In the aftermath of the earthquake and tsunami that hit Japan on 11 March 2011, the Daiichi nuclear plant in Fukushima was badly wrecked in a series of meltdowns and explosions that severely damaged three reactors and one spent-fuel pool.

The accident released enormous quantities of radionuclides (radioactive material) into the atmosphere and the sea. This led to the government setting up exclusion zones in regions around the plant and the evacuation of over 155,000 residents.

Three years on, calculating the injurious effects of this radiation on plant, animal and human health has become a matter of controversy, as different groups of researchers reach different conclusions.

Negative data ignored?

A broad scientific study by a United Nations committee, released earlier this year, was widely criticized by independent researchers for its generally benign findings and lack of reference to the negative data cited in a number of specific scientific studies published earlier. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report on the health impact of the Fukushima accident was signed by 80 scientists and published in April.

In respect to plants and animals, for instance, the UN report concluded, “Accumulated doses (of radiation over the first two months following the accident) were estimated to have fallen short of levels found to cause observable effects…” And for longer term effects, the report noted that while some individuals in species may have been harmed, the effects on plants and animals ” at the population level were considered unlikely to be observable.”

But such statements were made “with the complete absence of any supporting documentation”, said Timothy Mousseau, a professor of biological sciences at the University of South Carolina, one of many researchers troubled by such conclusions.

In response to the criticism, Carl-Magnus Larsson, Chair of UNSCEAR pointed out to Al Jazeera that the committee “used data that had been published in the open literature, and some data that had not been published at the time”, and then, “synthesized it for an overall assessment.” So UNSCEAR’s “mandate is for scientific review” of available scientific findings, not conducting its own field research, Larsson explained.

By contrast, Mousseau, as a member of a multidisciplinary group of scientists called the Chernobyl + Fukushima Research Initiative (CFRI), relies heavily on field studies for its reports. CFRI has extensively studied the consequences of radioactive contamination on animals at Chernobyl, the site of the devastating 1986 nuclear accident in Ukraine, and has conducted 10 similar studies in Fukushima since 2011.

Speaking to the foreign press in Tokyo on August 22, following CFRI’s latest findings, Mousseau noted that some half-dozen studies indicating the negative effects of Fukushima radiation had been released before the UNSCEAR report and many more related to Chernobyl effects, “which are quite similar in terms of the radiation and consequences”. Yet these reports “were clearly ignored” by UNSCEAR, which had to be out of “deliberate ignorance”, Mousseau said.

Other scientists agree with him. “Authorities in favour of nuclear energy tend to deny the negative results of researchers,” said Tetsuji Imanaka, an assistant professor of nuclear science at Kyoto University. “This happened after the Chernobyl accident when local scientists in Ukraine and Belarus reported the damaging effects of radiation.”

Only when the evidence became overwhelming, did the authorities acknowledge the results, he said. “And a similar denial is taking place now with Fukushima,” added Imanaka, who has visited the Chernobyl and Fukushima accident sites many times to conduct radiation contamination studies.

Butterfly genetic damage

One UNSCEAR omission Mousseau singled out is the study by scientists from Okinawa of the pale grass blue butterfly in the Fukushima contaminated zones, which he said has become “an important point of reference that should have been made in the UNSCEAR report”.

This study, published 9 August 2012 in the journal Scientific Reports, documented a variety of mutations occurring in the butterflies over time and concluded, “that artificial radionuclides from the Fukushima Nuclear Power Plant caused physiological and genetic damage to this species”.

UNSCEAR’s Larsson denies the charge.

“This article was used and discussed in the report. But it contained only a few field-based observations on effects that could be reliably linked to robust dosimetry.”

In other words the report’s findings were not sufficiently strong enough that UNSCEAR could declare with any degree of certainty that radiation was causing widespread damage to the species.

“One cannot draw firm conclusions on the basis of a few limited studies,” said Larsson. This is why, he added, UNSCEAR has stressed the need for more studies to better describe the relationship between radiation dosage and its effects on plants and animals.

Referring to CFRI studies, Mousseau noted that ecosystems around Fukushima are experiencing similar negative impacts as previously witnessed in Chernobyl.

“When we look at the high radiation areas (in Chernobyl), the numbers of birds are depressed by two-thirds,” said Mousseau. “And the same basic pattern holds for a variety of insects.”

In Fukushima, too, CFRI researchers observed that some bird species were already decreasing in numbers in hot zones, compared to adjacent clean zones, as early as July 2011, though the majority of species showed little impact. But by 2012 many more species were negatively affected. And, over three years of counting since the accident, the researchers found that the total numbers of birds in affected areas had declined in a consistent pattern, with the effects increasing over time.

Abundance of data

“Contrary to governmental reports,” said Mousseau, “there is now an abundance of information demonstrating consequences - in other words, injury - to individuals, populations, species and ecosystem functions stemming from the low dose radiation due to the Chernobyl and Fukushima disasters.”

So why does this matter?

“We cannot make a direct connection between these findings and human beings,” acknowledged Imanaka. “But they are a signal or a warning for us human beings. This is why we have to conduct research on plants and animals.”

Medical research is, of course, conducted on animals precisely because they share fundamental biological properties with humans, while science has shown that we share 99 percent of our DNA sequence with chimpanzees.

“So, of course, what we see happening in plants and animals has relevance for humans,” Mousseau said. The major difference, he notes, “is that the human populations in Fukushima are not facing the same level of exposures as the animals we’re working with”. Given this, “humans will have a much lower dose rate, [and] they are likely to require much longer for such consequences to show up.”

Mousseau emphasized that he is not an anti-nuclear activist, nor is he claiming that those in authority are attempting to minimize the danger of what is taking place in Fukushima. “Rather, what I am is an activist for evidence-based policy related to the environment,” he explained.

In this respect, he called for an international effort to fund and document the full range of biological consequences related to radiation in the Fukushima environment.

A key point here, he noted, especially as it relates to the contrary government reports, “is that this effort must be led by independent scientists who are committed to rigorous, unbiased analysis of the present situation with the goal of predicting long-term impacts”.