Dr. Tsubokura's Radiation Lecture Vol.29

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

57. The effect of radiation on pollen is small

Hay fever is an allergic reaction to pollens that irritates the nose and eyes. It causes a runny nose (rhinitis) and itchy eyes (conjunctivitis). Pollen levels in the air increase mostly in March. While it would be an overstatement to say there is no radioactive contamination in pollens, the cedar pollen test nonetheless revealed that its level is very low.

For example, the concentration level of radioactive cesium in the cedar pollens in Minamisoma city was approximately 240 becquerels per kilogram in 2015, and it has been decreasing year by year.

Furthermore, the amount of pollens inhaled by our bodies is quite small. The estimated internal exposure caused by inhalation of pollen with radioactive cesium is less than 1 billionth of 1 millisievert per hour in the difficult-to-return-to zone in Fukushima Prefecture. Pollens are not present in the air throughout the year, but even if they were, the annual internal exposure dose would be less than 1/10,000 of 1 millisievert. This accounts for 1/10th of the annual internal radiation dose we receive from environmental radiation.

Preventing hay fever to suppress symptoms such as rhinitis and conjunctivitis is necessary for some people, but it is unnecessary to have countermeasures against radioactive substances in the pollen.

58. Effects of radiation received in the location remained for a short period but did not contribute substantially.

“External radiation exposure” occurs when the body is exposed to penetrating radiation from an external source. After the Fukushima Daiichi nuclear accident, it was revealed that “external radiation exposure” contributed the greatest radiation effect, as “internal radiation exposure” was kept low by shipping restrictions on food items.

The total “radiation exposure dose” determines the health effect of radiation. The total dose of daily external exposure is influenced by the air radiation dose rate of the location where one stays for “a long time” during the day, such as home and school.

Conversely, walking through an area with a high air dose rate will not affect the health, as it will not contribute much to increase the total exposure dose.

The research results from children's cumulative dosimeter (glass badge) carried in Minamisoma city showed the association between the daily radiation exposure dose and the level of air radiation rate of the places where candidates spent most of their times, namely home or school. However, no significant relationship was observed between the level of daily radiation exposure dose and the level of external radiation exposure received during commutes to school or short outdoor activities.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on February 7th and 14th 2016 was reproduced for MRIC Global under the author's permission.

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