Interpretation Response #25-0104

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 03/12/2026

Company Name: Huntsman Advanced Materials Division

Individual Name: Matthew Austin

Location State: CA Country: US

View the Interpretation Document

Response text:

March 12, 2026

Matthew Austin
Huntsman Advanced Materials Division
5121 San Fernando Road West
Los Angeles, CA  90039

Reference No. 25-0104

Dear Mr. Austin:

This letter is in response to your July 25, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the classification of a hazardous material for transportation. You believe the substance, dapsone, may be toxic to humans when ingested (i.e., a Division 6.1 poisonous material) based on a data review of a 2001 study, while some manufacturers are known to transport the material as a Class 9 environmentally hazardous substance. You also state that under normal conditions of transportation, there is no foreseeable possibility of the material being ingested, and thus should not be considered a toxic hazardous material for transport. Specifically, you ask whether this is a correct interpretation of the HMR.

No. Classification as Division 6.1 is based on the intrinsic toxic properties of the material—the likelihood of ingestion is not a factor in classifying a material as Division 6.1. This Office cannot classify a material for you as it is the shipper's responsibility to classify a hazardous material (see § 173.22). However, we note that, as provided in § 173.132, a poisonous material (Division 6.1) means a material, other than a gas, which is known to be so toxic to humans as to afford a hazard to health during transportation, or which, in the absence of adequate data on human toxicity is presumed to be toxic to humans because it falls within any one of the identified categories when tested on laboratory animals (whenever possible, animal test data that has been reported in the chemical literature should be used). Furthermore, we note that classification, in the absence of human toxicity data based on oral toxicity should be based on the LD50 (median lethal dose), which is the statistically derived single dose of a substance that can be expected to cause death within 14 days in 50% of young adult albino rats when administered by the oral route (see § 173.132).

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

Regulation Sections