With the threat of cancer-causing asbestos making a comeback in the U.S. thanks to changing environmental protection policy, local experts are sounding the alarm over a health issue that has long burdened the region.

Philadelphia and asbestos go way back.

Prized for its heat-resistance and strength, asbestos — woven of naturally occurring silicate crystals — has long been used as insulation and fireproofing in many types of buildings. It is still crumbling in older structures including Philadelphia public schools, sending disease-causing fibers into the air people breathe and onto the surfaces they touch. It was used extensively in shipbuilding, a major industry in Philadelphia.

Scientific evidence linking asbestos exposure to cancer emerged throughout the 20th century. Part of that evidence was assembled in Philadelphia.

Arthur L. Frank, a professor in the Dornsife School of Public Health at Drexel University and adviser to Philadelphia's Air Pollution Control Board, has been researching asbestos-related diseases,  including mesothelioma, for 50 years.

He describes the Environment Protection Agency's changing stance on asbestos as "nothing short of outrageous."

Under the proposed EPA rule, new uses for the cancer-causing mineral could be approved, provided  they pass a revised risk-assessment process that considers fewer asbestos-related diseases. Allowing for more asbestos-laden products cuts against a decades-long trend that has seen the carcinogen banned in more than 60 countries, from Algeria and Argentina to the United Kingdom and Uruguay. It has never been entirely banned in the U.S.

There used to be thousands of asbestos-containing products in use in Pennsylvania and around the nation, noted Frank, but imports and domestic manufacturing plummeted as health risks and liability became clear.

EPA officials have said that the new review process would protect consumers, but the move is widely seen as part of the Trump administration's deregulation efforts.

Before taking office, President Trump expressed regret over the disappearance of asbestos, linking its decline to a mob-related conspiracy. In 2012 he tweeted, "If we didn't remove incredibly powerful fire retardant asbestos & replace it with junk that doesn't work, the World Trade Center would never have burned down." Experts dismiss the notion that asbestos (which was present in the north tower) or any other fireproofing could have prevented the towers' collapse following the terrorist attack Trump referenced.

In a statement released Wednesday, the EPA said it is open to considering new uses for asbestos in adhesives, sealants, millboard, roof coatings, roof felt, and "other building products." The use of asbestos in shipbuilding was banned in 2002.

To assess whether new asbestos-containing products and manufacturing processes are safe, the EPA would no longer consider oral or skin exposure, nor "emission pathways to ambient air from commercial and industrial stationary sources," according to a revised risk-assessment standard published in June. The agency also would no longer be "reaching back to evaluate the risks associated with legacy uses, associated disposal, and legacy disposal," according to the document.

In assessing specific health risks, only lung cancer and mesothelioma — an incurable tumor of tissue lining the lungs, stomach, heart, and other organs — will be considered. That's despite growing evidence that asbestos exposure causes laryngeal, ovarian, and a list of other cancers, said Frank.

The changes appear to have been made despite objections from the EPA's own scientists and lawyers, the New York Times reported on Friday.

Frank and other leading public health experts visited EPA offices in Washington earlier this year. "It was very clear that they … had very little interest in what any of us had to say," he said.

"I have no problem [with the fact] that they don't want to worry about the skin" as an exposure route,  Frank said. "However, there is evidence both from inhalation and ingestion that asbestos can get into many, many organs in the body. This data shows that asbestos has the ability to cross the placenta and enter the unborn baby."

Arthur Frank, asbestos expert, in the lab at Drexel University’s Dornsife School of Public Health.
JESSICA GRIFFIN / Staff Photographer
Arthur Frank, asbestos expert, in the lab at Drexel University’s Dornsife School of Public Health.

Frank began studying the health effects of asbestos as a medical student in 1968, using cultured organs and cells, though he notes that he still came late to the issue.

"The Romans 2,000 years ago knew about the hazards of asbestos because they mined it and provided some rudimentary respiratory protection to their slaves. So this is not exactly modern."

As part of the Inquirer and Daily News investigative series Toxic City, 19 Philadelphia schools were swabbed for asbestos fibers. City officials have begun cleanup at the seven schools where levels of asbestos fibers exceeded 50,000 per square centimeter.

Proof that asbestos exposure can cause cancer was cemented in the 20th century, but 21st-century tools continue to reveal the complexity of the biology behind how these naturally occurring fibers cause so much damage in the body.

Joseph R. Testa, director of the Genomics Facility at Fox Chase Cancer Center, was the first to show that inherited genetic changes can influence a person's risk of developing mesothelioma following asbestos exposure. He continues to study how the environment and genes interact to produce cancer.

Testa called the EPA's recent statements about asbestos "disingenuous."

"It seemed to be implying that they were doing something heroic," he said, but there is "no safe exposure to asbestos."