Chloroform is a colorless, sweetly scented liquid which is most well known for its historical use as an anesthetic, although it has since been abandoned due to safety concerns. Today, chloroform is used in a variety of industrial processes including the manufacture of chemicals, refrigerants, and solvents. It is produced by reacting chlorine with ethanol, and while relatively stable, it is also toxic and should be handled with care. Excessive exposure to chloroform can cause long term health damage to several major organs.

The use of chloroform as an anesthetic dates from 1847, but almost immediately afterwards, concerns were raised about the health of patients who were chloroformed. In 1848, a patient died because her heart went into fibrillation while she was chloroformed, and continued use of the drug only cemented the link between chloroform and cardiac events. By the early twentieth century, chloroform had been abandoned in favor of safer and cheaper drugs, and today has been replaced by anesthetics such as halothane, isoflurane, and sevoflurane, among many others. When a less expensive anesthetic is required, as is the case in some impoverished nations, ether, an older anesthetic, is preferred over chloroform.

The effects of chloroform on the human body, in addition to induction of anesthesia, include damage to the liver, kidneys, and heart. If skin is exposed to liquid chloroform, it will become irritated and form sores. Most agencies concerned with health consider chloroform to be a toxin, and suggest that workers who are exposed to it should use protection for their skin and face. Inhaling chloroform should be avoided, although in some areas people may inadvertently consume it because chloroform sometimes appears in trace amounts in chlorinated water.

Chloroform can easily be carried in water, and when it is exposed to oxygen and sunlight, a chemical reaction forms phosgene, a toxic gas. If chloroform is exposed outdoors, the phosgene will break down and ultimately become harmless, but in enclosed spaces, it can be highly dangerous: in addition to use in modern manufacturing processes, phosgene had a historical use as a deadly chemical weapon in both World War I. In groundwater, chloroform will build up and take a long time to break down, because it is not readily water-soluble. For this reason, most environmental agencies set safety levels for chloroform content, so that water can be routinely evaluated to see whether or not it poses a threat to consumers.