weight, is considered −log10(ld50). the dimensionless value found can be entered in a toxin scale. water as the baseline substance is neatly 1 in the negative logarithmic toxin scale. animal rights concerns animal-rights and animal-welfare groups, such as animal rights international, have campaigned against ld50 testing on animals. several countries, including the uk, have taken steps to ban the oral ld50, and the organisation for economic co-operation and development (oecd) abolished the requirement for the oral test in 2001 (see test guideline 401, trends in pharmacological sciences vol 22, february 22, 2001).