Those tables are presented in reverse chronological order by each type of study design. The committee reviewed over 500 epidemiologic studies on cancer related to exposure to fuels and combustion products and selected studies that met its inclusion criteria for more thorough evaluation. Briefly, the studies had to appear in peer-reviewed publications, identify exposure relevant to the committee’s charge, and identify a specific health outcome (for example, the study must specify a type of cancer as opposed to considering all cancers together). Chapter 2 discusses the committee’s inclusion criteria in more detail.
This chapter reviews epidemiologic studies of cancer in adults, which would be pertinent to the occurrence of cancer in Gulf War veterans themselves; studies of childhood cancer are reviewed in Chapter 7, on reproductive and developmental effects, because the committee was concerned with such outcomes in the offspring of Gulf War veterans as a possible result of parental exposure. Epidemiologic studies assessing gender-specific cancers (for example, female breast cancer and prostate cancer) are included in the committee’s review. Seven percent of the 697,000 US military personnel sent to the Persian Gulf were women.
For the combustion products of crude oil and petroleum-derived fuels, the epidemiologic data complement the vast amount of toxicologic information on poly cyclic aromatic hydrocarbons (PAHs) (particularly benzo[a]pyrene), other combustion products, and soot. There are numerous studies of occupational cohorts heavily exposed to PAHs (for example, from coal tar and asphalt), usually in combination with other products of combusted petroleum-derived fuels (for example, exhausts from various sources and metals) and soot. The conclusions from that large, complex body of information have been addressed by several expert bodies, including the International Agency for Research on Cancer (IARC 1985), which (IARC 1984a, 1984b) have been virtually unanimous in judging that PAHs and soot are most probably human carcinogens, particularly for skin after dermal exposure.
Urban firefighter studies were not included in the committee’s review. The committee agreed that urban fire fighters are likely exposed to a number of compounds that are not found in combustion products produced from oil-well fires, tent heaters, and vehicles (for example, plastics, asbestos, and PCBs). It would not be possible for the committee to distinguish between health effects in urban firefighters attributable to those compounds versus combustion products as were experienced in the Gulf War. Therefore, the committee made a decision not to include urban firefighter studies in this report.
Cancer sites or types are addressed in this chapter largely according to the ninth revision of the International Classification of Disease (ICD-9).1 That approach is taken in an effort to organize the multitude of site-specific evidence presented in the chapter. In many cases, the findings by various investigators do not follow the strict categorization of the ICD-9.
The cancers reviewed in this section include those of the oral cavity, that is, the lips, the lining of the lips and cheeks, the teeth, the gums, the tongue, the floor and roof of the mouth, and the area behind the wisdom teeth) (ICD-9 140–145); and the oropharynx and hypopharynx, the parts of the throat just behind the mouth (ICD-9 146 and 148, respectively). With cancers of the
ICD codes are revised and updated by WHO. Although ICD-10 codes have been published, ICD-9 codes remain the most widely recognized and used. ICD codes were established by WHO to promote international comparability in the collection, processing, classification, and presentation of mortality statistics. The codes group cancers according to their organ or tissue of origin and their histologic features.