William "Bill" Edward Pepelko was born June 6, 1934, in Youngstown, Ohio. After his father's death, he grew up on his grandparents' small farm in northwest Pennsylvania. He went on to earn a B.S. from Penn State, an M.S. from Michigan State, and a Ph.D. from the University of California at Davis.

Bill spent 10 years working for the Air Force in San Antonio before a long career with the EPA, first in Cincinnati and then in Washington. He was a member of the American Physiological Society, the Society of Toxicology, and Sigma Xi.

An avid outdoorsman, Bill was a member of the Potomac Appalachian Trail Club and maintained a section of the Appalachian Trail. He hiked often in the Shenandoah, biked all over the area, and ran regularly. He kept a large vegetable garden and yard, spent many hours on woodworking projects in his workshop, and was an avid bridge player.

He died February 23, 2026, at age 91.

He is survived by his wife of 63 years, Barbara; his children, Anne Jacobsen, Douglas Pepelko, and Katherine Newland; and four grandchildren.