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

1 Exposure estimates for more highly polluted locations are somewhat greater. Estimated
2 mean concentrations of DPM for Los Angeles were reported to be 2. 7 Jlg/m 3 (Sienicki and Mago,
3 1992). McClellan at al. (1986) estimated concentrations on urban freeways and street canyons to
4 be as great as 15 Jlg/m 3 • These exposure estimates are summarized in Table 2-19.
5 Recent Cal-EPA (1996) studies show winter period estimates in three California locations
6 for diesel PM 10 of 4 to 22 Jlglm 3 • A broader Cal-EPA analysis shows average ambient outdoor
7 diesel PM 10 to range from 0.2 to 3.6 Jlg/m 3 across 14 California air basins with a population-
S weighted average of 3.2 Jlglm 3 • Concentrations in occupational settings may be higher.
9 Potentially, diesel exhaust may contribute to levels of a very hazardous pollutant, dioxin.
1 0 Only scant information is available to quantify this, though some study data are available.
11 Dioxin concentrations were measured in a Baltimore tunnel used only by heavy trucks
12 (unpublished). Measurements were also made of the exhaust from a heavy-duty truck during
13 highway travel. Based on these measurements, estimated dioxin production from all truck
14 diesels was estimated to be only 29 gm versus 5,000 gm from all combustion sources in the
15 United States. It is therefore concluded that DE contribution to dioxin levels in the United States
16 is insignificant.
17 The changing composition of DE, (i.e., older engines vs. newer technology ones, heavy-
18 duty vs. light-duty, and engines run under varied operating conditions) gives rise to questions
19 about how the health data and the risk assessment findings in this report, which are based on pre-
20 1998 engines, can be applied to present-day engine exhaust emissions and the resulting ambient
Year
1986
1990
1995
2000
2010
211/98
Table 2-19. Estimated annual ambient concentrations of diesel exhaust particulate
matter (J.Lg/m 3 )
U.S. EPA U.S. EPA U.S. EPA U.S. EPA Sienicki McClellan
(1993) (1993) (1993) (1993) andMago (1986)
Method 1 Method 1 Method 1 Method2 (1992) Highly
Rural Urban National National Los Angeles Exposed
1.1 2.0 1.8 1.5 2.7
0.6 1.2 1.1
0.4 0.7 0.6
0.2 0.4 0.4
15.0
2-57 DRAFT--DO NOT CITE OR QUOTE
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