Since it made the headlines 10 years ago as one of the most polluted cities in the world, Italy's Milan has achieved general improvement of air quality, but needs to continue with more modern socio-economic measures, local experts said on Thursday.

The positive trend over the past decade was especially evident for primary pollutants. Levels of sulfur dioxide (SO2) and carbon monoxide (CO) halved, while nitrogen dioxide (NO2) concentrations fell by more than 20 percent, according to figures released by ARPA, the environmental protection agency of Lombardy region whose capital city is Milan.

ARPA found that policies have mainly focused on replacement of polluting vehicles and tightening of traffic restrictions. Regarding energy measures, action was directed towards improvement of energy efficiency, diversification of energy production and increased use of renewable energy sources (RES).

Yet, despite the significant improvements, PM and ozone have remained the most critical pollutants whose limits have often been exceeded, said Luigi Bisanti, a noted epidemiologist and author of a study showing that fine particulate matter (PM) combined with other pollutants have been the main cause for some 550 yearly deaths in Milan over the past years and until now.

Bisanti told Xinhua that further improvements appear to be the difficult, though possible, challenge to be addressed by changing the urban structure. "What is important is to acknowledge that, for each rise of 10 micrograms per cubic meter of PM, we pay a penalty of hundreds of annual deaths," he said.

In 2012, the concentrations of PM10, which stands for particulate matter up to 10 micrometers in size, reached an average level of 43 micrograms per cubic meter (slightly above the 40-microgram-average limit set by the European legislation) against the value of 54 hit in 2002. Though the daily limit of 50 micrograms was often surpassed during the years, the annual number of exceed-ance days has decreased by more than 140 days in the early 2000s down to 107 in 2012.

The exceeding of the 25-microgram annual average limit for PM2.5, or smaller particles that can penetrate the respiratory system even more deeply, to be respected by 2015, was also widespread but fell from 41 in 2006 to 30 in 2012.

"The yearly results show a descending trend, but limits are still exceeded for too many consecutive days, which is especially due to the unfavorable weather conditions of the northern city," said an environmental chemistry professor at the University of Milano-Bicocca and one of Italy's leading experts in atmospheric particulate, Ezio Bolzacchini.

He said that, due to its position at the center of populous Po Valley which runs along the Po River and is home of intensive industry and farming, Milan is exposed to a 300-meter-high "inversion layer," a sort of blanket which prevents the smog from dissipating higher in the atmosphere, especially during the winter season. "It is for this reason that we need to adopt more stringent criteria compared to other European cities," the professor told Xinhua.

Again this January, the monthly average levels of PM10 rised to 59 micrograms per cubic meter, while PM2.5 reached the value of 52 in the same spam of time. The readings being registered for more than 10 consecutive days prompted the municipality to adopt emergency measures from further limiting circulation of most polluting vehicles to reducing heating use and forbidding shops to leave their doors open in order to avoid wasting heat.

"Strengthening of controls on old diesel-powered vehicles, after the introduction of catalyzed filters, and the methanization of domestic heating in place of other fuels played a fundamental role," noted Michele Giugliano, a distinguished professor of atmospheric pollution at Politecnico di Milano University.

The "Area C," or the congestion charge introduced last year, though was not created to affect concentrations, also led to notable lowering by 30-40 percent of pollution markers such as black carbon emissions. Furthermore, it caused a reduction by more than 30 percent of vehicles inside the designated restricted zone and 7 percent outside it, according to official estimates.

Above all, the lowered congestion in the city center resulted in increased average speed and use of public transport, which is a fundamental factor linked to the necessary "culture-oriented approach" to the pollution problem, Giugliano stressed.

"Area C as well as the Car free Sundays have the merit for helping citizens actively realize the need for everybody to do their part in the fight against pollution," he said. But the more than 700,000 vehicles in Milan are still too many for a population of around 1.3 million, the second largest in Italy after capital Rome.

Much more needs to be done, the expert highlighted, in the direction of enhancing clean technologies, in compliance with the European regulations, and public transport with large investments both in Milan and, more importantly, in collaboration with the surrounding districts.

In view of the Expo 2015, Milan has equipped with additional 300 bus routes on 14 lines per day and a reinforced bike share system counting nearly 3,000 bicycles, 40 percent more than in 2012. By spring 2013, the business city will be embellished by 7,300 new trees, Xinhua also learnt from local officers.

Among the latest initiatives, there was a project aimed at promoting a better use and maintenance of tires, whose deterioration contributes to pollution.

On the heating side, Milan has been increasingly implementing "district heating", a system that transfers and distributes heat from one or more heating plants to residential, commercial and industrial consumers. More than 85,000 apartments or a rough figure of 20 million cubic meters, 6.5 percent more than last year, are being treated with district heating.

Furthermore, a new plan for control of environmental standards in heating plants was launched with the objective to reach nearly 13,000 checks a year, 25 percent more compared to 2011, while a series of new "energy desks" are being created across the city to provide information on energy efficiency.

The experts said that one of the next necessary steps would be holding back the use of wood or wooden pallets as a fuel that, though helps greenhouse gas reduction, deepens particulate concentrations. In fact, benzo(a)pyrene levels were generally overcoming the target value in the areas where the use of wood is more widespread.

"There is no miraculous technology to solve the complex threat of pollution," Giugliano said. Coordination and synergy on a large scale between all different players is therefore the decisive ingredient to make every single action effective in the long term, he concluded. Endi