1,2,3-Trimethylbenzene
CASRN 526-73-8 | DTXSID8047769
- Toxicological Review (PDF) (150 pp, 2.65 M)
- IRIS Executive Summary (PDF) (10 pp, 323 K)
- Supplemental Information on the IRIS Toxicological Review of Trimethylbenzene
Noncancer Assessment
Reference Dose for Oral Exposure (RfD) (PDF)
(10 pp, 323 K)
Last Updated: 09/09/2016
| System | RfD (mg/kg-day) | Basis | PoD | Composite UF | Confidence |
|---|---|---|---|---|---|
| Nervous | 1 x 10 -2
(Chronic) |
Decreased pain sensitivity in male Wistar rats |
BMDL1SD
(HED):
3.5
mg/kg-day |
300 | Low |
| Nervous | 4 x 10 -2
(Subchronic) |
Decreased pain sensitivity in male Wistar rats |
BMDL1SD
(HED):
3.5
mg/kg-day |
100 | Low |
Note: The RfD for 1,2,3-TMB is based on data for 1,2,4-TMB and route-to-route extrapolation. See Section 2.2.3 of the Toxicological Review for additional details.
Reference Concentration for Inhalation Exposure (RfC) (PDF)
(10 pp, 323 K)
Last Updated: 09/09/2016
| System | RfC (mg/m3) | Basis | PoD | Composite UF | Confidence |
|---|---|---|---|---|---|
| Nervous | 6 x 10 -2
(Chronic) |
Decreased pain sensitivity in male Wistar rats |
BMCL1SD
(HEC):
18.15
mg/m3 |
300 | Low/Medium |
| Nervous | 2 x 10 -1
(Subchronic) |
Decreased pain sensitivity in male Wistar rats |
BMCL1SD
(HEC):
18.15
mg/m3 |
100 | Low/Medium |
Note: The RfC for 1,2,3-TMB is based on data for 1,2,4-TMB. See Section 2.1.5 of the Toxicological Review for additional details.
Cancer Assessment
Weight of Evidence for Cancer (PDF)
(10 pp, 323 K)
Last Updated: 09/09/2016
| WOE Characterization | Framework for WOE Characterization |
|---|---|
| Inadequate information to assess carcinogenic potential | Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005) |
- Under the Guidelines for Carcinogen Risk Assessment (U.S. EPA 2005), there is “inadequate information to assess carcinogenic potential” of TMBs. This characterization is based on the fact that there is no information regarding the carcinogenicity of TMBs in humans and that the only animal study available on the carcinogenicity of 1,2,4‑TMB observed no statistically significant carcinogenic effects. No studies regarding the carcinogenicity of 1,2,3‑TMB or 1,3,5‑TMB were identified in the available scientific literature.
- This may be a synopsis of the full weight-of-evidence narrative.
Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (10 pp, 323 K)
Not assessed under the IRIS Program.
Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (10 pp, 323 K)
Not assessed under the IRIS Program.
Organ/System-Specific RfDs
| System | RfD (mg/kg-day) | Basis | PoD | UF | Confidence | Notes |
|---|---|---|---|---|---|---|
| Nervous |
1
x 10-2
(Chronic) |
Decreased pain sensitivity in male Wistar rats |
BMDL1SD
(HED):
3.5 mg/kg-day |
300 | Low | |
| Nervous |
4
x 10-2
(Subchronic) |
Decreased pain sensitivity in male Wistar rats |
BMDL1SD
(HED):
3.5 mg/kg-day |
100 | Low |
Organ/System-Specific RfCs
| System | RfC (mg/m3) | Basis | PoD | UF | Confidence | Notes |
|---|---|---|---|---|---|---|
| Nervous |
6
x 10 -2
(Chronic) |
Decreased pain sensitivity in male Wistar rats |
BMCL1SD
(HEC):
18.15 mg/m3 |
300 | Low/Medium | |
| Hematologic | 6 x 10 -2 | Decreased segmented neutrophils |
BMCL1SD
(HEC):
16.65 mg/m3 |
300 | Low/Medium | |
| Respiratory | 2 x 10 -1 | Inflammatory lung lesions |
NOAEL
:
66.56 mg/m3 |
300 | Low/Medium | |
| Nervous |
2
x 10 -1
(Subchronic) |
Decreased pain sensitivity in male Wistar rats |
BMCL1SD
(HEC):
18.15 mg/m3 |
100 | Low/Medium |
Sep 2016: IRIS Toxicological Review of Trimethylbenzenes (Final Report) (Report)
Jun 2016: IRIS Toxicological Review of Trimethylbenzenes (Interagency Science Discussion Draft) (Report)
Aug 2013: IRIS Toxicological Review of Trimethylbenzenes (Revised External Review Draft) (Report)
Jun 2012: IRIS Toxicological Review of Trimethylbenzenes (External Review Draft) (Report)
Jun 2012: IRIS Toxicological Review of Trimethylbenzenes (Interagency Science Consultation Draft) (Report)
May 2002: Health Effects Assessment for Trimethylbenzenes (Report)
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Critical Effect Systems
Chemical Structure for
1,2,3-Trimethylbenzene
