Organochlorine insecticide residues in field soils of the Kitakyushu district--Japan 1970-74.

Residues of organochlorine insecticides were monitored in field soils of the Kitakyushu District, Japan, from 1970 to 1974, before and after the insecticides were banned from agricultural fields. The arithmetic mean (AM) and geometric mean (GM) of BHC reached maximum levels in 1970 and 1971, then decreased rapidly during 1972 and 1974. Among BHC isomers, beta-BHC had highest mean levels and was therefore thought to be the most persistent of the isomers in field soils. Residues of aldrin, dieldrin, and endrin peaked in 1970 and/or 1971, and then decreased yearly. The percentage of sites which had aldrin contamination have decreased; those with dieldrin contamination have increased. Mean values of p,p'-DDE, p,p'-DDT, and sigmaDDT declined more slowly than did BHC and cyclodienes. Values of DDT and its related compounds were higher than were those of BHC, aldrin, dieldrin, and endrin. The residues of p,p'-DDE were most frequently detected of the DDT compounds.