AGRICULTURAL USE OF DDT AND RISK OF NON-HODGKINS-LYMPHOMA - POOLED ANALYSIS OF 3 CASE-CONTROL STUDIES IN THE UNITED-STATES

Objectives-The objective of this pooled analysis was to examine whethe r exposure to DDT was associated with the risk of non-Hodgkin's lympho ma among male farmers. Methods-Data from three case-control studies fr om four midwestern states in the United States (Nebraska, Iowa, Minnes ota, Kansas) were pooled to carry out analyses of 993 cases and 2918 c ontrols. Information on use of agricultural pesticides and other risk factors was based on interviews. Non-farmers (people who had never liv ed or worked on a farm) were used as a reference category. Results-The re were 161 cases and 340 controls who reported use of DDT on animals or crops, or on both, yielding an odds ratio (OR) of 1.2 (95% confiden ce intervals (95% CI) 1.0 to 1.6). Farmers who had used DDT for greate r than or equal to 15 years had an OR of 1.5 (95% CI 1.0 to 2.3). Adju stment for respondent status and use of other pesticides resulted in s lightly reduced ORs. Analyses by the number of days of use a year was limited to the Nebraska data. The most notable increase was found amon g farmers who used DDT for greater than or equal to 5 days a year (OR 2.6, 95% CI 1.1 to 5.9); however, additional adjustment for use of org anophosphates, phenoxyacetic acids, and the individual pesticides lind ane, malathion, and atrazine reduced the ORs to 1.0, 0.9, 1.1, 1.6, an d 1.9 respectively. Conclusions-No strong consistent evidence was foun d for an association between exposure to DDT and risk of non-Hodgkin's lymphoma. It seems that the excess risk initially found may be explai ned by use of other pesticides.