Lowest concentration or amount of a substance, found by experiment or observation,
which causes an adverse alteration of
morphology, functional capacity, growth, development, or life span of a target organism distinguishable
from normal (control) organisms of the same species and
strain under defined conditions of exposure.
Source:
PAC, 1993, 65, 2003
(Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993))
on page 2065