Warsaw is shrouded in a thick layer of smog on January 9, 2017 as coal and waste-fired home furnaces drive up levels of air pollution | Janek Skarzynski/AFP via Getty Images Air pollution linked to nearly 400,000 premature deaths Bulgaria and Poland have the highest levels of premature deaths attributed to particulate pollution.

Air quality in Europe is improving, but pollution is still killing a lot of people.

Fine particulate matter pollution caused 399,000 premature deaths in EU countries in 2014, according to the most recent estimates on the health impact of air pollution published Wednesday by the European Environment Agency (EEA). That is an 8 percent decrease compared to the previous year. The data was submitted by national authorities and analyzed by the EEA, which came up with the estimates of premature deaths.

Air pollution causes heart and respiratory diseases, and cuts life expectancy.

"As a society, we should not accept the cost of air pollution. With bold decisions and smart investments in cleaner transport, energy and agriculture, we can both tackle pollution and improve our quality of life," said EEA Executive Director Hans Bruyninckx in a press release.

Bulgaria had by far the highest rate of premature deaths attributable to particulate pollution, according to EEA data crunched by POLITICO. Next was Poland, where more than a third of the population heats their homes with polluting coal-fired furnaces. Sweden and Ireland had the lowest rates.

The main source for particulate pollution overall is domestic heating, followed by road transport and industrial processes.

Most countries had lower health impacts in 2014 than in 2013, but premature deaths rose in Cyprus, Denmark, Estonia, Finland, Latvia, Lithuania and Sweden.

The picture looks grimmer for specific air pollutants. Premature deaths linked to nitrogen dioxide (NO2), which is closely linked to diesel vehicle exhaust, increased to 75,000 in 2014 from 68,000 in 2013. Breaches of EU legal limits were reported in 22 of the 28 EU countries in 2015.

EU legal limits for fine particulate matter were breached less frequently in 2015, but over 80 percent of Europe's urban population was still exposed to concentrations above World Health Organization guidelines. WHO limits are tougher than those set by the EU.

The proportion of people exposed to harmful levels of pollution was even higher for ozone (over 95 percent), which surges during heat waves, and benzo[a]pyrene (over 85 percent) — closely linked to low-quality domestic heating and of particular concern in Central and Eastern Europe.

The European Commission has launched infringement proceedings against more than 20 EU countries for breaching EU air pollution limits.