Formaldehyde asthma: challenge exposure levels and fate after five years.

Because of current concern regarding possible adverse health effects of formaldehyde, we have reinvestigated two renal dialysis unit nurses shown to have formaldehyde asthma by inhalation provocation tests in 1973 and 1975, respectively. Their original tests were repeated and the formaldehyde levels generated (previously unknown) were measured. One nurse had not worked with formaldehyde since 1976 and had had no further symptoms. Her 1981 test (15-minute exposure to 6 parts per million [ppm] formaldehyde) provoked no asthmatic response. The other nurse had continued to work with formaldehyde, though under much improved conditions, and mild intermittent attacks of asthma had continued. Her test (five-minute exposure to 3 ppm formaldehyde) provoked a late asthmatic reaction similar to that observed in 1975. We conclude that in sensitized subjects specific late asthmatic reactions may be provoked by brief exposures to formaldehyde at about the current Occupational Safety and Health Administration standard (3 ppm); and that while asthmatic responsiveness may persist with continuing low levels of intermittent exposure, it may be lost following complete cessation of exposure.