The average radiation level in central Tokyo was 0.0339 microsieverts per hour in Shinjuku Ward on March 6, data from the Tokyo Metropolitan Institute of Public Health show. That’s about the same as the day before the March 11, 2011 earthquake and tsunami caused the meltdown of three reactors at the Fukushima plant 220 kilometers (137 miles) to the northeast.
That reading compares with 0.085 microsieverts in London and 0.108 microsieverts in Seoul on March 3, and 0.057 microsieverts in Paris on Feb. 27, according to a compilation of world monitoring sites on the website of the Japan National Tourism Organization. Radiation levels in central Tokyo were as high as 0.809 microsieverts per hour on March 15, 2011 before declining to 0.0489 microsieverts by the morning of March 18.
Radiation occurs naturally in the environment. While a careful search could still reveal trace levels of Fukushima-linked radioactivity in Tokyo, it now barely registers over readings from background sources, such as solar particles, rocks and soil, said Kathryn Higley, who heads the nuclear engineering and radiation health physics department at Oregon State University in Corvallis. Other cities probably have higher radiation levels because of natural sources, she said.
“You have this widely ranging natural background,” Higley said in a phone interview. “It varies because of the geology. It varies because of your elevation”
Radiation levels in central Tokyo on March 15, 2011 peaked at about 24 times the day before the accident, prompting thousands of expatriates to flee Japan in the following months. Last year’s record number of foreign visitors and rising enrollment at international schools show how those concerns have abated, as Tokyo’s radiation readings fall below those in other major cities.
New York recorded 0.094 microsieverts an hour on May 31, 2011, according to the last available Geiger counter reading from Background Radiation Survey, a project where owners of the equipment feed their readings into a central database.
By comparison, a commercial flight exposes passengers to about 10 microsieverts per hour, according to the Health Physics Society’s website.
Closer to the wrecked plant in Fukushima, levels remain high enough to prevent the return of many of the 160,000 residents evacuated after the nuclear accident. In Namie town about 10 kilometers northwest of the plant, levels were as high as 17.59 microsieverts per hour at 8 a.m on March 7, according to prefectural data.
If sustained for a full year, that would be 154 times the maximum possible dose of 1 millisievert per year recommended for public exposure by the International Commission on Radiological Protection. The high radiation has made Namie town part of an area of northeast Japan where it will be a “long time” before residents can return, according to a Feb. 18 presentation by Masako Ogawa, an environment ministry director.
Tests also still find levels higher than the government safety guidelines of 100 becquerels per kilogram of cesium in small amounts of fish caught in Japanese waters, a level that bars those fish from entering the food supply.
The Japan Fisheries Agency found fish with levels exceeding guidelines in 24 of the 2,777 samples tested in January and February, including a rockfish caught off the Fukushima coast with 500 becquerels per kilogram, according to Haruo Tominaga, associate director of the agency’s processing and marketing division.
Health officials in Fukushima prefecture have tested 254,000 residents aged 18 or under at the time of the disaster and have detected 75 with definitive or suspected thyroid cancer as of Feb. 7, the Asahi Shimbun reported.
Hokuto Hoshi, a doctor involved in the prefectural survey, said the cases aren’t thought to be connected to the Fukushima meltdowns because not enough time has elapsed since the accident for the cancer to develop, according to the Asahi.
Enrollment at the American School in Japan, meanwhile, is now only about 40 students shy of its pre-quake level of 1,550 students, said school head Ed Ladd. The school had lost 800 students in the days after the quake and finished the school year in 2011 down about 250.
Fears of radiation don’t seem to be hurting tourism, with foreign visitors to Japan rising to a record 10.4 million in 2013, up 24 percent from the previous year, according to the Japan National Tourism Organization, which cited the weak yen as one reason for the increase.
Michaela Winter, who was visiting Japan from Finland where she works as a project manager at a technology company, said her own fears have abated since the months after the accident.
“I wouldn’t have come here then,” said the 28-year-old German native after touring Tokyo’s Imperial Palace on Friday. “But now I have friends here and they are fine, so I guess I’m fine too. I don’t fear it at the moment.”
To contact the reporter on this story: Jacob Adelman in Tokyo at firstname.lastname@example.org
To contact the editors responsible for this story: Jason Rogers at email@example.com Brian Fowler, Iain Wilson