Dr. Tsubokura's Radiation Lecture Vol.97
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
193. Chemical substances induce cancer
It has been assumed that high-dose radiation exposure significantly contributes to cancer development. To understand the nature of cancer, I would like to introduce the history of cancer in this article.
In the late 18th century, a high incidence of scrotal cancer was reported among chimney sweepers in London. This turned out to be caused by soot exposure. It was 100 years later, along with advancements in chemical manufacturing, that various types of occupational cancers were reported among factory workers and coal miners. Most of them had skin cancer caused by occupational exposure to coal tar. Bladder cancer in chemical dye factory workers had also become a publicly known issue.
Meanwhile, lung cancer among workers in uranium mines was reported in Eastern Europe. Later, it was found that long-term radiation exposure from inhaled high-dose radioactive uranium, a naturally occurring radioactive substance that turns into radon, was the causative agent inducing occupational lung cancer.
By the way, Dr. Katsusaburo Yamagiwa, a Japanese professor of pathology, was the first to prove chemical carcinogenesis in a laboratory experiment. In 1915, Dr. Yamagiwa demonstrated the carcinogenesis of chemical substances, artificially inducing cancer on a rabbit’s ears by applying coal tar.
194. The development of radiological protection measures
It has been argued whether high-dose radiation exposure leads to cancer development. In this context, I would like to introduce the history of cancer to understand the nature of cancer. A wide range of occupational cancer in industrial workers and coal miners has been reported worldwide since the discovery of a high incidence of scrotal cancer among chimney sweepers in London in the late 18th century.
On the other hand, cancer caused by radiation exposure has been attracting worldwide attention since the 20th century. Furthermore, skin cancer and leukemia associated with radiation exposure was not only reported among scientists who developed or conducted experiments using X-rays, but also among physicians and diagnostic radiographers. Back at the beginning of the 20th century, when radiation protection awareness was insufficient, leukemia mortality among radiologists was several times higher compared to that of physicians with other specialties.
However, after World War II, the cancer mortality rate among radiologists who started working since the 1950s was no different from that of physicians in other fields. This is because the radiation protection measures have gradually evolved, and the level of occupational radiation exposure has been strictly managed according to guidelines.
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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 23rd and 30th September 2018 was reproduced for MRIC Global under the author's permission.