My goodness, so many reasons, so little space - I could stand on my own little soapbox and talk for hours on this one . . . I'll try and headline the basic points - it can be split into 2 sections really; the environmental and social impact and the health implications for you, the wearer . . . here goes.

Environmental and Social Impact of Organic Cotton Vs Conventional Cotton
20,000 people die each year because cotton is the most heavily pesticided crop in the world. Not just the farmers applying the chemicals, usually too poor or ill educated to wear any protection, but their pregnant wives and children too. Maize and other food crops are often planted around borders of these small cotton fields - it's impossible to spray one without the other. Many of the pesticides used in the cotton growing regions are banned here - like endosulphan. Visit the PANUK site to find out a lot more.

Pesticides are indiscriminate - they kill good and bad predators and pests, they work their way up the food chain by a process called bio-accumulation, so fish, birds and animals die a gruesome death. They take away bio-diversity and pollute water courses. Environmentally there is nothing good that can be said of them.
Health Implications for the wearer:

During the processing of conventional cotton many carcinogenic and toxic chemicals are used - many of these stay as residues on conventional cotton clothing. Be particularly aware of “easy care” finishes as these leave formaldehyde, a known carcinogen, on the garment itself.

When you wear organic cotton you can be assured that none of the following, commonly used in the conventional textile industry, have been used.

1. Formaldehyde
2. Aromatic Solvents
3. Heavy Metals
4. Toxic Chemicals
5. Chlorine Bleach
6. Azo dyes that release cancer causing substances

Visit the PANUK www.wearorganic.org site for a lot more interesting (if a bit scary) reading!