Am. J. Respir. Crit. Care Med., Vol 150, No. 6, Dec 1994, 1697-1701.
Prevalence of occupational asthma among workers exposed to eastern white cedar
JL Malo, A Cartier, J L'Archeveque, C Trudeau, JP Courteau and L Bherer
Department of Chest Medicine, Hopital du Sacre-Coeur, Montreal, Quebec, Canada.
We assessed the prevalence of occupational asthma among current (n = 29/31,
94%) and former (n = 13/49, 27%) employees of a sawmill in which eastern
white cedar has been made into shingles during the past 3 yr. All
participants answered a respiratory questionnaire, and all except one
underwent spirometry and methacholine inhalation tests. All those with
bronchial hyperresponsiveness (PC20 methacholine < or = 19 mg/ml) were
invited to undergo specific inhalation challenges. Mean duration of
exposure was 13 mo (19 workers > 12 mo). Twenty-eight workers (65%)
reported a history compatible with asthma, and 25 (58%) had symptoms that
were suggestive of occupational asthma. Only two subjects had significant
airway obstruction (FEV1 < 80% pred) (mean value = 98% pred). Eighteen
subjects (42%) had a PC20 < or = 16 mg/ml. Specific inhalation tests
with plicatic acid and/or western red cedar (which contains twice as much
plicatic acid as eastern white cedar), were done on 12 subjects who had a
PC20 < or = 16 mg/ml when they were assessed. Three subjects were
considered to have positive tests (one had an isolated immediate reaction,
one had a late reaction, and one had significant changes in PC20 each time
he was exposed but no changes in FEV1). Environmental monitoring showed
concentrations of total dusts above 2 mg/m3 in half of the samples. The
prevalence of occupational asthma in this workplace was three of 42
participants (7%) or at least three of 80 (3.8%) of all current or
ex-workers. This is comparable to the prevalence of occupational asthma in
subjects exposed to western red cedar.
