Quasifree electron attachment to carcinogens

The quasifree electron attachment rate constants k k of recognized carcinogens and noncarcinogens have been measured in nonpolar liquids by a pulse‐conductivity technique. In our initial study of the k k in cyclohexane, we reported that the k k of 37 of 42 carcinogens are diffusion controlled, whereas the k k of 30 of 34 noncarcinogens are less than diffusion controlled [Cancer Biochem. Biophys. 5 , 103 (1981)]. Since k k is strongly dependent upon the electron mobility u u values of k k of the same carcinogens and noncarcinogens were measured in liquid isooctane [ u u (isooctane) = 5.2 as compared to u u (cyclohexane) = 0.22 cm 2 /V · s at 21°C] to determine the effect of the solvent on the k k ‐carcinogenicity correlation. In isooctane, the k k of 29 of 35 carcinogens tested are diffusion controlled, and 23 of 27 noncarcinogens are less than diffusion controlled. These results yield a sensitivity and a specificity, which are two criteria used to evaluate screening tests, of 83 and 86%, respectively. In cyclohexane the sensitivity and specificity are both 88%. These results will be compared with the sensitivity and specificity of the Ames test for the same chemicals, and implications of k k ‐carcinogenicity correlation to designing a carcinogen prescreen test that is based on k k will be discussed.