Page 28 - Curriculum Visions Dynamic Book

Chlorine and the environment
One of the main uses of chlorine is
to combine it with organic substances. This produces organochloride compounds, liquids which can be important solvents (for dissolving other substances), or added to textiles to make them fire resistant. They are also vital as pesticides and fungicides, and they are widely used throughout the world.
The use of these chemicals has made it possible for some pests and diseases to be kept under control. However, most of these substances are extremely poisonous and do not readily break down in the environment. Halogens therefore pose some quite severe environmental problems if used unwisely.
 New insecticides are being developed all the time so that they can be more effective and less harmful to the environment.
PCBs
One group of the most notorious organochlorides is known as PCBs (polychlorinated biphenyls). They have been widely used in making electrical appliances, power station transformers, etc. At the time of their use, until a series of accidents occured, nobody realised that waste water containing traces of PCBs was highly dangerous. Much of this material becomes mixed up in the river muds. In one site on the Hudson River in eastern USA, PCBs gradually worked their way up the food chain from worms in the river muds, through fish, to humans until traces of PCB could be found in mother’s milk.
The problem exemplified here, however, applies to many chlorine- containing compounds because chlorine reacts with all other materials. No one knows what the effects are of some of the compounds created as a result
of something so well meaning as the chlorination in public water supplies.
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