Dr. Tsubokura's Radiation Lecture Vol.98

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

195. The quantity and quality of risk factors determine their impact on health

It has been argued that a high-dose radiation exposure significantly contributes to cancer development. To understand the nature of cancer, this paper briefly introduces its history.

In 1915, Dr. Katsusaburo Yamagoku, a Japanese pathologist, demonstrated the carcinogenesis of chemical substances by applying coal tar on rabbits' ears to induce cancer for the first time in history.

Later, it was revealed that various types of chemical substances could cause cancer. Specifically, the researches on chemical substances familiar in our daily lives, such as food additives and pesticides, have made extensive progress since the 1960s and has led to natural food trends subsequently.

On the other hand, vegetables and fruits that we eat every day also contain various types of carcinogens in very small amount besides additives and/ pesticides, though I would avoid listing the names of carcinogens contained in them. Of course, I do not mean to say that we should avoid eating vegetables and fruits.

In conclusion, the impact of chemical exposure on health is determined by the extent of the exposure dose, not by whether one has any experience of being exposed.

196. "the extent of exposure dose" is the crucial determinant

Vegetables and fruits that we eat every day contain various types of carcinogens besides additives and pesticides. Certainly, it is frightening to hear that they contain carcinogens, and this may drive you to avoid them at all costs.

Several years ago, an international organization announced the association between consumption of processed meat and increased colorectal cancer. This announcement provoked controversy regarding eating processed meat, particularly in countries with high meat consumption. Furthermore, a lot of highly inflammatory remarks such as "sausages and ham cause cancer" appeared in the public domain.

Conversely, exaggerated nutritional information, which suggests positive health effects of certain products, often results in exhaustion of their stock at supermarkets as such news enhances people to eat them every day.

I understand the state of mind behind this behaviour; however, please do not be fooled by such information. The concept of health determinants is not explained by the all-or-nothing approach but by the extent of exposure dose.

For example, unhealthy habits such as smoking, heavy drinking, obesity, and lack of exercise, have a greater health impact than being exposed to 100 mSv of radiation. This level of radiation exposure is an order of magnitude higher than the level of radiation exposure we receive every day. It is often harder to see what's right in front of us, however, it's very important to understand the nature of each risk factor and prioritize which one to target based on the relative risk value.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 7th and 14th October 2018 was reproduced for MRIC Global under the author's permission.