Arsenic is a chemical element (atomic number 33). It is a common cause of heavy metal poisoning. Before the development of synthetic pesticides, it was commonly used in agricultural pesticides, and is still used in household products as, despite its highly poisonous nature, it is considered organic. It is also used in integrated circuits as a compound in semi-conductors, and in certain types of metalwork. Until recently, it was also used as an insecticide in pressure treated wood. It was also used as a compound in pigments for artists.
Arsenic acts at the cellular level, preventing the chemical-to-energy reactions that fuel cells from taking place.
Historically, some arsenic compounds were used in medicine, although all such treatments have now been replaced with safer alternatives.
Accidental arsenic poisoning is extremely rare, and most such cases are the result of deliberate poisoning. Individuals exposed to environmental arsenic (for example, in contaminated water) rarely show acute symptoms, although they are at higher risk for several disorders. There are several arsenic compounds that are essentially tasteless. However, arsenic poisoning is now easy to detect both by chemical tests and gas chromatography. Arsenic will also accumulate in hair, and the location of molecules in the hair can often pinpoint when the patient was exposed to the toxin.
In Emancipation, House suspects arsenic poisoning from the patient's use of pressure treated wood to make furniture. However, modern pressure treated wood does not contain arsenic.