Pakistan Journal of Biological Sciences1028-88801812-5735Asian Network for Scientific Information10.3923/pjbs.2007.2900.2904ShayeghiMansoreh KhoobdelMehdi VatandoostHassan 1220071017In this study, the amount and origin of the pollution of Karaj river and Amir-Kabir dam, which is the most important supply of Tehran's (capital of Iran) drinking water with malathion and diazinon, have been assessed by High Performance Thin Layer Chromatography (HPTLC) technique. This is a descriptive and cross-sectional study. After initial assessments, four stations were selected for water sampling. In all stations, sampling was done in one day, one week, two weeks, one month, two months and three months after insecticide spraying. Extraction and separating of organophosphorus insecticides from water samples was done by acetone and methylen chloride solvents, using decanter. Then, the residue of malathion and diazinon insecticides was determined using HPTLC technique. The residue of malathion and diazinon in water decreases with increasing the distance and time of spraying. The residues of malathion and diazinon insecticides at station 1 and 2, which were close to spraying places, 1-2 months after spraying was more than allowed limits. But at the ending stations (3 and 4), malathion and diazinon were detectable just in the 1 day and 1 month after spraying, respectively. It is unlikely that Tehrans drinking water be polluted with these two insecticides and the most adverse effect can be seen in the area of spraying. Therefore not only the environment, but also the people in area of Karaj river are at risk of chronic toxicity with malathion and diazinon through consuming polluted water and agriculture products.]]>Abdel-Halim, K.Y., A.K. Salam, E.N. EL-Khateeb and N.M. Bakry,20066314911498Ahmad, F.E.,200120649661Ahmad Karam, A. and A. Tahir,2000268992Butz, S. and H.J. Stan,199567620630Castilho, J.A.A. and N. Fenz,1999110523533Denistrop, H.E.,20002000Dogheim, S.M., E.Z. Mohamed, S.A. Gad Alla, S. EL-Saied, S.Y. Emel, A.M. Mohsen and S.M. Fahmy,199679111116Futagami, K., C. Narazaki, Y. Kataoka, H. Shuto and R. Oishi,1997704369373Hela, D.G., D.A. Lambropoulou, I.K. Konstantinou and T.A. Albains,20052415481556Krol, W.J., T.L. Arsenult, H.M.J. Pylypiw and M.J. Incorvia Mattina,20004846664670Na, T., Z. Fang, G. Zhanqi, Z. Ming and S. Cheng,2006123351370Obendore, F.S.K., A.T. Lemley, A. Hedage, A.A. Kline and T. Tank Dokuchanyeva,2006503144Pedersen, J.A., M.A. Yeager and I.H. Suffet, 20064021202127Puglise, P., J.C. Molto, P. Damiani, R. Marin, L. Cossignani and J. Manes,20041050185191Rawn, D.F., S.C. Quade, J.B. Shield, G. Conca, W.F. Sun and G.M. Lacroix,20065419431948Wilsont, P.C. and J.F. Foos,20062528472852