Conclusion

No consistent association between fuels or combustion products and stomach cancer was observed in the studies reviewed by the committee. Two of the studies of fuel exposure (Hanis et al. 1979; Ritz 1999) analyzed esophageal and stomach cancers together, so the committee cannot determine which cancer type may have been associated with exposure. For combustion-product exposure, two studies reported an increased risk of stomach cancer; however, the method used to assess exposure was limited and there was no adjustment for confounders.

The committee concludes, from its assessment of the epidemiologic literature, that there is inadequate/insufficient evidence to determine whether an association exists between exposure to fuels or combustion products and stomach cancer.

COLON CANCER

This review focuses on cancer of the colon (ICD-9 153). Risk factors for this cancer are family history, increasing age, ethnicity, dietary habits, weight and inactivity, and tobacco and alcohol use (ACS 2004p).

In 2000, there were 38.5 new cases of colon cancer per 100,000 people (43.5 among men and 34.8 among women) and 17.6 deaths per 100,000 (21.1 among men and 15.2 among women) in the United States (Ries et al. 2004).

Fuels

Table 4.9 presents the most relevant findings reviewed by the committee in drawing its conclusion on the possibility of and association between exposure to fuels and colon cancer.

Cohort Studies

In a cohort of 3,814 uranium-processing workers, kerosene exposure was associated with a greater risk of death from large intestine cancer, but the CIs included the null (Ritz 1999). Kerosene exposure was assessed with a detailed industrial hygiene survey.

A cohort of 10,763 workers employed at an Amoco Corporation oil refinery in 1970–1980 was retrospectively studied (Nelson et al. 1985, 1987). Exposure was classified by an industrial hygienist on the basis of job type and “rough exposure categories”. Increased SMRs were found for jobs associated with exposure to light aromatic hydrocarbons for all digestive tract cancers (SMR 1.39). Occasional exposure to heavy oils was also associated with increased SMRs for digestive tract cancers (SMR 1.79). No specific digestive-cancer sites were included in the analysis. On the basis of data from the National Cancer Institute, the age-adjusted incidences of gastrointestinal cancers indicate that men are much more likely to be diagnosed with colorectal cancer than esophageal and stomach cancers (Ries et al. 2003). Therefore, it is likely that the increase in digestive tract cancers in the Amoco Corporation oil-refinery workers is due to colorectal cancer.

A cohort of workers at Imperial Oil Limited in Canada was evaluated for cancer outcomes, including colorectal cancer (Hanis et al. 1979; Lewis et al. 2000b; Schnatter et al. 1993). Moderate exposure (defined as less than daily contact with petroleum or its products) and daily exposure were not associated with a greater risk of cancers of the intestines and rectum (the



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