The 11th annual Congress of the European Respiratory Society (ERS) chose to devote one of its symposia in Berlin to the serious issue of the pulmonary consequences of asbestos exposure. While the symposium's aim was to discuss in greater depth how to improve the management of workers who had suffered occupational exposure experts found it was impossible to ignore the global problem caused by the mineral.
Despite increasingly strict exposure standards, which have contributed to a fall in asbestos-related pulmonary fibroses, and a cessation of production in several countries and prohibitions on use in an increasing number of others, there is an alarming increase in asbestos-related cancers, according to ERS.
This is partly because the effects of asbestos exposure manifest themselves years or decades after the event. However, millions of people continue to suffer daily exposure, largely in the poorer countries.
Antti Tossavainen, of the Finnish Institute of Occupational Health in Helsinki, one of the symposium's speakers, said global asbestos production was over two million tons last year.
The hands-down winner was the Russian Federation, with 700,000 tons. China came in a very respectable second, with 450,000 tons. And the bronze medal went to Canada, which produced 335,000 tons and exported almost all of it, according Tossavainen.
The specialists participating in the Berlin Congress emphasized that, in the countries that had taken draconian measures, experience showed that the full scope of the damage inflicted by asbestos only became evident long after the exposure took place.
Tossavainen hammered his message home in the following terms: "We know that occupational asbestos exposure in Western Europe, North America Japan and Australia was at its peak in the 1970s. Now, recent estimates indicate that 30,000 new asbestos-related cancers continue to be diagnosed there every year. They include some 10,000 mesotheliomas and approximately 20,000 cases of lung cancer."
The Congress heard that, in reality, the introduction of increasingly strict limits for exposure had produced a reduction mainly in the diseases together known as asbestosis, namely disabling pulmonary fibroses linked to very high asbestos exposure.
This was demonstrated in the study presented to the Congress by Pascal Dumortier, of the Erasmus Hospital in Brussels (Belgium). By way of an introduction, he explained that asbestos imports into Belgium had fallen steadily since 1975, from some 85,000 tons to below 1,000 in 1999, and that maximum exposure standards had been tightened several times. From examination of 4,773 samples taken from workers exposed to asbestos between 1983 and 2000 (220 to 320 cases annually), a very slight decrease in the average concentration of asbestos bodies could be seen over time.
Dumortier emphasized, "This reduction is lost entirely if the 27 most heavily exposed individuals are excluded from the calculation. While epidemiological studies confirm that the risk of dying from asbestosis as such is now very low, at least in the countries that now have regulations ensuring only a very low exposure rate, we will continue to see new cases of mesotheliomas for years to come."
Cancer rates set to rise until 2020
For other asbestos-linked pathologies, particularly cancers of the pleura, known as mesotheliomas, it is not at all clear that the concept of cumulative exposure dose plays an important role.
According to the Berlin speakers, there does certainly seem to be a linear correlation in the industrialized countries between the quantity of asbestos used per head of population per year and mesothelioma rates. Beside that, the risk of developing cancer appears to increase over time.
Marc Letourneux, of University Medical Center Cote de Nacre in Caen (France), told the symposium that, "The epidemiological outlook is clear: there will be a steady rise in the frequency of asbestos-linked cancers until at least 2010 or 2020 because they take years to manifest themselves. The mesothelioma rates are expected to rise in France by as much as 25 percent every three years, with some 150 fatalities every year between 2010 and 2020, almost twice the rate of 1996-1997."
Another study, presented to the Congress by Krassimir Mitchev, of the Erasmus Hospital in Brussels (Belgium), provides an idea of the scope of exposure in a randomly chosen urban population. Of 160 autopsies performed consecutively between 1998 and 2000 (100 men and 60 women), pleural plaques (indicating a thickening of the pleura) were found in 14 percent of subjects (20 percent of male subjects) and concentrations of over 1,000 asbestos bodies per gram of dry lung tissue were found in 13 percent of subjects. This means that, at present, almost one person in seven bears the scars of asbestos exposure.
How to respond?
Should we then screen systematically for the signs of past exposure in all patients who have had contact with asbestos? "This is the crux of the question, and there are no uniform satisfactory answers at present," commented Paul De Vuyst, co-chairman of the symposium and chairman of the Occupational and Environmental Health Group in the ERS Occupation and Epidemiology Assembly.
The Congress discussed various responses, including that in France, where there is now a rush for thoracic screening to detect any signs that could be grounds for a compensation suit on the basis of earlier asbestos exposure. France has taken steps to improve the targeting of these scans on the basis of duration and intensity of exposure. The feasibility and appropriateness of these recommendations is under evaluation, but according to Pierre Alain Gevenois, co-chairman of the symposium and president of the Imaging Group in the ERS Clinical Assembly, "During the period between two scans, it is perfectly possible for a bronchopulmonary cancer to appear, develop and evolve."
Edited by Virginia Foran