One of the major assumptions made by the nuclear industry is, that there are no signiﬁcant indicators of health or environmental consequences associated with “low doses” of radiation, or the ingestion of small amounts of radionuclides.
The impacts of releases of radionuclides from the Fukushima Daiichi nuclear disaster remain unclear.
Extreme caution is required to not confuse the vague term, “low doses” with “safe doses” of radiation.
A new study in PLoS ONE finds that three decades after Chernobyl’s nuclear disaster gives new perspective to the hypothesis that an area exceeding 30,000 km2 in Chernobyl’s surroundings constitutes an ecological trap that causes dramatic excess mortality.
The authors write that their findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation:
Between 2006 and 2009 the authors of the study used nets to capture birds in Chernobyl’s most affected areas. The research found that age ratios were skewed towards younger yearling birds—meaning older birds were dying—especially in the most contaminated areas.
The research data implies that the bird populations were only being maintained by immigration of young birds from uncontaminated areas nearby.
- Higher rates of mortality in female birds led to a sex ratio strongly skewed towards males in the most contaminated areas.
- Adult survival rate for male barn swallows in areas of Ukraine impacted by the Chernobyl accident was 0.327, while it was 0.431 in uncontaminated control areas, equaling a reduction by 24%
- For females the corresponding estimates were 0.233 and 0.542, respectively, or a reduction by 57%. This sex by radiation effect was highly significant implying that females suffered disproportionately from high levels of radiation.
- These males then sang disproportionately more frequently, presumably because they had difficulty finding and acquiring mates.
- The results were not caused by permanent emigration by females from the most contaminated areas.
These results suggest significant mortality costs of low-dose radiation with severe consequences for breeding populations of birds in vast areas of contamination in Ukraine, Russia and Belarus, exampled by the behavior of male birds who live in Chernobyl’s most contaminated areas, who sing more often because there’s hardly a female to be found.
Comparisons to the Fukushima Nuclear Disaster –
In July of 2011, scientists in Japan identified and counted birds at 300 locations in Fukushima Prefecture between 15 and 30 miles (25 and 48 km) from the nuclear complex. Most of these areas were still open to human occupation and were experiencing external radiation levels from 0.5 to 35 microsieverts per hour.
The team compared the results to their similar investigation in the Chernobyl Exclusion Zone between 2006 and 2009, 20 to 23 years after that nuclear disaster.
The findings showed, just as in the Ukraine, the bird community in Fukushima declined significantly in the more contaminated areas.
For 14 species of birds that appeared in both Fukushima and Chernobyl, the decline in population size was more pronounced at Fukushima than Chernobyl.
The scientists hypothesized that the Fukushima birds have never experienced radiation of this intensity before and may therefore be especially sensitive to radioactive contaminants.
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