Khamisiyah Plume' Linked to Brain and Memory Effects in Gulf War Vets

Study Supports Lasting Harms of Exposure to Chemical Weapons

Gulf War veterans with low-level exposure to chemical weapons show lasting adverse effects on brain structure and memory function, reports a study in the October 2017 Journal of Occupational and Environmental Medicine.

In previous research, Linda Chao, PhD, and colleagues of San Francisco VA Medical Center reported decreased volume of the hippocampus — a brain area involved in memory processing—in Gulf War veterans exposed to the Khamisiyah plume. In that 1991 event, demolition of an Iraqi munitions depot caused US soldiers to be exposed to low levels of nerve agents, carried downwind in a smoke plume.

The previous studies had some key limitations, including a lack of data on other risk factors. The new study compared an independent group of 113 veterans with predicted exposure to the Khamisiyah plume, based on Department of Defense models, and 62 nonexposed veterans.

On brain magnetic resonance imaging scans, the hippocampus was significantly smaller in veterans with predicted exposure. The difference remained significant even after accounting for a wide range of other factors, including meeting criteria for Gulf War illness, the presence of an Alzheimer's disease risk gene (ApoE4), brain injury, or depression.

Among veterans with predicted exposure to the Khamisiyah plume, smaller hippocampus volume was correlated with lower scores on a test of verbal learning and memory. Scores on the memory test were also lower for veterans with higher estimated exposure and those with self-reported memory difficulties.

The finding that these effects are still present 25 years later, after adjusting for potential confounding factors, supports the conclusion that exposure to the Khamisiyah plume had lasting adverse effects on Gulf War veterans. Since memory problems and smaller hippocampal volumes have both been linked to the risk of late life dementia, Dr. Chao and colleagues believe that exposed veterans should receive regular follow-up, especially as they approach old age.
About the Author — Dr. Chao may be contacted for interviews at

About ACOEM — The American College of Occupational and Environmental Medicine (, an international society of 4,500 occupational physicians and other health care professionals, provides leadership to promote optimal health and safety of workers, workplaces, and environments.

About JOEM — The Journal of Occupational and Environmental Medicine ( is the official journal of the American College of Occupational and Environmental Medicine. Edited to serve as a guide for physicians, nurses, and researchers, the clinically oriented research articles are an excellent source for new ideas, concepts, techniques, and procedures that can be readily applied in the industrial or commercial employment setting.


Chao LL, Raymond MR, Leo CK, Abadjian LR. Evidence of hippocampal structural alterations in Gulf War Veterans with predicted exposure to the Khamisiyah Plume. J Occup Environ Med. 2017;59(10):923-9.