For a look at just how long radioactivity can hang around, consider Germany's wild boars.
A quarter century after the Chernobyl nuclear disaster in the Soviet Union carried a cloud of radiation across Europe, these animals are radioactive enough that people are urged not to eat them. And the mushrooms the pigs dine on aren't fit for consumption either.
The German boars roam in forests nearly 950 miles (1,500 kilometers ) from Chernobyl. Yet, the amount ofradioactive cesium-137 within their tissue often registers dozens of times beyond the recommended limit for consumption and thousands of times above normal.
"The contamination won't go away any time soon — with cesium's half-life being roughly 30 years, theradioactivity will only slightly decrease in the coming years."
Cesium can build up in the body and high levels are thought to be a risk for various other cancers. Still, researchers who studied Chernobyl could not find an increase in cancers that might be linked to cesium.
Cesium also accumulates over time in the soil, which makes boars most susceptible They snuffle through forest soil with their snouts and feed on the kinds of mushroom that tend to store radioactivity, Environment Ministry spokesman Thomas Hagbeck said.
The problem is so common that now all wild boars bagged by hunters in the affected regions have to be checked for radiation. Government compensation to hunters whose quarry has to be destroyed has added up to €460,000 ($650,000) over the past 12 months, Hagbeck said.
Thousands of wild boars killed in southern Germany every year register unacceptable levels of radiation. It's calculated in becquerels, a measurement of radiation given off. Anything beyond 600 becquerels per kilogram isn't recommended, according to Germany's Federal Office for Radiation Protection.
Normal meat has an average contamination of 0.5 becquerel per kilogram, and a German would normally consume about 100 becquerels per year from plants and dairy products, the agency said.
About 2 percent of the 50,000 boars hunted are above the legal radioactivity limit, Reddemann said. And the government's radiation protection office says some mushrooms have registered up to 20 times the legal cesium limit.
Even farther away in France, there is still soil contamination, though levels have dropped significantly. It is now rare to find unsafe levels of cesium in boars and mushrooms, said radiation expert Philippe Renaud of France's Institute of Radiation Protection and Nuclear Safety.
In Austria, too, traces of radioactive cesium remain in the soil. Along with boars and mushrooms, deer have been affected — some testing at five times the legal limit, that country's environment agency says.
Japan's Fukushima plant has so far not leaked nearly as much radiation as Chernobyl, but authorities there have banned the sale of milk, spinach, cabbage and other products from surrounding regions as a precaution.
European officials insist that occasionally eating contaminated boar meat or mushrooms does not pose an immediate health risk. Public health agencies are typically conservative in setting limits for radioactivity in food.
Eating 200 grams of mushrooms tested seven times above the legal cesium limit, for example, would amount to the same exposure as the altitude radiation taken in during a 2,000-mile flight, according to Germany's Office for Radiation Protection.
In Austria, authorities say that eating the unlikely amount of 2 pounds of contaminated boar meat that is 10 times above the legal cesium limit would amount to two-thirds of an adult's normal annual radiation intake by food.
However, the possibility of exposure will not be going away anytime soon.
"We assume that wild game will still be similarly affected until 2025 and then very slowly recede," said Reddemann, of Bavaria's hunting association. "The problem will certainly still be around for the next 100 years, and Chernobyl will still be an issue for our children and grandchildren."