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 – and we have by no means seen the end. 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.
Russia, China and Canada top the charts
As recalled in Berlin by Antti Tossavainen, of the Finnish Institute of Occupationnal Health in Helsinki, one of the symposium's speakers, 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!
This data, revealed at the 11th European Congress on lung disease and respiratory medicine, makes it clear that the ravages of asbestos are far from over and that the transition and developing countries are storing up a bleak future for themselves.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 of bronchoalveolar lavage 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 the following, however: "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 Côte 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% every three years, with some 150 fatalities every year between 2010 and 2020, almost twice the rate of 1996-1997". These figures send shivers up the spine, for they make it clear that any level of exposure can increase the risk of developing a cancer of the lungs.
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% of subjects (20% of male subjects) and concentrations of over 1,000 asbestos bodies per gramme of dry lung tissue were found in 13% 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".
The participants of the 11th Congress also recalled the outcome of the international expert conference held at the beginning of the year in Helsinki. That forum had discussed the distinction between manifestations that certainly indicated exposure but were not life-threatening (for example most pleural plaques) and true pathologies related to asbestos, particularly cancers. As there is little hope of curing mesotheliomas once detected, the experts recommended focusing screening efforts on lung cancers, for which an early diagnosis may indeed improve chances of survival.
On this subject, Dr. Gregory R. Wagner, of the National Institute for Occupational Safety and Health, presented a review of American research which looks promising. While the research provides some hope that the survival rate may be improved through the use of annual or biennial low dose CT scan in smokers who have been exposed to asbestos, the technique needs to be evaluated carefully in controlled trials to determine if mortality is actually reduced. It will be recalled that today's five-year survival rate for those undergoing resection of Stage 1 bronchopulmonary cancers is as high as 70%.
It is therefore urgent -- more than a century after the ravages of asbestos were first documented -- to determine the best ways of dealing with this time-bomb. At the close of the symposium, De Vuyst called for the creation of a "European Task Force responsible for centralizing data and defining precisely what groups can benefit most from new types of early screening for serious and potentially curable pathologies".