dangerous presence of asbestos fibers in a construction site

construction material building activity industry architecture site alert air pollution mesothelioma asbestos removal sign signboard warning signpost placard dangerous danger roof testing abatement fibers asbestoscement removing fiber tumor carcinogen lung cancer risk dust amiante asbestosis safety environmental damage cancerous illness carcinogenicity fibrous toxic substance waste aging process sickness particles inhalation hazard presence metallic protection net against intrusion unauthorized persons