Three decades on from the 1986 Chernobyl disaster, radioactive fallout continues to affect the health of local wildlife in a number of ways, and may be responsible for high rates of cataracts among animals within the exclusion zone. According to a new study that appears in the journal Scientific Reports, local voles inhabiting areas with high background radiation levels were found to be more likely to suffer from the condition than those occupying sites with lower radiation levels.
A cataract is a clouding of the lens, resulting in a decrease in the amount of light that reaches the retina. Vision is subsequently impaired, and total blindness can occur in extreme cases. In humans, cataracts are associated with old age, although a number of other factors such as smoking, dehydration, and exposure to ultraviolet radiation have been shown to accelerate the rate at which cataracts form.
All of these factors are known to cause an imbalance between levels of highly reactive, oxygen-containing molecules that are produced during normal chemical reactions and our body's natural defense again these: antioxidants. This results in damage to cells via a process called oxidative stress. The researchers therefore sought to determine if the background radiation generated by the Chernobyl explosion could have this same effect and provoke the development of cataracts in local fauna.
To test this hypothesis, they collected 80 voles from 41 different locations in the area surrounding Chernobyl. Background variation levels recorded at these sites varied from 0.05 to 59.70 microsieverts per hour – the average background level around Europe is 0.27. In addition, they found that more than 70 percent of the animals examined had cataracts.
Such a high prevalence suggests that the radioactive fallout caused by Chernobyl may be driving lens deformities – a conclusion that would appear to be supported by the fact that the frequency of cataracts was higher in voles from regions with greater background radiation.
By assessing the wear and tear of the animals’ teeth, the study authors were able to estimate their age, and used this to calculate their lifetime radiation exposure. Interestingly, this was found to correlate directly with the frequency of cataracts in female voles, but not in males. Though the researchers are unable to explain why this is the case, they propose that it could have something to do with the strain of reproduction causing greater oxidative stress in females.
Significantly, females with more severe cataracts were also found to have less offspring. This suggests that lower rates of reproductive success could be caused either by cataracts, possibly because the poor vision impairs their ability to find mates, or by the radiation directly.
The Chernobyl Exclusion Zone is a 30-kilometer (18.6-mile) area that was evacuated in the aftermath of the explosion at the nuclear power plant, and to this day remains uninhabited by humans. Special permits must be obtained in order to enter the zone, and full body scans are compulsory upon exit, in order to ensure that absorbed levels of radiation are within the acceptable limit.