Unintentionally produced during forms of combustion, including burning of municipal and medical wastes, backyard burning of trash, and industrial processes
Also can be found as trace contaminants in certain herbicides, wood preservatives, and PCB mixtures [8]
Dioxin refers to family of 75 toxic chemicals known as chlorinated dibenzo-para-dixoins or CDDs
Co-occur with chlorinated dibenzofurans (CDFs, or "furans")
Furans are family of 135 chemicals, many are chemically similar to dioxins
Two families often discussed as one group
Not produced for industrial purposes
Toxic products
CDDs and CDFs formed during the chlorine bleaching processes at pulp and paper mills
Released into air via emission from municipal solid waste and industrial incinerators
Can travel long distances in air
Bioaccumulants
Stable, persistent with a half-life of seven to twenty years in human body
International Agency for Research on Cancer classified 2,3,7,8 TCDD a known human carcinogen
CDDs and CDFs are endocrine disruptors
Current Status in US [3]
Under FIFRA:
Regulated as hazardous air pollutant (CAA)
Dioxin in the form of 2,3,7,88-TCDD is a priority toxic pollutant (CWA)

Furans[1]
eating contaminated fish and shellfish
infant exposed through breast milk
eating imported food exposed to DDT
eating crops grown in contaminated soil
Eating milk, meat, and by-products
Infants exposed from breast milk, or through mother's bloodstream in the womb
Breathing in air in building with PCB electrical equipment
air, soil, sediments, food
incineration of municipal solid waste, medical waste
secondary copper smelting
forest fires
land application of sewage sludge
cemet kilns, residential wood burning, chlorine bleaching of wood pulp
backyard burning of household waste may too?
[1] UNEP - Persistent Organic Pollutants: Chemical Information. - www.chem.unep.ch/pops/alts02.html
[2] EPA - Persistent Organic Pollutants: A Global Issue, A Global Response. EPA 160-F-02-001. - www.epa.gov/international/toxics/pop.htm
[3] EPA Priority PBT Profiles - www.epa.gov/opptintr/pbt/cheminfo.htm
[4] ATSDR Toxicological Profile for Aldrin and Dieldrin. September 2002. - www.atsdr.cdc.gov/toxprofiles/tpw.html

Dioxins[1]