Dr. Tsubokura's Radiation Lecture Vol.96
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
191. With the prolongation of life expectancy, cancer becomes a major public health issue
It has been argued that high-dose radiation exposure can lead to increased numbers of cancer patients. In order to comprehend this issue more thoroughly, I would like to take a quick look at the history of cancer.
The earliest record of cancer was described in an ancient Egyptian text. However, cancer was not a major public health issue for a long period of history, as the life expectancy of people used to be around 30 to 40 years. Instead, deaths caused by natural disasters, famines, malnutrition, infectious diseases, tribal struggles and wars/conflicts, accidents, and many other causes were more of a problem during this period.
In Japan, the average life expectancy in the period immediately after World War II was only about 50 years for both men and women. As you may already know, though, due to economic expansion and technological advancements, Japan has achieved food security and a diminished rate of infectious disease–associated deaths across the country. As a result, life expectancy in Japan has increased to over 80 years for both men and women.
As life expectancy has increased, cancer has now become a major public health issue worldwide. In Japan, cancer has since 1981 dominated as the leading cause of death, above diseases of the heart and central nervous system. According to the national cancer statistics in 2016 published by the Japanese government, lung, stomach, and colon cancer were the leading causes of cancer death for men, whereas colon, lung, and pancreas cancer were the leading causes for women.
192. The first cancer study documented cancer incidence among chimney sweeps
It has been assumed that high-dose radiation exposure significantly contributes to cancer development. In order to understand the nature of cancer, in this paper I would like to introduce the history of cancer.
In the late 18th century, Sir Percivall Pott, a British surgeon, found a high incidence of scrotal cancer among chimney sweepers in London. Pott then formulated a hypothesis that soot accumulated in the chimney was irritating the skin and inducing cancer. This was the first study to demonstrate an association between cancer incidence and occupational chemical exposure.
In his study, Pott reported the following three findings: higher cancer incidence was associated with 1) a high level of exposure and with 2) a longer exposure period, and 3) cancer can develop several years after the first exposure to soot.
The key concept of association between soot exposure and cancer incidence is similar to the concepts of tobacco smoking and radiation exposure. For example, smoking tobacco does not immediately cause lung cancer, but smoking dozens of cigarettes for decades has significant adverse health effects on the human body. Similarly, the impact of radiation on human health is associated not with "whether a person has ever received radiation exposure or not" but rather with "the level of radiation exposure received."
The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 9th and 16th September 2018 was reproduced for MRIC Global under the author's permission.