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European Directives for Air Quality: Analysis of the New Limits in Comparison With Asthmatic Symptoms in Children Living in the Oporto Metropolitan Area, Portugal

Posted on: Sunday, 31 July 2005, 03:00 CDT

ABSTRACT

This study analyzes the air pollutant concentrations in the Oporto Metropolitan Area, Portugal, comparing them with the limits fixed by the previous legislation currently in force, as well as by European Union (EU) Directives. The impacts were estimated using the prevalence of asthmatic symptoms and asthma in children as indicators. The objectives were: (i) to evaluate the impact on air quality associated with the reduction of sulphur content in fuels, (ii) to compare health impacts associated with SO^sub 2^ and particles with the limits fixed by both legislations, and (iii) to assess whether the delayed application of the EU Directives can be associated with health risks. It was concluded that: (i) after the reduction of sulphur content in fuels, a reduction of 60% of the annual averages of SO^sub 2^ concentration was observed, as well as a decrease in the rates of asthmatic symptoms and asthma in children, (ii) the limits fixed by the previous legislation do not protect against health impacts of SO^sub 2^ and particles, but the new EU Directives are protective; the EU limits for PM^sub 10^ are very difficult to attain, being probably unnecessarily low concerning the impact on asthmatic symptoms and asthma in children, and (iii) the delayed application of the EU Directives can be associated with unnecessary health risks.

Key Words: air pollution, impact on asthma, particles, sulphur dioxide, air quality legislation.

INTRODUCTION

There is increasing interest worldwide in the adverse health effects that can result from exposure to atmospheric pollutants. Several acute episodes with mortality consequences have occurred since the first half of the 20th century (1930: Belgium; 1948: Donora, Pennsylvania; 1952: London) (Dockery and Pope III 1994). Nevertheless, the London episode was the first to attract international attention, because the increase of SO^sub 2^ and particle concentrations during 5 days in December 1952 was clearly associated with more than 1000 extra deaths.

Stieb et al. (2002) concluded that short-term air pollutant exposure is a significant contributor to mortality risks. Studies performed in the United States have shown that long-term exposure to suspended atmospheric particles could be associated with increased cardiopulmonary mortality (Hoek et al. 2002). Brunekreef and Holgate (2002) also showed that exposure to airborne particulate matter (PM) could be associated with increases in mortality and hospital admissions due to respiratory and cardiovascular diseases, the effects being observed at very low levels of exposure. Neuberger et al. (2002) analysed the influence of atmospheric concentrations of NO^sub 2^, SO^sub 2^ and suspended atmospheric particles on lung function, noting that improvements in outdoor air quality could be correlated with health benefits, and suggesting that adverse effects on lung function can be reversible before adulthood. McConnell et al. (2002) concluded that air pollution can contribute to the development of asthma in children.

For more than 20 years, special efforts have been taken in Europe to reduce the adverse impacts of atmospheric pollutants (Leeuw et al. 2001; Larssen et al. 2003). These efforts have led to a reduction of risks and effects, but the residual impacts are still a matter of concern, being considered as environmental and health priorities in the European Union (EU) (EEA 2002; Larssen et al 2003). In 2000, the World Health Organization produced the Air Quality Guidelines aimed at protection of human health; based on these guidelines, new objectives for air pollutant concentrations have been established in the EU, through the following Directives: 92/72/EEC; 96/62/EC; 99/30/EC (sulphur dioxide, nitrogen dioxide, particles and lead); 2000/69/EC (carbon monoxide and benzene); and 2002/3/EC (ozone) (Larssen et al. 2003). Standard values for heavy metals and polycyclic aromatic hydrocarbons are yet to be settled. Concerning the control of atmospheric emissions, the Auto-oil Directives (proposed by the Auto-oil programme created in 1992) are an example of the efforts made to use cleaner fuels in industry and motor vehicles, through the reduction of sulphur content in fuels (DGXI 1996; EC Directive 1998a,b; CEC 2000).

The European Directives must be transposed to the internal laws of all EU Member States. In Portugal the Auto-oil Directives were transposed in 2000 (Decreto-lei n 104/2000; Decreto-lei n 281/ 2000). The Directives that established the new limits for air pollutant concentrations were transposed in 2002 and 2003 (Decreto- lei n 111/2002; Decreto-lei n 320/2003), but in fact, until 2005 or 2010, Portugal's previous legislation will apply. For most pollutants the European Directives are much more restrictive; therefore, the analysis of the air quality in a defined region can lead to completely different conclusions, depending on the legislation considered. Against the general idea that there are not problems of air quality in Portugal, some difficulties can be predicted in achieving the new limits (Borrego et al. 2002). This means that human health can not being protected, and that unnecessary risks can be associated with the delay on the application of the EU Directives.

The Oporto Metropolitan Area (Oporto-MA) is the second largest region in Portugal, with about 1.2 million inhabitants and a population density of 540 inhabitants per km^sup 2^. In the north of Portugal, Oporto-MA is the region with the highest power consumption per capita and per industry, which is related to a relatively high industrial density. The motorization rate is the second highest in Portugal. In Oporto-MA the most important stationary sources of atmospheric pollutants are one oil refinery, one petrochemical plant, one thermoelectric plant working with natural gas, one waste incineration unit, and one international shipping port. Nevertheless, motor traffic is supposed to be responsible by a significant amount of the pollutants emitted to the atmosphere. Studies already conducted showed that atmospheric pollutants affect lung diseases in Oporto-MA, even at pollutant concentrations lower than those allowed by the previous legislation (Alvim-Ferraz et al. 1988).

Asthma is a complex disease whose symptoms include dyspnea, wheezing, chest tightness and recurrent cough. Several studies have been performed to analyze the impact of air pollution on the incidence of asthma or asthma symptoms (Barros et al. 1999; Stone 2000; Donnaldson et al. 2000), showing that for children the strongest association occurred during episodes involving NO^sub 2^, CO, and SO^sub 2^, whereas for adults particles smaller than 10 m (PM^sub 10^) were the most important pollutant (Stone 2000).

This study analyzes air pollutant utant concentrations in Oporto- MA, comparing them with the limits fixed by the previous legislation currently in force, as well as by the EU Directives. Special attention was given to two pollutants, SO^sub 2^ and PM, whose limits would be reduced more through European Directives (SO^sub 2^ and particles). The temporal trend in SO^sub 2^ concentrations was analyzed considering the impact of the implementation of the Auto- oil Directives transposed in 2000. The impacts were estimated using the prevalence of asthmatic symptoms and asthma in children as indicators. The objectives were: (i) to evaluate the impact on air quality associated with the implementation of measures to reduce sulphur content in fuels; (ii) to compare health impacts associated with SO^sub 2^ and particles with the limits fixed by the two analyzed legislations; and (iii) to assess whether the delayed application of the EU Directives can be associated with health risks.

METHOD

Three sites were selected for our study. Two of them belong to the Air Quality Monitoring Network of Oporto-MA, managed by the Commission of Coordination and Development of North Region (Comisso de Coordenao e Desenvolvimento Regional do Norte), under the responsibility of the Ministry of Environment; the third site was located in a rural reference area. Air monitoring site I (S^sub I^) is situated about 5 km from the coastline, located in an open area of a suburban industrial zone of Oporto city and on the west of the refinery and petrochemical plants. According to the human activities in the area where S^sub I^ was installed, road traffic and urban activities do not significantly influence air quality in a direct way; the main influence comes from industrial emissions of the refinery, petrochemical plant, and other industries, transported by prevailing winds from W and NW. Site II (S^sub II^) is located 6 km far from the coastline in a suburban rural area. According to the human activities in the surroundings, it is not significantly influenced in a direct way by traffic, urban, and industrial emissions. As Portugal is not significantly influenced by pollutants coming from other countries, the air quality in S^sub II^ is mainly influenced by intra-regional transport of pollutants, being considered with background behavior for a\tmospheric pollution in Oporto-MA. Site III (S^sub III^) is located in a remote rural location without direct or indirect influence of anthropogenic emissions of atmospheric pollutants.

The demographical densities of S^sub I^, S^sub II^, and S^sub III^ are, respectively, 5870, 2990, and 897 inhabitants per km^sup 2^. Air monitoring sites S^sub II^ and S^sub III^ were installed in the playgrounds of the schools frequented by the children whose asthmatic symptoms and asthma were evaluated, and S^sub I^ was located about 300 m from the schools where the study was performed. S^sub I^ and S^sub II^ were selected because the emissions influencing the air quality of those sites affect mainly the concentrations of SO^sub 2^ and PM^sub 10^, the pollutants selected to be analyzed throughout this study. At S^sub I^and S^sub II^ those concentrations were continuously analyzed between the years 1999 and 2002. None of the reference sites of the Air Quality Monitoring Network of Oporto-MA, where continuous monitoring is being performed, is located close enough to a school. Therefore, S^sub III^ was installed specifically to analyze the impact of air quality on asthmatic symptoms. As the pollutant concentrations at S^sub III^ were similar to the other reference sites of the Air Quality Monitoring Network, just two experimental campaigns were performed there (one in 1999 and other in 2002), monitoring SO^sub 2^ and PM^sub 10^ during March, June, September, and December.

The SO^sub 2^ concentrations were obtained by the UV fluorescence method according to EU Directive 1999/30/CE and Decreto-Lei n 111/ 2002, using AF21M equipment from Environment SA. The PM^sub 10^ concentrations were obtained using the beta radiation attenuation method, considered equivalent to the one indicated in EU Directive 1999/30/CE and by Decreto-Lei n 111/2002, using MPSI1001 et E equipment from Environment S.A. All equipment was submitted to a rigid maintenance program and periodically calibrated. Measurements were made continuously, registering hourly averages of concentrations in g m^sup -3^. Statistical treatment was performed only when valid data had been obtained in at least 75% of the maximum possible for the analyzed period.

The prevalence of asthmatic symptoms and asthma in the children living in the area was assessed through written questionnaires similar to those used in the International Study of Asthma and Allergies in Childhood (ISAAC) (clayton 2003). The questionnaires were distributed to the children (with consented participation), studying at primary or secondary schools where the monitoring sites were installed (S^sub II^ and S^sub III^) or at schools about 300 m from the monitoring place (S^sub I^). Two campaigns were performed: one relating to 1999 (CR99) and the other relating to 2002 (CR02). During CR99, the children's parents or guardians completed the questionnaires. In order to increase the number of answers, during CR02 the children's parents or guardians were contacted directly by medical assistants to stimulate participation in the study, but not interfering in the responses to the questionnaires. The answers were validated by medical doctors. The random samples for CR99 and CR02 were composed, respectively, of 720 and 956 children, aged 6 to 12 years. The children considered for the study had no tobacco smokers at home and belonged to families of medium socioeconomic status. Through the questionnaires, asthmatic children were identified when dyspnea and wheezing were mentioned in the absence of upper respiratory infections (Barros et al. 1999); this first asthma identification was confirmed through tests of bronchic reactivity with methacoline. Therefore, three groups were identified: children without symptoms, children with asthmatic symptoms, and children with asthma. The rates of asthmatic symptoms and asthma were compared with SO^sub 2^ and particle concentrations, considering the standards imposed by the previous legislation as well as by the EU Directives.

RESULTS

The analysis of SO^sub 2^ data from 1999 to 2002 showed that concentrations are significantly higher for S^sub I^ than for S^sub II^ (Pereira et al. 2003). This reflects the higher influence of industrial emissions at S^sub I^. At S^sub III^ the concentrations are even lower than at S^sub II^. As was already noted, the objective of the measurements at S^sub III^ was only to evaluate the impact of air quality on the prevalence of asthmatic symptoms and asthma in the children living in the area. Therefore, as the pollutant concentrations in S^sub III^ were similar to those measured at the reference sites of the Air Quality Monitoring Network of Oporto-MA, the measurements were performed only during March, June, September, and December. Thus, the minimum number of measurements fixed by legislation, to be considered for the statistical treatment established on an annual base of measurements, could not be observed for S^sub III^, avoiding the statistical treatment according to the legislation, and consequently, the comparison with the legal limits. Nevertheless, as the pollutant levels were similar to those measured at the reference sites of the Air Quality Monitoring Network of Oporto-MA, the pollutant concentrations could be assessed by comparison.

At S^sub I^ and S^sub II^, the analysis of SO^sub 2^ concentrations relative to the previous legislation (currently in force) showed that no exceedances were observed (limit values of 100 and 250 g m^sup -3^ for the 50th and 98th annual percentiles, respectively). Relative to the EU Directive, the hourly limit for protection of human health (350 g m^sup -3^ not to be exceeded on more than 24 hours a year) was not surpassed, and the daily limit for protection of human health (125 g m^sup -3^ not to be exceeded on more than 3 days a year) was exceeded at S^sub I^ only during 1999 (Table 1). The annual limit for protection oi ecosystems (20 g m^sup -3^) was also exceeded only at S^sub I^ during 1999 and 2000. From 2001 until 2002 this limit was not exceeded in both sites.

The clear decrease in the number of exceedances of SO^sub 2^ at S^sub I^ over the years is in agreement with the decrease of approximately 60% of the annual averages shown in Figure 1. S^sub I^ is mainly influenced by the industrial emissions transported by prevailing winds. The concentration temporal trend was the consequence either of technological innovations or of implementation of emission control programs. The decrease observed in SO^sub 2^ concentrations is mainly related to the implementation of the Auto- Oil Directives transposed in 2000, and implemented to reduce sulphur content in fuels. This observation allows concluding that the implementation of measures to reduce sulphur content in fuels have had a clear impact on the air quality of Oporto-MA, allowing a reduction between years 1999 and 2002 of approximately 60% of the annual averages of SO^sub 2^ concentrations.

Table 1. Exceedances of the limits for the hourly and daily averages of SO^sub 2^ concentrations aiming the protection of human health.

Figure 1. Annual average of SO^sub 2^ concentrations in Oporto- MA (1999-2002).

In distinction to what happened with SO^sub 2^, the PM^sub 10^ concentrations are less different at S^sub I^ and S^sub II^, and there was no tendency for a decrease in the concentrations observed. The analysis of PM concentration relative to the previous legislation also showed that no exceedances were observed at S^sub I^ and S^sub II^ (limit values of 150 and 300 g m^sup -3^ for the annual average and annual 95th percentile, respectively). By the same reasons expressed for SO^sub 2^, this analysis could not be made for S^sub III^. The EU Directive considers two different implementation phases (the first one until 2005 and the second one until 2010), with limits each time more demanding. Concerning the daily averages, the PM^sub 10^ limit is 50 g m^sup -3^, not being allowed more than 35 exceedances per year (10% of the total year days) until the end of the first phase of implementation, and not more than 7 exceedances (2%) until the end of the second phase. Data in Table 2 show that this limit was highly exceeded at both S^sub I^ and S^sub II^.

Table 2. Exceedances of the limit for the daily average of PM^sub 10^ concentrations aiming the protection of human health (number and percentage)a.

Table 3. Annual averages of PM^sub 10^ concentrations in Oporto- MA (gm^sup -3^).

As previously noted, at S^sub III^ the monitoring was performed during only four months, leading to a number of measurements much smaller than the minimum required by legislation (328 days per year). Even so, either in 1999 or in 2002 the daily average limit was exceeded 3 times in June and 5 times in September, showing that even at the reference site (S^sub III^), during only 4 months, the number of exceedances were bigger than the one allowed for 1 year (7) in the 2nd phase of application of EU Directives. This means that many difficulties can be expected if these limits are to be met, making sense to assess if they are unnecessarily low. For the annual average, two standards were also established: 40 g m^sup -3^ until the end of the first phase of implementation, and 20 g m^sup - 3^ until the end of the second phase. Data in Table 3 show the annual average that could be calculated according to the minimum number of measurements imposed by the EU Directives. The comparison of the annual average with the corresponding limits shows that only S^sub II^ meets the limit corresponding to the first phase of implementation in three of the years. When the limit to be reached during the second phase of implementation is considered, it can be observed that concentrations were considerably higher than the limit (2.2 to 2.5 times higher for S^sub I^ and 1.6 to 2.3 times higher for S^sub II^). It should be emphasized that all the other sites of the Air Quality Mo\nitoring Network of Oporto-MA, including the reference sites, did not meet the European Directives for PM^sub 10^.

It can be concluded that limits of the previous legislation were not exceeded, both for SO^sub 2^ and PM. Nevertheless, the limits of the European Directives for PM^sub 10^ were clearly exceeded revealing that even suburban areas not directly influenced by particle emissions (such as S^sub II^) have background concentrations (related to intraregional transport of pollutants) that do not meet the European Directives.

The rates of asthmatic symptoms and asthma for the children living in the areas of the selected sites are summarized in Table 4. The asthma rate observed in 1999 for S^sub I^ was slightly lower than the values previously published for Oporto (11.2%), decreasing in 2002. For S^sub III^ it was in agreement with the values published for rural areas in Portugal (less than 2%), both in 1999 and 2000 (Pereira 1998; Barros et al. 1999;Almeida 2003).

Table 4. Prevalence rates of asthmatic symptoms and asthma in children (6-12 years, without tobacco smokers at home and a family of medium socio-economic status).

Considering the 95% confidence level, the asthma rates for S^sub I^ and S^sub II^ (either in 1999 or 2002) were different but not significantly different, which is related to the small numbers of asthmatic children samples; on the contrary, the rates of asthmatic symptoms for each campaign were significantly different for the different sites (Sanders 1990; Miller and Miller 2000). When the two campaigns were compared, a significant difference was observed only at S1 for the rate of asthmatic symptoms that decreased between 1999 and 2002. Therefore, the comparison of rates should be based mainly on the rates of asthmatic symptoms.

Many factors can influence the differences observed between sites; nevertheless, according to the results of the International Study of Asthma and Allergies in Childhood, it is likely that environmental factors can be responsible for the major differences between places (Clayton 2003). As the sites considered in this study differ mainly in their environmental characteristics, that was the criterion considered in the present analysis. Therefore, the rates of asthma and asthmatic symptoms were compared with the concentrations of SO^sub 2^ and PM^sub 10^ and with the respective limits fixed by the two analyzed legislations.

At S^sub I^ the PM^sub 10^ concentrations did not show any temporal trend, but the SO^sub 2^ concentrations decreased between 1999 and 2002, as a consequence of measures to reduce sulphur content in fuel. Similarly, the rate of asthmatic symptoms decreased from 36.8 to 25.6% and the asthma rate decreased from 10.3 to 8.2%. At S^sub II^, the PM^sub 10^ concentrations also did not show any temporal trend between 1999 and 2002, and the EU limits for SO^sub 2^ were attained. Accordingly, the rates of asthmatic symptoms and asthma were significantly similar at S^sub II^ in both years, suggesting that SO^sub 2^ concentrations influence the rates of asthmatic symptoms and asthma. If this is true, the obedience in both years of SO^sub 2^ limits fixed by the previous legislation, suggests that health impacts of SO^sub 2^ cannot be conveniently protected by the previous legislation, which means that the delayed application of the EU Directives can be associated with unnecessary health risks.

At S^sub II^ and S^sub III^, the SO^sub 2^ concentrations were similar, but the PM^sub 10^ concentrations were higher at S^sub II^ than at S^sub III^. Accordingly, the rates of asthmatic symptoms and asthma were higher at S^sub II^ than at S^sub III^, either in 1999 or in 2002, also suggesting the influence of PM concentrations. S^sub II^ is a site not significantly influenced by particle emissions in a direct way, having a background particle concentration. Therefore, it can be concluded that the background concentration of PM^sub 10^ in Oporto-MA can influence the worsening of asthma in children, not guaranteeing the protection of public health, in contrast to the conclusions obtained analyzing the concentrations with the previous legislation whose limits were not exceeded. As well as for SO^sub 2^, the health impacts of particles are not conveniently protected by the previous legislation, confirming that the delayed application of the EU Directives can be associated with health risks.

At S^sub II^ and S^sub III^, the EU limits for SO^sub 2^ were not exceeded, but the limits for PM^sub 10^ concentrations were not met, as well as at all the reference sites of the Air Quality Monitoring Network of Oporto-MA. Nevertheless, the rates of asthmatic symptoms and asthma were significantly higher at S^sub II^ (background site) than at S^sub III^ (reference site), the asthma rate at S^sub III^ being less than 2%, in agreement with the baseline prevalence of the target population (Almeida 2003). This means that no effects were observed even when the limits were not met, suggesting that the EU limit for PM^sub 10^ is exaggeratedly low relative to the impact on asthmatic symptoms and asthma. This hypothesis was confirmed by identifying the months of asthma symptoms that worsened in the children at S^sub III^: March and mainly December, not coincident with the months of exceedances of the limit of PM^sub 10^ daily averages: June and September. This probably means that the pollen effect in spring and the traditional viral respiratory infections of winter were more important than the PM concentrations, if these concentrations are within the range of the restrictive limits established by the EU Directives, or even if they are slightly higher.

CONCLUSIONS

The results obtained between 1999 and 2002 allowed concluding that:

* The implementation of measures to reduce sulphur content in fuels has led to a reduction of 60% in the annual averages of SO^sub 2^ atmospheric concentrations; consequently, the rates of asthmatic symptoms and asthma have decreased from 36.8 to 25.6%, and from 10.3 to 8.2%, respectively, showing the impact of SO^sub 2^ concentrations on asthma and asthmatic symptoms in children. The EU Directive limit that was exceeded in 1999 was obeyed in 2002.

* Suburban areas not directly influenced by PM emissions have a background concentration of PM^sub 10^ that does not meet the European Directive for Air Quality, and that influences the worsening of asthma and asthmatic symptoms in children. That Directive was also not attained in a rural reference place, which means that many difficulties can be expected to meet the limits for PM^sub 10^ fixed by the European Directive. No effects were observed at the reference place, S^sub III^, even when the limits were not attained, suggesting that the EU limits for PM^sub 10^ are exaggeratedly low relative to the impact on asthmatic symptoms and asthma in children. It seems that the pollen effect in spring and the traditional viral respiratory infections of winter were more important than the PM concentrations, if these concentrations are within the range of the restrictive limits fixed by the EU Directive, or even if they are slightly higher.

* In comparison to the conclusions obtained by analyzing the pollutant concentrations with the EU Directives, all the limits of Portugal's previous legislation were met, both for SO^sub 2^ and PM. Therefore, their health impacts are not protected in the previous legislation, which means that the delayed application of the EU Directives can be associated with unnecessary health risks.

ACKNOWLEDGMENTS

The authors are grateful to the Comisso de Coordenao e Desenvolvimento Regional do Norte for their collaboration on this study, providing the data of the Air Quality Monitoring Network of the Oporto Metropolitan Area.

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M. C. M. Alvim-Ferraz,1 M. C. Pereira,1 J. M. Ferraz,2 A. M. C. Almeida e Mello,1 and F. G. Martins1

1 LEPAE, Departamento de Engenharia Qumica, Faculdade de Engenharia, Universidade do Porto, Oporto, Portugal; 2 Departamento de Pneumologia, Centro Hospitalar de Vila Nova de Gaia, Vila Nova de Gaia, Portugal

Received 22 April 2004; revised manuscript accepted 14 October 2004.

Address correspondence to M. C. M. Alvim-Ferraz, LEPAE, Dept. de Engenharia Qumica, Faculdade de Engenharia, Universidade do Porto, Oporto, Portugal. E-mail: aferraz@fe.up.pt

Copyright CRC Press Jun 2005

Source: Human and Ecological Risk Assessment

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