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19 SECTION 4 Health Effects of Aviation-Related Hazardous Air Pollutants Several studies have assessed the public health risk posed in laboratory animals, and in some cases for individuals by airport emissions. For example, the 2003 human health exposed to these HAPs in occupational settings. Types of can- risk assessment for the Oakland International Airport (OAK) cer associated with exposure to aviation-related HAPs are pri- considered the incremental risk of increased emissions marily lymphoreticular cancers (i.e., leukemia, lymphoma) related to the proposed Airport Development Program on and respiratory tract tumors. Types of noncancer effects four exposure groups: airport workers, off-airport workers, associated with the aviation-related HAPs include alterations residents, and school children (CDM 2003). The assessment of the respiratory epithelium2, neurological effects, develop- concluded that the HAPs of greatest concern were diesel par- mental toxicity, and reproductive toxicity. For some of the ticulate matter, 1,3-butadiene, benzene, and acrolein. Aircraft HAPs, acute effects3 such as irritation of the eyes and respira- particulate matter was not explicitly addressed. The toxicity tory tract, exacerbation of asthma, as well as nausea and dizzi- of aircraft particulate matter is poorly understood (see ACRP ness, may be a concern for shorter-term exposures to higher Report 6: Research Needs Associated with Particulate Emissions concentrations. at Airports). Among the HAPs reviewed, benzene and 1,3-butadiene are A 2001 study of cancer rate statistics concluded that there classified as human carcinogens by the EPA. This classifica- was no general elevation of cancer incidence among popula- tion is based on increased incidence of leukemia in workers tions living near ORD and Chicago Midway Airport (MDW). exposed to either benzene or 1,3-butadiene (USEPA 2002, This study contained no explicit mention of individual HAPs, 2003a). Several other HAPs are considered potential human and stated that the available information was insufficient to carcinogens via the inhalation pathway, based on sufficient evaluate cancer risk for a lifelong exposure to airport pollutants evidence of carcinogenic potential in animals, and limited (Shen and Lehnherr 2001). A separate study concluded that the or inadequate evidence in humans. These HAPs include "hypothetical lifetime incremental cancer risks associated with acetaldehyde and formaldehyde, which cause nasal cell tu- concentrations measured at ORD's airport fence line are ap- mors in rats; and the polycyclic aromatic hydrocarbons proximately five-fold higher than the cancer risks associated (PAHs) benzo[a]pyrene (B[a]P), benzo[b]fluoranthene, and with `background' air quality" (ENVIRON 2000), and that the benzo[k]fluoranthene, which cause respiratory tract tumors chemicals that contribute the most to these risks (i.e., alde- in hamsters and mice (USEPA 1991a, 1991b, 1994a, 1994b, hydes, benzene, naphthalene) are detected in aircraft emissions. 1994c). In addition, in their draft Toxicological Review for naphthalene, EPA classified naphthalene as likely to be car- cinogenic to humans via inhalation exposures, based on 4.1 Health Effects Associated increased incidence of respiratory tract tumors in rats with Aviation-Related (USEPA 2004a). For the remaining HAPs, EPA has deter- Hazardous Air Pollutants mined that there is inadequate evidence to characterize their Chronic exposure1 to many of the aviation-related HAPs carcinogenic potential in humans. has been associated with both cancer and noncancer effects. These health effects have been observed in controlled studies 2 The epithelium consists of cells that line both the outside of the body (i.e., the skin) as well as internal spaces, such as the lung and the gastrointestinal tract. 3 Acute effects occur immediately following exposure to a chemical, as opposed 1 Chronic exposure refers to repeated exposure to chemicals over the course of to chronic effects, which may occur after repeated, prolonged exposure to a several years or longer. chemical.