38 CFR § 3.316 - Claims based on chronic effects of exposure to mustard gas and Lewisite.
(a) Except as provided in paragraph (b) of this section, exposure to the specified vesicant agents during active military service under the circumstances described below together with the subsequent development of any of the indicated conditions is sufficient to establish service connection for that condition:
(1) Full-body exposure to nitrogen or sulfur mustard during active military service together with the subsequent development of chronic conjunctivitis, keratitis, corneal opacities, scar formation, or the following cancers: Nasopharyngeal; laryngeal; lung (except mesothelioma); or squamous cell carcinoma of the skin.
(2) Full-body exposure to nitrogen or sulfur mustard or Lewisite during active military service together with the subsequent development of a chronic form of laryngitis, bronchitis, emphysema, asthma or chronic obstructive pulmonary disease.
(3) Full-body exposure to nitrogen mustard during active military service together with the subsequent development of acute nonlymphocytic leukemia.
(b) Service connection will not be established under this section if the claimed condition is due to the veteran's own willful misconduct (See § 3.301(c)) or there is affirmative evidence that establishes a nonservice-related supervening condition or event as the cause of the claimed condition (See § 3.303).