Chemical Contamination Suspected in Cytotoxic Effects of Incubators on BALB 3T3 Cells

We investigated the cytotoxic effects of CO₂ incubators manufactured by company A on the growth of three cell lines, BALB 3T3, L-929 and V79. Proliferation of BALB 3T3 and L-929 cells was markedly inhibited, although BALB 3T3 were more highly susceptible than L-929, and cell growth decreased with decreasing cell density: no colonies were formed when 100 BALB 3T3 or L-929 cells per dish were plated. The growth of V79 cells, however, was not affected. Further, a drastic reduction in colony formation was observed when BALB 3T3 cells were plated in media that had been preincubated in an incubator from company A, then cultured in a different incubator that had previously been shown to have no such cytotoxic effects. All the incubators used in this investigation were shown to be mechanically and electronically in good condition, and to be operating perfectly, being able to maintain temperature, humidity and CO₂ concentration satisfactorily. This study suggests that the cytotoxic effect of company A's incubators is being caused by chemical contamination from materials used during manufacture.