Occupational asthma is new-onset asthma in which the underlying cause is exposure to an agent at work. It is distinguished from work-aggravated asthma in that the individual has not had asthma previously. That is, in occupational asthma, workplace exposures cause new cases of asthma, while in work-aggravated asthma, workplace exposures provoke (or ‘trigger’) symptoms of existing asthma. Occupational asthma can be either allergic or non-allergic. Allergic occupational asthma is often referred to as sensitiser-induced occupational asthma, while non-allergic occupational asthma is commonly referred to as irritant-induced occupational asthma. Sensitisers are agents that make the airways sensitive so that they react to subsequent exposure to the same agent and often to other sensitisers, irritants and triggers such as cold air. Therefore, people with sensitiser-induced occupational asthma are sensitised to at least one allergen in their workplace, which on subsequent exposure causes an allergic immune response in the airways. Irritants are agents, such as chemicals, that cause adverse reactions in the airways, particularly localised inflammation.
About 9–15% of adult-onset asthma cases can be attributed to exposures at work. Precise data are not available, but based on research from Australia and overseas, there may be as many as 1,000–3,000 new cases of occupational asthma each year in Australia. People with occupational asthma often have to change jobs or careers to relieve their symptoms; hence, work disruption and economic hardship are common consequences of the disease. The highest occupational lung disease mortality rate has been registered in Austria (1,1/100,000). From November 1997 to October 2004, there were about 820 reported diagnoses of occupational respiratory disease (Sim et al. 2005). Of these diagnoses, about 265 (32.5%) were of occupational asthma and about 200 (24.5%) were of non-malignant pleural plaques. In 2008 there were 449 deaths due to asthma, which was an increase from 2007 when there were 385 deaths. This is an average of more than one person dying due to asthma every day. From 1989–2006 there was a 69% decrease in the mortality attributed to asthma. The majority of deaths from asthma occur in people over 65.Current researches on Occupational Asthma are happening at National Asthma Council, Asthma Research Australia.