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The effectiveness of chlorine and oxygen bleach soak pre-treatments in removal of chlorpyrifos from cotton was examined. A 0.5 mL aliquot of chlorpyrifos (1.0% a.i., emulsifiable concentrate) was pipetted onto fabric specimens cut from 100% cotton. Laundering treatments included: no pre-treatment/one and two washes; Spray ‘n Wash® pre-treatment/one and two washes; oxygen bleach soak/1 wash; and chlorine bleach soak/one wash. Analysis of variance indicated significant differences (p < 0.001) in percent residue remaining among laundry treatments. The most effective laundry protocol included a 0.4% chlorine bleach 3-hour soak at 50°C (0.03% residue remaining), followed by the 2.5% oxygen bleach 12-hour soak at 50°C (3.3% residue remaining). The least effective was a single wash with no pre-treatment (44.7% residue remaining). Specimens subjected to 0, 5, 10 and 25 chlorine bleach soak/washes became progressively weaker, but users may accept workwear with lower durability in exchange for low residues of chlorpyrifos when the chlorine bleach pre-treatment is used.

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