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Workplace Exposures to Corrosion-Inhibiting Chemicals from a Steam Humidification System -- Ohio, 1988

On December 5, 1988, at 11:45 a.m., boiler steam was released to humidify an electrical components manufacturing plant in Ohio. At noon, employees returning from lunch noticed an odor described as musty, pungent, "ammonia-like," or "radiator-like," and the work area was evacuated. During the next several hours, 77 (64%) of the 121 employees working in the plant became ill; symptoms included rapid onset of headache; nausea; vomiting; dizziness; and eye, nose, and throat irritation. Forty employees were evaluated by the company nurse; 11 of these received further examination at local hospitals but were subsequently released. The steam humidification was turned off in most work areas by 1:15 p.m.

On December 8, boiler steam was reintroduced into the work area, producing the same odor and resulting in evacuation of affected areas; no illnesses were reported. Company management and the local union jointly requested an investigation of the problem by CDC's National Institute for Occupational Safety and Health (NIOSH). Investigators determined that during the third week of September, two corrosion-inhibiting chemicals, diethylaminoethanol (DEAE) and cyclohexylamine (CHA), had been added to the boiler water at four times normal strength, as recommended by the supplier; the boiler was left idle, and the concentration of DEAE and CHA was not diluted before the boiler was used on December 5.

Persons working in the humidified area on December 5 were at increased risk for becoming ill (illness defined as the presence of at least two of the above symptoms), compared with employees in other areas of the plant that were not humidified by steam (relative risk: 4.3; 95% confidence interval=2.1-9.1). On December 9, after workers had left for the day, steam was released into the work area, and samples of air and boiler water were collected for analysis (1). DEAE and CHA were not detected in either air or water. Reported by: Hazard Evaluations and Technical Assistance Br, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: When present in boiler water, DEAE and CHA can become airborne in boiler steam, which can result in inhalational and/or dermal uptake by exposed persons. Higher acute exposures through this mechanism are more likely if these chemicals are added to a steam-generating system in a single large quantity rather than continuously in small amounts.

Most boilers require daily addition of fresh water to compensate for losses from escaping steam and drained condensate. Although the amount of water added to this boiler between the outbreak and the time when samples were obtained is not known, dilution of the treated boiler water during the intervening 4 days may account for the failure to detect DEAE or CHA.

DEAE and CHA are both strong mucosal irritants. In one report, a laboratory worker who was inadvertently exposed for less than 30 seconds to DEAE at an estimated concentration of 100 ppm (480 mg/m3) developed nausea and vomiting within 5 minutes (2). No data are available on human health risks associated with long-term, low-level airborne exposure to these amines.* The Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs) for DEAE and CHA are, respectively, 50 mg/m3 (10 ppm) and 40 mg/m3 (10 ppm) (4) and are established at levels intended to prevent mucosal irritation symptoms. NIOSH has no recommended exposure limit for either substance.

NIOSH has previously investigated three clusters of illnesses related to exposure to boiler steam that contained DEAE or related corrosion-inhibiting chemicals. In 1981, 24 employees in the office area of a production building developed skin rashes; many of the employees also reported dry throats, headaches, and chest tightness (5). Investigators concluded that the dermatitis resulted from exposure to a condensation or reaction product of DEAE that had been added to the air-handling system. In 1982, employees in a museum where DEAE had been added to a humidification system reported eye irritation and dermatitis (6). Air sampling detected DEAE concentrations of only 0.05 mg/m3 and 0.04 mg/m3, and direct contact with released DEAE that had subsequently condensed on surfaces was proposed as an exposure pathway (6). In 1988, hospital staff nurses reported symptoms of eye and upper respiratory tract irritation after the introduction of CHA and morpholine (a similar nitrogen-containing corrosion inhibitor) into boiler water used to humidify a nursery and neonatal intensive care unit (NIOSH, unpublished data).

The OSHA PELs for DEAE and CHA were promulgated for the protection of industrial workers and are not intended to protect members of the general public, which may include children, the elderly, those in ill health, and others who may be particularly sensitive to the effects of these substances. As a result of the investigation in this report, NIOSH recommended that the electronics manufacturer discontinue use of amine-based corrosion-inhibiting chemicals in boiler steam that is intentionally released to humidify occupied buildings. At least one major supplier of corrosion-inhibiting chemicals has recognized this potential health hazard associated with DEAE and, in 1983, advised its customers against such use (Union Carbide Corporation, unpublished data, 1985).


  1. NIOSH. NIOSH manual for analytical methods. 3rd ed. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1984; DHHS publication no. (NIOSH)84-100.

  2. Cornish HH. Oral and inhalation toxicity of 2-diethylaminoethanol. Am Ind Hyg Assoc J 1965;26:479-84.

  3. Meiners AF, Gadberry H, Carson BL, Owens HP, Lapp TW. Volatile corrosion inhibitors and boiler water additives: potential of nitrosamine formation. Washington, DC: US Environmental Protection Agency, 1980; EPA report no. 560/11-80-023.

  4. Office of the Federal Register. Code of federal regulations: occupational safety and health standards. Subpart Z: Air contaminants--permissible exposure limits. Table Z-1-A. Washington, DC: Office of the Federal Register, National Archives and Records Administration, 1989. (29 CFR ***1910.1000).

  5. McManus K, Baker D, NIOSH. Health hazard evaluation report no. HETA 81-247-958. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1981.

  6. Fannick N, Lipscomb J, McManus K, NIOSH. Health hazard evaluation report no. HETA 83-020-1351. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1983.

    • Under certain conditions, it is theoretically possible that DEAE (or related compounds) in boiler water may be converted to nitrosamines, which are suspected human carcinogens. No experimental evidence exists to indicate whether this occurs, particularly in boiler systems of the type discussed here (3).

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