Researchers at Imperial College London have published their findings following a study of adult onset asthma. The study, published in the journal Thorax, tracked 9,488 people who were born in Britain in 1958.

Of the 7,406 people who had not had asthma or wheezy bronchitis in childhood, 639 (8.6%) had developed asthma by the age of 42. One in six instances was attributed to risks in the workplace, far greater than the one in nine cases attributed to smoking.

The research found clear links to 18 occupations. Four were cleaning jobs and three more were jobs that involved exposure to cleaning products. Other occupations which were found to have an increased risk were hairdressers, printing workers. Farmers were also at risk, and were four times more likely to develop adult asthma than office workers.

Other irritants which are known to cause asthma are textiles, flour, metal and enzymes.

Occupational asthma is widely under-recognised

Lead author Dr Rebecca Ghosh, of the MRC-HPA Centre for Environment and Health at Imperial College London, said: 'This study identified 18 occupations that are clearly linked with asthma risk, but there are others that did not show up in our analysis, mainly because they are relatively uncommon. Occupational asthma is widely under-recognised by employers, employees and healthcare professionals.'

Malayka Rahman of Asthma UK commented: 'We advise anyone who works in the industries highlighted in this study and who have experienced breathing problems to discuss this with their GP, and we urge healthcare professionals to make sure they consider possible occupational causes in adult onset asthma and tailor their advice to people with asthma accordingly.

TUC head of safety Hugh Robertson said: 'Asthma is easily preventable by ensuring that workers do not come into contact with the allergens yet in some industries the levels of occupational asthma are increasing. This condition can be extremely debilitating and can prevent some people from working. Much more must be done by employers and regulators to enforce the existing laws and stop exposures.'

Judith Gledhill, Head of Personal Injury at Thompsons Solicitors said: "Asthma is a huge health issue in the UK. This report makes it very clear that occupational factors play a big role in the onset of asthma. Employers in the cleaning sector need to be very sure that the products they ask their workers to use are safe. Failure to properly risk assess products opens employers up to claims from employees who develop asthma as a result.".