Kostyniak joined the Department of Pharmacology and Therapeutics, now the Department of Pharmacology and Toxicology, as an assistant professor in 1977. He was promoted to associate professor in 1984 and a year later was named to head the Toxicology Research Center. He will retain this position while serving as chair of the Department of Clinical Laboratory Sciences.

Holder of a doctorate in toxicology from the University of Rochester, Kostyniak is a specialist in the biological impact of toxic metals on humans. He has been certified by the American Board of Toxicology since 1980.

He is a co-investigator on the New York State Angler Study, which is assessing effects of eating Great Lakes fish on anglers and their families.

Kostyniak has been involved since 1993 in training workers to clean up sites containing hazardous and radioactive wastes from the Manhattan Project, and in training personnel in hazardous materials recognition and response through the UB Toxicology Research Center.

His professional memberships include the American Association for the Advancement of Science, American Chemical Society, New York Academy of Sciences, International Society for the Study of Xenobiotics and the Society of Toxicology, of which he is past president of the metals specialty section.

He has published more than 35 papers in professional journals and has written 10 book chapters.