Occupational asthma due to spot-welding

A case of occupational asthma from fumes due to spot-welding is described. The hazards from resistance welding have been considered minimal as compared to other types of welding. This paper illustrates the possible hazards of occupational asthma among welders including those doing spot-welding. It also illustrates the difficulties encountered in identifying the specific causative agent in such cases.     

Occupational asthma due to isocyanates in Singapore

Nine cases of occupational asthma due to isocyanates are described. The isocyanates involved included toluene diisocyanate (TDI), diphenyl-methane diisocyanate (MDI) and polyisocyanates. The importance of asking the occupational history in a patient with asthma is illustrated. The importance of early diagnosis and removal from further exposure is also discussed.     

Occupational asthma

A brief review of the definition, prevalence, predisposing factors, clinical features and possible causes of occupational asthma is presented, together with an overview of the appropriate steps in the management of this condition. In terms of the prognosis, the need for effective prevention and early detection of sufferers is emphasized.     

Occupational asthma

Occupational asthma is important both as a potentially curable and preventable cause of asthma and as a model of adult onset asthma. It is induced by sensitization to a specific agent inhaled at work; for many of its causes, including inhaled proteins and the low molecular weight chemicals acid anhydrides and reactive dyes, it is probably IgE dependent. The risk of developing specific IgE and associated asthma is markedly increased in cigarette smokers, probably as a consequence of non-specific damage to the respiratory mucosa. Asthma caused by several agents, which include some of its most frequent causes, isocyanates, colophony and plicatic acid (Western Red Cedar) persists in some 50% of cases for years, and possibly indefinitely, after avoidance of exposure. The development of chronic symptomatic asthma seems particularly to occur in those with longer duration of symptomatic exposure.     

Occupational asthma.

Occupational asthma is probably much more common than is generally realized. Though many causes have been described, undoubtedly many more are yet to be recognized. One of the diagnostic difficulties lies in the fact that in most forms of this disease a late asthmatic reaction occurs in the evening rather than at work. The pathogenetic mechanisms differ in various forms of occupational asthma. In some, an immunologic mechanism is likely; in others, a "pharmacologic" action of the offending agent is implicated. Asthma due to inhalation of dusts of western red cedar, isocyanates, detergent enzymes and textiles is considered in detail. Periodic examination of workers at risk is of value for early diagnosis and prevention of irrversible airway obstruction.