Workplace asthma costs the UK at least £100 million a year, and may be as high as £135 million, reveals research published online in Thorax.

An estimated 3,000 new cases of occupational asthma are diagnosed every year in the UK, but the condition is under diagnosed, say the authors.

They reviewed published data on the costs of all asthma and workplace asthma, as well as the impact costs.

The evidence was then used to calculate the costs of workplace asthma on an individual's ability to work and their wider life, including their use of health services, based on a series of six likely scenarios.

These included a male and female employee who developed asthma after being exposed to one of three likely and common sources. These were: isocyanates, used in products such as insulation, paints, car seats, underlay, and laminate; latex (gloves used in healthcare); and flour or grain.

The financial impacts were then divided up among those likely to be borne by the individual, the employer, and the state. Direct costs, such as use of healthcare and benefits; indirect costs, such as lost income and productivity; and employer costs were added together to come up with a total cost generated over time at 2003 prices.

The authors calculated that the true costs lay between £72 and £100 million over the life course of those affected, or £3.4 to £4.8 million a year. The costs for male employees were more than twice those for female employees.

But taking account of an underestimation of occupational asthma diagnosis by a third, the total could be closer to £135 million, suggest the authors.

Half the costs fall on the individual; just under half falls on the state. But only 3-4% falls on employers.

The authors suggest that there is scope for huge savings to be made if steps were taken to reduce the levels of exposure to agents which cause workplace asthma.

"The findings also suggest that the employer should bear more responsibility for establishing approaches to disease reduction by introduction of appropriate exposure control interventions and changes in work processes," they conclude.