British scientists have found a clear and lineal relationship between asbestos imported into the country and the number of annual deaths attributed to idiopathic pulmonary fibrosis (IPF). The more asbestos imported, the more people of both sexes died of IPF — a relationship that also held, less surprisingly, for mesothelioma.
The association between asbestos and mesothelioma is hardly new. Numerous studies have shown a direct link between asbestos use and mesothelioma development. Asbestosis, a form of chronic interstitial lung disease that can develop in people exposed to asbestos through their work, is also directly linked to the handling of asbestos.
IPF is a main feature of asbestosis. Considering differences in treatment and eligibility for benefits between asbestosis and IPF (a lung disease with a similar fibrosis pattern but no identifiable cause), study authors argued that it is crucial to distinguish between the two conditions, according to a study published in the journal Occupational Medicine.
A differential diagnosis is, however, not a straightforward task. Clinical findings might be identical unless a surgical lung biopsy is performed, and patients cannot always accurately recall asbestos exposure. In addition, while IPF and asbestos exposure share demographic risk factors, epidemiological studies have not found any link to asbestos exposure in IPF patients.
Deaths rates due to IPF have increased over the last decades in the U.K. There is no apparent reason for the rise, but scientists have noted that it seems to follow the same pattern as mesothelioma. The research team from the Health and Safety Laboratory, therefore, wanted to compare the relationships between historical asbestos import, and three conditions: mesothelioma, asbestosis, and IPF.
The team collected data on asbestos imported into the U.K. between the years 1914 and 1965. Because an earlier model of asbestosis suggested that 48 years after exposure is the optimal time point to study asbestos-related deaths, the team compared the data to death rates 48 years later — or between 1962 and 2013.
Results, presented in “UK asbestos imports and mortality due to idiopathic pulmonary fibrosis,“ showed a striking agreement between import volumes and both mesothelioma and IPF development. Mortality rates in these two conditions rose proportionally to increasing import during the first half of the 1900s. This relationship was found in both men and women, although a link between asbestosis and import could only be seen in men.
Study data contradicts earlier research finding no relationship between IPF and asbestos exposure. Because of this and the study’s limitations, the authors caution that the observed link between IPF and asbestos might be explained by factors not investigated in their study.
Nevertheless, they pointed out that a proportion of the IPF increase might really be linked to asbestos exposure. It is often difficult to prove that a patient was exposed to high enough levels of asbestos, and current reference thresholds might not be adequate. If a patient cannot provide a reliable exposure history, he or she is likely to receive an IPF, rather than an asbestosis, diagnosis.
More research is needed to develop a job exposure matrix for asbestos adapted to British industrial conditions, and to strengthen the evidence of how to best distinguish between IPF and asbestosis.