The plasma cholinesterase measurement will make it possible to identify farmers with abnormal levels. If such cases occur the farmer will be excluded from the study and given advice on how to proceed. The small amount of blood required is not considered as damaging to the farmers' health. However, the finger stick may have minor risks such as momentary pain when the lancet goes into the finger, bruise, visible and sore puncture site for a short period, feeling of dizziness or light headedness. Disposable finger stick lancets will be used to avoid any infectious transmission.