Black Lung Benefits Improvement Act of 2019 This bill revises requirements for miners' claims for pneumoconiosis (black lung) benefits. Specifically, the bill requires the Department of Labor to pay the attorneys' fees of prevailing parties on a qualifying benefit claim; give a claimant the opportunity to substantiate a claim for benefits through a pulmonary evaluation; authorize a CT (computerized tomography) scan in diagnosing complicated pneumoconiosis; educate certain individuals who work on black lung benefits about medical evidence relevant to claims; use data from continuous personal dust monitors to determine whether to make changes to respirable dust concentration standards, controls, and measurements; and develop a strategy to reduce delays in adjudication of black lung benefits claims. The bill also requires the Government Accountability Office to report on barriers to health care faced by coal miners with black lung. The bill authorizes (1) black lung clinics to use federal funds to help individuals file claims, and (2) previously denied claimants to file a new claim for black lung benefits within one year. The bill prohibits a person from (1) knowingly and willfully making a false statement or misrepresentation in increasing or reducing black lung benefits, or (2) threatening or misleading a participant in a proceeding regarding black lung benefits. Further, the bill revises (1) the standards of medical evidence that establish a presumption that a miner is totally disabled by black lung, and (2) payments to such miners. Lastly, the bill provides statutory authority for the Office of Workers' Compensation Programs.