A study by University of Tartu researchers has revealed that in the years 1992–2015, the rate of lung cancer among men living in the Estonian oil shale industrial regions was higher compared to the rest of Ida-Viru County and the Estonian average.
The incidence rate is 133.6 in industrial regions and 95.5 in Estonia as a whole per 100,000 men. Other cancer sites did not show any difference in incident rates between Ida-Viru County and the rest of Estonia. On the positive side, the lung cancer incidence rate in industrial regions has been decreasing.
Since the beginning of the 20th century, Ida-Viru County has been the main industrial area of Estonia, focusing on oil shale mining and the production of electricity and shale oil. Industrial activities emit large amounts of air pollutants, many of which are toxic and carcinogenic.
Hans Orru, associate professor in Environmental Health of the University of Tartu said: "The air of industrial regions may include particulate matter, benzene, phenols and other pollutants, all of which affect health and increase the risk of cancer."
Polluted air, soil, and water are a major problem in most industrial areas all over the world. Research articles have described an increasing correlation between living near industrially contaminated sites or exposure to industrial air pollution and the general incidence rate of cancer and cancer-related mortality. The International Agency for Research on Cancer has also confirmed that air pollution and pollutants including particulate matter and benzene increase the risk of cancer.
Cancer is one of the leading causes of death in Europe and worldwide. In 2018, there were 18.1 million new cancer cases globally. The total registered numbers of observed cancer cases between 1992–2015 in Estonia and Ida-Viru County were 51,525 and 6,752, respectively. In Estonia, cancer holds second place among causes of death both in women and men, after cardiovascular diseases.
To get an overview of the incidence rate of different types of cancer in regions affected by oil shale industry and compare it to the general cancer incidence rate and trends in Estonia, researchers of the University of Tartu Faculty of Medicine in cooperation with the Estonian Health Board analysed the data of the Estonian Cancer Registry on selected cancer sites that have been previously indicated to have relationships with industrial processes.
The incidence rates of lung cancer, kidney cancer, urinary bladder cancer, breast cancer, leukaemia and non-Hodgkin's lymphoma in the years 1992–2015 were analysed. The findings have been published in the International Journal of Environmental Research and Public Health.
Lung cancer is the most common
The study revealed that lung cancer incidence rate in males was significantly higher in the industrial region than in Estonia overall. In industrial regions, 133.6 men in 100,000 had lung cancer compared to 95.5 in Estonia overall. The incidence of other types of cancer was similar in the oil shale regions and the rest of Estonia.
Hans Orru said one of the explanations for the higher lung cancer morbidity among males in Ida‑Viru County could be associated with industrial pollution.
"Several earlier studies have shown that long-term occupational exposure to high levels of exhaust gas is associated with an increased risk of lung cancer, and mining industry machines mostly use diesel fuel. In total, 16 percent of males in Ida-Viru County are occupied in the oil shale industry, and could therefore be at a higher risk of developing lung cancer," said Orru.
However, as the Estonian Cancer Registry does not record occupational information, the researchers could not analyse the effects of occupational exposures in more detail.
The researchers admit that even more than environmental factors, smoking affects the development of lung cancer.
According to the Estonian Health Behaviour Survey, the daily smoking prevalence in males in the 1990s was around 50 percent and has decreased since 2006. Therefore, an important cause of lung cancer is the habit of smoking, and a majority of males in the oil shale industrial areas of Ida-Viru County is exposed to direct or indirect contact with tobacco smoke every day.
Another lung cancer risk factor prevalent in Ida-Viru County is radon. The main health damage caused by inhaling radon and its degradation products is lung cancer, with 3–20 percent of all lung cancer cases worldwide being attributable to radon.
According to previous research, in one third of the Estonian territory, including Ida-Viru County, the radon risk exceeds the limit considered safe, i.e., 50 kBq/m3. Other explanations to the higher lung cancer incidence could be lifestyle-related factors such as obesity, hypertension and alcohol consumption.
However, in recent decades, the difference in lung cancer incidence rates between Ida-Viru County and the rest of Estonia has been decreasing. Over the years included in the study, the incidence rate for lung cancer in Ida-Viru County decreased by 28.9 percent. At the same time, it increased significantly in non-oil shale areas (13.3 percent) and in Estonia overall (1.5 percent).
The decrease in lung cancer morbidity in Ida-Viru County can be explained by improved environmental quality in that region, as the oil shale mining companies have implemented more environmentally friendly production technologies.
This year's Cancer Awareness Week (5 to 11 October) focused on lung cancer.
Editor: Helen Wright