Part VIII, Subpart iii, Chapter 3, Section BRating Claims for Disabilities Associated With Mustard Gas or Lewisite Exposure

Revised April 13, 2026

VIII.iii.3.B.1.a#Presumptive SC Based on Exposure to Mustard Gas or Lewisite

Under 38 CFR 3.316, presumptive service connection (SC) can be established when there is

• in-service full-body exposure to a vesicant agent (mustard gas or Lewisite), and
• a diagnosis of a condition associated with the type of verified exposure as listed in 38 CFR 3.316(a).

The presumption removes the need to prove a nexus between the current diagnosis and the in-service exposure. Therefore, when the evidence is sufficient for the presumption to arise, SC is established (assuming that generally applicable requirements such as Veteran status based on a qualifying discharge have been met) unless other evidence rebuts the presumption. Reference: For more information on the definitions of full-body exposure, mustard gas, and Lewisite, see M21-1, Part VIII, Subpart iii, 3.A.1.a.

VIII.iii.3.B.1.b#History of Presumptive SC Under 38 CFR 3.316

The Department of Veterans Affairs initially began recognizing certain disabilities when it published 38 CFR 3.316 on July 31, 1992. This regulation established a presumption of SC based upon mustard agent or Lewisite exposure, provided that the Veteran was subjected to full-body exposure during field or chamber experiments to test protective clothing or equipment during World War II. These Veterans must have subsequently developed a chronic form of one of the following: laryngitis, bronchitis, emphysema, asthma, or diseases of the eye including conjunctivitis, keratitis, or corneal opacities. The current version of 38 CFR 3.316, which became effective January 6, 1993, expanded the list of recognized disabilities and the methods of exposure.

VIII.iii.3.B.1.c#Disabilities for Which SC May Be Awarded by Presumption Under 38 CFR 3.316(a)

Use the table below to identify the disabilities for which SC may be awarded by presumption under 38 CFR 3.316(a) based on full-body exposure during active military service.

Notes:

• SC will not be awarded if the claimed condition is due to the Veteran’s own willful misconduct or there is affirmative evidence that establishes a non-service-related supervening condition or event as the cause of the claimed condition.

• Consider claims for non-presumptive disabilities under the toxic exposure risk activity (TERA), direct SC provisions.

Reference: For more information on TERA, see the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics (PACT) Act of 2022 Implementation Standard Operating Procedure (SOP).

VIII.iii.3.B.1.d#What to Consider When Rating Mustard Gas or Lewisite Claims

When rating mustard gas claims, consider that the

• acute effects of exposure to mustard gas or Lewisite may be evident in the service treatment records
• delayed effects of exposure may appear even though no acute effects were noted in service, and
• Veteran may have been exposed to mustard gas or Lewisite outside of service.

References: For more information on

• developing claims based on mustard gas or Lewisite exposure, see M21-1, Part VIII, Subpart iii, 3.A, and
• presumptive SC, see M21-1, Part V, Subpart ii, 2.B.

VIII.iii.3.B.1.e#Rating Decision Requirements in Mustard Gas or Lewisite Claims

In order to clearly identify issues awarded or denied as due to mustard gas or Lewisite exposure, decision makers must complete the following steps in the Veterans Benefits Management System - Rating (VBMS-R):

• select the appropriate Mustard Gas special issue and the relevant special issue basis specific to the nature of exposure claimed or shown
• if denying the claim, select the relevant decision rationale in VBMS-R to ensure the decision notice fully informs the claimant of the reason for the decision, and
• if deciding the claim under TERA provisions, follow the TERA rating guidance outlined in the PACT Act Implementation SOP.

References: For more information on

• VBMS-R, see the VBMS Rating User Guide
• rating narrative requirements, see M21-1, Part V, Subpart iv, 1.A, and
• decision notice requirements, see
  • 38 CFR 3.103(f), and
  • M21-1, Part VI, Subpart i, 1.B.