AbstractHigh‐boiling coal liquids from the solvent‐refined coal‐I and ‐II (SRC‐I, ‐II) processes, respectively, were fractionally distilled. In the case of SRC‐I process solvent (PS), 50°F distillation cuts were obtained between 550 and 850°F, while for the SRC‐II material, the 50°F cuts were only obtained between 700 and 850°F. These cuts, as well as the parent material, were tested for their ability to initiate skin tumors by applying a single dose (25 mg) to the shaved backs of Charles River female CD‐1 mice. After 2 weeks, the mice received twice weekly applications of 5 μg of the promoter, phorbol myristate acetate. Only a few tumors were found for SRC‐I fractions boiling below 700°F; tumor‐initiating activity increased as the boiling point increased. A similar increase in response with increasing boiling point was seen for the SRC‐II cuts. The initiating activities for the parent materials were similar to those observed for their
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