Environmental and Occupational Exposure to Asbestos as a Result of Consumption and Use in Poland

Asbestos is harmful to human health; exposure to asbestos causes a wide range of asbestos-related diseases. Aim: Malignant mesothelioma (MM) is unique to occupational and environmental asbestos exposure. Methods: Environmental asbestos exposure was examined in relation to asbestos use and manufacturing, the quantity of the asbestos-containing products still in use, the concentrations of asbestos fibres in the air and the number of MM cases diagnosed each year per county. Results: The correlation coefficient of the measurements of the asbestos fibre concentrations in the air and the quantity of asbestos-cement products in use is high and amounts to 0.68. Meanwhile, the correlation coefficient of the measurements of asbestos fibre concentrations in air and MM morbidity rate resulting from environmental exposure calculated for particular counties in provinces is low and amounts to 0.37. The highest MM morbidity rate was observed for Małopolskie and Śląskie, a typical industrial area of Poland. Conclusions: There are MM cases which are still attributable to occupational asbestos exposure, although MM cases resulting from environmental exposure to asbestos have an increased MM risk. Poland is among those countries with a low MM incidence rate, which seems to be an underestimation of environmental asbestos exposure. As long as asbestos-cement products are used in the environment, actions should be undertaken to protect public health.


Introduction
The term "asbestos" refers to a group of naturally occurring fibrous serpentine or amphibole minerals [1]. Asbestos was broadly used in industrial production due to its extraordinary tensile strength, poor heat conduction, and resistance to chemical attack [2]. In 1955-1998, over 2.2 million tons of asbestos fibres were imported into Poland [3], including over 60,000 tons of asbestos per year in the years 1970-1990 [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Chrysotile was used mainly in the asbestos-cement construction industry, and asbestos-containing products were manufactured in 28 plants, of which 10 produced asbestos-cement products [19]. Asbestos-cement flat and corrugated sheets were used for roof coverings; pressed, flat, cladding, and panels were used as facades of multi-family buildings [20]. During the period from 1950 to 1998, 1391 million m 2 of asbestos-cement products were manufactured in Poland, i.e., approximately 15.3 million tons. The peak production period was in the 1970s, when more than 50 million m 2 of corrugated and flat sheets used in construction were produced annually [19].
The first mention of an adverse effect of asbestos was reported in 1906, and the results of the comprehensive study of the health effects of asbestos were published in 1928 [21]. The World Health

Materials and Methods
We have used data on imports of asbestos fibres derived from the United States Geological Survey [2,42,43] and the Statistical Yearbook of Foreign Trade for Poland gathered for the period of 1955 to 1997 [4]. Data on asbestos use and manufacturing plants were collected during the literature review and the field survey undertaken to establish the current state of asbestos manufacturing plants in Poland [20]. The results of the estimation of the amount of asbestos-cement products in Polish provinces obtained by Wilk et al. [3] were used to estimate the amount of asbestos-cement products. All available data on MM cases were derived from the National Cancer Registry, which contains data on MM cases in accordance with the ICD-10 classification under the code of C45, broken down by gender, for the period of 1999-2013 [44]. The research period is related to the introduction in 1994 of the Tenth Revision of the International Statistical Classification of Diseases and Related Health Problems (ICD). In Poland, this revision was enforced in 1996. Measurements of the asbestos fibre concentrations in the air were carried out from 2004-2013 for the Ministry of Economy [41]. Data collected on the amount of the asbestos-cement products and the results of the measurements of asbestos fibre concentrations in the air have then been aggregated to the county level in order to determine the impact of the environmental exposure to asbestos. A structured database was developed based on data gathered and constituted the input for further analysis.

Asbestos Consumption and Manufacturing
There are no asbestos deposits in Poland that are to be extracted on an industrial scale [45]. In total, in 1955-1998, over 2.2 million tons of asbestos were imported to Poland [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The construction industry was the largest recipient of asbestos fibres in Poland and accounted for about 80-90% of all asbestos-containing products manufactured [45][46][47][48][49][50]. Asbestos-cement flat and corrugated sheets were used for roof coverings; pressed, flat, cladding, panels were used as facades of multi-family buildings. Asbestos-cement pipes were used as pressure pipes in water pipes and gravity pipes in sewers [51]. There were 28 manufacturing plants across Poland [19], of which 10 produced asbestos-cement products ( Figure 1). Wilk et al. [20] have estimated the quantity of the asbestos-cement products in use based on best Random Forest models to be 738,068,000 m 2 (8.2 million tons). The quantity of asbestos-cement products in use [5] with the reference to the asbestos manufacturing plants.

MM Cases in Counties
The total number of reported MM cases in the National Cancer Registry [44] among men and women in Poland in the period of 1999 to 2014 amounted to 3348 ( Figure 2).  A total of 138 MM cases were reported resulting from the prophylactic examinations referred to as the "Amiantus" programme, dedicated to former employees of asbestos manufacturing plants.
It allowed the Polish Ministry of Health to provide former asbestos-plant workers with periodic medical examinations and free access to medicines. According to the Nofer Institute of Occupational Medicine, a reliable estimate of the number of asbestos-related occupational diseases is provided within the framework of the "Amiantus" programme [52]. During the period of 2000-2013, 7020 former employees of asbestos manufacturing plants were surveyed within the "Amiantus" programme. The program of preventive examinations was mainly covered by men, who accounted for 2/3 of patients, which reflects the proportion of the employees in the asbestos manufacturing industry, where women accounted for about 30% of employees [52]. A total of 15 cases of MM were detected in Dąbrowski county, where the Szczucin Asbestos Manufacturing Plant was operating. Over 70% of crocidolite asbestos imported to Poland was used in this plant for the manufacturing of large-diameter asbestos-cement pipes [51]. A total of size MM cases were reported in Sandomierz, where, in glassworks, chrysotile was used in the production of flat glass. MM cases were also reported among employees, who worked in asbestos-cement roofing in Gniezno, Radom, Ogrodzieniec, Chrzanów, Ostrów, and Lublin, as well as in Kamienna Góra (brakes and seals) and Piaseczno (asbestos cartons). The remaining number of cases relates to environmental and para-occupational asbestos exposure ( Figure 4). In Southern Poland, in Małopolskie in Dąbrowski county, the total number of registered MM cases amounts to 158. In this county, the Szczucin Asbestos Manufacturing Plant was located, where crocidolite was used for production, and asbestos-cement waste was also used for 30 years in the Szczucin community for road hardening, courtyards and sports facilities [53], which had a significant impact on the number of diagnosed MM cases related to environmental exposure. The next county with the highest morbidity rate is Busko-Zdrój inŚwiętokrzyskie in Central Poland, where no asbestos plant was located, but a large quantity of asbestos-cement roofing was used. Until now, the amount of products used in this county is one of the highest in Poland and amounts to almost 500 kg of asbestos-cement products per capita. InŚląskie, the lowest value of MM morbidity rate is 4.62, whereas, in 24 out of 36 counties, the MM morbidity rate is higher than 10. A similar situation is observed in Małopolskie.

Asbestos Fibres Concentrations Measurements in Counties
The analysis of measurements of asbestos fibre concentrations in the air in the period 2004-2013 was made on the basis of data provided by the Ministry of Economy [54]. Measurements of asbestos fibre concentrations were undertaken in 279 counties, which constitute 73% of the total number of counties in Poland ( Figure 5).

Correlation of the Amount of Asbestos-Cement Products in Use in Relation to Asbestos Fibres Measurements and the Number of MM Cases
The correlation coefficient of the measurements of the asbestos fibre concentrations in the air and the quantities of asbestos-cement products in use in counties is high and amounts to 0.68. If Lubuskie is excluded, since there were no measurements undertaken, and Kujawsko-Pomorskie and Zachodniopomorskie, for which the results of measurements in all counties were below the defined level of the method, the correlation coefficient increases to 0.70. Since in 1997 a ban on asbestos was introduced in Poland and the asbestos fibre concentrations in the air measurements were made more than 20 years later, it may be assumed that exposure to asbestos is the result of using asbestos-cement roofs.
The correlation coefficient of the measurements of asbestos fibre concentrations in the air and MM morbidity rate resulting from environmental exposure calculated for counties in provinces is low and amounts to 0.37. Further analysis was performed in counties, including the following (Table 1)

Discussion
Environmental asbestos exposure is identified in the literature through a questionnaire completed by participants or their proxies or the number of asbestos sources [56]; however, the low quality of proxy responders is increased [57]. It is also underlined that using the registry of MM patients, it is desirable to document the impact of the asbestos environmental exposure [34]. The incidence of MM in the female population is mentioned as having great potential as an indicator of environmental asbestos exposure [58]. Moreover, the information on asbestos manufacturing plants is of great importance for the assessment of the potential influence of environmental exposure to asbestos [56]. As it is desirable to include other explanatory factors of environmental exposure to asbestos [59], results of measurements of asbestos fibre concentrations in the air as the result of the release of asbestos fibres from products were considered.
Since in Poland, all employees of former asbestos manufacturing plants have been included in the "Amiantus" programme, it is possible to determine the number of MM cases in counties through a development of a database gathering and ordering data from different sources, in particular in relation to the number of MM cases due to the occupational exposure and all MM cases, which are collected in the National Cancer Register [44]. It is expected that environmental exposure to asbestos will constitute an increasing factor of MM risk [60]. The widespread low-level environmental exposure to asbestos, most importantly asbestos-cement roofs in buildings, results in a higher number of MM cases [34]. In many countries, measures have been taken to limit or completely prohibit asbestos mine extraction and the production of asbestos-containing products [61], but products containing asbestos are still used, and their influence on asbestos environmental exposure still requires confirmation [62].
The  Compared to Italy and Germany, where the consumption of asbestos products per capita is similar to that in Poland (Poland and Italy 13 kg per capita; Germany 17 kg per capita) (Figure 8), the number of reported MM cases in other European countries are much higher than in Poland.  [64]. This is about three-times more diagnosed MM cases per year in Germany when compared to Poland.
Comparing annual data on MM incidence rates in selected European countries [65] (Figure 9), the highest, and still increasing, MM incidence rate is observed for Great Britain. In Italy, the peak was observed in 2012, and the MM incidence rate is still increasing. In Poland, the MM rate is at the lowest level, and a growing trend is observed. Environmental asbestos exposure in the general population is related to the occurrence of asbestos fibres in the air. Measurements of asbestos fibre concentrations in the air show relatively low levels of atmospheric air pollution with asbestos fibres, which amount to an average of 400-900 fibres per m 3 in the area of Western and Northern Poland, and in Southern, Central and Eastern Poland-over 1000 to 2240 fibres per m 3 , which does not exceed the cumulative, normative values. It is worth noting, however, that asbestos concentrations occurring in municipal exposure are sufficient to initiate the development of asbestos-related cancers [66].
The observed increase in MM morbidity rate in the last decade in Poland probably results not only from the higher incidence rate but also from the improvement of diagnostic methods, both in the possibility of collecting material for research and precise pathological evaluation allowing for the proper diagnosis [67,68]. Taking into account the long latency period, environmental asbestos exposure is difficult to study, and it should be evaluated with reference to environmental contamination [34,69]. The risk of MM incidence increases with the air pollution level [41]. The high level of air pollution was determined in a five-year assessment of the air quality in zones in Poland [55]. The areas with the highest degree of air pollution with substances that pose a health risk can be found inŚląskie, Małopolskie andŚwiętokrzyskie [55]. Due to biological reasons, it is reasonable to assume that different exposures to the same factor have an effect [70]. This may explain the very high rate of disease iń Sląskie and Małopolskie, where the air quality assessment revealed levels exceeding the permissible level of PM2.5 and PM10 in the air (Table 1).

Conclusions
The undertaken study is focused on presenting the asbestos issue in Poland with regard to the underestimation of environmental asbestos exposure. Environmental asbestos exposure was examined in relation to asbestos use and manufacturing, the quantity of asbestos-containing products still in use, the measurements of asbestos fibre concentrations in the air and the number of MM cases diagnosed each year per county (local administrative unit). This may constitute a basis for research on determining spatial patterns of asbestos-related diseases in relation to the number of products used in counties, which are the lowest division in the administrative system of Poland. In-depth research will be undertaken in order to develop a model on the number of cases with the use of a developed database relating to the asbestos fibre concentrations in the air and the amount of asbestos-cement product in use divided into counties. The undertaken study confirms that asbestos pollution is a threat to people living in polluted areas, due to not only the occupational exposure in an industrial environment with the direct use of asbestos but also the presence of asbestos in the environment, in particular, from asbestos-cement roofing. As long as asbestos-cement products are used in the environment, actions should be undertaken to protect public health. Since the extraction, production and use of asbestos products is still taking place in many countries, the problem of the incidence of pleural mesothelioma will increase in subsequent years.
Author Contributions: M.K., E.W. contributed to conceiving, writing and revising the paper. All authors participated in the analyses and interpretation of the findings.
Funding: This research received no external funding.

Conflicts of Interest:
The authors declare no conflict of interest.