Pleural plaques, or a thickening of lung membranes due to asbestos exposure, were found in one in eight lung cancer patients, according to medical research papers jointly released Monday by 12 medical institutions in Japan.
The research team said the number of people who died from asbestos-related lung cancer might amount to several thousand people a year.
About 60,000 people die from lung cancer each year in the nation.
In fiscal 2007, only 660 people were recognized as suffering from asbestos-related lung cancer and thus eligible for government aid, indicating that many lung cancer patients are excluded from the aid as the exposure has not been confirmed as the cause of their diseases.
Between 2006 and 2007, the 12 medical institutions in six prefectures, including Tokyo, Hokkaido and Aichi, examined 471 patients, aged 26 to 94 who were diagnosed with nonmetastatic lung cancer, to check if they had developed pleural plaques.
The 12 institutions belong to the Japan Federation of Democratic Medical Institutions.
The research team discovered pleural plaques in 28 patients, or 5.9 percent, through chest X-rays, and in 58 patients, or 12.3 percent, through high-resolution computer tomography.
Pleural plaques were detected through the CT scan mainly in people engaged in professions involving repeated asbestos exposure, with 14 out of 35 patients working in the construction industry and six out of 23 in the metal manufacturing and processing industry.
According to a study panel of the Japanese Health, Labor and Welfare Ministry, asbestos exposure is the sole cause of pleural plaques.
Akihiko Tamura, director of Kyushu Institute of Social Medicine and a member of the research team, said: "Only a small population of lung cancer patients has been recognized as eligible for the worker's compensation insurance system and other aid. I presume that many lung cancer patients are excluded from government relief."
(c) 2009, The Yomiuri Shimbun.
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