Oak Street Beach needs to be retested for asbestos because previous tests for the cancer-causing substance weren’t done properly, a scientist on the U.S. Environmental Protection Agency’s asbestos advisory board is urging.

“They should go back and retest,” said the scientist, James Webber, who teaches at the State University of New York in Albany.

In 2004, University of Illinois at Chicago scientists found asbestos fibers in 11 of 12 samples taken at Oak Street, the city’s signature beach. It was a surprising and troubling finding. Inhaled asbestos fibers can cause a cancer called mesothelioma. Another concern: The most deadly form of asbestos—amphibole—was found at Oak Street.