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Interpretation Response #13-0073 ([Aceto Corporation] [Ms. Suhey Francisco])

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

Interpretation Response Details

Response Publish Date:

Company Name: Aceto Corporation

Individual Name: Ms. Suhey Francisco

Location State: NY Country: US

View the Interpretation Document

Response text:

July 23, 2013



Ms. Suhey Francisco
Sr. Regulatory Affairs Specialist
Aceto Corporation
4 Tri Harbor Court
Port Washington, NY 11050

Ref. No.: 13-0073

Dear Ms. Francisco:

This is in response to your March 12, 2013 email requesting clarification on acute toxicity test requirements for inhalation toxicity in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180).  

According to the information in your letter, you have classified your material Methylene-bis(4-cyclohexylisocyanate) or synonym Cyclohexane,1,1'-methylenebis[4-isocyanato- (CAS# 5124-30-1) using publicly available test data as UN2206, Isocyanates, toxic, n.o.s., 6.1, PG II.  The acute toxicity test data values used in your classification are as follows:

LC50  Rat (male, head only exposure to an aerosol) inhalation 0.295 mg/L/4hr
LC50 Rat (female, head only exposure to an aerosol) inhalation 0.307 mg/L/4hr

After adjusting the four-hour exposure data in accordance with § 173.132(b)(3)(i) you indicate the one-hour exposure results as LC50 Rat (male) 1.18 mg/L/1hr and LC50 Rat (female) 1.228 mg/L/1hr.  In accordance with the § 173.133(a)(1) table, this material is assigned to packing group II.  

Specifically, you seek clarification on the suitability of  test result data as the exposure was to an aerosol and not to either a dust or mist as prescribed in §§ 173.132 and 173.133 and if these results should be applied when classifying your material.

The answer to your question is yes.   The test results would be applicable when exposure is administered as a liquid aerosol that emerges as a mist, if a mist is likely to be generated in a leakage of the transport containment as prescribed in § 173.132(b)(3)(iii). As provided in §173.22, it is the shipper's responsibility to make this determination.

In addition, you also request clarification that if the aforementioned test method is not appropriate for determining the toxicity of the material, would it still require classification as UN2206, Isocyanates, toxic, n.o.s., Class 6.1, because of its chemical family.

Under § 173.22 of the HMR it is a shipper's responsibility to properly classify a hazardous material.  A poisonous material (liquid) is defined in § 173.132 as a material, other than a gas, which is presumed to be toxic to humans because it falls within one of the following categories when tested on laboratory animals: oral toxicity, dermal toxicity and inhalation toxicity.  If your material meets the LC50 or LD50 criteria for any of these categories, it meets the definition of a Division 6.1 material.  Thus, if your material meets the definition of a Division 6.1, or any other hazard class, then it must be classified accordingly, and the determination should not be based solely on its chemical family.    

I hope this information is helpful.  If you have further questions, please do not hesitate to contact this office.


Delmer Billings
Senior Regulatory Advisor
Standards and Rulemaking Division

173.132, 173.133, 173.22

Regulation Sections

Section Subject
173.132 Class 6, Division 6.1-Definitions
173.133 Assignment of packing group and hazard zones for Division 6.1 materials
173.22 Shipper's responsibility