poison

Any substance that causes injury, illness, or death, especially by chemical means. In biology, the word poison is reserved for substances that are most likely to enter the body via the mouth or airways. Poisonous substances injected by biting or stinging animals are called venom, while those released by bacteria in an infection are known as toxins. The liver removes some poisons from the blood. The majority of poisons may be divided into corrosives, such as sulphuric, nitric, and hydrochloric acids; irritants, including arsenic and copper sulphate; narcotics, such as opium and carbon monoxide; and narcotico-irritants, from any substances of plant origin including phenol acid and tobacco.

How poisons work

At the molecular level, many poisons address one specific biochemical receptor, transporter, or channel. For instance, both carbon monoxide and cyanide ions bind irreversibly to the oxygen transporter haemoglobin, and thereby lead to internal suffocation.

Treatment In noncorrosive poisoning every effort is made to remove the poison from the system as soon as possible – usually by gastric lavage (stomach ‘washout’). For some corrosive and irritant poisons there are chemical antidotes, but for recently developed poisons (for example, the herbicide paraquat) that produce proliferative changes in the system, there is no specific antidote. Drugs (legal and illegal), including nicotine and alcohol, are toxins to the human body.

Legislation and disposal In most countries the sale of poisons, as such, is carefully controlled by law and, in general, only qualified and registered pharmacists and physicians may dispense them; however, industrial and agricultural poisons are dumped into our waters and onto our lands, entering the food chain, and poisoning us and our planet.