The fate of carbofuran in rice-fish and livestock farming.
A supervised residue trial was conducted in the Philippines with 5 insecticides, 1 fungicide (benomyl) and 1 herbicide (butachlor) to determine which pesticides remain in rice at harvest. Only the insecticides carbofuran and chlorpyrifos residues were detected in the whole grains, stalks and leaves. Carbofuran 3G was applied to rice paddy by broadcast. The paddy water was drained into a fish pond after 3 h to determine the movement, distribution and loss in an aquatic ecosystem. The residues in fish were concentrated in entrails, some in fillet and least in the head, all at levels below the maximum residue limit (MRL) of 0.02 mg/kg for meat. The residues in pond water were absorbed by kangkong plants (Ipomoea aquatica) for up to 15 days, and declined thereafter. The highest carbofuran residues in kangkong were within the acceptable daily intake for man (0.003 mg/kg). No MRL has been set for kangkong, but an MRL of 0.5 mg/kg has been recommended for cabbage. When [14C]carbofuran-contaminated leaves were fed to lactating goats for 7 consecutive days, the radioactivity was rapidly excreted in urine (77%), and some was eliminated in faeces (1%) and secreted in milk (0.5%). Residues were accumulated in the different tissues of goats but thin-layer and gas chromatographic analysis showed that residues were mostly non-toxic metabolites.