Cutting oils and squamous-cell carcinoma. II. An experimental study of the carcinogenicity of two types of cutting oils.

That mineral oils and their derivatives would induce squamous-cell carcinoma when painted on to the skin of mice was reported by Twort and Twort (1931), and in a series of other papers by these authors which have since been statistically analysed by Irwin and Goodman (1946). More recent work has demonstrated that both straight-run distillates (Woodhouse and Irwin, 1950) and high boiling point fractions of catalytically cracked petroleum oils (Smith, Sunderland, and Sugiura, 1951) may contain numerous carcinogenic hydrocarbons, although to date no pure carcinogens have been isolated from such compounds. The literature which we have reviewed contains surprisingly few references to occupational cancers directly attributable to cutting oil exposure in the engineering industry. However, the relationship between excessive exposure to such products and a high incidence of other occupational skin diseases is well documented (Cruickshank, 1950; Shapiro, 1950). Cruickshank and Squire (1950) have presented evidence, from both clinical observations and biological tests on mice and rabbits, implicating exposure to cutting oils as an occupational cancer hazard. A later publication by Cruickshank and Gourevitch (1952) supported this opinion. In the latter paper the authors suggested that it was quite possible that this cancer risk (exposure to cutting oils in the engineering industry) had not been long enough in existence for it to become apparent from mortality rate studies such as those of Henry (1947). It is interesting to note that in recent years the numbers and uses of the so-called " cutting fluids " have increased considerably. Such cutting fluids generally consist of a relatively stable aqueous emulsion of sulphurized petroleum oil distillates