In biology, poisons are substances that cause disturbances in organisms, usually by chemical reaction or other activity on the molecular scale, when an organism absorbs a sufficient quantity.
The fields of medicine (particularly veterinary) and zoology often distinguish a poison from a toxin, and from a venom. Poisons are toxins produced by organisms in nature, and venoms are toxins injected by a bite or sting (this is exclusive to animals). The difference between venom and other poisons is the delivery method. Industry, agriculture, and other sectors use poisons for reasons other than their toxicity. Pesticides are one group of substances whose toxicity to various insects and other animals deemed to be pests (e.g., rats and cockroaches) is their prime purpose.
In 2013, 3.3 million cases of unintentional poisonings occurred. This resulted in 98,000 deaths worldwide, down from 120,000 deaths in 1990.