By Vessela SERGUEVA, Diana SIMEONOVA

SOFIA (AFP) — As the winter smog season in Bulgaria arrives, experts are concerned over a "perfect storm" of health risks: the country's high air pollution and the coronavirus — in a country with one of Europe's highest Covid-19 death rates. 

The danger is particularly acute given that several times last month the Bulgarian capital Sofia ranked as the world's most polluted city according to the Swiss IQAir air quality monitoring website.

As the temperature drops, the air above the capital Sofia has acquired its usual winter-time smoky grey hue, thanks in part to the surrounding mountains, which trap the air.

"When you look down at the city from Mount Vitosha it resembles a greyish lake of dirt and we are reluctant to go back down," says 39-year-old IT specialist Georgy Pavlov.

Long before the pandemic, he says, he started wearing a mask with a filter simply to walk his dog.

Ina Hristova, a 28-year-old biology researcher also dons a mask for a stroll in a Sofia park: not just because of the virus, but all the dust in the air, she says.

A gauze cloth covers her baby's pram.

Dust, stoves, traffic

Air-quality maps of Sofia have once more been going viral on social media, angering people in the European Union's poorest country. 

Environment ministry data confirmed that in November, on the days IQAir recorded its worst readings, the 24-hour concentration of (PM10) fine dust particles was four times the World Health Organization recommended limit.

Last week, the European Commission referred Bulgaria to the European Court of Justice, over what it said was its systematic failure to meet the PM10 limits. It had already failed to respond to a 2017 court judgement against it, the Commission noted.

A recent Sofia city council study identified the main culprits as dust, wood- and coal-burning stoves and car traffic. In poorer neighbourhoods, car tyres, old furniture or plastics are still burned for heating.

Several recent studies have shown that long-term exposure to air pollution combined with coronavirus makes Bulgarians extremely vulnerable, say experts. 

Record mortality

"Practically there isn't any organ or system in the body that is not impacted by fine-particle air pollution," lung specialist Alexander Simidchiev told AFP.

The pollution can not only undermine the immune system's response to the Covid-19 virus but also aggravate the illness, he said. 

Air pollution could even help spread the virus, attaching itself to the particles, he added.

"If you look at the air pollution map of Europe, there are two or three real hotspots of air pollution, and those were also hotspots for Covid.

"So it's very difficult to fail to notice the association between the air pollution map and the Covid severity map."

Between November 27 and December 3 the country suffered its deadliest week since the start of the pandemic with 980 deaths for a population of under 7 million: one of the highest Covid-19 death rates.

"If air pollution has made people vulnerable through chronic illnesses, the virus tends to get rid of them," said Simidchiev. 

The government, initially reticent to impose harsh anti-virus measures, finally imposed new restrictions on November 27, closing restaurants, schools and shopping malls.

But already, between 15,000 and 18,000 people die every year because of air pollution, says Simidchiev.

A high smoking rate and underfunded and understaffed pulmonology departments have helped create "a perfect storm around lung health in our country", laid bare by the virus.