For definition of Groups, see Preamble Evaluation.
VOL.: 45 (1989) (p. 239)
Fuel oils are complex and variable mixtures of alkanes and alkenes, cycloalkanes and aromatic hydrocarbons, containing low percentages of sulfur, nitrogen and oxygen compounds. Kerosene fuel oils are manufactured from straight-run petroleum distillates from the boiling range of kerosene . Other distillate fuel oils contain straight-run middle distillate , often blended with straight-run gas oil  and light vacuum distillates , and light cracked distillates [24, 30]. The main components of residual fuel oils are the heavy residues from distillation and cracking operations [8, 21, 31]; various refinery by-products and heavy distillates [20, 26, 27] may be added. In fuel oils consisting mainly of atmospheric distillates, the content of three- to seven-ring polycyclic aromatic hydrocarbons is generally less than 5%. In fuel oils that contain high proportions of heavy atmospheric, vacuum and cracked distillates or atmospheric and vacuum residues, the content of three- to seven-ring polycyclic aromatic hydrocarbons may be as high as 10%; if large quantities of cracked components are incorporated, levels may approach 20%. Fuel oils are used mainly in industrial and domestic heating, as well as in the production of steam and electricity in power plants. Skin and inhalation exposures to fuel oil may occur during its production, storage, distribution and use and during maintenance of heating equipment. During the cleaning of fuel oil tanks, high, short-term exposures to total hydrocarbon vapours have been measured at levels ranging from 100-1600 mg/m3.
A cracked bunker fuel was tested both alone and blended with the residue from the thermal cracking of catalytically cracked clarified oil  by skin application to mice. When applied alone, it induced benign and malignant skin tumours; a further increase was observed when cracked residue was added to the blend.
A West Texas uncracked residue [8 or 21] was tested alone or in combination with the residue described above . When tested alone, it produced one skin papilloma, but a high incidence of skin papillomas and carcinomas was observed when cracked residue was added to the blend.
One sample of fuel oil No. 2 was tested by skin application to mice and produced skin carcinomas and papillomas.
Two samples of straight-run kerosene , one sample of light vacuum distillate , several samples of heavy vacuum distillates  and three samples of light catalytically cracked distillates  produced skin tumours in mice. Several heavy catalytically cracked distillates , residues of catalytically cracked clarified oils , thermally cracked residues  and steam-cracked residues  produced high incidences of benign and malignant skin tumours in mice. (See the monograph on occupational exposures in petroleum refining.)
N.B. - Subsequent to the meeting, the Secretariat became aware of one article accepted for publication which reported that skin tumours developed in mice after skin application of furnace oil [probably fuel oil No. 2] in initiating/promoting studies (Gerhart et al., 1988), and another study which reported that skin tumours developed in mice after skin application of several samples of commercial No. 2 heating oil [fuel oil No. 2] (Biles et al., 1988).
Two large historical cohort studies of workers were conducted in Japan. In the first, an excess of lung cancer was observed among men exposed to kerosene, diesel oil, crude petroleum and mineral oil considered as a group. In the second, an excess of stomach cancer was observed among workers possibly exposed to kerosene, machine oil or grease. Leukaemia was reported to have occurred in excess in industries where kerosene, paraffin oil or petroleum combustibles were said to have been used or produced. Since none of the exposures could be defined clearly, these results are difficult to interpret.
In a large case-control study, a significant excess of colorectal cancer was associated with estimated exposure to solvents and fuel oil. In a second, an excess of stomach cancer was associated with exposure to kerosene, and excesses of rectal cancer and oat-cell lung cancer with exposure to heating oil.
Three case-control studies found a relationship between lung cancer and use of kerosene stoves for cooking in women in Hong Kong. No distinction was made between exposure to kerosene and exposure to its combustion products.
Kerosene ingestion is a common cause of childhood poisoning and may result in lung damage.
No report specifically designed to study genetic and related effects in humans following exposure to fuel oil was available to the Working Group.
In single studies, kerosene did not induce chromosomal aberrations in rat bone marrow, nor did it induce mutation in cultured mammalian cells or in bacteria.
In single studies, fuel oil No. 2 induced chromosomal aberrations in rat bone marrow and mutation in cultured mammalian cells and in bacteria. Aromatic fractions of fuel oil No. 2 induced sister chromatid exchange, but not chromosomal aberrations, in cultured mammalian cells. One four- to seven-ring polycyclic aromatic hydrocarbon fraction of fuel oil No. 2 induced mutation in bacteria.
In single studies, a heavy fuel oil [B-class] induced chromosomal aberrations in cultured mammalian cells; bunker fuel did not induce mutation in bacteria or algae.
There is inadequate evidence for the carcinogenicity in humans of fuel oils.
There is sufficient evidence for the carcinogenicity in experimental animals of residual (heavy) fuel oils.
There is limited evidence for the carcinogenicity in experimental animals of fuel oil No. 2.
In formulating the overall evaluation, the Working Group also took note of the following supporting evidence reported in the monograph on occupational exposures in petroleum refining. There is sufficient evidence for the carcinogenicity in experimental animals of light and heavy catalytically cracked distillates, of light and heavy vacuum distillates and of cracked residues derived from the refining of crude oil. There is limited evidence for the carcinogenicity in experimental animals of straight-run kerosene.
Residual (heavy) fuel oils are possibly carcinogenic to humans (Group 2B).
Distillate (light) fuel oils are not classifiable as to their carcinogenicity to humans (Group 3).
For definition of the italicized terms, see Preamble Evaluation.
Last updated 01/21/98
See Also: Toxicological Abbreviations