Abstract
Cultured Chinese hamster ovary (CHO) cells were exposed to dilutions of shale oil retort process waters obtained from three different retorting processes located in the Green River oil shale formations in the western part of the United States. Although the intensity of the response was dictated by the process water used, all induced a cytotoxic (reduction in colony‐forming ability) and mutagenic (induced at the hypoxanthine‐guanine phosphoribosyl transferase (HGPRT) locus) response in cells pretreated with dilutions of the waters and subsequent exposure to near ultraviolet light (NUV). Combinations of process water plus NUV yielded mutation frequencies as great as 50% that witnessed for the mutation frequency induced by the potent carcinogen far ultraviolet light. NUV alone was nontoxic and nonmutagenic at the doses of radiation used. Exposure of CHO cells in the dark to nontoxic dilutions of the process waters resulted in small but significant increases in 6‐thioguanine resistant mutants (1–2 times background rates). The biological consequences resulting from the disposal of retort process waters into the delicate environment present in this oil shale region could be further complicated by this photoactivating process.