This content is current only at the time of printing. This document was printed on 1 February 2015. A current copy is located at http://apvma.gov.au/node/12586
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Maldison Chemical Review
Maldison is a broad-spectrum organophosphorus insecticide and acaricide used to control a wide range of agricultural and veterinary insect pests.
Maldison is considered to be one of the least toxic of all the organophosphorus compounds but it can contain some toxic impurities. The impurities may be formed during the manufacturing process or when maldison is stored, either for long periods or at high temperatures. The safety, efficacy and environmental impact of agricultural and veterinary products can be significantly affected by these impurities.
In 1978, a report of worker poisonings and deaths following the use of maldison indicated that the cause was a toxic degradate, isomalathion. Several subsequent studies have identified other very toxic degradates, such as O,S,S–trimethylphosphorodithioate and O,O,S–trimethylphosphorothioate.