RELATIONSHIP BETWEEN SINGLE-PERORAL ONE-WEEK AND 90-DAY RAT FEEDING STUDIES

To facilitate the planning of critical dosage levels for 90-day and longer-term feeding studies and to predict their probable outcome, 20 materials, predominantly pesticides and surfactants, were fed for 7-day periods in the diets of rats. The lowest dosage level that resulted in minimum effect (MiE) for this period was compared to the single dose peroral LD50 and the MiE for 90 days for each material. The relationship between the single-dose peroral LD50 and the corresponding 90-day or 2-year study MiE was inefficient as compared to the MiE7-day MiE90-day and MiE90-day MiE2-year ratios. The coefficients of rank correlation for these latter ratios were +0.943 and +0.946. Therefore, the following formulas may be used to predict the most probable (median) minimum effect dosage level limit for inclusion of a material in the diet of rats for 2 years, as well as the limit which is predicted to include the MiE 95 times in 100: {A table is presented}. © 1969.