Determination of toxic products released in combustion of pesticides

The manufacturing, distribution and wide use of synthetic pesticides engender new hazards to people and the environment. In addition to mammalian and unintended toxicity of some pesticides, ecosystems face the risk of toxic products released from the unintentional combustion of pesticides; e.g., accidental chemical fires or burning of pesticide-treated biomass. This review summarises and analyses the pertinent literature of the techniques employed to determine toxic products released in thermal decomposition of pesticides, including contributions on large scale experiments from international collaborations sponsored in early 1990s by the European Commission and on small-scale bench top investigations undertaken by a number of independent research groups around the world. The small-scale experimental methodologies are categorised into thermogravimetry apparatus (TG), specialised pyrolysers (Py), calorimeters and tubular flow reactors. Each experimental methodology affords a range of analytical techniques which can be used to identify and quantify decomposition products; such as, thermogravimetry, differential scanning calorimetry, quadrupole mass spectrometry (TG, DSC, QMS). A critical evaluation of these techniques forms an integral part of this review. Both TG and Py serve as fast techniques to study the combustion products of pesticides, but are unsuitable for determining ultra-trace pollutants, e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). The cone calorimeter has been widely applied to assess the fire behaviour of materials. Unfortunately, sample sizes required for experiments in the cone calorimeter and in larger scale tests may lead to emissions of toxic species to the environment with the exhaust gases, requiring careful planning of experiments. Tubular flow reactor systems are designed to elucidate the reaction mechanisms that operate during decomposition of pesticides in the combustion systems. The coupling of a flow reactor to various analytical techniques can offer the comprehensive analysis of combustion products, including gaseous species, volatile and semi-volatile organic compounds (VOC, SVOC) and PCDD/F. Although much remains to be done, advances in the field have provided regulators and the scientific communities with qualitative and quantitative knowledge of toxic products formed in the combustion of some pesticides, to reduce the potential risks of pesticides combustion and gain an understanding into their thermal decomposition mechanisms. (c) 2012 Elsevier Ltd. All rights reserved.