FIGURE 7-3 Benchmark dose (o) and lower 95% confidence limit on the benchmark dose (+): P₀ = BMR = 0.05, K-power model. Abbreviations: WJ, Woodcock-Johnson Tests of Achievement; CPT, Continuous Performance Test; CVLT, California Verbal Learning Test; TOLD, Test of Language Development; WISC-R:PIQ, Wechsler Intelligence Scale for Children-Revised Performance IQ; WISC-R:FSIQ, Wechsler Intelligence Scale for Children-Revised Full-Scale IQ.

appropriate to choose the lowest BMDL as the point of departure because that could easily result in choosing an unreliable end point (i.e., one with great uncertainty). One suitable option might be to choose the BMDL corresponding to the end point with the lowest BMD, selected from among those end points that show a statistically significant effect of exposure. That would lead to choosing the BMD or BMDL based on McCarthy Perceptual Performance from the New Zealand study. The BMD for this end point estimated from the K-power model is 8 ppm; the corresponding BMDL is 4.

The committee had some reservations about choosing the New Zealand study as the basis for risk assessment. First, it is a relatively small study, with only 237 children in contrast to over 700 studied in both the