Which factors influence the radioactivity

Increased cancer risk from radioactive rays

Contribution of the editors from 06/22/2011 on the occasion of the Fukushima reactor disaster in March 2011

Author: Dr. med. Gesche Tallen, MD, PhD, created on: January 18, 2017, editing: Ingrid Grüneberg, approval: Prof. Dr. med. Ursula Creutzig, MD, PhD, last changed: 19.09.2019

introduction

What is the risk of developing cancer after exposure to radioactive radiation? What effects will the ongoing meltdown in Fukushima have on people in the immediate vicinity and also in the wider area of ​​the disaster? www.kinderkrebsinfo.de would like to introduce you to the problem of being able to assess this special cancer risk [ZYL2011] and also draw the attention of interested parties to further literature.

The current state of knowledge is mainly based on the evaluations of the data of a total of 500,000 victims of the reactor accident in Chernobyl by the Scientific Committee of the United Nations (UNSCEAR) [UNS2000] and 120,000 survivors of the atomic bombing disasters in Hiroshima and Nagasaki by the BEIR Committee [EPA2008] [BEI2006].

Ionizing Radiation: Definition and Units of Measure

  • Radioactive rays belong to the group of ionizing rays. Ionizing rays have a lot of energy that they give off to the tissue when they pass through an organism. As a result, body cells can be damaged so severely that their genetic material is changed and they turn into cancer cells. Ionizing radiation occurs in the earth's crust and the atmosphere as a natural part of our environment. However, it can also be generated artificially for targeted use in medicine and technology. An example of this are electromagnetic rays such as X-rays and gamma rays, which are used, among other things, in cancer diagnosis and treatment.
  • Radiation doses are used internationally in Sievert and in Gray specified. "Gray "(Gy) describes the Amount of energythat is absorbed by radiation per kilogram of body weight. However, it says nothing about the effect of this energy on the body. "Sievert "(Sv) however, refers to the Radiation exposure of biological organisms, i.e. on the received harmful radiation energy. This unit of measurement is therefore preferred when assessing radiation risks (unit for Gray and Sievert: 1 joule per kilogram).

Radiation exposure, limit values ​​and radiation protection

  • Everyone on the ground is exposed on the one hand to remaining cosmic radiation on the ground, and on the other hand to radiation from natural radioactive substances, mainly from the rock in the earth's crust. In Germany, the total dose from this natural radiation averages around 2.1 mSv per year [BFS2011]. Both an x-ray of the lungs and a flight from Frankfurt to New York and back are each associated with an average radiation dose of 0.1 mSv5. For comparison: The workers in the vicinity of the reactor in Fukushima are said to have been exposed to a dose of around 170 mSv [ZYL2011].
  • According to the German Radiation Protection Ordinance The ionizing radiation emitted, for example, from nuclear power plants and various industrial plants or used in medicine (so-called civilizing radiation), must not exceed a dose of 1 mSv per year for the population. Adults who are exposed to radioactive radiation in the course of their work may not ingest more than 20 mSv in one year. For employed young people under the age of 18, this limit is 1 mSv per year. The working life dose was set at 400 mSv. For non-pregnant women who are exposed to ionizing radiation for work-related reasons, the same dose limits per calendar year apply as for men. However, in women of childbearing age, the organ dose to the uterus may only be a maximum of 2 mSv per month. In pregnant women, this dose must not exceed the limit of 1 mSv from knowledge until the end of pregnancy [BFS2011].

Cancer risk

Cancers do not reveal what caused them. Correspondingly, malignant diseases caused by radioactive radiation cannot be differentiated from other cancers. In addition, every person has an individual, natural risk of developing cancer at some point in their life (lifetime risk). Other factors that have an influence on the risk and also the type of radiation-related cancer are, for example, the age at the time of radiation exposure, the gender of the person concerned, the radiation dose, additional exposure to cancer-causing substances such as nicotine, the individual sensitivity to radiation and the date on strongest irradiated organ [BEI2006]. All of these factors involve uncertainties that must be taken into account when assessing risk.

Radiation can only be assumed to cause the disease if the disease can be shown to occur more frequently in irradiated people than in non-irradiated people (control group), and if such an observation can also be repeatedly confirmed (for example by evaluating several large groups of people who have been exposed to radiation) and corresponding control groups). To ensure that these requirements are met and that reliable data are available for a realistic risk assessment, carefully managed cancer registries are required [SCH2011]. Since this did not yet exist in Russia in the 1980s, the UN report UNSCEAR [UNS2000] on the effects of the Chernobyl catastrophe continues to be controversial [ZYL2011].
The atomic bomb survivors from Hiroshima and Nagasaki, on the other hand, were carefully registered, adequately (> 50 years) observed and their data comprehensively documented. The latest evaluations are summarized in the 7th report "Biologic Effects of Ionizing Radiation" (BEIR VII) 3 of the National Academies of Sciences [BEI2006] on the subject of radiation effects.

BEIR VII3 presents models for the eleven most common types of cancer (10 solid tumors and leukemia), which can be used to estimate the risk of developing cancer or dying from it after exposure to radiation. These models include the uncertainty factors mentioned above to the best of our knowledge. BEIR VII is currently used by both the US Department for Environmental Protection (EPA) [EPA2008] and the Federal Office for Radiation Protection [BFS2011a] as the most reliable basis for statements about the risk of cancer after exposure to radiation.

BEIR models for estimating a radiation risk

More than 60% of atomic bomb survivors were exposed to radiation doses of less than 100 mSv. Therefore, the analyzes in BEIR VII3 [BEI2006] refer to the harmful effects of low radiation doses (< 100="" msv).="" eine="" der="" schlussfolgerungen="" des="" berichts="" besagt,="" dass="" bereits="" niedrige="" strahlendosen="" die="" wahrscheinlichkeit="" für="" das="" auftreten="" von="" spätfolgen="" wie="" krebserkrankungen="" erhöhen,="" dass="" es="" also="" keine="" mindestdosis="" (schwellendosis)="" für="" ein="" strahlenbedingtes="" krebsrisiko="" gibt.="" statistisch="" signifikante="" risiken="" für="" die="" entstehung="" von="" krebs="" und/oder="" für="" das="" versterben="" an="" einer="" krebserkrankung="" waren="" bei="" den="" atombomben-überlebenden="" bei="" organdosen="" oberhalb="" von="" 20="" msv="" erkennbar.="" sehr="" hohe="" strahlendosen="" können="" bereits="" nach="" wenigen="" tagen="" zu="" unterschiedlichen,="" schweren="" gewebeschäden="">

The BEIR models make it clear that certain types of cancer develop faster and more frequently than others after exposure to radiation. The period between the cause (in this case due to the radiation exposure) and the occurrence of the disease is called the latency period. This is the shortest for radiation-induced leukemia. The shortest latency periods are given for children (an average of two to three years for leukemia and an average of eight years for other cancers).

The model analyzes also show that - with the best possible inclusion of the above-mentioned uncertainty factors - the carcinogenic effect of ionizing radiation is directly related to the radiation dose, provided that the radiation doses are low. Experts also speak of a "linear" dose-effect relationship. This means that, for example, half of a certain radiation dose is only half as strong, but a double dose has twice as strong a carcinogenic effect on an organ. It is different with leukemia: Here the dose-effect relationship is not a linear one, but a "linear-quadratic" one. This means that the risk of developing leukemia increases with increasing radiation dose significantly more than the risk of solid tumors. A genetic radiation risk, i.e. the probability of the radiation-induced occurrence of genetic damage in future generations, was considered to be very low compared with the radiation-independent frequency of hereditary diseases [EPA2008].

Risk assessment for the lifetime risk of 100,000 people of all age groups to develop a solid tumor or leukemia. Interpretation: The probability of developing leukemia after exposure to radioactive radiation is around 1: 8 in men and women in relation to leukemias that develop without radiation exposure, while this ratio for solid tumors in men is around 1:57 in women 1:28 is.

 

Solid tumors *
male

Solid tumors * female

Leukemias
male

Leukemia female

Number of sick people / 100.00 after exposure to radiation of 100mS

800

1300

100

70

Number of sick people / 100,000 without additional radiation exposure

45.500

36.900

830

590

* Solid tumors originating from the following organs: stomach, intestines, liver, lungs, breast (only in females), prostate, uterus, ovary, urinary bladder, thyroid
Source: [NAP2006]

Conclusion

  • It becomes clear that no threshold dose can be defined for a cancer risk and that radiation risk studies are models that are influenced by numerous uncertainties. The level of radiation exposure (in Sv) and the distribution of exposure over a period of time play a role.
  • The risk of developing leukemia is generally higher than that of solid tumor diseases. This can be described as linear-quadratic within low dose ranges (less than 0.1 Sv = 100 mSv).
  • Overall, knowledge of the cancer risk for humans from radioactive rays is not yet complete.Future studies on the effect of low doses of radiation on the damage and repair ability of the genetic material in our body cells, the individual risk of cancer, individual radiation sensitivity, the health of workers in the nuclear industry and of citizens of Ukraine, Belarus and Russia and many more will be important additional Provide information.

UNSCEAR

Chernobyl

Report of the United Nations Scientific Committee: United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) here

BEIR reports

are created by the BEIR Committee, National Academy of Sciences Advisory Committee on the Biological Effects of Ionizing Radiation: Working group made up of physicians and physicists, on behalf of the American Environmental Protection Agency (EPA). BEIR VII report in letter here

Federal Office for Radiation Protection

Dose limits

in an overview table here