epa08368492 Smog haze hangs over Kiev, Ukraine, 17 April 2020. As of 17 April morning, Kyiv ranks second in the Air Quality Ranking as the world's most polluted city after topping the list late 16 April. On 17 April 2020, US Air Quality Index (AQI) for Kyiv is 163, with the norm being up to 50m as reported by a Swiss-based IQAir, which monitors the level of air quality across the globe. The dirtiest air is recorded in the Chinese city of Chongqing. On 16 April night, AQI for Kyiv stood at an unprecedented 380, turning Ukraine's capital into the most polluted city in the world. Municipal authorities strongly advise that local residents stay inside and keep their windows shut as local media report. EPA-EFE/SERGEY DOLZHENKO 
According to Swiss monitor IQAir, Kiev had the highest level of air contamination of major world cities, ahead of Hangzhou, Chongqing and Shanghai in China.
Though the 1986 Chernobyl disaster sent clouds of nuclear material across much of Europe, there was no new radiation risk from the fires and pollution, Ukraine's health ministry said.
"Smog has been formed in Kiev and Kiev region. It does not carry a chemical or radiological threat, the radiation background is within normal limits," it said in a statement.
The city's roughly 3.7 million people were, however, urged to remain indoors - where most are anyway due to restrictions intended to contain the coronavirus - and close windows.
"This smoke can cause headaches, coughs, difficulty breathing, eye irritation, inflammation of the mucous membrane of the nose and larynx, as well as a number of diseases and allergies," the ministry added.
Police said a huge fire was started by arsonists in the forests around Chernobyl earlier this month. It was put out this week, but new blazes broke out on Thursday evening, fanned by heavy winds.
Forest fires were also registered in the neighbouring Zhytomyr region, destroying some houses and causing a car accident that killed several people.
On Friday, the state emergency service said there was no open fire across the Chernobyl station area or in Zhymomyr, though there was some smouldering of dry grass.
The Chernobyl plant and abandoned nearby town of Pripyat have become a tourist draw, especially since a U.S. television miniseries about the accident aired last year. The site is currently shut as part of the nationwide lockdown. (Reporting by Pavel Polityuk; Editing by Andrew Cawthorne)