Moira Chan-Yeung

Natural history of occupational asthma: Relevance of type of agent and other factors in the rate of development of symptoms in affected subjects

It is unknown whether factors such as the nature of the agent, gender, age, atopy, smoking habits, continuous or noncontinuous exposure, and pattern of asthmatic reaction can influence the rate of development of symptoms in subjects with occupational asthma. We compared several clinical and functional parameters among three groups of subjects with occupational asthma caused by Western red cedar (group 1, n = 433), isocyanates (group 2, n = 107), and high molecular weight agents acting through an IgE-mediated mechanism (group 3, n = 121). Survival analysis showed that the three curves relating years of exposure before onset of symptoms to the proportion of subjects without symptoms were significantly different in two respects: (1) almost 40% of subjects in groups 1 and 2 as compared with 20% of subjects in group 3 became symptomatic within 1 year of exposure; (2) after 5 years of exposure, the rate of sensitization was slower for subjects in groups 2 and 3 as compared with those in group 1. Having a nonimmediate reaction at the time of specific inhalation challenges, being continuously exposed and being younger slightly increased the risk at each time point on the curve of developing symptoms in subjects with occupational asthma. These data suggest that the natural history for onset of occupational asthma is different depending on the sensitizing agent. Factors such as age, type of exposure, and pattern of reaction on exposure to the agent also modulate the rate of development of this condition.

A Follow-up Study of the Grain Elevator Workers in the Port of Vancouver

Abstract A second respiratory survey was conducted on 587 grain elevator workers in the Port of Vancouver and on 111 civic workers, 25 years after the first health survey. The prevalence of respiratory symptoms and lung function findings among grain elevator workers in the second survey were almost identical with those in the first health survey, even though the dust concentration was lower in the elevators during the second survey. The longitudinal study in 396 grain workers showed that the prevalence of respiratory symptoms increased slightly during the second health survey among workers who had the same smoking habits during both surveys. Of the smokers who had respiratory symptoms or lung function impair-ment in the first survey, 23.5% followed our advice and gave up smoking; the prevalence of cough and sputum pro-duction decreased among these workers. The annual decline in function was greater for grain workers than civic workers particularly among workes over the age of 50 years when the differences...

Occupational asthma in a technologist exposed to glutaraldehyde

BACKGROUNDnOccupational asthma can be caused by several sterilizing agents, including glutaraldehyde, which has been shown to cause irritation of the eyes and upper respiratory tract and skin rash. We report a case of occupational asthma that was caused by exposure to glutaraldehyde.nnnMETHODSnTo document the diagnosis of occupational asthma in a respiratory technologist, the following tests were performed: preshift and postshift spirometry, serial measurements of peak expiratory flow rate and nonspecific bronchial hyperresponsiveness, and workplace challenge test.nnnRESULTSnMonitoring of peak expiratory flow rate showed improvement when the subject was away from the workplace. Improvements in forced expiratory volume in 1 second (FEV1) and provocative concentration causing a 20% fall in FEV1 were also observed. A workplace challenge test showed a progressive fall in FEV1 when the subject was exposed to glutaraldehyde in a sterilizing agent used to clean bronchoscopes at her workplace. After the diagnosis of occupational asthma was confirmed, the subject continued to assist with bronchoscopy but no longer cleaned the bronchoscopes.nnnCONCLUSIONSnThis case study illustrates the usefulness of a workplace challenge test in confirming the diagnosis of occupational asthma. It also indicates the importance of preventing or reducing exposure to sterilizing agents such as glutaraldehyde by means of effective ventilation and proper storage and enclosure during use.

Immediate skin reactivity and its relationship to age, sex, smoking, and occupational exposure

To evaluate potential predictors of atopy, 3353 workers from various occupations were classified according to airborne exposures into three groups: (1) 1213 control workers with no measurable exposures, (2) 815 workers with gas and fume exposure, and (3) 1325 workers with organic dust exposure. Atopic status was determined by prick skin testing with common allergens. Workers exposed to organic dusts had a lower prevalence of skin test reactivity than either controls or gas- and fume-exposed workers. Skin test reactivity also decreased with age and was higher in nonwhite workers compared to white workers. No difference in skin test reactivity was seen between female and male workers, nor between smoking and nonsmoking workers. A logistic regression analysis that controlled for the correlation between the predictive factors confirmed the results of the crude analyses. It is suggested that atopic workers exposed to organic dusts might selectively leave the industry.

Comparison of dust related respiratory effects in Dutch and Canadian grain handling industries: a pooled analysis.

OBJECTIVES: Four previously conducted epidemiological studies in more than 1200 grain workers were used to compare exposure-response relations between exposure to grain dust and respiratory health. METHODS: The studies included Dutch workers from an animal feed mill and a transfer grain elevator and Canadian workers from a terminal grain elevator and the docks. Relations between forced expiratory volume in one second (FEV1) and exposure were analysed with multiple regression analysis corrected for smoking, age, and height. Exposure variables examined included cumulative and current dust exposure and the numbers of years a subject was employed in the industry. Sampling efficiencies of the Dutch and Canadian measurement techniques were compared in a pilot study. Results of this study were used to correct slopes of exposure-response relations for differences in dust fractions sampled by Dutch and Canadian personal dust samplers. RESULTS: Negative exposure-response relations were shown for regressions of FEV1 on cumulative and current exposure and years employed. Slopes of the exposure-response relations differed by a factor of three to five between industries, apart from results for cumulative exposure. Here the variation in slopes differed by a factor of 100, from -1 to -0.009 ml/mg.y/m3. The variation in slopes between industries reduced to between twofold to fivefold when the Dutch transfer elevator workers were not considered. There was evidence that the small exposure-response slope found for this group is caused by misclassification of exposure and a strong healthy worker effect. Alternative, but less likely explanations for the variation in slopes were differences in exposure concentrations, composition of grain dust, exposure characteristics, and measurement techniques. CONCLUSION: In conclusion, this study showed moderately similar negative exposure-response relations for four different populations from different countries, despite differences in methods of exposure assessment and exposure estimation.

Evaluation of the respiratory health of dock workers who load grain cargoes in British Columbia.

OBJECTIVES--To investigate the respiratory health of dock workers who load grain cargoes. METHODS--The respiratory health of 118 dock workers who load grain cargoes in the ports of Vancouver and Prince Rupert was compared with that of 555 grain elevator workers from the same regions. 128 civic workers were used as an unexposed control group. RESULTS--The prevalences of chronic cough and phlegm were at least as high in dock workers as those found in the elevator workers, and when adjusted for differences in duration of employment and smoking, dock workers had an eightfold higher risk of developing chronic phlegm than did civic workers. Symptoms of eye and skin irritation that were experienced at least monthly were highest for dock workers. Average percentage of the predicted FEV1 and FVC for dock workers (mean 100.6% and 105.3% respectively) were similar to the civic workers but significantly higher than those found for elevator workers. Higher subjective estimates of duration of exposure to grain dust (hours/day) were associated with lower values of FEV1. CONCLUSIONS--The more intermittent grain dust exposure patterns of dock workers may have allowed for some recovery of lung function, but chronic respiratory symptoms were less labile.