In J. McMullen v. WCAB (City of Philadelphia) a city firefighter alleged asbestosis. The Commonwealth Court, who apparently knows what the meaning of "is" is, held where the Claimant testified his firehouse underwent asbestos removal, the rebuttable presumption of Section 301(e) of the Act applies.
Section 301(e) provides: If it is shown that the employe, at or immediately before the date of disability, was employed in any occupation or industry in which the occupational disease is a hazard, it shall be presumed that the employe's occupational disease arose out of and in the course of his employment, but this presumption shall not be conclusive.
The Commonwealth Court's ruling highlights that the section does not say the disease has to be a particular or usual or common hazard, just a hazard. Accordingly, any testimony of the possibility of exposure raises the presumption, and the Employer has to rebut it.