Presumptive Benefits for War Fighters Exposed to Burn Pits and Other Toxins Act of 2021 This bill establishes a presumption of service-connection for specified diseases associated with exposure to burn pits (an area used for burning solid waste in open air without equipment) and other toxins by veterans who were awarded specified medals on or after August 2, 1990. Under a presumption of service-connection, specific conditions diagnosed in certain veterans are presumed to have been caused by the circumstances of their military service. Health care benefits and disability compensation may then be awarded. Under the bill, if the Department of Veterans Affairs (VA) receives a written petition to add a disease to the list, the VA must request a determination by the National Academies of Sciences, Engineering, and Medicine with respect to whether there is a positive association between the exposure of humans to a covered toxin and the occurrence of the disease in humans. The bill makes disability or death of certain employees from specified diseases compensable as a work injury. Specifically, such employees are those who were employees of the Department of State, the Department of Defense, or an element of the intelligence community on or after August 2, 1990, and carried out job responsibilities for at least 30 days during a contingency operation.