Evaluation of exposure to asbestos from the cutting of cement pipe with a powered saw.

Abstract

Objective: This study characterized occupational asbestos exposure during the cutting of asbestos-containing cement (A/C) pipe using a gas-powered abrasive saw. Seven pipe sections (25% chrysotile, 10% crocidolite) were cut during two scenarios: above ground and within a shored trench.

Materials and methods: Airborne fiber concentrations were quantified by phase contrast microscopy (PCM) and transmission electron microscopy (TEM), with TEM results converted to PCM-equivalent (PCME) concentrations. Mean 30-minute PCME concentrations were 0.81 f/cc during above-ground operations and 10.55 f/cc during in-trench cutting.

Results: Eight-hour time-weighted averages (TWAs) and cumulative lifetime exposures were estimated assuming one eight-minute cutting event per week over a 45-year career. Above-ground cutting yielded eight-hour TWAs of 0.010 f/cc (chrysotile) and 0.004 f/cc (crocidolite); in-trench cutting produced 0.16 and 0.021 f/cc, respectively.

Discussion and conclusions: All calculated TWAs were well below contemporaneous OSHA permissible exposure limits of 2 f/cc and higher. Estimated cumulative exposures were 0.061 f/cc-years (chrysotile) and 0.023 f/cc-years (crocidolite) for above-ground cutting, and 0.98 f/cc-years (chrysotile) and 0.13 f/cc-years (crocidolite) for trench conditions. These doses were below published no-observed-adverse-effect levels (NOAELs) for both fiber types. Chrysotile exposures were substantially lower than reported NOAEL ranges (100-300 f/cc-years), while crocidolite exposures approached but did not exceed estimated acceptable levels of exposure as derived from epidemiology studies (0.3-0.8 f/cc-years). Although abrasive saw use represents a worst-case scenario, findings indicate that historical occupational risks associated with A/C pipe cutting for the vast majority of workers were overestimated, particularly where manual methods for cutting or exposure controls were implemented.