NC Asbestos Abatement cheat sheet

Asbestos minerals are hydrated silicates forming long, thin, separable fibers; the six regulated types are chrysotile (serpentine) and the amphiboles amosite, crocidolite, anthophyllite, tremolite, and actinolite.

Regulatory definition of asbestos-containing material (ACM) in the U.S. is material containing more than 1 percent asbestos by weight, determined by polarized light microscopy (PLM) per the prescribed bulk method.

Fibers with length greater than 5 micrometers, aspect ratio of at least 3:1, and width under roughly 3 micrometers are counted as fibers under phase contrast microscopy (NIOSH 7400 method).

Asbestos-related diseases: asbestosis (fibrosis, dose-related, latency typically 10-20+ years), lung cancer (synergy with smoking multiplies risk), and mesothelioma (latency 20-50 years, no safe threshold established).

Amphibole fibers (amosite, crocidolite) persist in lung tissue far longer than chrysotile, which is more readily cleared and dissolves in acidic environments; crocidolite is the most potent for mesothelioma.

Bulk sampling follows a three-tier hierarchy: friable ACM, then non-friable ACM likely to become friable, then all remaining suspect material; minimum sample counts are based on homogeneous area size and material type.

Friable material can be crumbled, pulverized, or reduced to powder by hand pressure when dry; non-friable material cannot, but may become regulated ACM if sanded, ground, cut, or abraded.

Control strategies in order of preference: removal, enclosure (seal off with airtight barrier), encapsulation (seal surface with penetrating or bridging sealant), and operations and maintenance (O&M) programs for material left in place.

Exposure control hierarchy: engineering controls (glove bags, local exhaust, negative pressure), then work practice controls (wet methods, HEPA vacuuming), then PPE including respirators and disposable coveralls.

Negative pressure enclosure (NPE): containment under pressure differential of at least 0.02 inches of water column relative to adjacent areas, verified with a manometer and maintained by HEPA-filtered negative air machines sized to provide at least 4 air changes per hour.

Wet methods are required for removal and cleanup to suppress fiber release; dry sweeping and compressed air are prohibited because they aerosolize fibers.

Decontamination unit sequence for workers exiting: dirty room, then shower, then clean room; a three-stage unit is standard, with a separate equipment/washroom stage in larger projects.

Waste handling: ACM waste is wetted, placed in leak-tight containers (typically 6-mil or thicker bags, double-bagged, or sealed drums), labeled with the required warning, and transported under applicable rules.

Personal air monitoring uses NIOSH 7400 PCM analysis; a result at or above the permissible exposure limit (0.1 f/cc as an 8-hour TWA) triggers respiratory protection and medical surveillance obligations.

Respirator selection: half-mask air-purifying respirators with P100 filters are minimum for many tasks; full-face powered air-purifying respirators (PAPR) or supplied-air respirators are used for high-exposure work.

Clearance involves visual inspection for dust and debris, then air sampling (aggressive sampling in many programs) with final results below the clearance criterion before containment is removed or reoccupied.

A certified supervisor must be on site for most regulated abatement projects, and workers must be trained to the appropriate level (worker, contractor/supervisor, inspector, management planner, project designer, or competent person).

Personal hygiene: no eating, drinking, or smoking in the work area; wash hands and face before breaks; shower at end of shift; launder or dispose of contaminated clothing separately from family laundry.