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