Ken Takahashi: Asbestos-Related Diseases as a Global Health Challenge

2018/11/16

In 2005, asbestos became a major social issue in Japan. This was because it became clear that an increasing number of people were suffering from asbestos-related diseases (hereinafter referred to as "asbestos diseases") such as malignant mesothelioma (hereinafter referred to as "mesothelioma") and lung cancer. Shortly thereafter, asbestos was completely banned in Japan. Recent media reports have mostly focused on victim certification, lawsuits, and residual asbestos in old buildings, with only a few topics on the latest diagnosis and treatment of mesothelioma mixed in. Public perception may be that asbestos and asbestos diseases are concerns for only a few victims and patients, or are a fading social issue.

For several years, the author has continued research activities based on the recognition that asbestos disease is a global health challenge for the future. Recently, the term "global health" has been included in the names of several organizations and university graduate schools. "Global" involves many countries and people around the world, and "health" refers to healthcare. Traditionally, "international health" has been a concept close to global health, but there are differences in the themes handled and the nature of international cooperation. It would be appropriate to call one-way cooperation from developed to developing countries, such as measures against endemic diseases, "international health," and cases requiring bidirectional and reciprocal cooperation, such as the health effects of smoking or climate change, "global health." Another characteristic of global health is that the "Burden of Disease" is an important indicator.

Why can asbestos disease be called a global health challenge? Looking at mesothelioma, a typical asbestos cancer, it is known that more than 90% of cases are caused by exposure to asbestos. In other words, it almost never occurs without asbestos exposure (though exposure does not necessarily mean it will occur). Asbestos has been used in almost every country as an inexpensive and readily available industrial raw material, and although mesothelioma is difficult to diagnose, it has been reported in half of the countries in the world. The latest research estimates that more than 220,000 people die every year due to occupational exposure to asbestos, including mesothelioma, asbestos lung cancer, and asbestosis. The World Health Organization (WHO) warns that countries should eradicate asbestos diseases by stopping the use of asbestos, but only about 60 countries have completely banned it.

A major characteristic of asbestos disease is the very long time (the so-called latency period) from when a person is exposed to asbestos until the disease appears. For mesothelioma, it takes 30 to 50 years. Analyzing macro data at the national level, a mesothelioma epidemic curve (Phase 2) always appears several decades after the asbestos consumption curve (Phase 1). In most developed countries, the Phase 1 curve rises with industrialization and then decreases, and the Phase 2 curve is drawn in a similar shape following it. However, at present, the epidemic of asbestos disease has turned to a clear decline only in a few developed countries (such as the US and Sweden) that were early to reduce or ban asbestos. In developed countries that were late to move away from asbestos use, the epidemic of asbestos disease is still on the rise. Unfortunately, Japan belongs to the latter group.

On the other hand, many developing countries still continue to use asbestos in the process of industrialization. Asbestos use here includes asbestos mining, manufacturing asbestos-containing products (hereinafter referred to as "asbestos products") such as building materials from raw asbestos, and cases of simply consuming asbestos products. Asbestos use began at the beginning of the last century, but as of 2015, five countries still mine asbestos, and about 30 developing countries manufacture asbestos products. There are nearly a hundred countries that consume asbestos products (countries where asbestos is not banned), mainly developing countries. In these developing countries, even if there are diagnoses or reports of asbestos diseases, they are extremely few, so the momentum for banning asbestos does not increase. As a result, a "discrepancy" has arisen: while asbestos is banned or significantly reduced in developed countries where the disease burden of asbestos disease has become apparent, asbestos use continues in developing countries where the disease burden has not yet manifested.

While there is a broad consensus that mesothelioma, asbestos lung cancer, and asbestosis are the primary asbestos diseases, differences in legal systems regarding compensation for other diseases reflect national variations. For example, in Japan, in addition to these three diseases, benign asbestos pleural effusion and diffuse pleural thickening are treated as "diseases clearly related to asbestos." Furthermore, based on an extensive literature review, the WHO recently concluded that there is sufficient evidence that cancers of the larynx and ovary are also caused by asbestos exposure, and that a relationship with asbestos exposure is also recognized for cancers of the pharynx and stomach. Just as lung cancer was initially brought to the table as a tobacco-related disease and later various other cancers and non-cancerous diseases were confirmed to be related to smoking, the concept of asbestos disease may expand in the future.

Apart from the evaluation of causal relationships, accurate and effective diagnosis and treatment must be performed in clinical settings. Improving clinical outcomes for mesothelioma, which is particularly difficult to treat and has an extremely poor prognosis, is an urgent issue. Note that 80% of mesothelioma cases occur in the pleura, nearly 20% in the peritoneum, and rarely in the pericardium or tunica vaginalis; unfortunately, technology for early detection of this cancer through imaging or markers before subjective symptoms appear has not been established. Since pleural mesothelioma is often accompanied by pleural effusion, the main symptoms are chest pain, shortness of breath, and weight loss, and pleural thickening can be confirmed by CT scans. Diagnosis is confirmed by immunohistochemical evaluation of cells in the pleural fluid or surgically collected tissue. Confirming past asbestos exposure during medical interviews is essential not only to aid in mesothelioma diagnosis but also for compensation and relief.

As medical treatment for mesothelioma patients, combination therapy with the anticancer drugs pemetrexed and cisplatin is the standard. In terms of surgery, methods to preserve the normal lung called pleurectomy/decortication and methods to remove the pleura and lung together have been used, but the latter is no longer recommended as much because it is a heavy burden on the patient and results from large-scale clinical trials were poor. The role of radiation therapy is limited to purposes such as combination with surgery or prevention of recurrence. As a latest direction, immunotherapy using immune checkpoint inhibitors such as Keytruda is in the spotlight, but it is not yet standard, and results from future clinical trials are awaited. For patients in poor general condition, palliative care for pain and shortness of breath is central. Many patients die within less than a year after diagnosis, making a support system for patients and their families indispensable.

To eradicate asbestos diseases, it is necessary not only to widely promote asbestos bans worldwide but also to take public health measures such as disposal of residual asbestos, prevention of new exposure, and tracking of exposed persons even after the ban, as well as clinical medicine measures such as diagnosis, treatment, and rehabilitation for asbestos diseases (WHO). To obtain objective evidence for this, broad-based scientific research is required. Field-based research serves as the foundation for establishing effective public health measures, and laboratory-based research on the mechanisms of asbestos disease serves as the foundation for improving diagnostic techniques and developing therapeutic drugs. Previously, when the author applied for a large Grant-in-Aid for Scientific Research on the theme of asbestos and asbestos diseases, a reviewer said, "Such a theme is not suited for scientific research," and I was disappointed (the application was rejected). It was a moment when I realized how difficult it is to specialize in asbestos disease research in Japan.

Here, I would like to contrast the situation in Australia, where I am based, with that in Japan. The number of mesothelioma deaths in Australia is less than half that of Japan, but the adjusted mortality rate considering population and age composition is four times higher in Australia than in Japan. Also, as mentioned earlier, Japan's mesothelioma epidemic curve is on the rise, while Australia's is reaching its peak. In Australia, asbestos disease did not surface as a social issue in a short period like in Japan, but social interest has remained high. The "Asbestos Safety and Eradication Agency" exists as the world's only federal government agency specializing in residual asbestos measures, and various sectors of society cooperate on the challenges of asbestos disease regardless of social position or ideology. Incidentally, my research institute's board of directors is composed of representatives from the state government, labor unions, employers (companies), universities, medical care, and NPOs, and we focus on activities closely linked to citizens and the community.

Japan also has many strengths in conducting international cooperation on the themes of asbestos and asbestos diseases. Since developing countries continue to manufacture and use asbestos products, a transition period is necessary until a complete ban is achieved. During that time, the priority should be minimizing exposure, so Japan's system, which excels in regulatory compliance and has a top-down administrative system, is easy for developing countries to learn from. Also, among developed countries, Japan was late in reducing and banning the use of asbestos (which was unfortunate for Japan), so it is likewise easy for developing countries to learn from. Of course, the standards of public health and clinical medicine in Japan are high. Above all, developing countries that depend on asbestos are concentrated in Asia, and Japan is in close proximity.

As mentioned earlier, the essence of global health lies in the necessity of bidirectional and reciprocal cooperation. While it is natural that the greatest benefit lies with the recipient countries that receive technology and experience, there are also many merits for the donor countries regarding asbestos and asbestos diseases. If developing countries stop manufacturing and using asbestos products, it can prevent illegal exports to banning countries (a recent problem in Japan and Australia) and prevent exposure of Japanese nationals living in or traveling to non-banning countries. Furthermore, since the removal and disposal of residual asbestos and the use of asbestos substitutes extend to every corner of society, the economic effects are large, and donor countries can also benefit. Additionally, since dealing with asbestos diseases involves everything from public health to general medical care, an improvement in the status (so-called soft power) of the donor country providing technical assistance can be expected. Moving away from the current state of dependence on asbestos requires structural transformation in various fields and involves pain. The same applies to updating obsolete technologies and systems and transitioning employment. However, asbestos-banning countries, including Japan and Australia, have decided that the eradication of asbestos diseases can only be achieved by overcoming such obstacles. There is an accumulation of valuable experience and technical backing there, and the world is called upon to utilize these in a bidirectional and reciprocal manner in non-banning countries. This is why I believe asbestos disease is a global health challenge for the future.