Dioxin compounds are common
covalent chlorine pollutants. To use
Neal Stephenson's metaphor from
Zodiac, a dioxin
molecule is basically a
six-pack (or more, or less) of
covalent chlorine atoms -- or a
raft of covalent chlorine
gunmen come to shoot up your
chromosomes. Covalent chlorine is quite ridiculously bad for you -- and for pretty much any other
organism.
Dioxins are produced by several industrial processes, including the manufacture of paper from wood pulp. (Hemp paper does not involve dioxins.) Several plastics and other petrochemicals also produce dioxins when burned incompletely.
A dioxin compound was the contaminant in Agent Orange that caused a lot of folks in Vietnam to get sick from it.
Dioxins are related to polychlorinated biphenyls, which differ in that they have phenyl rather than benzene rings.