Low-Levels Of Radiation Around Fukushima Affecting Insect Survival

Charles Lam, 'Open Wings,' via Flickr. CC BY-SA 2.0

Even ingesting low doses of radiation can have serious impacts on insects living around the Fukushima Daiichi Nuclear Power Plant, researchers have found. Butterflies dining on contaminated foliage collected from surrounding areas are more likely to suffer abnormalities and higher mortality rates than those fed clean leaves, according to a new study. Some of the effects could also be passed on to progeny, but interestingly, feeding offspring uncontaminated leaves seemed to surmount the negative impacts, suggesting decontaminating the food source could save the next generation. The work has been published in the open access journal BMC Evolutionary Biology.

On March 11, 2011, the Fukushima Daiichi Nuclear Power Plant experienced catastrophic failure that resulted in the meltdown of three of the plant’s reactors. Large amounts of radioactive material consequently spewed into the surrounding area which local wildlife has been exposed to ever since.

To examine the potential biological impacts of this radiation exposure, a group of researchers from the University of the Ryukyus has been conducting both field and lab studies on relevant animals for several years. In particular, they’re interested in how radiation could be affecting the development and genetics of the pale grass blue butterfly, a common butterfly in Japan.

In an earlier investigation, the team, headed by Joji Otaki, collected highly contaminated foliage from surrounding areas shortly after the disaster and fed it to butterfly pupae. The radiation in the plants was in the thousands of Becquerels per kilogram (Bq/kg), much higher than humans would ever be consuming (the limit in Japan is 100 Bq/kg for human food products).

They found that the butterflies dining on tainted leaves were more likely to suffer physical abnormalities and high mortality rates than those chomping on uncontaminated leaves. But the study didn’t address the effects of low-level radiation ingestion, which is what the latest investigation set out to do.

The researchers collected vegetation a year and a half after the disaster from six different localities ranging from 59 to 1,760 kilometers from the plant. The radiation levels were significantly lower than before, ranging from 0.2 Bq/kg to 161 Bq/kg. Once again, they found that butterflies fed the contaminated leaves showed higher mortality and physical abnormality rates, and that the effects were dose dependent. But even doses as low as 100 Bq/kg could be seriously toxic to some organisms, according to the study.

To extend this, they then split the offspring of these butterflies into two groups; one group was fed the same tainted foliage, whereas the other was fed uncontaminated leaves. They found that those ingesting contaminated leaves had even lower survival rates than that of their parents, suggesting the effects are transgenerational. However, those fed uncontaminated leaves had a near-normal lifespan, irrespective of what their parents consumed. This means that while some effects of the radiation can be passed on to offspring, they can be largely overcome by eating uncontaminated leaves.

Taken together, these results clearly show that ingesting low doses of radiation can impact organisms, which is unfortunately unavoidable in this area. However, this doesn’t necessarily translate to humans as it is likely that insects are far more sensitive than we are. 

[Via Biomed Central, BMC Evolution and Science]

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