Response of a human tumour cell line to chronic potassium dichromate exposure.

Cultures of the human cell line NHIK 3025 were exposed over an 18-month period to 0.5 mumol/1 potassium dichromate (K2Cr2O7) containing 1 mumol/1 hexavalent chromium. The chronically exposed cells increased their tolerance to K2Cr2O7 in comparison to control populations. The doubling time of the chronically exposed cell populations increased even in the absence of K2Cr2O7, but they did not change their morphology (light level), nor contain as many giant cells as newly exposed control populations. Cells returned to control medium for 6 months after 12-months exposure to K2Cr2O7 showed a gradual but incomplete reversal of these effects. The results are compared with those obtained from cells of non-tumour origin.