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Part of the problem of determining the safety of thesesolvents for our purposes, is in defining the products. "Pure spirits of gum turpentine" is supposed to be definitive, but lately is applied to the "stumps and limbs" brew that reeks of creosote. It is NOT the same as the turps distilled only from the gum exudations of suitable pine species. Some grades are refined to the extreme and are used in . . . cosmetics! (as are highly refined petroleum distillates as well)
Information on the toxicity of turps and MS is "generically" available if you access the OSHA pages on each, but include a wide range of materials and grades which are not applicable to studio painting. Specific materials are not clearly identified. I really don't know what benefit information from that quarter is to us, since exposure levels stated are ridiculously high, and the bottom line is, if you drink or bathe in either one for a long enough time, you're gonna die .
Mineral spirits is a catch-all term, many grades of MS derive from that fraction of petroleum distillation that entails everything from #2 diesel fuel and kerosene through highly refined grades with specific uses. The most refined being white spirit and the "press wash solvent" printers use to clean their presses. The range includes solvents which are more or less flammable, such as solvents used to clean mechanical parts in repair shops.
K-1 kerosene is probably the best solvent for cleaning oil paint from brushes and tools because it is the most penetrating solvent in that "genus". It is not particularly odorous. It would also be the worst possible additive in oil paint!
Mr. Harding's comments reiterate what I was taught a long many years ago, i.e. the "cutting" or solvent action of petroleum distillates is deleterious to the strength of paint films bound by natural oils and resins in ways turpentine is not.
Certainly Tom has very good reason to avoid turpentine, but this discussion is more than academic, as he can adjust his painting materials and methods to accommodate the omission of turpentine, and the discussion of the merits and disadvantages of materials should be useful for arriving at the best alternatives.
It's possible mediums and varnishes containing turpentine may not distress individuals with a turpentine sensitivity, even when the "straight stuff" does, since resins and oils dissolved in turps change its vapor pressure and volatility.
In all cases, whether one has materials sensitivities or not, avoiding contact with the skin, and ample ventilation in the studio are inviolate rules for the use of all materials associated with oil painting.
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