Published online 26 April 2010 | Nature | doi:10.1038/news.2010.199

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Missing data spark fears over land clean-up

Proposed home for world's largest fish market is contaminated land.

Tsukiji fish marketAttempts to clean up the new site for the Tokyo Central Wholesale Market have come under scrutiny.K. Sasahara /AP Photo

A row has broken out in Tokyo over the proposed relocation of the world's largest fish market. Soil at the new site contains dangerous levels of toxic chemicals and critics claims that the local government is suppressing key data detailing its clean-up efforts.

The local government launched trials to clean up the site on Tokyo bay in January. It released a report last month stating that the tests had been successful, but some local politicians in the Tokyo Metropolitan Assembly say the report omits crucial data, making it impossible to judge how well the tests worked. On 15 April, these critics — assembly members from the Japanese Communist Party — demanded that the data be released, but they were rebuffed by city authorities last Thursday.

The Tokyo Central Wholesale Market handles more than 2,000 tonnes of fish and other seafood each day. But the 75-year-old facility is cramped and beset by parking and transportation problems. There are also fears that it would not survive an earthquake.

Plans to move the market from its current 23-hectare site in Tsukiji to a larger 40-hectare location in Toyosu about 2 kilometres further east on the Tokyo bay were approved more than a decade ago. But soil surveys at the new site, formerly home to a gas plant, showed high levels of seven toxic chemicals including arsenic, benzene and cyanide. A survey in 2008 found that soil benzene levels in one area were 43,000 times higher than the levels considered to be safe by national law.

Clean sweep

Tokyo's governor, Shintaro Ishihara, has vowed to push forward with the move nonetheless, and the city started testing various detoxification methods earlier this year. These include breaking down chemicals in the soil using heat or microorganisms, digging up and washing the soil with an agitation device to remove chemicals, and pumping out groundwater to a processing plant. The city plans to spend ¥58.6 billion (US$630 million) to clean up the site.

These methods work, but not all the time and not always with the same efficacy in all places, says Tatemasa Hirata, a groundwater pollution expert and director of Wakayama University in western Japan. Factors such as the amount of rain and the size of soil particles can affect the rate at which the ground can be cleaned. "The soil there is different from the soil here and elsewhere," says Hirata, who chaired the committee that carried out the 2008 survey.

Click for a larger version of this table.

The tests are scheduled to run throughout June, and on 10 March, the city released an interim report claiming that two methods — heating and washing — reduced toxic chemical concentrations to within the recommended safety levels at test sites. In particular, the heating method successfully reduced benzene concentrations from 430 milligrams per litre to 0.003 milligrams per litre.

Nobuo Yoshida, a Japanese Communist Party representative and Tokyo Metropolitan Assembly member, states that there were holes in the data. He says that the success was based on a comparison between results made after the clean-up experiments in January and the survey results taken in 2008, which had been made using a different sampling method. Instead, he says, results should have been compared with data taken immediately before and after the experiments, using the same methods and at precisely the same sites. At a budgetary meeting of the Tokyo Metropolitan Assembly on 11 March, the day after the release of the interim report, Yoshida drew attention to the inconsistency but was told only that "the pre-experiment data could not be released".

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The following day, the Japanese Communist Party filed an information disclosure request, and on 26 March received documents containing a table of the experimental results for seven plots, including the area where the highest concentrations of benzene had been found. But the pre-test concentrations for all sites appeared to have been crossed out by hand with a thick marker pen.

"How can we know if the methods are working if you don't see results before and after?" Yoshida says.

In a letter on 15 April to Ishihara and Itaru Okada, the head of the fish market, the Japanese Communist Party demanded that the city immediately release pre-test data for the heating and washing methods, explain why results from other tests had not been released and submit all the data to external experts for independent evaluation.

But on 22 April, Okada sent a reply indicating that the pre-experiment results would not be released until all of the tests were concluded in June and then verified with their own experts.

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Haruhiro Yamagata, a representative of the metropolitan government planning division overseeing the preparation of the new site, says that the pre-experiment data were omitted because they did not match data found in 2008 and that the difference might have confused people. "We have an obligation to explain matters to the public in a way that is easy to understand," he says.

Yamagata says that the city is now checking with specialists, whom he declined to name, to determine the best way to explain the differences. In response to a query from Nature, he acknowledged that the pre-test figures could have been included with a footnote indicating that the inconsistency had been noted.

Yoshida, however, wants answers now. "If the figures from January 2010 are much lower than in 2008, they have to explain why. And they also have to explain whether the test results are still valid," says Yoshida. "We need to know whether they are working at the areas where the chemicals are in the highest concentrations." 

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  • #61319

    I actually read that price tag in the voice of Scooby Doo :)

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