Does the introduction of exposure limits reduce the incidence of occupational asthma?
The SWORD voluntary reporting scheme for occupational lung diseases in the UK has been used to investigate whether the introduction of exposure limits for asthmagens is associated with a reduction in incidence. Agents with and without an exposure limit have been compared, looking at incidence before and after the limit was introduced. The introduction of an exposure limit was associated with a relative risk of 0.7 (95% CI 0.52-0.93). It seems that this was heavily weighted by glutaraldehyde, which was withdrawn from the UK sterilising market 3 years after an exposure limit was introduced. It probably also includes latex, where there is no exposure limit but mandatory guidance was issued.
In a companion paper incidence before and after interventions including guidance and training, by the UK Health and Safety Executive, were compared. There were significant reductions in colophony flux asthma and an increase in bakers’ asthma, with no significant effect in isocyanate spray painters, wood workers and workers exposed to metal-working fluids.
It seems that elimination or substitution (glutaraldehyde, latex and colophony) works and control of existing exposures (isocyanates, woods, metal-working fluids), does not.
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