{"operation":"document","citation":"25-0104","title":"Huntsman Advanced Materials Division — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-03-12","effective_on":null,"summary":"25-0104 response to Huntsman Advanced Materials Division concerning 173.132, 173.22.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0104.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0104.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0104","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-03/250104.pdf","body":"<<<PAGE 1>>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nMarch 12, 2026\nMatthew Austin\nHuntsman Advanced Materials Division\n5121 San Fernando Road West\nLos Angeles, CA 90039\nReference No. 25-0104\nDear Mr. Austin:\nThis letter is in response to your July 25, 2025 email requesting clarification of the Hazardous\nMaterials Regulations (HMR; 49 CFR Parts 171-180) applicable to the classification of a\nhazardous material for transportation. You believe the substance, dapsone, may be toxic to\nhumans when ingested (i.e., a Division 6.1 poisonous material) based on a data review of a 2001\nstudy, while some manufacturers are known to transport the material as a Class 9\nenvironmentally hazardous substance. You also state that under normal conditions of\ntransportation, there is no foreseeable possibility of the material being ingested, and thus should\nnot be considered a toxic hazardous material for transport. Specifically, you ask whether this is a\ncorrect interpretation of the HMR.\nNo. Classification as Division 6.1 is based on the intrinsic toxic properties of the material—the\nlikelihood of ingestion is not a factor in classifying a material as Division 6.1. This Office cannot\nclassify a material for you as it is the shipper’s responsibility to classify a hazardous material\n(see § 173.22). However, we note that, as provided in § 173.132, a poisonous material\n(Division 6.1) means a material, other than a gas, which is known to be so toxic to humans as to\nafford a hazard to health during transportation, or which, in the absence of adequate data on\nhuman toxicity is presumed to be toxic to humans because it falls within any one of the identified\ncategories when tested on laboratory animals (whenever possible, animal test data that has been\nreported in the chemical literature should be used).\n\n<<<PAGE 2>>>\n\nFurthermore, we note that classification, in the absence of human toxicity data based on oral\ntoxicity should be based on the LD50 (median lethal dose), which is the statistically derived\nsingle dose of a substance that can be expected to cause death within 14 days in 50% of young\nadult albino rats when administered by the oral route (see § 173.132).\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nDirk Der Kinderen\nChief, Standards Development Branch\nStandards and Rulemaking Division\n\n<<<PAGE 3>>>\n\nCasey, C.\n25-0104\nFrom: INFOCNTR (PHMSA)\nTo: Baker, Yul (PHMSA)\nCc: Hazmat Interps\nSubject: FW: letter of interpretation request Dapsone (80-08-0)\nDate: Friday, July 25, 2025 15:07:03\nHi Yul,\nPlease see the below interpretation request.\nLet us know if you need anything.\nJanaye\nFrom: Matt Austin <matthew_austin@huntsman.com>\nSent: Friday, July 25, 2025 12:21 PM\nTo: INFOCNTR (PHMSA) <INFOCNTR.INFOCNTR@dot.gov>\nSubject: letter of interpretation request Dapsone (80-08-0)\nYou don't often get email from matthew_austin@huntsman.com. Learn why this is important\nCAUTION: This email originated from outside of the Department of Transportation (DOT). Do\nnot click on links or open attachments unless you recognize the sender and know the content\nis safe.\nHello,\nWe are shipping a chemical commercially called dapsone (CASRN 80-08-0). It has\nreported oral LD50 values ranging from 250 mg/kg to 1000 mg/kg. Dapsone is shipped\nby various manufacturers as a hazardous material UN3077 Environmentally hazardous\nsubstance, solid, n.o.s. Our toxicologists recently reviewed the data on dapsone and\ndetermined “In an acute oral toxicity study (Denton, 2001) adverse effects such as\nhigh levels of methemoglobin formation and elevated Heinz body count were\nidentified. Such high levels of methemoglobin findings were also seen in repeat\ndose toxicity studies in rats treated with dapsone. These effects are known to be\nadverse effects of Dapsone. In addition to the experimental data on acute oral\ntoxicity in laboratory animals, multiple case studies of human poisoning cases have\nbeen published in the scientific literature. Dapsone poisoning causes haemolytic\nanemia and an increase of methemoglobin levels in blood which decrease the\nblood oxygen levels and in more severe cases can result in hypoxia and death. The\ndose which can cause a potentially fatal outcome without medical treatment\nranges from 200 mg/person (ca. 3.3 mg/kg bw) to 15 g/person (ca. 250 mg/kg bw).\n\n<<<PAGE 4>>>\n\nThere is a large range of Dapsone doses that cause severe and, in some cases,\nlethal effects in humans, the majority of severe cases at doses below 250 mg/kg bw.\nIn summary, considering the data from the acute oral toxicity study in rabbits and\nthe data from the human poisoning cases, we estimate that the ATE is ca. 250 mg/kg\nbw. The findings are in line with information from studies conducted to support the\nmedical use of Dapsone and additional information from the public literature on\nDapsone. Based on the overall Weight of Evidence, 250 mg/kg dose for acute oral\ntoxicity study is considered as a median lethal dose”\nThe adoption of the lower LD50 value resulted in our classifying the material as a GHS\noral toxic 3 under OSHA guidelines. This would also result in dapsone being classed as\na toxic solid based on 49CFR173.132(a)(1)(i) “A liquid or solid with an LD50 for acute oral\ntoxicity of not more than 300 mg/kg”. Dapsone is a talc like powder that is shipped in\ndurable bags. Under normal conditions of transport there is no foreseeable possibility of\ndapsone being ingested and therefore we feel that it should not be considered a toxic\nhazardous material for transport. Is this a correct interpretation of the hazardous\nmaterials regulations?\nRegards,\nMatthew Austin, SDSRPTM\nSenior Advisor, Product Safety Communication\nHuntsman Advanced Materials Division\n5121 San Fernando Road West\nLos Angeles, CA 90039\n818-265-7244\nPSRC Global Contact Matrix for Business Colleagues","truncated":false,"body_characters":5942}