A SURVEY COMPARING THE CHEMICAL-COMPOSITION OF DICOFOL FORMULATIONS SOLD IN THE UK BEFORE AND AFTER THE INTRODUCTION OF THE EC PROHIBITION DIRECTIVE-79/117/EEC

Analysis of 38 formulations marketed by five companies indicated that the active ingredient contents of these products are within the range of 92 to 112%, for dicofol, and 107 to 142%, for tetradifon, of that declared. Manufacturing procedures for dicofol produce impurities related to DDT. The adoption of a prohibition directive in Europe requires that DDT-related impurities represent less than 1 g kg-1 of the dicofol content. Formulations manufactured before the prohibition directive contained these impurities at up to 575 g kg-1 of the dicofol in the formulation. Formulations manufactured after the directive contained these impurities at up to 7 g kg-1 of the dicofol in the formulation. Fewer impurities were detected in the more recent formulations; only o,o'-DDE, o,m'-DDE, o,p'-DDE, m,p'-DDE, p,p'-DDE, o,p'-chloro-DDT and p,p'-chloro-DDT were present. Eight of the 13 samples contained DDT-related impurities at less than 0.1 g kg-1 of the dicofol in the formulation. The major impurities found in formulations manufactured after the directive (in concentration terms) are non DDT-related manufacturing byproducts such as o,p'-dichlorobenzil.