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.
Sources:
PAC, 1993, 65, 2003. 'Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)' on page 2065 (https://doi.org/10.1351/pac199365092003)
PAC, 2001, 73, 993. 'Risk assessment for occupational exposure to chemicals. A review of current methodology (IUPAC Technical Report)' on page 1023 (https://doi.org/10.1351/pac200173060993)