A burn pit is an area devoted to open-air combustion of trash. Modern waste contains significant amounts of plastic and other material which may emit toxic aerial compounds and particulates when burned. In Iraq and Afghanistan the U.S. military, or its contractors such as KBR operated large burn pits for long periods of time burning many tons of assorted waste. Active duty personnel reported respiratory difficulties and headaches in some cases and some veterans have made disability claims based on respiratory system symptoms.
Materials burned and combustion products
It has been reported that every type of waste was burned including: plastics, batteries, appliances, medicine, dead animals, even human body parts with jet fuel being used as an accelerant. Clouds of black smoke resulted. According to an Air Force fact sheet, "Burning solid wastes in an open pit generates numerous pollutants. These pollutants include dioxins, particulate matter, polycyclic aromatic hydrocarbons, volatile organic compounds, carbon monoxide, hexachlorobenzene, and ash. Highly toxic dioxins, produced in small amounts in almost all burning processes, can be produced in elevated levels with increased combustion of plastic waste (such as discarded drinking water bottles) and if the combustion is not at high incinerator temperatures. Inefficient combustion of medical or latrine wastes can emit disease-laden aerosols."
Joint Base Balad, the largest U.S. base in Iraq had a burn pit operation as late as the summer of 2008 burning 147 tons of waste per day when the Army Times published a major story about it and about health concerns. An Air Force spokesman speaking for the 609th Combined Air and Space Operations Center Southwest Asia vigorously contested allegations of health effects and emphasized mitigation efforts. In Afghanistan, at its peak, more than 400 tons of trash were disposed using burn pits a day.
Within a mile of BIAP (Baghdad International Airport) and also within a mile of camps Cropper and Stryker was one of these burn pits. The ash rained down on us like snowflakes. Not only on US troops, but also Iraqi detainees and Iraqi correctional officers (aka ICO's) There were flakes of ash the size of half a sheet of notebook paper. That installation was perpetually downwind of one particular burn pit, and while this wasn't an everyday occurrence, during winter of 2007 into 2008 it did happen often. This is not to speak for the frequency of the burnings, but the ash literally came down like snowfall over the facility.
Burn pits were adopted as a temporary measure but remained open long after alternative methods of disposal such as incineration were available. After some years the American military did adopt other methods. 
Defense Department position
A statement was made August 6, 2008 by the Defense Department Office of Force Health Protection and Readiness:
While exposure to burn pit smoke may cause temporary coughing and redness or stinging of the eyes, extensive environmental monitoring indicates that smoke exposures not interfering with breathing or requiring medical treatment at the time of exposure usually do not cause any lasting health effects or medical follow-up.
At the request of the Veteran's Administration (VA)and the Department of Defense The Board on the Health of Select Populations of the Institute of Medicine formed the Committee on Long-term Health Consequences of Exposure to Burn Pits in Iraq and Afghanistan which held its first meeting February 23, 2010 - February 24, 2010 in Washington, D.C. If there is sufficient evidence of a connection between exposure to burn pits and subsequent illness and disability it might serve as the basis for congressional enactment of a “presumption of service connection” similar to that in place for exposure to Agent Orange.
In November 2009, at the request of VA, the National Academy of Sciences Institute of Medicine (IOM) had begun an 18-month study to determine the long-term health effects of exposure to burn pits in Iraq and Afghanistan. The report for the study should be completed and available by summer 2011.
That report was released in the summer of 2012, and is available for free on the web.
There is also now a VA registry with which veterans of Iraq and Afghanistan that believe they have medical problems associated with burn pit smoke may register.
- "Veterans Sound Alarm Over Burn-Pit Exposure" article by James Risen in The New York Times August 6, 2010, accessed August 7, 2010
- "Open Pit Burning: U.S. Air Force fact sheet. Copied text is in the public domain as the work of an employee of the United States government while in the performance of their duties, accessed August 7, 2010
- "Burn pit at Balad raises health concerns: Troops say chemicals and medical waste burned at base are making them sick, but officials deny risk" article by Kelly Kennedy in Army Times Oct 29, 2008, accessed August 7, 2010
- Vlahos, Kelley Beaucar (14 February 2015). "‘Indefensible’: Report reveals extent of ‘burn pit’ pollution inhaled by US troops in Afghanistan". Fox News. Retrieved 21 February 2015.
- First Meeting of the Committee on the Long-Term Health Consequences of Exposure to Burn Pits in Iraq and Afghanistan Keck Center of the National Academies, accessed August 8, 2010
- "VA, DoD seek better data on burn-pit exposure" article by Kelly Kennedy in the Army Times Feb 24, 2010, accessed August 8, 2010
- Department of Veterans Affairs, accessed August 19 2010
- "Open Pit Burning: U.S. Air Force fact sheet Broken link
- "Report: Army making toxic mess in war zones" article by Kelly Kennedy in Military Times Oct 3, 2008
- David E. Mosher, Beth E. Lachman, Michael D. Greenberg, Tiffany Nichols, Brian Rosen, Henry H. Willis, Green Warriors: Army Environmental Considerations for Contingency Operations from Planning through Post-Conflict, Rand Corporation (2008), trade paperback, 252 pages, ISBN 9780833043184
- Environmental Health Surveillance Registries (EHSR) website - U.S. Department of Defense (DoD) information page for VA Burn Pit Registry