EXTRAPOLATION FACTORS FOR SMALL SAMPLES OF PESTICIDE TOXICITY DATA - SPECIAL FOCUS ON LD50 VALUES FOR BIRDS AND MAMMALS

For the registration procedure of pesticides it is necessary to have s pecific information and testing data in order to conduct an ecological hazard/risk assessment. The hazard/risk assessment for acute exposure is usually based on a quotient method, where the estimated environmen tal concentration is compared with the lowest available 50% lethal dos e (LD50) value. Generally there are only one or two LD50s available fo r birds and mammals, and an underestimation of the potential hazard/ri sk could be a real possibility. In this article, we propose to estimat e a hazardous dose for 5% of the species (HD5) for LD50 data, correspo nding with the hazardous concentration for 5% of the species fo.-the n o-observed effects concentration (NOEC) data. In addition we describe a method for calculating safety factors that can be used in the case o f small sample sizes, especially those smaller than 4 and including n = 1. The safety factors to be applied to the geometric mean of the LD5 0s for a median estimate of the HD5 of birds and mammals are 5.7 and 3 .8, respectively. Thr safety factors for the 95% confidence limit of t he HD5 of birds for n = 1, 2, and 3 are 33, 20, and 16, respectively. For mammals these safety factors are 15, 10, and 8.