Aquatic Pollution and Coastal Management

Unit 4 : Pesticide pollution

4.9.1.4.Dioxins and Furans
Poly chlorinated dibenzo-p-dioxins (dioxins) and poly chlorinated dibenzo furans are a group of organic chemicals that contain 210 structurally related individual chlorinated dibenzo-p-dioxins (CDDs) and chlorinated dibenzo furans (CDFs)

These are two groups of tricyclic compounds containing 1 to 8 chlorine atoms. Dioxins have 75 possible isomers and furans have 135 positional isomers. Both dioxins and furans are generated from a variety of combustion, incineration of chemical processes. The most significant sources of release to the air include accidental fires and open burning of agricultural wastes, iron and steel wires, power stations and vehicles. Incineration of waste used to be the biggest single source of emission into the atmosphere. Dioxins have been detected in soils, water, sediments, plants and animal tissues in all the regions of the earth.

The most toxic dioxine is 2,3,7,8-TCDD (tetrachloro-dibenzo-p-dioxin)
Dioxins and furans are crystalline solids, insoluble in water, but readily soluble in organic solvents, fats and oils.Dioxins are highly resistant in the environment with reported half-lives in soil and sediment ranging from months to years. Because dioxins have very low solubility in water and low volatility, most are contained in soil and sediments that serve as environmental reservoirs from which dioxins may be released over a long period of time.

Dietary intake is the most important source of exposure to dioxins for the general population. Meat,dairy products, fish and other sea-foods contribute more than 90% of the daily intake for the general population.