Exposure to organophosphorous pesticides is generally assessed by monitoring:blood cholinesterase (ChE) inhibition and urinary metabolite excretion. Assay of blood cholinesterase activities is the most common and reliable biological indicator of human exposure to organophosphorous pesticides (OPs)

The purpose of this chapter is to describe the analytical methods that are available for detecting, measuring, and/or monitoring malathion, its metabolites, and other biomarkers of exposure and effect to malathion. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used for environmental samples are the methods approved by federal agencies and organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that modify previously used methods to obtain lower detection limits and/or to improve accuracy and precision.