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(9) Fritz, F. S.; McCarthy, J. J.; Lee, R. J. Interactive software for automated particulate analysis. In Microbeam Analysis; Griss, R. H., Ed.; San Francisco Press: San Francisco, CA, 1981; pp 57-60. (10) Leong, K. H. J . Aerosol. Sci. 1981, 12, 417-435. (11) Kerker, M. Adv. Colloid Interface Sci. 1975,5, 105. (12) Hem, J. D. Study and interpretation of the chemical characteristics of natural water. U S . Geol. Surv. WaterSupply Pap. 1985, No. 2254, 69. (13) Wood, R. W.; Loomis, A. L. Philos. Mag. 1927,22,417-436. (14) Lang, R. J. J. Acoust. Sac. A m . 1962, 34, 6-10. (15) Sollner, K. Trans. Faraday SOC.1935, 32, 1532-1536. (16) Boguslavskii, Y. Y.; Ednadiosyants, 0. K. Sou. Phys.Acoust. (Engl. Transl.) 1969, 15, 14-21. (17) Boucher, R. M. G.; Kreuter, J. Ann. Allergy 1968, 26, 591-600. (18) Rodes, C. E.; Smith, T.; Crouse, R.; Ramachandran, G. Aerosol Sci. Technol. 1990, 13, 220-229. (19) Sterk, P. J.; Plomp, A.; van de Vate, J. F.; Quanjer, P. H. Bull. Eur. Physiopathol. Respir. 1984, 20, 65-72. (20) Marks, L. B.; Oberdoster, G.; Notter, R. H. J. Aerosol Sci. 1983,14,683-694. (21) Mercer, T. T.; Goddard, R. F.; Flores, R. L. Ann. Allergy 1965,23,319-326. (22) Shen, A. T.; Ring, T. A. Aerosol Sci. Technol. 1986, 5, 477-482. (23) Hinds, W. C. Aerosol Technology: Properties, Behavior,
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Received for review January 30, 1991. Revised manuscript received September 9,1991. Accepted September 17,1991. This research was supported through the U.S. E P A Office of Research and Development Indoor Air Program, Research Triangle Park, N C 27711. Although the research described i n this article has been funded wholly or i n part by the United States Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
Indoor Asbestos Concentrations Associated with the Use of Asbestos-Contaminated Tap Water in Portable Home Humidifiers Richard J. Hardy Morrison Knudsen Corporation, Environmental Services Group, P.O. Box 79, Boise, Idaho 83707
V. Ross Hlghsmlth" Atmospheric Research and Exposure Assessment Laboratory, U S . Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1
Danlel L. Costa Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1
Joseph A. Krewert McCrone Environmental Services, Inc., 1412 Oakbrook Drive, Suite 100, Norcross, Georgia 30093
One ultrasonic and one impeller humidifier were charged with asbestos-contaminated waters (0.057-280.0 BAS/L) and individually operated in a room-sized chamber to evaluate the potential for portable home humidifiers to aerosolize suspended materials contained in the charging waters. The resulting aerosol concentrations were highly correlated with both the charging water total solids concentrations and the humidifier emission rates. TEM analysis showed the ultrasonic humidifier aerosol as primarily 1 MAS/L) correspondingto only modest increased turbidity (27). Since 1974, ACP use has increased and currently represents nearly 14% of the US.water main piping (27-29). Asbestos fibers can be lost from the ACP walls through either mechanical processes, aggressive waters, or breakdown of the pipe (27). Mechanical abrasion of ACP water mains occurs during routine maintenance activities such as cutting, tapping, and cleaning through polypigging (27), during which high concentrations of asbestos fibers may be released if the lines are not properly flushed. Studies Environ. Sci. Technol., Vol. 26, No. 4, 1992 661
Table I. Bulk Water Quality and Corresponding Chamber Particle Concentrations
bulk water source
TDS,” mg/L
TS,* mg/L
Spada Reservoir
25
19
leached-ACP
330
360
abraded-ACP
250
310
bulk water asbestos, BAS/Lc 0.057 45.4 280
humidifier type
fine, pg/m3
coarse, pg/m3
impeller ultrasonic impeller ultrasonic impeller ultrasonic
73.1 136.0 346.5 1547.0 319.1 1306.3
12.4 63.6 220.7 137.0 410.9 104.3
“TDS, total dissolved solids. *TS,total solids. “AS/L, billion asbestos structures per liter.
showed increased chrysotile concentrations (1.6-87.5 MAS/L) when the inner ACP walls were disturbed and the distribution lines not adequately flushed (30). Elevated asbestos fiber concentrations were observed (76 MAS/L after 90 min), even when the main water line was flushed. Flushing low-flow,dead-end, and tapped water mains may also increase fiber concentrations (27). ACP deterioration by aggressive waters may release high concentrations of asbestos fibers and may significantly impact areas affected by acid deposition (31). Deterioration of the Woodstock, NY, ACP water main yielded drinking water asbestos concentrations of >10 BAS/L (12). Threadlike blue and white fibers, visible in the cloudy tap water suspension, clogged faucet strainers. Health advisories included warnings to avoid using the asbestos-contaminated water in vaporizers (12). Indoor air asbestos concentrations of 50.24 fiber/cm3 were detected in impacted houses 2 months later, although tap water fiber counts were reduced to 24 MAS/L. Even though home humidifiers were not evaluated, several possible asbestos aerosolization pathways were identified that included clothes washing and drying, carpet shampooing, and the evaporation of suspended water droplets from showers. E x p e r i m e n t a l Design a n d A n a l y s i s
An outdoor 23-m3polyethylene chamber approximating the size of a bedroom was constructed over a poly(viny1 chloride) pipe frame. A door was constructed at one end of the chamber with a self-sealing flap similar to those used in asbestos removal work. Glovebox-style nitrile gloves were sealed into the opposite wall in order to change samples without entering the chamber. A high-volume blower motor exhausted chamber air (0.9 m3/min) through a high-efficiency particulate filter (>99.9% removal for particles of >0.3 pm), provided a chamber air-exchange rate (AER) of 2.3 h-l, and maintained “negative-air” pressure conditions. A small electric heater and a room fan were operated inside the chamber to maintain typical residential temperatures and to enhance mixing, minimizing channeling and stratification. No furniture was present in the room with the exception of the 0.5-m-high smooth plastic humidifier stand. Three bulk water samples simulating the three primary asbestos-contaminated water sources were collected. A “natural” asbestos water sample was collected from the Spada Reservoir, in eastern Washington, a water source previously reported as having asbestos concentrations of >200 MAS/L (12). Water contaminated by abrasive maintenance of ACP (abraded-ACP) was simulated by hand-drilling underwater two 1-in. holes, each in. in diameter, in a small piece of ACP. The cloudy suspension was diluted (approximately1:16) in a 5-gal water container. Water contaminated by deteriorated or leached-ACP was simulated by soaking a small piece of ACP in 12 N hydrochloric acid for 2 h, scraping lightly, and diluting the resulting fibrous slurry in a 5-gal container until clumps 882
Environ. Scl. Technol., Vol. 26, No. 4, 1992
of fibers were no longer visible (approximately 1:64). All three bulk water samples were analyzed for total solids (TS) and total dissolved solids (TDS). Aliquots were preserved for EPA level I1 (32) transmission electron microscopy (TEM) to determine fiber type, length, width, and distributions and total fiber concentrations (33-38). One ultrasonic and one impeller humidifier, units previously determined to have water consumption rates of 0.48 and 0.17 L/h, respectively (8,9),were charged with each bulk asbestos water sample and operated independently in the flow-equilibrated chamber until near-steady-state conditions were achieved (minimum of three volume exchanges) prior to sampling. A series of aerosol samplers were set up at the opposite end of the chamber, approximately 2.0 m from the humidifier. A PM,, dichotomous sampler collected fine (
