most common leukemia and usually affects adults, particularly men, although it can occur in children (ACS 2004f). Chronic myeloid leukemia (CML) mostly affects adults and is rare in children (ACS 2004h). These 4 types of leukemias can be further divided into sub-types, based on progression of the cancer and cell sub-types.

In 2000, there were 11.9 new cases of leukemia per 100,000 people (15.2 among men and 9.4 among women) and 12.4 deaths per 100,000 (15.9 among men and 9.8 among women) in the US (Ries et al. 2004).

Fuels

The second Gulf War committee found sufficient evidence to conclude that benzene is associated with leukemia, AML in particular. Benzene is a component of all the petroleum-derived fuels under consideration by the current committee and of their exhaust. For example, gasoline contains 0.5–2.5% benzene, and kerosene and the related jet fuels contain 0.1–1% benzene (Ritchie et al. 2003). This committee, therefore, did not revisit the literature related to the possibility of an association between fuels and leukemia.

Combustion Products

Table 4.46 presents the most relevant findings considered by the committee in drawing its conclusion on the possibility of an association between exposure to combustion products and leukemia, in reverse chronologic order within type of study design.

Cohort Study

Boffetta et al. (1988) tracked the vital status of participants in the ACS II prospective cohort 2 years after enrollment, when information that included detailed occupational histories had been gathered. After adjustment for age, smoking, and other occupational exposures, all leukemias considered together (ICD-9 204–208) had an imprecisely estimated risk (RR 1.29) associated with self-reported exposure to diesel-engine exhaust among men who were 40–79 years old at the time of enrollment. The deaths analyzed include those of persons newly diagnosed during the followup period and any occurring among those already diagnosed with leukemia at the time of the cohort’s inception; this introduces the possibility of recall bias into the exposure factor defining the cohort in this nominally prospective study.

Nested Case-Control Study

Wong et al. (1999) conducted a nested case-control study of leukemia in a cohort of US land-based petroleum-distribution workers. The entire group of 35 leukemias and the subgroup of 13 AMLs were analyzed for association with several relevant occupational subcategories (mechanics, drivers, and loaders). None of those occupational groups was associated with increased rates of leukemia or AML.

Case-Control Studies

The early case-control study of patients at the Roswell Park Memorial Institute yielded no clearly positive findings on all leukemias in association with occupations that had likely exposure to combustion products (Decoufle and Stanislawczyk 1977). The most increased risk estimates were in small sets of taxi drivers and mine workers (RR 2.08 and 2.16, respectively),



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