Health Effects of High Radon Environments in Central Europe: Another Test for the LNT Hypothesis?

Abstract

Among the various "natural laboratories" of high natural or technical enhanced natural radiation environments in the world such as Kerala (India), Brazil, Ramsar (Iran), etc., the areas in and around the Central European Ore Mountains (Erzgebirge) in the southern parts of former East Germany, but also including parts of Thuringia, northern Bohemia (now Czech Republic), and northeastern Bavaria, are still relatively little known internationally.Although this area played a central role in the history of radioactivity and radiation effects on humans over centuries, most of the valuable earlier results have not been published in English or quotable according to the current rules in the scientific literature and therefore are not generally known internationally. During the years 1945 to 1989, this area was one of the world's most important uranium mining areas, providing the former Soviet Union with 300,000 tons of uranium for its military programs. Most data related to health effects of radon and other carcinogenic agents on miners and residents became available only during the years after German reunification. Many of the studies are still unpublished, or more or less internal reports.By now, substantial studies have been performed on the previously unavailable data about the miners and the population, providing valuable insights that are, to a large degree, in disagreement with the opinion of various international bodies assuming an increase of lung cancer risk in the order of 10% for each 100 Bq/m(3) (or doubling for 1000 Bq/m(3)), even for small residential radon concentrations. At the same time, other studies focusing on never-smokers show little or no effects of residential radon exposures. Experiments in medical clinics using radon on a large scale as a therapeutic against various rheumatic and arthritic disease demonstrated in randomized double-blind studies the effectiveness of such treatments.The main purpose of this review is to critically examine, including some historical references, recent results primarily in three areas, namely the possible effects of the inhalation of very high radon concentrations on miners; the effect of increased residential radon concentrations on the population; and the therapeutic use of radon. With many of the results still evolving and/or under intense discussion among the experts, more evidence is emerging that radon, which has been inhaled at extremely high concentrations in the multimillion Bq/m(3) range by many of older miners (however, with substantial confounders, and large uncertainties in retrospective dosimetry), was perhaps an important but not the dominating factor for an increase in lung cancer rates. Other factors such as smoking, inhalation of quartz and mineral dust, arsenic, nitrous gases, etc. are likely to be more serious contributors to increased miner lung cancer rates. An extrapolation of miner data to indoor radon situations is not feasible.Concerning indoor radon studies, the by far dominating effect of smoking on the lung cancer incidence makes the results of some studies, apparently showing a positive dose-response relationship, questionable. According to recent studies in several countries, there are no, or beneficial, residential radon effects below about 600 to 1000 Bq/m(3) (the extensive studies in the U.S., in particular by B. Cohen, and the discussions about these data, will not be part of this review, because they have already been discussed in detail in the U.S. literature). As a cause of lung cancer, radon seems to rank - behind active and passive smoking, and probably also air pollution in densely populated and/or industrial areas (diesel exhaust soot, etc.) - as a minor contributor in cases of extremely high residential radon levels, combined with heavy smoking of the residents.As demonstrated in an increasing number of randomized double-blind clinical studies for various painful inflammatory joint diseases such as rheumatism, arthritic problems, and Morbus Bechterew, radon treatments are beneficial, with the positive effect lasting until at least 6 months after the normally 3-week treatment by inhalation or bathes. Studies on the mechanism of these effects are progressing. In other cases of extensive use of radon treatment for a wide spectrum of various diseases, for example, in the former Soviet Union, the positive results are not so well established. However, according to a century of radon treatment experience (after millenniums of unknown radon therapy), in particular in Germany and Austria, the positive medical effects for some diseases far exceed any potential detrimental health effects.The total amount of available data in this field is too large to be covered in a brief review. Therefore, less known - in particular recent - work from Central Europe has been analyzed in an attempt to summarize new developments and trends. This includes cost/benefit aspects of radon reduction programs. As a test case for the LNT (linear non-threshold) hypothesis and possible biopositive effects of low radiation exposures, the data support a nonlinear human response to low and medium-level radon exposures.

Keywords: LNT hypothesis; lung cancer; radiation risks; radon; radon balneology.

Figure 1.

Distribution of radon air in top soil in Germany. Areas in black indicate more than 500,000 Bq/m³, in white less than 50,000 Bq/m³, and circles around the main uranium mining areas Schneeberg/Schlema (after Radon-Handbuch Germany Figure 2.1, 2001).

Figure 2.

Average of the radon in the ground floor of living rooms of communities in Germany (black above 400 Bq/m³, white less than 100 Bq/m³) (Siehl 2000).

Figure 3.

Relative lung cancer risk as a function of residential radon according to a meta-analysis of case-control studies in various countries (modification of Figure 1, p. 52, Lubin and Boice 1997).

Figure 4.

Lung cancer risk as a function of residential radon levels (Bq/m³): estimated odds ratio and 95% confidence intervals according to the “East German Radon Study”. (Reproduced from Wichmann et al. 1999, used with permission of Ecomed and the editor.)

Figure 5.

The relative lung cancer risk as a function of residential radon levels (Bq/m³) according to ICRP (LNT hypothesis — straight line), the “German radon study” by Wichmann et al. (1998, , and the “Schneeberg study” (lower line) by Conrady et al. (1999).

Figure 6.

Odds ratio for lung cancer as a function of residential radon concentration (Bq/m³) among nonsmoking females in the Schneeberg Study, compared to the also nonsmoking females in the Sheniang study. (Reproduced from Conrady et al. 2003, Proceed. 3. Biophysikal. Arbeitstagung Schlema 2001, registered with the German Library in Frankfurt, ISSN 1610-5079, used with permission of RADIZ.)

Figure 7.

Tender points used for testing the pressure pain sensitivity of patients with rheumatic/arthritic problems. (Baumann 2003, Proceed. 3. Biophysikal. Arbeitstagung Schlema 2001, registered with the German Library in Frnakfurt, ISSN 1610–5079, used with permission of RADIZ.)

Figure 8.

Tender point measurements of pain threshold with cervical spondylosis patients during, and after the end of the treatment with Rn and placebo tap water (note change of time scale at end of treatment). (Reproduced from Pratzel et al. 1997, used with permission of ISMH.)

Figure 9.

A complex “painless parameter” comparing in a study the radon and the control group at the end of the treatment period (left) with the effects 3 months (middle) and 6 months (right) after the treatment; radon group black, controls light. (Reiner 2003, Proceed. 3. Biophysikal. Arbeitstagung Schlema 2001, registered with the German Library in Frankfurt, ISSN 1610–5079, used with permission of RADIZ.)

Figure 10.

Summary of the pain-reducing effects of four randomized double-blind radon studies between 1993 and 1997, showing in comparison with the control groups (bars indicating the 95% confidence limits) the short-term effects (upper third), mid-term (middle), and long-term (lower part) effects; summary of all studies bottom line. (Reiner 2003, Proceed. 3. Biophysikal. Arbeitstagung Schlema 2001, registered with the German Library in Frankfurt, ISSN 1610–5079, used with permission of RADIZ.)

Figure 9.

Schematical diagram of the biopositive and bionegative radiation effects as a function of dose, with the damage induction superimposed by the biological defense mechanism, with a de facto threshold generally in the area between 0.2 and 2 Gy (Becker 2002, after Feinendegen).