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At least 73 records · Page 4Linked to original sources
PubMed1994

Mechanism of occupational asthma due to western red cedar (Thuja plicata).

Occupational asthma due to Western red cedar is the most common form of occupational asthma in the Pacific Northwest and affects 4-13.5% of the exposed population. It has been shown to be caused by plicatic acid, a low molecular weight compound present uniquely in the wood. The mechanism of asthma induced by plicatic acid is not known, as specific IgG antibodies were found only in about 20% of patients. Sera from patients with red cedar asthma failed to passively sensitize human lung fragments of human basophils. Basophils from patients with this disease released histamine when challenged directly with plicatic acid in a specific manner. Immunologic mechanisms other than Type I hypersensitivity reaction are likely to be involved.

Allergens↗
PubMed1982

Clinical features and natural history of occupational asthma due to western red cedar (Thuja plicata).

After an average follow-up interval of three and a half years (range one to nine years), 125 patients with occupational asthma due to red cedar exposure were re-examined. Fifty patients remained in the same job. All of them continued to have asthmatic attacks requiring regular medication for relief of symptoms. They had worse lung function and ther bronchial reactivity to methacholine increased. Seventy-five patients left the industry; half of them became asymptomatic, whereas the remaining half continued to have recurrent attacks of asthma. Several factors were of prognostic significance. Those with a shorter duration of exposure as well as a shorter duration of symptoms prior to diagnosis and removal from exposure showed improvement. Those who remained symptomatic tended to be older; they had longer duration of exposure and a longer duration of symptoms prior to diagnosis. They tended to have more abnormal results of lung function studied and more marked bronchial hyper-reactivity to methacholine at the time of diagnosis. They also tended to have dual asthmatic reaction rather than late asthmatic reaction to inhalation challenge with red cedar extract. Smoking, race and degree of peripheral blood eosinophilia did not play a role in determining the outcome. Since none of these patients had symptomatic asthma before employment and since they reacted to inhalation challenge of red cedar, it could be assumed that persistent asthma in those who failed to recover is the result of their previous occupational exposure. Early diagnosis and removal from exposure were found to be associated with recovery.

Adult↗
PubMed1987

Follow-up study of 232 patients with occupational asthma caused by western red cedar (Thuja plicata).

A total of 232 patients with red cedar asthma diagnosed by inhalation provocation tests were observed an average of 4 years after the initial diagnosis. The status during the follow-up examination was as follows: 96 patients continued to work with red cedar, and 136 left the industry and had no further exposure to red cedar in their jobs or hobbies. Of the 136 patients who left the industry, only 55 (40.4%) recovered completely, whereas the remaining 81 (59.6%) continued to experience attacks of asthma of varying severity. The initial pulmonary function tests were significantly higher among the asymptomatic group compared to the symptomatic group (FEV1 99.3 +/- 2.7% versus 90.5 +/- 2.2% predicted, respectively). Methacholine PC20 during the initial examination was higher among the asymptomatic group than in the symptomatic group (1.46 +/- 3.96 mg/ml versus 0.77 +/- 4.52 mg/ml, respectively). These findings indicate that the patients in the asymptomatic group were diagnosed at an earlier stage of the disease. This observation was confirmed by the significantly shorter duration of symptoms before diagnosis among the asymptomatic patients compared to the symptomatic patients (1.6 +/- 1.9 versus 2.6 +/- 4.3 years). Race, smoking status, immediate skin reactivity, and presence of plicatic acid-specific IgE antibodies did not influence the outcome of these patients. Of the 96 patients who continued to work with red cedar, 47 were exposed daily, whereas 41 were exposed intermittently.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Pattern of specific airway response in asthma due to western red cedar (Thuja plicata): relationship with length of exposure and lung function measurements.

In order to investigate the relationship between the pattern of response (immediate, late and dual) to specific bronchial challenge test with plicatic acid or red cedar extract and the clinical features of asthma, 332 patients with asthma induced by western red cedar dust were examined at the time of diagnosis. Specific challenge test induced in thirty-one patients (9.3%) an isolated immediate reaction, in 144 patients (43.4%) an isolated late reaction and in 157 patients (47.3%) a dual reaction. Patients with a dual reaction had a longer period of exposure to red cedar dust between the onset of the respiratory symptoms and the time of the definitive diagnosis, a lower FEF 25-75% and a greater degree of non-specific bronchial hyperresponsiveness compared to patients with isolated immediate or isolated late reactions; the difference in bronchial hyperresponsiveness to methacholine among the three groups persisted when the values were adjusted for the different baseline value of FEV1. There was no difference in the prevalence of specific serum IgE antibodies to plicatic acid-human serum albumin conjugate among the three groups of patients with different type of response to red cedar. Except for the greater degree of non-specific bronchial hyperresponsiveness, patients with isolated late reactions were not different from those with isolated immediate reactions in other clinical findings. These findings indicate that a dual reaction in patients with occupational asthma due to simple chemical agents is indicative of a greater severity of disease at diagnosis. The pathogenetic mechanism of various types of asthmatic reaction is unknown and it is likely to be different between isolated immediate and isolated late reactions.

Adult↗
PubMed1992

Bronchial hyperresponsiveness and level of exposure in occupational asthma due to western red cedar (Thuja plicata). Serial observations before and after development of symptoms.

Four workers from a cedar sawmill who developed red cedar asthma are described. They had serial measurements of lung function and nonspecific bronchial hyperresponsiveness (NSBH) several years before and after the development of chest symptoms. Measurements of dust concentration and specific IgE antibodies to plicatic acid-human serum albumin (PA-HSA) conjugate were also carried out before the onset of disease. NSBH developed in parallel with the development of asthma and was not present in any of the workers beforehand, indicating that it is not a predisposing host factor. Nasal symptoms preceded chest symptoms in three workers, suggesting that this may be an early marker of the disease. Although dust concentrations for jobs located both inside and outside the sawmill were low, jobs associated with somewhat higher exposures were associated with the initiation of asthma symptoms.

Adult↗
PubMed1977

Fate of occupational asthma. A follow-up study of patients with occupational asthma due to Western Red Cedar (Thuja plicata).

Thirty-eight patients with red cedar asthma proved by inhalation provocation test were studied after they had left exposure for more than 6 months. Twenty-seven patients became asymptomatic, with normal lung function (group A). Three patients had persistent chronic bronchitis with a moderate degree of airway obstruction, probably as a result of cigarette smoking (group B1). Eight patients continued to have recurrent attacks of asthma that decreased in severity after cessation of exposure, and their symptoms were probably due to previous exposure (group B2). The effect of breathing helium on maximal expiratory flow at 50 per cent of the vital capacity was studied. All except one patient in group A were responders (change in maximal expiratory flow at 50 per cent of vital capacity greater than 30 per cent). Two patients in group B1 and 2 in group B2 were nonresponders, suggesting obstruction in the small airways. All patients with red cedar asthma demonstrated bronchial hyperreactivity to methacholine to the same extent as patients with nonoccupational asthma. This hyperreactivity persisted after they left exposure, irrespective of symptoms. It is not known at present whether bronchial hyperreactivity is the predisposing factor in occupational asthma or is the result of the disease.

Adult↗