monocrotophos and alachlor

The dissipation rate of seven currently used soybean and corn pesticides in two tropical soils (Ustox and Psamments) of Brazil was studied in a laboratory incubation experiment. Dissipation half-lives of pesticides ranged between 2 (monocrotofos) and 90 days (endosulfan-beta). The contrasting clay contents of the studied tropical soils (130 versus 470 g of clay kg(-1) of soil) did not influence the dissipation dynamics of pesticides substantially. Mineralization to CO(2) was high [up to 78% of the applied radioactivity (AR)] for the studied organophosphorus compounds and deltamethrin, which also formed considerable amounts of bound residues (>20% of AR) during the 80 days of incubation. The highest portion of nonextractable residues was found for alachlor and simazine (55-60% of AR). In contrast, the nonpolar trifluralin and endosulfan formed only small amounts of bound residues (mostly <20% of AR) but showed the highest dissipation half-lives (>14 days) in the studied soils, also due to a low mineralization rate. When endosulfan-sulfate, as the main metabolite of endosulfan, was considered, the half-life time of endosulfan compounds (sum of -alpha, -beta, and -sulfate) was enhanced to >160 days in both soils. In comparison with the laboratory experiments, dissipation half-life times of chlorpyrifos, endosulfan-alpha, and trifluralin were shortened by a factor of 10-30 in field trials with the same soils, which was related to the volatilization potential of pesticides from soils.

Topics: Acetamides; Brazil; Carbon Radioisotopes; Chlorpyrifos; Endosulfan; Glycine max; Half-Life; Herbicides; Insecticides; Isotope Labeling; Monocrotophos; Nitriles; Pesticide Residues; Pesticides; Pyrethrins; Simazine; Soil; Trifluralin; Tropical Climate; Zea mays

Paraquat, alachlor, butachlor, phorate and monocrotophos, several of the most extensively used pesticides in Taiwan, were investigated for their clastogenicity using chromosome aberration (CAb) induction in Chinese hamster ovary (CHO) cells. Significance levels of the binomial trend analysis and binomial mutagenicity data test were two criteria for the summary judgement of the pesticide clastogenicity. Except for phorate, all pesticides tested were clastogenic to CHO cells in the absence of in vitro metabolic activation by S9. 5 microliters/ml rat-liver extract, S9, were used as the source of in vitro metabolic activation. 3 different outcomes were found after the addition of S9. Paraquat: significant decrease in induced CAbs. Monocrotophos: concomitant occurrence of decreased cytotoxicity and increased clastogenicity. Alachlor, butachlor and phorate: increased cytotoxicities with no sign of enhancement in clastogenicity.

Topics: Acetamides; Animals; Biotransformation; Cell Cycle; Cell Survival; Chromosome Aberrations; Cricetinae; Microsomes, Liver; Monocrotophos; Mutagens; Paraquat; Pesticides; Phorate; Sister Chromatid Exchange; Taiwan