Nordic experience: expected decline in the incidence of mesotheliomas resulting from ceased exposure?

BACKGROUND

As a result mainly of information to workers and the public on prevention of effects of asbestos exposure, the use of asbestos for insulation was reduced to a minimum in the Nordic countries during the second half of the 1970's and the early 1980's. Stringent regulations when handling asbestos were introduced, and prohibition of use began in the early 1980's. Depending on the duration of the latency period between first exposure and the period of most intense exposure, a decline might be expected in the incidence of Malignant Mesothelioma (MM) 20-45 years after interruption of exposure.

OBJECTIVES

to describe the incidence of MM after cessation of asbestos exposure in Nordic countries.

METHODS

Nordic countries have cancer registers with information on all new cases of all cancers, over the past 4-6 decades. Cancer incidence data in these registers could describe long-term effects of interruption of asbestos exposure.

RESULTS

Current male and female incidence in Norway is about 1.5 x 10(-5)/year and 0.2 x 10(-5)/year respectively, and appears to be increasing. Based on personal observations among 32 MM cases, a number of which resulting from low total asbestos exposure with mean latency of about 45 years, examples are presented of the MM incidence in Nordic countries, illustrating when a significant decline in MM incidence may be expected.

CONCLUSIONS

25 years after interruption of asbestos exposure, the expected rapid decline in MM incidence is still lacking, which appears to agree with population-based selection phenomena, with survival of a large pool of asbestos-exposed subjects with minimal exposure.