Joan Barrows, 90, a congressional liaison and public affairs officer for the National Endowment for the Humanities and later the National Oceanic and Atmospheric Administration, died July 9 at a nursing home in Fairfax County. The cause was cancer, said a niece, Judith Barry. Dr. Barrows, who lived in Annandale, was born Joan Barry in Buffalo and grew up in the Washington area. She taught at George Washington University and was a covert operative for Army intelligence in the Soviet Union before joining the National Endowment for the Humanities in the 1960s, her family said. She retired from federal service in the 1980s.