Clarification of footnote (i) to the table of A1 and A2 values for radionuclides
Pipeline and Hazardous Materials Safety Administration · Jan 14, 2009 · Reference No. 08-0282
Interprets: 49 CFR § 173.435
Reggie’s quick take
A company asked whether the special A2 value for Mo-99 in footnote (i) to the radionuclide table in § 173.435 can be used for the domestic leg of a shipment that continues to Canada. PHMSA said yes. The footnote's value of 0.74 TBq (20 Ci) covers any domestic transport of Mo-99, including the U.S. portion of an international trip. The shipment still has to meet Canada's Transport of Dangerous Goods rules once it crosses the border.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This responds to your November 10, 2008 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask for clarification of footnote (i) to the table of A1 and A2 values for radionuclides in § 173.435. Footnote (i) provides that A2 = 0.74 TBq (20 Ci) for Molybdenum (Mo-99) for domestic use. You ask if this A2 value may be used for the domestic portion of an international shipment from the United States to Canada.
The answer is yes. The A2 value (A2 = 0.74 TBq (20 Ci)) authorized by footnote (i) to the table of A1 and A2 values for radionuclides in § 173.435 permits the use of that value for any domestic transportation of Mo-99 including the domestic portion of an international shipment. Note that the shipment to Canada must also comply with the Transport of Dangerous Goods (TDG) regulations, which govern the transportation of hazardous materials in Canada.
I hope this information is helpful. Please contact us if you require additional assistance.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.