The ACOP aims to reduce the tolls associated with occupational asthma. Each year between 1,500 and 3,000 people develop occupational asthma as a result of breathing in substances used in their workplace. It is estimated that the total benefit of preventing all new cases of the disease over the next decade would be between 460 million and 1,080 million. Certain substances cause occupational asthma when exposure results in a biological change to the person's airways - the small tubes that carry air in and out of the lungs. This change is known as the hypersensitive state.
Subsequent exposures can then trigger the asthma attack.
The hypersensitive state is irreversible and although symptoms may disappear when exposure stops they can re-appear if exposure occurs again, even after several years. Common asthma symptoms include attacks of wheezing, coughing and shortness of breath. They can occur immediately on exposure or several hours after. They can be severe in the evening or during the night, so those affected may not believe it is attributable to work. The ACOP does not introduce new legal duties.