1 in 6 cases of adult asthma caused by workplace environments

The types of job linked to asthma, include farming, which more than quadrupled the risk, hairdressing, which almost doubled the risk, and printing, which tripled the risk.

Four of these 18 jobs were cleaning jobs, and a further three were likely to involve exposure to cleaning agents.

After taking account of factors likely to influence the results, people exposed to low risk agents were 20 per cent more likely to have asthma diagnosed as an adult than those who had not been exposed to any risk.

Those exposed only to high risk agents were 53 per cent more likely to have the condition, while those exposed to both types of agents were 34 per cent more likely to do so.

The high risk agents implicated were flour, enzymes, cleaning/disinfectant products, metal and metal fumes, and textile production.