19085-1701857-UL_Prop_65_Test_Results_2019

CA Prop 65 Cumene NSRL February 11, 2019 Page 7 | 12
Table 3: Animal and Human Cancer Potency Estimates for Cumene.
Sex, strain,
species
Type of neoplasm
Animal cancer
potency (mg/kg-d)
-1
Average body
weight
(kg)
Human cancer
potency (mg/kg-d)
-1
Male B6C3F
1
Mice
Lung
(alveolar/bronchiolar
adenoma)
0.009
0.044
0.058
Lung
(alveolar/bronchiolar
carcinoma)
0.0122 0.078
Lung
(alveolar/bronchiolar
adenoma or carcinoma)
0.023 0.144
Female B6C3F
1
Mice
Lung
(alveolar/bronchiolar
adenoma)
0.0255
0.043
0.162
Lung
(alveolar/bronchiolar
carcinoma)
0.0139 0.089
Lung
(alveolar/bronchiolar
adenoma or carcinoma)
0.039 0.252
Male F344 Rats
Nose (respiratory
epithelial adenoma)
0.0001 0.39 0.0004
Since the studies in male and female mice were of similar quality and suitable for potency
estimation, and since there is often lack of site concordance between rodent and human
responses to carcinogens, the two potency estimates from the combined lung tumors in male
and female mice (most sensitive species) reported within the NTP 2009 studies were combined.
The geometric mean of the human cancer potency estimates derived from the combined liver
tumors from each of the two studies was taken as the basis of the overall cancer potency
estimate, yielding a mean potency of 0.191 (mg/kg-d)
-1
. Taking the geometric mean, as
opposed to the arithmetic mean, provides some control for values that may be outliers that
dominate the magnitude of the combined estimate.
5 NO SIGNIFICANT RISK LEVEL
Daily intake levels associated with lifetime cancer risks at or below 10
-5
are considered to pose
no significant risk of cancer under Proposition 65 (Title 22 California Code of Regulations,
Section 12703). Thus, for a 70-kg adult, the intake level posing no significant cancer risk under
Proposition 65 is given by: The human cancer potency estimate of 0.191 (mg/kg-d)
-1
for cumene
based on the geometric mean for lung tumors (alveolar/bronchiolar adenoma or carcinoma) in
B6C3F
1
mice, was used to calculate the NSRL for this chemical. The value of 3.7 μg/day was
derived as shown below.