NIOSH Seeks Comments on Draft IDLH Value for Lewisite

NIOSH is requesting comments on its draft immediately dangerous to life or health (IDLH) value for lewisite, a chemical developed for use as a blister agent during World War I. The agency identifies 0.03 ppm (0.25 mg/m3) as the lewisite IDLH value, which is the maximum concentration that unprotected workers can be exposed to for 30 minutes without experiencing health effects that impair escape, are irreversible, or result in death.

Short-term exposure to lewisite, an extremely toxic, oily substance that fumes into a colorless gas, can cause stinging and burning in the eyes, nose, and throat. Skin contact causes blisters, inhalation causes fluid in the lungs, and inhalation or skin absorption can result in death. 

The IDLH value is based on experiments conducted by the United States military. NIOSH notes that although the U.S. produced substantial quantities of lewisite, no records confirm battlefield usage. In compliance with the 1997 Chemical Weapons Convention treaty, the U.S. destroyed its stockpile of lewisite but the chemical may still exist in small quantities at sites where it was manufactured, tested, or stored. It may also be found in pits where it was improperly disposed of or in storage areas where it was mislabeled.

The draft IDLH value document is available as a PDF from the NIOSH website. The Federal Register notice lists specific questions for stakeholders to consider when submitting comments. The deadline for comments is May 18.