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

1 the Ishinishi et al. (1988) study that were amenable to BMC analysis were the incidence of
2 hyperplastic lesions in male, female, and combined. These results are shown in Table 6-4.
3 The BMC for the most sensitive effect is very similar to the NOAEL (HEC). Most of the
4 BMC values fall between the LOAEL (HEC) and the NOAEL (HEC) from the same data set.
5 Two of the BMCs for the heavy-duty diesel experiment exceed the LOAEL (HEC). This could ·
6 result from the large nuniber of animals and close dose spacing, which allows identification of a
7 lower LOAEL (HEC). These data sets were characterized by very low incidence of lesions at the
8 lowest exposure level, and the assignment of the LOAEL (HEC) was difficult because of the low
9 incidence and the lack of detailed description of the extent or severity of the response. The BMC
1 0 procedure makes determination of the effect level more objective for these data.
11 · Two other studies contained information that was amenable to the BMC approach: the
12 chronic study dqne at GM and the Nikula et al. (1995) study. Results of these analyses are
13 shown in Table 6-5.
Table 6-4. Results of benchmark concentration analyses using the
polynomial model and data from the HERP study
Data set, model
HERP light-duty diesel, hyperplastic lesions, male and female
combined
Polynomial, threshold, background
HERP light-duty diesel, hyperplastic lesions, male rats
Polynomial, no threshold, background
HERP light-duty diesel, hyperplastic lesions, female rats
Polynomial, no threshold
HERP heavy-duty diesel, hyperplastic lesions, male and female
combined
Polynomial, no threshold
HERP heavy-duty diesel, hyperplastic lesions, male rats
Polynomial, no threshold
HERP heavy-duty diesel, hyperplastic lesions, female rats
Polynomial, no threshold
'mg/mJ.
Source: Ishinishi et al. (1988).
Benchmark
response
10
lO
10
10 .
10
10
MLE•
0.39
0.35
0.24
0.49
0.67
0.43
BMC"
2/1/98 6-22 DRAFT --DO NOT CITE OR QUOTE
0.34
0.32
0.19
0.38
0.46
0.30