Between 1973 and 1978 major changes occurred in the type of insecticides used for the production of flue-cured tobacco (Nicotiana tabacum L.) in Ontario. These changes are reflected in residues observed in the marketed crop. Residues are presented for the commercial crop collected 1976 and 1977 from the sales floors of auction warehouses and from selected farms between 1976 and 1978. Residues of endosulfan in tobacco exhibited a marked decline from 1976 to 1978, reflecting the Province’s action in 1975 to remove endosulfan from the recommended list of insecticides. Residues of organophosphorus insecticides being used on tobacco, had virtually disappeared by the time the cured leaf reached the auction floors. With no further uses permitted for DDT and dieldrin, residues in soil continued to decline slowly indicating a half-life disappearance of 8 to 10 years; over the three years of the study, residues in tobacco leaf appeared static at approximately 0.5 µg/g for Σ DDT and 0.02 µg/g for dieldrin. No buildup of endosulfan in soil as a result of repeated use over several years was observed. Organophosphorus insecticide residues were present only rarely in soil and tobacco leaf and when found in the crop were at levels near the detection limits. Mean contents of Cr, NI, and Pb in cured leaf were at a fraction of the levels found in dried soils. Hg and MO levels were present in approximately equal concentrations. Cadmium levels in the leaf were 4 to 8 times higher than those found in soil. Metal concentrations decreased between sand and tip leaves.

(Full article published with kind permission from "Tobacco International")