In Vivo Investigation of Dietary Exposure to 5

In Vivo Investigation of Dietary Exposure to 5 Pesticides

7 Overall conclusions

Effects are seen at lower levels when rats are exposed to the five pesticides in combination than when the rats are exposed to the individually pesticide. This complicates risk assessment for exposure of a combination of pesticides. The assumption of an additive effect as used as a basis for health assessment of residues of pesticides in food seems appropriate and feasible.

The unespected effect on CNS and on brain acetylcholinesterase seen in the initial study could not be repeated in the combined exposure study. However, since the level of mancozeb in the diet in the combined exposure study was only 18-26% of the intended, the effect on CNS in the initial study still might be a true effect.

Combination effects were seen in the combined exposure study, as there was weight increase in the relative liver weight, the thyroid gland weight and a decrease in the weight of the thymus in the combination groups. There were changes in the histology of the liver and the thyroid gland and changes in both white and red blood cells in the combination groups.

Increased liver metabolism of chlorpyrifos to the active metabolite chlorpyrifos could not be confirmed, since the metabolite chlorpyrifos-oxon could not be found in plasma. However, there were some problems with the method used to measure chlorpyrifos. The effects seen in the initial study might be trough other mechanisms e.g. change of toxico-kinetics.