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Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

Epidemiology of radiation-induced diseases

Epidemiology (derived from Greek epi "on, upon", demos "people", logos "study") is a scientific discipline studying the distribution of diseases in a population (descriptive epidemiology) and the factors influencing this distribution (analytical epidemiology).

Radiation epidemiology focuses on investigating possible associations between ionising radiation (for example due to medical X-ray examinations, irradiations or cosmic radiation during long-haul flights) or non-ionising radiation (for example between radiation from mobile phones, mobile phone base stations or electric and magnetic fields around high-voltage lines) and the risk of developing cancer or, for instance, cataract or cardiovascular diseases.

Which methods are used in epidemiology?

In general, the health effects of radiation on humans cannot be investigated with experimental studies under controlled conditions for ethical and practical reasons. Hence epidemiological studies are conducted.

These studies are purely observational. They allow a direct investigation of the risk for humans as well as the quantification of the level of risk. The most important types of epidemiological studies are cohort studies and case-control studies. Altogether there are four major different types of epidemiological studies:

Cohort studyshow / hide

In a cohort study, selected individuals who are exposed to a risk factor of varying degrees are investigated over an extended observation period. The central research question in a cohort study is for example whether there is a higher incidence of certain diseases in higher-exposed individuals than in less-exposed or non-exposed individuals.

An example for a cohort study is the German uranium miners study with 60,000 former Wismut miners conducted by the BfS. This study investigates the cancer risk depending on past radiation exposure in uranium ore mining.

Case-control studyshow / hide

Case-control studies are based on the presence of the disease and trace back to identify past exposures. The studies investigate whether diseased individuals had been exposed more often or more exposed than comparable non-diseased individuals. To this end, individuals suffering from the disease to be studied are selected from a given population. As only diseased individuals ("cases") and comparable non-diseased individuals ("controls") are investigated, case-control studies can be conducted with a considerably smaller number of individuals than cohort studies.

Case-control studies can also be "nested" into cohort studies in order to perform more extensive data collection for specific subgroups in a cohort.

One example is the KiKK study commissioned by the BfS. In this study children living in Germany in the surrounding areas of German nuclear power plants and who had developed leukaemia or cancer were compared with non-diseased children of the same age and gender living in the same region. The study investigated whether diseased children (cases) live closer to the nuclear power plant than assigned control children.

Cross-sectional studyshow / hide

In a cross-sectional study, radiation exposure (e.g. the measured exposure to the electromagnetic fields of mobile phone base stations) and the disease to be investigated (e.g. sleep disturbance or headache) are determined simultaneously and are put into correlation.

These studies are only useful for relatively common diseases and are generally only suitable for generating hypotheses.

Ecological studyshow / hide

"Ecological" studies are studies which do not investigate individuals, but use aggregated data categorised according to place or time (e.g. the incidence rate and radiation exposure in a particular area) to investigate the relationship between radiation and disease. Ecological studies are prone to error, because it is assumed that the studied groups only differ with regard to the risk factor of interest (e.g. radiation), but not with regard to other risk factors (e.g. smoking). They can provide indications about possible causes but are basically not suitable for risk estimates.

One example is the German nation-wide comparison of the lung cancer mortality rate and radon concentration in housing: the most significant risk factor for lung cancer is smoking. Not taking into account the regionally varying share of smokers in the population in such an investigation may lead to distorted findings regarding radon and lung cancer.

Epidemiological studies by the BfS

In the field of ionising radiation, the BfS is conducting a large cohort study on the effects of ionising radiation in former miners of the Wismut SDAG in former East Germany. Furthermore, the BfS commissioned a study on cancer in children living in the surroundings of nuclear power plants (KIKK study).

In the field of non-ionising radiation, a large number of epidemiological studies on the possible health effects of high-frequency electromagnetic fields were initiated and promoted by the BfS in the framework of the German Mobile Telecommunication Research Programme.

Further current research projects you will find in the Research Programme of the BfS (2013-2017).

State of 2018.01.22

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