptoms such as nausea, headache, intense pain, vomiting and diarrhoea are dominant.
The strange case of arsenic poisoning
Despite the apparent demise of Agatha Christie-like poisonings, arsenic remains a hazard in today's society. According to a 1996 edition of the Medical Journal of Australia, a middle-aged man, his wife, his father and his dog developed severe abdominal pain, vomiting and diarrhoea after eating a meal grilled on a wood-fired barbecue. Later, symptoms such as tingling of the fingers, facial numbness, painful cramps in the torso and flaking skin on both hands appeared. Tests on one of the men revealed abnormally high levels of arsenic in his urine.
This wasn't a murder attempt. In preparing the fire for the barbecue, the family had obtained wood off-cuts from a nearby building site. Although proof was not obtained, it is believed that some of these off-cuts had been impregnated with copper-chrome-arsenate, a substance commonly used to protect non-durable timbers from insect and fungal attack. When burnt, the arsenic in the wood vaporised, contaminating the meat. Fortunately, all victims survived.
Boxes
Box 1. Chances and risks
Box 3. DDT and biological concentration
Related sites
Cyanide (WorkSafe Western Australia)
Arsenic and compounds fact sheet (Department of the Environment and Water Resources, Australia) Arsenic and its compounds
(National Occupational Health and Safety Commission, Australia)
Cyanide poisoning
(National Occupational Health and Safety Commission, Australia)
Page updated June 2006.