Protection for Veterans' Burn Pit Exposure Act of 2019 This bill requires the Department of Veterans Affairs (VA) to make a determination, after receipt of a study by the National Academies of Sciences, Engineering, and Medicine (NASEM) titled Respiratory Health Effects of Airborne Hazards Exposures in the Southwest Asia Theater of Military Operations, on whether a positive association exists between (1) the exposure of humans to toxic airborne chemicals and fumes caused by open air burn pits (areas used for burning solid waste in open air without equipment) and other airborne hazards, and (2) the occurrence of a diagnosed illness in humans. Upon determination of a positive association, the VA must prescribe regulations providing that (1) a presumption of service-connection is warranted for certain illnesses manifesting in certain time frames, and (2) covered veterans shall be presumed to have been exposed to toxic airborne chemicals caused by open burn pits unless conclusive evidence proves otherwise. Covered veterans are veterans who were deployed on or after September 11, 2001, in support of a contingency operation and based at a location where an open burn pit was used. If the VA determines a presumption of service-connection is not warranted, a notice must be published and include an explanation of the basis for the determination. The bill also requires the VA to remove previous presumptions if evidence indicates such presumption is not warranted. The Department of Defense must provide NASEM with access to information it requests for the study on Respiratory Health Effects of Airborne Hazards Exposures in the Southwest Asia Theater of Military Operations .