Dr. David ClarkeTo ask the Minister of Agriculture, Fisheries and Food whether he has made an assessment of the length of time traces of dioxins from pesticides remain in soil after application; and if he will make a statement.
§ Mr. MacGregorI understand that where traces of dioxins have reached the soil they may remain for some years, depending on a variety of physical, chemical and biological processes favourable to degradation. My Department, in conjunction with the Department of the Environment and the Department of Health, has been working on a statement on dioxins in the environment which will be published shortly and will include a discussion of this aspect.
For pesticides, where reaction mechanisms and manufacturing process conditions suggest the possible co-production of dioxin contaminants, the approval of the pesticide is dependent on the manufacturer meeting an acceptable specification for his product. If necessary, maximum limits for dioxin contamination can be set. For example, an upper limit of 0.1 mg/kg for the presence of the most toxic dioxin, 2.3, 7.8—Tetra chloro dibenzo-p-dioxin (TCDD) in the herbicide 2, 4, 5-T was imposed in 1970 and this was reduced to 0.01 mg/kg in technical 2, 4, 5-T in May 1980 as soon as suitably sensitive methods of analysis had been developed and validated. This condition of approval has statutory force under the Control of Pesticides Regulations 1986.