Asbestos, lead, all kinds of crazy carcinogens from the past (and present!). That just further strengthens the argument that the workers who undertake this gargantuan task must be unionized with fellow workers leading it. When it's you breathing in flakes of fiberglass and aerosolized rat shit, suddenly mandating the usage (or at the absolute least: availability) of properly fitted respirators suddenly becomes an actual issue of importance not just rhetorical statement to gain popularity.