content has slowly increased in American-brand cigarettes over the years. This is a potent alkaloid made in the roots and accumulated in the leaves of plants of the nightshade family (Solanaceae). The presence of nicotine deters herbivores. Thus nicotine was used as an insecticide in the past and currently versions such as imidacloprid are used for this purpose.

is produced by nerve cells and acts as neurotransmitter in both the peripheral and central nervous system of many organisms, including humans. In the peripheral nervous system this chemical stimulates increased activity of skeletal muscle. However, in cardiac tissue this neurotransmitter inhibits the action of heart muscle thus lowering heart rate. Acetylcholine plays a role in memory, learning, and mood in the central nervous system. Inhibiting the transmission of acetylcholine is one way that toxicants can interfere with normal physiological processes.

is an analgesic used to relieve aches and pains, reduce fever, and as an anti-inflammatory. Aspirin also reduces blood clotting through an antiplatelet effect. One of the most widely used drugs, aspirin can cause gastrointestinal bleeding. Also known as acetylsalicylic acid, it was first isolated in 1897 by Felix Hoffmann for the German company Bayer, although abstracts of willow bark, a source of the compound, were used for pain relief by early Egyptians.

is the shorthand for dichlorodiphenyltrichloroethane, an organochlorine insecticide that was first synthesized in 1874. Its insecticidal properties were discovered in 1939 and it was used with great success to kill the insects which transmitted malaria and typhus during the second half of World War II. Subsequently it was determined that accumulation of DDT in the environment had major ecological impact, such as the thinning of the shells of bird eggs which lead to a reduction in hatching success for birds at the top of the food chain.

live in estuaries and marine environments. The family (Tetraodontidae) includes many familiar species, which are called a number of additional names such as puffers, balloonfish, blowfish, and swellfish. These are considered the second most poisonous vertebrates in the world after the golden poison frog. The poison is localized in certain organs such as the liver. Chefs prepare pufferfish as a special delicacy for those who trust their skills preparing the parts that are safe to eat, in Japan (as 河豚, pronounced as fugu), Korea (as bok), and China (as 河豚 hétún).

was introduced in the late 1950s to be used as a sleeping aid, but was then widely distributed for its anti-nausea properties to reduce morning sickness in pregnant women. In 1962 it was withdrawn after it became clear that it is a teratogen, a substance that induces birth defects.

produces opium and poppy seeds. The botanical name (Papaver somniferum) means the sleep-bringing poppy in reference to the sedative properties of opiates. Opium is the source of many narcotics, including morphine and its derivative heroin. The alkyloids in opium bind to receptors in the central nervous system and can lead to addiction and increasing tolerance with use.