Asbestos Exposure and Malignant Pleural Mesothelioma
The relationship between exposure to asbestos and malignant pleural mesothelioma (MPM) is already well established. Nevertheless, much remains to be known about exposure thereto and the incidence and mortality from MPM. Objective: This systematic review aims to map the relationship between asbestos and MPM by studying the exposure to asbestos and the incidence and mortality of MPM.
Methods: A systematic review was conducted relating asbestos and MPM. Exposure to asbestos, incidence, and mortality by MPM was reviewed. PubMed, Web of Science, Cochrane Library, RCAAP, DART-Europe, and the reference lists of included studies were searched, from January 1, 1960, to December 31, 2020. Methodological quality was checked, the risk of bias analysis was performed, a level of evidence grade was assigned, and descriptive data analysis was performed.
Results: 3,484 unique citations were identified, which included seventeen observational studies that met inclusion criteria with a total of 1,104 patients. Heterogeneity is present between the included studies which range from a case series of 16 retrospective studies and 1 prospective study. Studies were mostly conducted in Europe, particularly in Italy (6), and were published between 1969 and 2020.
The mean age of patients is approximately 66 years with a latency period between the first exposure and diagnosis of approximately 42 years. 14 studies present data regarding the occupational context and chrysotile and crocidolite are the most studied types of fibre. The incidence of cases occurred between the interval 1966 and 2014 and in 9 studies the mortality rate was 100% of patients.
Conclusion: There is high evidence to support the relationships between asbestos and MPM. However, the relatively scant information provided by the studies reinforces the need for well-conducted research and implementation of National Mesothelioma Surveillance Centres at a global level.
Widely used since ancient times for its important chemical and physical characteristics [1, 2], asbestos is recognized in all its varieties as a human carcinogen by the International Agency for Research on Cancer (IARC) [3] and as the leading cause of cancer-associated occupational exposure in industrialized countries [3‒5]. Since 2004,
the World Health Organization (WHO) estimates that approximately 125 million individuals were exposed to asbestos at their workplace and that 107,000 deaths and 1,523,000 disability-adjusted life years occurred each year as a result of diseases related to their exposure [6, 7]. Asbestos can cause diseases such as lung, laryngeal, ovarian, and gastrointestinal cancer, asbestosis, and mesothelioma [8‒10], but it is malignant pleural mesothelioma (MPM), of monofactorial origin, that has been assumed to be the determining factor in the study of this subject [5, 8, 11, 12]. Although the relationship between asbestos exposure and MPM is well known [13],
the most studied occupational agent since 1965 with more than 12,000 bibliographic references on MEDLINE, many of the published studies is related to litigation against asbestos manufacturers, suppliers, and providers of asbestos-containing products [14] leading to the fact that much is still unknown about asbestos consumption and its location, as well as about incidence and mortality from MPM.
Increased incidence and mortality rates from MPM reflect the massive use of asbestos in industrialized countries in the past but also the current production and consumption in many developing countries [13, 15]. Despite all the efforts to ban its use, to date, only 67 countries have banned its use [16]. In the USA, it remains legal with an estimated consumption,
between 2016 and 2020, of 535 tonnes [17]. In 2016, India and China were the world’s leading asbestos consumers (308.000/288.000 tonnes, respectively) and, in 2018, Russia represented the largest producer of asbestos used worldwide (710.000 tonnes) [16]. For this reason, it is also estimated that diseases related to this exposure, notably MPM, will continue to be a major health problem for many decades to come, increasing 5–10% per year, in industrialized countries, in a heterogeneous manner [8, 15, 18].
In order to define directives to raise awareness and to allow a public institution to plan and aim for its elimination, as a response to the joint work of the International Labour Organization (ILO) with the World Health Organization (WHO), which led to the Parma Declaration in 2010 [19], many countries have already set up ongoing epidemiological
surveillance projects of both mortality and incidence of this disease [20] (National Mesothelioma registries in Australia, France, South Korea, and Italy [21] and mesothelioma mortality in UK [22], US [23], Spain [24], Greece [25], Brazil [26], and Italy [27]). This systematic review aims to map the relationships between asbestos and MPM by studying the exposure to asbestos and the incidence and mortality of MPM. By mapping these aspects,
can contribute to bringing to the fore the actuality of this problem and consequently to the need to broaden the focus of research and implementation of National Mesothelioma Surveillance Centres at a global level.
