Air pollution - State and impacts (Portugal)

Air quality evaluation in Portugal is compliant with Community legislation. The results are made available to the public on an on-line database (http://www.qualar.org/) using an air quality index (AQI) with a simple, easy-to-understand classification of air quality.

This index was implemented in 2001 and is calculated by area, using the average of the pollutants measured in the sites, including at least the following pollutants: nitrogen dioxide (NO₂), ozone (O₃) and fine or inhalable particles measured as PM₁₀.

In Portugal, the pollutants responsible for low and bad AQI were always PM₁₀ and O₃.

An analysis was made on the average number of days per site (urban and rural) in which air quality is low or bad according to the AQI, and it was noted that air quality has tended to improve in Portugal from 2005 onwards (Figure 1).

However, it should be noted that in urban areas with a higher population density and/or industrial installations nearby, the number of days on which AQI was ’Low‘ or ’Bad‘ remained high, whereas in 2008 there was a notable increase in the number of days on which air quality was ’Very Good‘ compared to previous years, in which this score was hardly ever achieved[1].

Figure 1 Number of days on which air quality is low or bad (2001-2008) 

Source: APA, 2009

The ozone analysis, split between the urban and rural environment, was based on the progression of the average concentration relative to the long-term target by type of site from 2001, and showed values above 120 µg/m³ in both areas, with levels slightly higher at rural sites (Figure 2).

Figure 2 Average annual concentrations of tropospheric ozone 

Source: APA, 2009

Annual concentrations of PM₁₀ have tended to fall (Figure 3), in line with European levels, showing the effect of legislation limiting emissions of atmospheric pollutants[2].

Figure 3 Average Annual Concentration of PM₁₀ particles by type of Environment/Influence 

Source: APA, 2009

Average daily PM₁₀ concentrations in Portugal can be caused partly by transboundary movement of particles from natural events, particularly from the Sahara desert or forest fires.

Emissions of gases causing eutrophication and acidification phenomena in the atmosphere have fallen in recent years, reflecting Portugal's efforts to control and reduce emissions with a major impact on the natural environment.

Figure 4 Relative progression of emissions of acidifying substances with GDP and primary energy consumption 

Source: APA, 2009; INE, 2009; DGEG, 2009

Figure 5 Aggregate emissions from acidifying and eutrophying pollutants by sector of activity 

Source: APA, 2009

Sulphur dioxide (SO₂) gas is the main cause of soil and water acidification. Nitrogen oxide and ammonia (NOx and NH₃) are the principal causes of eutrophication in many land and sea ecosystems, and also increasingly contribute to acidification.

A specific indicator called the Acid Equivalent is often used to evaluate the progression of acidifying and eutrophying substances. This indicator makes it possible to aggregate emissions of these pollutants, after each is assigned a specific weight.

Figure 6 Aggregate emissions from acidifying and eutrophying pollutants 

Source: APA, 2009

An analysis of the National Inventory of Atmospheric Pollutant Emissions, published in 2009 and presented to the Convention on Long-range Transboundary Air Pollution (CLRTAP), shows the significant efforts made by Portugal to meet its commitments to reduce emissions of acidifying and eutrophying substances.

In 2007, such emissions fell nearly 25 % in relation to 1990 levels, mainly due to a 42 % reduction in SO₂ emissions. This decrease, which was already evident in 2003, can be attributed fundamentally to the obligation to use low-sulphur fuels that came into force that year.

An analysis by type of pollution reveals that in 2007 SO₂ and NOx were responsible for 39 % and 38 % of emissions of acidifying substances respectively, with the remainder caused by NH₃.

The energy sector accounted for 31 % of acidifying and eutrophying substance emissions in 2007, followed by industry (25 %), agriculture (19 %) and transport (16 %). The waste and energy sectors experienced the most significant reduction in emissions compared to 1990 values.

[1] APA (2009). Relatório do Estado do Ambiente 2008. Agência Portuguesa do Ambiente. Amadora.

http://www.apambiente.pt/divulgacao/Publicacoes/REA/Documents/REA%202008_Final.pdf

[2] APA (2008). Relatório do Estado do Ambiente 2007. Agência Portuguesa do Ambiente. Amadora.

http://www.apambiente.pt/divulgacao/Publicacoes/REA/Documents/REA07_06out09.pdf