The mechanisms by which a variety of occupational agents may evoke asthma are largely unknown. There has been much debate over the distinction between occupational asthma caused by an immune response and that caused by exposure to a highly irritating agent. As explained in a publication from the UK Health and Safety Executive, this distinction is unclear because of a lack of understanding of the underlying toxicological mechanisms, confused terminology, the absence of internationally accepted experimental tests, inconclusive clinical data, and doubt concerning how different exposure patterns and routes impact the risk of occupational asthma. Occupational asthma is one of the most important occupational respiratory illnesses in terms of the degree of disability it causes and the total number of cases.
Occupational asthma can result in severe and potentially fatal breathing problems.
Today we are seeing a movement toward focusing less on categorizing asthma as immune or irritant, and more on classifying any chemical that can produce such a reaction as a respiratory sensitizer . This represents a significant change in thinking, since the term respiratory sensitizer has traditionally been interpreted to imply an underlying immunological mechanism for the production of asthma. In Europe, regulators have accepted a broader definition for this hazard classification. The EU identifies individual, well-substantiated cases of such substances having caused asthma and considers the prevalence of such instances, relative to the number of people exposed. Respiratory tract sensitization is defined as the development in a person who is not atopic of severe asthma-like symptoms on exposure to a substance to which the person has been exposed .