Bus fleet change improved air quality, State Of The Environment report shows

The introduction of a new bus fleet in Malta in 2011 contributed to a significant reduction in fine particulate matter, known scientifically as PM2.5 in Msida between 2011 and 2012.

The State of the Environment Report said it was “tempting to ascribe this change” to the introduction of the Arriva bus fleet with its Euro V and Euro VI diesel engines, which are much cleaner than the older engines of the older fleet.

PM2.5 consists of tiny particles or droplets in the air that are two-and-a-half microns or less in width: particles in this size range are able to travel deeply into the respiratory tract, reaching the lungs.

Moreover, the averages of PM2.5 levels between 2012 to 2015 are statistically significantly lower than those from 2008 to 2011.

Yet exceedances of the EU limits have been observed for both ozone and PM10 – particulate matter which is 10 micrometers or less in diameter. Traffic congestion and to a lesser extent power plants are the main source of this pollutant.

But a relatively large fraction of PM10 can be apportioned to salt from sea spray as well as Saharan desert dust. Ozone is a trans-boundary pollutant arriving in Malta from Europe.

St Anne’s Street in Floriana remains the most polluted street in terms of nitrogen dioxide (NO2), where the annual mean concentration stood at 79.6 micograms per cubic metre (µg/m³) in 2014 and 80.2 µg/m³ in 2015.

These levels are twice the EU annual mean limit for this pollutant. But the annual mean concentration recorded in St. Anne’s Street in 2014 and 2015 was substantially lower than that reported in 1999.

This locality was followed by St Joseph Street in Hamrun, which had recordings of 73.4 µg/m³ and 74.0 µg/m³ annual mean of NO2 in 2014 and 2015 respectively.

Both these streets are characterised by heavy traffic and poor ventilation due to high buildings yielding a street canyon.

Nitrogen dioxide inflames the lining of the lungs, and it can reduce immunity to lung infections. This can cause problems such as wheezing, coughing, colds, flu and bronchitis.

Pollution from power plants

The report describes the shift to the use of liquefied natural gas as the fuel used in power stations and the purchase of power from the Italian grid through the interconnector as the most significant measures taken in the energy sector to improve air quality.

But the full extent of the impact of this shift on air quality can only be assessed in the next State of the Environment Report as the present one is limited to an assessment of the situation between 2008 and 2015.

“It remains to be seen to what extent the change from a heavy fuel oil-based energy sector to a liquefied natural gas-based one will influence the concentration of airborne PM. This switch will take place during the next reporting period”.

The ERA report confirms a significant decrease in sulphur dioxide concentrations, which is attributed to the phasing out of heavy sulphur content fuels.

What is sure is that the closure of the Marsa power station in 2015 has resolved one of the environmental problems blighting the south of Malta-namely the deposition of ‘black dust.’ The phenomenon started before the turn of the century and was largely experienced in the Grand Harbour towns and continued throughout 2010.

A report on the nature, distribution and likely source of coarse black dust particles authored by Prof Alfred Vella concluded that the Marsa Power Station was the likely source of the problem. “It seems that the bane of the black dust is no longer an issue.”