ABSTRACT
Halogens are the related elements chlorine (Cl), bromine (Br), uorine (F), and iodine (I). They may exist as gases (Cl2, F2), a liquid (Br2), or a solid (I2). Halogenated hydrocarbons, also known as organohalogens, are a group of organic compounds of diverse structure to which one of these halogens has been attached. The core structure may be either simple, consisting of one or two carbons, or it may be a more complex aromatic one (halogenated aromatic hydrocarbons or HAHs). Because they have been implicated almost universally in toxic reactions in mammals and lower species (including carcinogenesis in some), it is appropriate to consider them as a group despite their chemical diversity. Polycyclic aromatic hydrocarbons (PAHs) are multiringed, planar chemicals that share many of the same toxicological properties as HAHs.
