When data are available, the degree of substitutability may be evaluated through customer preference surveys, analysis of purchasing patterns, estimation of the cross-price elasticities of the products involved fn, or diversion ratios fn.

The basic tool used in the decision making is the PEC/PNEC ratio or, if this is not available, a qualitative estimation.

Due consideration shall be given to the accuracy of this ratio due to variability in the data used both in measurements of concentration and of estimation.

Gollapudi, B. and McFadden, L. G. (1995), Sample size for the estimation of polychromatic to normochromatic erythrocyte ratio in the bone marrow micronucleus test, Mutation Res., 347, pp. 97-99.

When data are available, the degree of substitutability may be evaluated through customer preference surveys, analysis of purchasing patterns, estimation of the cross-price elasticities of the products involved(38), or diversion ratios(39).