Document 99qxjeNwYRkjBwo2q35BGXq3q
careinogenicity inlmimais ^v.Xonsequently^
animal studies is n' w rated "stiffici `rrt>'ra__ "limited," and the weight- - vidence group'ischanged fr'm to B2. Thus, the hazard ranking for 3,3'-dimethylbenzidin "is J1:
now "medium," and the RQ 10 pouhds. . For a full discussion f the data used to derive the hazard ranking for 3 # 3-dimethylbenzidine, see the document entitled: "Evaluation of the Potential Carcinogenicity of 3,3'-Dimethylbenzidine" which is contained in the RQ rulemaking docket.
9. N-Nitroso-N-ethylurea -- The original potency factor estimate . vg&
for N-nitroso-N-ethylurea did not take into account the low r survival time of the experimental animals in the study used.
',:i
In accordance with the Agency's policy for estimating the full
lifetime risk from less than lifetime studies (45 B 79318,
79352, November 28, 1980), the potency factor was
recalculated. This new potency factor results in a change in
the hazard ranking for this subptance to "high," which
corresponds to an RQ of 1 pound. For a full discussion of the
data used to derive the hazard ranking for
N-nitroso-n-ethylurea, see the document entitled: "Evaluation
Ivl
of the Potential Carcinogenicity of N-nitroso-n-ethylurea"
which is contained in the RQ rulemaking docket.
10. 1,2-Propylenimine -- The original potency factor of '4.64 (mg/kg/day)-1 was based on the increase in aggregate tumors in male and female rats. Not all of the increases in the number of individual tumor sites or types were statistically significant, according to Agency guidelines. Quantitative risk extrapolations should not be made on the basis of totals that include tumor sites without statistically significant elevations (51 R 33992, 33887, September.24, 1986). The potency factor was recalculated based on the increased proportion of animals in the experimental group versus the control group that developed particular tumors (i.e., adenomas
- and adenocarcinomas of the breast in female rats). The new potency factor of 252 (mg/kg/day)-1 results in a change in the
hazard ranking for this substance to "high," which corresponds to an RQ of 1 pound. For a full discussion of the data used to derive the hazard ranking for 1,2-propylenimine, see the document entitled: "Evaluation of the Potential Carcinogenicity of 1,2-Propylenimine" which is contained in the RQ rulemaking docket.
11. Vinyl chloride -- A 10-pound RQ was proposed for this hazardous substance in the NPRM, based on a "medium" hazard ranking. However, the study originally used for deriving the potency factor was judged to be inadequate for that purpose by the CAG, and instead, a new sthdy yielding a mid-range potency group of 2 is assigned to this substance. As a result, the hazard ranking is changed to "high," with a corresponding RQ . of 1 pound. For a full discussion of the data used to derive
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CAM 121632
entitled:
Vinyl Chloride" which is contained in the RQ rulemaking'S^
docket.
:
The revised proposed RQ for vinyl chloride of 1 pound will ' also affect the final RQs of w^ste streams K019, K020, K028, : and K029. Each of these waste streams contains vinyl chloride as a constituent, and each received a 10-pound proposed RQ in the March 16, 1987 NPRM. Since; the revised proposed RQ of vinyl chloride is l pound, the proposed RQs of each of these . waste streams is also revised tp 1 pound.
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CMA 121633