lowest-observed-effect concentration (LOEC)

Lowest concentration of a material used in an aquatic toxicity test that has a statistically significant ad-
verse effect on the exposed population of test organisms compared with controls.
Note:       When derived from a life cycle or partial life cycle test, it is numerically the same as the
upper  limit  of  the  maximum  acceptable  toxicant  concentration (MATC).  Also  called
lowest-observed-adverse-effect level (LOAEL).