IRIS

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

Key IRIS
Values
Organ/System
Specific Values
Chemical
Documents
Other EPA
Information

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	BMDL_1SD (HED): 3.5 mg/kg-day	300	Low
Nervous	4 x 10^-2 (Subchronic)	Decreased pain sensitivity in male Wistar rats	BMDL_1SD (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	BMCL_1SD (HEC): 18.15 mg/m³	300	Low/Medium
Nervous	2 x 10^-1 (Subchronic)	Decreased pain sensitivity in male Wistar rats	BMCL_1SD (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)

Basis:

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.

Additional EPA toxicity information may be available by visiting the following sites:

Human Health Benchmarks for Pesticides (HHBP). This database provides human health benchmarks for pesticides that may be present in drinking water.
Office of Pesticide Programs Pesticide Chemical Search. This database provides links to health effects information and registration status for pesticides.
Chemistry Dashboard. This database provides information on chemical structures, experimental and predicted physicochemical, and toxicity data.

Organ/System-Specific RfCs

System	RfC (mg/m³)	Basis	POD	UF	Confidence
Nervous	6 x 10^-2	Decreased pain sensitivity in male Wistar rats	BMCL_1SD (HEC):(): 18.15 mg/m³	300	Low/Medium
Hematologic	6 x 10^-2	Decreased segmented neutrophils	BMCL_1SD (HEC):(): 16.65 mg/m³	300	Low/Medium
Respiratory	2 x 10^-1	Inflammatory lung lesions	NOAEL : 66.56 mg/m³	300	Low/Medium