Even firefighters tackling the blazes, which officials say have hit forests in Russia’s Bryansk region polluted by radioactive dust from the 1986 Chernobyl reactor disaster, are unlikely to run any added nuclear contamination risks.

The amount of radiation in smoke would be only a fraction of the original fallout, they say.

“Of the total radioactivity in the area, much less than one percent of it will be remobilized,” said Jim Smith, an expert on Chernobyl and a specialist in Earth and Environmental Sciences at Britain’s University of Portsmouth.

Radioactive contamination in the area has substantially diminished in the almost two and a half decades since explosions at Chernobyl’s reactor No. 4 caused the world’s worst civil nuclear disaster on April 26, 1986.

“Most of the radioactivity is in the soil, which will not be affected by the fires, and only a small proportion is in the vegetation,” Smith said in a telephone interview. “And of that only a very small proportion of that will get re-suspended in the smoke from the fires.”

Russia’s forest protection agency said on Wednesday that fires covering an area of 39 sq km had been registered in regions with forests polluted with radiation. The regions affected included Bryansk province, which borders Ukraine, southwest of Moscow.

Russia’s Emergency Situations Ministry said Thursday all wildfires in areas contaminated by the 1986 Chernobyl nuclear disaster have been quickly extinguished and radiation levels have remained normal. Both France’s Institute for Radiation Protection and Nuclear Safety and Germany’s Federal Office for Radiation Protection said on Thursday that while some radiation was likely to be remobilized in smoke, the health risks were minimal and would have no impact on either Russia or neighboring countries.

“The fires do not have any radiological consequence for the rest of Europe and Germany since the dispersion of the radioactive substances is regionally limited,” the German organization said on its website.

According to experts, the types of radioactive isotopes that might still be active in the Bryansk area include strontium 90 and caesium 137. These substances have half lives of about 30 years, meaning that only about half the radioactive material emitted by Chernobyl is still around now.

“Even though the contaminated territories are affected by the fires in Russia, the situation would not lead to health concerns for the population, locally and in other countries in Europe,” said France’s Institute for Radiation Protection.

It said there may be a slight increase in radioactivity in the nearby environment due to re-suspension of caesium-137, “but it would be very much lower than the natural radioactivity.”

Portsmouth’s Smith and Stig Husin, an analyst in emergency preparedness at the Swedish Radiation Safety Authority, said the main threat from the fires both locally and nationally in Russia was the choking smoke from forest and peat fires, and the smog which is clouding the air in Moscow — all of which can cause lung and heart problems. “I would be much more concerned about the smog in Moscow and the health impacts of that — not because of radiation but because of people inhaling harmful air pollution,” said Smith.

On Thursday, the skies were clear over Moscow, giving residents a desperately needed break from air pollution thanks to favorable winds and some success in fighting wildfires that have choked the capital with clouds of acrid smog.

People walked through the streets without the masks that have become ubiquitous. The towers of the Kremlin and domes of Orthodox cathedrals could be seen without the yellowish veil that’s shrouded them for a week.

“I can finally open the balcony door to let my cat warm in the sun,” said economics student Evgeniya Lavrova, 21.

“You walk in a street, feel a light breeze and want to breathe again.”

Weather experts warned that the smog could return over the weekend after winds change again, but chief of Russia’s main weather service, Roman Wilfand, said that the unprecedented heat wave that has tormented Russia for most of the summer would end next week.

The Emergency Situations Ministry said Thursday that the area engulfed by fires around the capital has shrunk by more than quarter over the past 24 hours. It said firefighters have also managed to significantly reduce the size of fires in other parts of Russia, but 562 fires covering over 80,000 hectares (nearly 200,000 acres) were still burning Thursday.