These were the findings of a large study led by Imperial College London published online first in the BMJ journal Thorax on 21 January.
Lead author Rebecca Ghosh, of the National Heart and Lung Institute at Imperial College, says in a statement:
"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. Raising awareness that this is an almost entirely preventable disease would be a major step in reducing its incidence," she urges.
There are about 5.4 million people in the UK living with asthma, including children and those who develop the disease in later life.
The StudyFor the study, the researchers retrieved data on nearly 9,500 adults born in 1958 taking part in the National Child Development Study, which is tracking the long term health of over 11,000 people in Britain.
The study collected information about asthma symptoms or wheezy bronchitis at ages 7, 11, 16, 33 and 42, and asked participants questions about their jobs and job histories at ages 33 and 42.
The analysis excluded some 2,000 participants who reported having symptoms before the age of 16.
The remainder underwent allergen sensitivity and lung function tests between the ages of 42 and 45.
Participants' exposure to substances known to have links with asthma was calculated using the Asthma Specific Job Exposure Matrix (ASJEM), which assigns workplace exposures to 18 high-risk substances, such as cleaning products, flour, and metal fumes.
By the age of 42, just under 1 in 10 (9%) of the participants had developed asthma after the age of 16, one in four were smokers, most (87%) were employed, and more than half (55%) had office-based jobs.
According to the ASJEM assessment, about 1 in 4 participants had only worked in zero risk jobs, while just under 1 in 10 (8%) had ever been exposed to high risk agents and another 28% had ever been exposed to low risk agents. About 1 in 3 (34%) had ever been exposed to both high and low risk agents.
Occupations Linked to Adult Asthma18 occupations were clearly linked to adult onset asthma risk, four of which were cleaning jobs and another three of which were likely to expose workers to cleaning products.
People working in farming, hairdressing, and printing were also found to have increased risk, as reported in previous studies.
Farmers were around four times more likely to develop asthma in adulthood as office workers.
The study identifies flour, enzymes, metals and textiles as well as cleaning products as among workplace materials linked to asthma risk.
"Approximately 16% ... of adult onset asthma was associated with known asthmagenic occupational exposures," write the authors.
However, when the researchers looked at results of the lung function tests only (ie excluded the self-reported data), they found only 4 of the 18 occupations were significantly linked to raised risk of adult asthma. These were office and hotel cleaners, doorkeepers (an undefined term that may refer to security guards and bouncers), manufacturing labourers, and "hand packers".
The study was funded by Asthma UK and the Colt Foundation.
Malayka Rahman, Research Analysis and Communications Officer at Asthma UK, says the study highlights a new group of jobs where workers may have developed adult asthma as a results of exposure in the workplace.
"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," urges Rahman.
Written by Catharine Paddock PhD