Male to Female Ratio at Birth: the Role of Background Radiation vs. Other Factors

An increase in the male to female (M/F) ratio at birth supposedly under the impact of radiation exposures from nuclear testing (worldwide) and Chernobyl fallout (in Europe) has been investigated by Victor Grech, professor at the Department of Pediatrics, Mater Dei Hospital, Malta [1,2]. The conclusions were that “elevated levels of man-made ambient radiation may have reduced total births, affecting pregnancies carrying female pregnancies more than those carrying male pregnancies, thereby skewing M/T (male live births divided by total live births) toward a higher male proportion” and “birth rates are greatly reduced and the M/T ratio is skewed upward significantly with population exposure to ionizing radiation, even at great distances from major nuclear events” [1,2]. However, social factors that could have influenced M/F ratios at birth were not analyzed. The natural radiation background (NRB) was not mentioned, although additional doses due to contamination were often negligible compared the NRB. Worldwide annual doses from NRB are generally expected to be in the range of 1-10 mSv, with 2.4 mSv being the estimated global average [3]. Some national averages are ≥10 mSv [4]. In Europe, mean annual doses from NRB are ≥5-7 mSv in several countries [5]. There are many places in the world where the dose rate from NRB is 10-100 times higher than the average e.g. 260 mGy/a in Ramsar, Iran [6], or 70 mGy/a at certain locations in Kerala, India [7]; yet there are no reliable data on shifts of sex ratios at birth in such areas. For example, a study based on ≥150,000 consecutive live singleton newborns in Kerala did not indicate any impact of elevated NRB on the sex ratio [8]. The maximum annual dose from the global fallout due to nuclear tests was estimated to be 0.14 mSv in 1963, having decreased by almost an order of magnitude by 1979 [3]. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), “as far as whole body doses are concerned, the six million residents of the areas of the former Soviet Union (SU) deemed contaminated received average effective doses for the period 19862005 of about 9 mSv, whereas for the 98 million people considered in the three republics, the average effective dose was 1.3 mSv, a third of which was received in 1986. This represents an insignificant increase over the dose due to background radiation over the same period (~50 mSv)” [9]. In other countries, individual doses from the Chernobyl fallout were lower: the first year doses after the accident reached 1 mSv only at singular locations in Central Europe; all country overages are ≤1 mSv/a [5,10]. For comparison, a single computed tomographic (CT) examination produces a dose within the range 2-20 mSv, while doses from interventional diagnostic procedures usually range from 5 to 70 mSv [11]. Health risks have never been proven for the abovementioned doses [12]. Annual individual doses in the vicinity of reactors have been in the range 0.001-0.5 mSv [3], so that the above dose comparisons pertain also to the reported shift of sex ratios at birth in people residing near nuclear facilities [13].

[5], which is a small addition to national averages from NRB (around 3.6 mSv/a in Germany; 3-7 mSv/a in the majority of European countries) [5,48]. The slight increase in the perinatal mortality in the Eastern part of Germany after 1986 was discussed in support of the role of radiation after the Chernobyl accident [49][50][51]. The ratio perinatal deaths/total births in GDR and West Berlin: 1986-2,183/242,068=9.02 per 1,000 total births; 1987-2,281/246,704= 9.24 per 1,000 [49]. This increase might have been caused by social factors (decline of the communist regime) and emigration of some medical personnel from the former GDR to the West. In general, oscillations of the perinatal mortality in Central and Eastern Europe after the Chernobyl accident [49,52]  Hagen Scherb et al.: Without specific empirical evidence and reference, Sergei V. Jargin insinuates a possible cause of the observed long-term increases in perinatal mortality in contaminated prefectures after Fukushima: "It is not surprising that cataclysms with evacuation of people, associated with stress, temporary derangements of perinatal care services, of diets, etc., are accompanied by an increase in the perinatal mortality".
Our data clearly show that in highly tsunami-impacted regions there is indeed a more than 50% increase in perinatal mortality, but this is confined to March and April 2011 only. From May through December 2011, nowhere in Japan perinatal mortality remained elevated. Moreover, the perinatal mortality increase in Chiba, Saitama, and Tokyo 10 months after the natural and technical catastrophes cannot be explained by "derangements of perinatal care" as the general infrastructure had not been compromised at all in these 3 prefectures [39].
Author: It is known by the example of Chernobyl accident that evacuations of people, psychological stress and anxiety favored by exaggerated risks ascribed to the low-dose radiation are noxious factors. In particular, exposures to stress after a nuclear accident may have detrimental effects on pregnant women [53,54]. Expectant mothers with anxiety and post-traumatic stress were reported to be at a higher risk of preterm birth [55]. There was an increase in the induced abortion rate after the Chernobyl accident [56][57][58][59]. Certain publications in professional journals may prevent physicians from giving adequate advice to pregnant women inquiring about a possible abortion. Radiation phobia with psychosomatic manifestations [60] is probably more prevalent in more contaminated areas thus contributing to dose-effect correlations. Reiterations of the perinatal mortality "jump" [61,62] after the Fukushima Daiichi accident can contribute to anxiety in pregnant women and elevate the abortion rate. Moreover, it cannot be excluded that radiophobia contributed to illegal abortions during the last trimester of pregnancy possibly influencing perinatal mortality figures. Considering that certain percentage of abortions after a prenatal ultrasonic gender testing must have been sex-selective, the enhanced abortion rate might contribute to an increased M/F ratio at birth.

Hagen Scherb:
The doubling of the background radiation level, say, from 1 mSv/a to 2 mSv/a, represents a doubling of an important physical environmental parameter relevant for the development of life on the earth, and cannot as such be considered a "low dose" and of no effect [38]. Author: The literature on the LNT was overviewed previously [63]. In brief, the LNT postulates that linear dose-effect correlations, proven to some extent for higher doses, can be extrapolated down to minimal doses. The DNA damage and repair are permanent processes in dynamic equilibrium. Living organisms have probably been adapted to NRB in a similar way as to other environmental factors: various chemical substances, products of radiolysis of water, ultraviolet light, and various stressors. Natural selection is slow; adaptation to a changing environmental factor would probably correspond to some average from the past. The NRB has been decreasing during the time of life existence on the Earth [64]. The conservative nature of mutation repair mechanisms in contemporary living organisms suggests that these mechanisms evolved in the distant past and that organisms may have retained some capability of efficient reparation of damage from higher NRB than that existing today [64]. With the dose rates tending to a wide range NRB level, radiation-related risks would probably tend to zero, and can even fall below zero within some dose range in accordance with hormesis confirmed by many experiments [65][66][67][68][69][70].
Admittedly, experiments do not always agree with epidemiological research. Epidemiological studies of low-dose radiation effects may be prone to bias, for example, surveillance basis, dose-dependent selection and self-selection, higher participation of cases (cancer patients) compared to controls etc. [71][72][73][74]. Better recollection by cases of the facts related to radiation (recall bias) [75] may contribute to overestimation of doses in the cases. It can be reasonably assumed that people informed on their higher doses would visit medical institutions more frequently being given averagely more attention. In the author"s opinion, the reported relationships of low-dose exposures with the sex ratio at birth and with other non-cancer endpoints, being devoid of physiological plausibility, witness against cause-effect relationships of the same doses with cancer, reported on the basis of epidemiological research.
In this connection, ideological bias aimed at the strangulation of nuclear energy should be pointed out, well in agreement with the interests of fossil fuel producers. Nuclear power has returned to the agenda because of the concerns over increasing global energy demand, declining fossil fuel reserves and climate changes. Health burdens were reported to be greatest for power stations based on lignite, coal, and oil. The health burdens are smaller for natural gas and still lower for nuclear power. This ranking also applies for greenhouse gas emissions [76]. The global development of nuclear energy must be managed by a powerful international executive based in the most developed parts of the world. It would prevent dissemination of nuclear technologies to unstable regions, where wars and terrorism are not excluded. It would enable construction of nuclear power plants (NPP) in optimally suitable places, disregarding national borders, considering all socio-political, geological and other preconditions, quality of working by local professionals, etc. [77]. In this way, nuclear accidents like in Fukushima (2011), caused by the earthquake and tsunami, or in Chernobyl (1986), favored by disregard for written instructions [5,78,79], would be prevented.