Björn Ekwall, an outstanding Swedish cell toxicologist.

Dr. Björn Ekwall (1940-2000) was an outstanding Swedish cell toxicologist who made pioneering contributions to the field of in vitro toxicology. In particular, he formulated the so called "basal cytotoxicity concept" (1983) which provided a conceptual basis for the estimation of acute systemic toxicity of chemicals in humans by the use of in vitro tests. Björn Ekwall formulated, initiated and, together with a group of dedicated Scandinavian toxicologists, guided the MEIC project (Multicentre Evaluation of In Vitro Cytotoxicity Programme, 1989-1999), in which 50 reference chemicals were voluntary tested in 100 laboratories worldwide by 61 different in vitro assays. This project was unique because human sub-lethal and lethal blood concentrations were used for a first time as a reference system for the evaluation of predictability of in vitro tests for human acute systemic toxicity. The results of MEIC project have shown good correlation between human LC₅₀ values (50% lethal concentrations) and IC₅₀ values (50% inhibitory concentrations from basal cytotoxicity tests), by the use a battery of three 24-h basal cytotoxicity tests (R²=0.77). The MEIC project paved the way to the present validation projects, under EU 6th Framework programme, such as ACuteTox, Sens-it-iv, and ReProTect.