Health Assessment Document for Diesel Emissions - NSCEP | US ...

1 to reflect the potency of several combustion emissions reasonably well, DE differs from these
2 emissions because of the presence of an insoluble carbon core.
3 Despite these uncertainties, they are considered, collectively, adequate to place reasonable
4 bounds on risk. An upper-bound lung cancer risk from lifetime exposure to DE at a particulate
5 matter concentration of 1 J.lg/m 3 of 2 x 10· 3 , based on the estimate derived by McClellan et al.
6 (1989), using the case-control study of Garshick et al. (1987) and assuming a mean exposure
7 concentration of 125 J.lg/m 3 is recommended. It is considered to be a reasonable upper bound
8 because relative risk ratios were either less or only slightly greater in other epidemiology studies
9 withDE. Furthermore, exposures were unlikely average less than 125 J.lg/m 3 particulate matter
10 assumed. A lower bound of 1 x 1 o-s /(J.lg/m 3 ) is recommended. MLEs slightly less than this value
11 were obtained from animal bioassay data by Chen and Oberdorster (1996) using a biologically
12 based dose-response model and assuming nonthreshold effects for particles and by estimates
13 based on use ofB[a]P as a dosimeter according to the Pike and Henderson (1981) report and
14 B[a]P content ofDE reported by Heinrich et al. (1995). Most comparative potency estimates
15 were only slightly greater than 1 x .1Q- 5 IJ.lglm 3 • ·The lower bound is considered to be reasonable
16 for at least two reasons. First, the latter two approaches are based on effects of the organic
17 constituents. Second, while they are likely to be the primary cause of lung cancer at low doses,
18 other factors such as particle effects and reactive oxygen species may play some role. Thus, risk
19 is unlikely to be significantly lower. This conclusion is supported by animal data-based
20 calculations of Chen and Oberdorster ( 1996) using a biologically based, low-dose extrapolation
21 model.
22 Finally, the 95% lower-bound estimate of risk, assuming exposures of 500 J.lg/m 3 , is 5 x
23 10- 5 /J.lg/m 3 • The range of human data-based risk estimates therefore encompasses a large portion
24 of the recommended bounds of 1 to 200 x 10" 5 /J.lg/m 3 •
25
26 11.5. REFERENCES.
27
28 Ahlman, K; Koskela, RS; Kuilla, P; Koponen, M; Annanmilld, M. (1991) Mortality among sulfide ore miners. Am J
29 Ind Med 19:603-617. ·
30
31 Albert, RE; Chen, C. (1986) U.S. EPA diesel studies on inhalation hazards. In: Ishinishi, N; Koizumi, A; McClellan,.
32 R; StOber, W, eds. Carcinogenicity and mutagenicity of diesel engine exhaust. Amsterdam: Elsevier, pp. 411-419.
33
34 Albert, RE; Lewtas,J; Nesnow, S; Thorslund, TW; Anderson, E. (1983) Comparative potency method for cancer
35 risk assessment: application to diesel particulate emissions. Risk Anal3: 101-117.
36
37 Benhamou, S; Benhamou, E; Flamant, R. (1988) Occupational risk factors of lung cancer in a French case-control
38 study. Br J lnd Med 45:231-233.
39
40 Bhatia, R; Lopipero, P; Smith, AH. (1998) Diesel exhaust exposure and lung cancer. Epidemiology 9:84-91.
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