The Chemicals in Cotton

The World Health Organisation classifies pesticides according to acute toxicity, using the LD50 (Lethal Dose 50%) benchmark. LD50 

III Slightly hazardous Over 500 Over 2000 Over 1000 Over 4000 

Soon after the Second World War, global cotton production changed dramatically when a number of newly discovered neurotoxic chemicals - such as DDT - were first introduced as an alternative means of pest control. Perceiving these chemicals to be a cheaper alternative to the use of labour and machinery, cotton farmers began to use these and former methods of pest control were largely abandoned However, for many developing world couon farmers, the switch to toxic pesticides is a comparatively recent phenomenon. In Pakistan for example, just 5-10% of cotton cropland in the Punjab was treated with pesticides in 1983 By 1991 this figure had escalated to 95-98%. 

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Studies of the inorganics in cotton dust have incorporated the use of a wide variety of techniques. These include X-ray fluorescence spectroscopy, atomic absorption spectroscopy, electron microscopy, energy dispersive analysis of X-rays, X-ray diffraction, atomic absorption spectroscopy, neutron activation analysis and petrographic microscopy. It is necessary to use a wide array of techniques since no single technique will permit the measurement of all trace elements. Steindard chemical techniques to determine the ash content of samples and of various extracts have also been used. In most of these studies the ash fraction has been considered to be a reasonably accurate measure of the inorganic content. 

Due to the potential regression in supply and use of disazo directs and vats as well as more strenuous wet fastness requirements, textile firms dyeing cotton-containing fabrics are projected to switch production to reactive dyes in increasing numbers. Reactive dyes are unique in that the dye with the cellulose in cotton or rayon. In the process the material is impregnated with the reactive dye, base is added to the bath to effect the dye/fiber chemical reaction, and the fabric is then carried through an afterscour. Reactive dyes have several severe drawbacks ... 

Acute dermal toxicity tests are an important method employed in assessing the safety of insecticides to workers. For dermal toxicity tests, typically, an albino rabbit weighing 2-3 kg is shaved around the abdomen and back, and the chemical in question is painted (dry power is moistened with isotonic saline to prepare a paste) over the area, which is then covered with either a rubber sleeve or cotton gauze held in place with a wire screen for up to 24 hr. The mortality is recorded and the median lethal dose obtained is referred to as dermal LD3(). 

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