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J.A. Aziz¹

ABSTRACT While enforceable National Environmental Quality Standards for pollutants exist in Pakistan, ambient air quality guidelines have never been established. However, there is no reliable epidemiological/toxicological monitoring system in place in Pakistan to provide a basis for establishing guidelines for various air pollutants. This paper reviews the World Health Organization air quality guidelines as well as standards applied in countries of the Eastern Mediterranean and South-East Asia Regions. Based on these, and available data on the existing air pollution situation in Pakistan, national air quality guidelines are proposed for 6 major pollutants.

Vers l’établissement de lignes directrices pour la qualité de l’air au Pakistan

RÉSUMÉ Si des normes nationales de qualité environnementale applicables aux polluants existent au Pakistan, des lignes directrices afférentes à la qualité de l’air ambiant n’ont jamais été établies. Cependant, il n’y a pas de système de surveillance épidémiologique/toxicologique fiable en place au Pakistan pouvant servir de base à l’établissement de lignes directrices pour les différents polluants atmosphériques. Le présent article examine les directives de l’Organisation mondiale de la Santé relatives à la qualité de l’air ainsi que les normes appliquées dans les pays des Régions de la Méditerranée orientale et de l’Asie du Sud-Est. Sur cette base, et sur la base des données disponibles sur la situation actuelle concernant la pollution atmosphérique au Pakistan, des lignes directrices nationales pour la qualité de l’air sont proposées pour 6 principaux polluants.

¹Faculty of Civil Engineering, University of Engineering and Technology, Lahore, Pakistan (Correspondence to J.A. Aziz: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).
Received: 19/10/03; accepted: 22/11/04
EMHJ, 2006, 12(6): 886-893

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Introduction

The protection of ambient air quality in Pakistan is provided through the enforcement of the National Environmental Quality Standards, introduced in July 1996. These standards impose limits on the concentration of specified gaseous emissions from industrial units and automobiles. The standards were imposed, however, without giving careful consideration to the desired ambient air quality. As such, the real objective of minimizing the risk to health of humans and animals and of damage to the environment in general may not be being achieved. There is therefore a need to establish national air quality guidelines in Pakistan.

Depending upon natural phenomena and human activities, the ambient air may contain a number of pollutants. The 6 pollutants that account for the large majority of air pollution worldwide and for which standards are usually specified include carbon monoxide (CO), ozone (O3), oxides of nitrogen (NOx), sulfur dioxide (SO2), lead (Pb) and suspended particulate matter (SPM). For SPM, 2 classifications are generally employed, i.e. total suspended particulate matter (TSP) and particulate matter less than 10 μm in diameter (PM10). NOx are generally reported as nitrogen dioxide (NO2). The impacts of these pollutants, when present in excessive quantities, on human health, vegetation and property have been described by the United States Environmental Protection Agency [1] and in many textbooks.

No reliable epidemiological/toxicological studies have been undertaken in Pakistan to provide recommended pollutant concentration limits in order to protect human health. It is therefore necessary to consult worldwide guidelines and the standards enforced in countries where the geographical and socioeconomic conditions and the level of available pollution control technology are similar to Pakistan. This paper reviews World Health Organization (WHO) air quality guidelines as well as standards applied in countries of the Eastern Mediterranean and South-East Asia Regions. Based on these, and available data on the existing air pollution situation in Pakistan, national air quality guidelines are proposed for 6 major pollutants.

Setting the guidelines

Air quality guidelines are derived from epidemiological/toxicological data. The criteria used in establishing air quality guidelines have been discussed by Schwela [2] and are generally based on the concept of acceptable risk of occurrence of effects caused by air pollutants. Due to the incomplete knowledge about the effects of pollutants, uncertainty factors are applied to lower the risk of an effect induced by air pollutants.

Depending on the pollutant, different averaging times are considered in establishing the guideline values of human exposure to air pollutants. In general, short and medium periods of time (10 minutes, 24 hours) are applied for pollutants that have acute effects on the respiratory tract (SO2, NOx, O3) or on the oxygen-carrying capacity of the blood (CO). Longer periods of time (1 month, 1 year) are applied for pollutants that have chronic effects on human health (Pb, particulate matter and SO2).

Perhaps the most widely publicized ambient air quality guidelines are those recommended by WHO [3,4]. Many countries use these guidelines for establishing air quality standards, especially those that lack basic data about exposure to pollutants in their country. The WHO 2000 guidelines for air pollutants [4] are reproduced in Table 1 courtesy of WHO Regional Centre for Environmental Health Activities (CEHA) [5]), along with WHO 2000 guidelines for Europe [3]. Ambient air quality standards that have been set in some countries of the Eastern Mediterranean Region and South-East Asia Region are shown in Tables 2 and 3.

A detailed review of these guidelines reveals that 24-hour and 1-year averaging times have usually been used for particulate matter. WHO guidelines do not include values for suspended particulate matter [4]. It was argued that a threshold for this compound including the size-dependent fraction, PM10, could not be established. It was therefore left to individual countries to establish standards with respect to the exposure level. For an annual average, a minimum of 104 measurements are taken in a year, twice a week and 24 hourly at uniform intervals. For SO2, NO2 and O3, 1-hour, 8-hour and 24-hour averaging times have been employed in different countries.

Air pollution in Pakistan

Regular monitoring of ambient air quality is still not systematic in Pakistan. All the available information is based on random and short-term sampling conducted to assess the concentrations of various pollutants. Many such studies have reported the ambient concentration of air pollutants in various urban and rural centres of Pakistan, including Karachi, Hyderabad, Jamshoro, Lakhra, Multan, Dera Ghazi Khan, Faisalabad, Lahore, Gujranwala, Pind Dadan Khan, Sargodha, Fateh Jang, Khewra, Sialkot, Rawalpindi and Peshawar [6–21]. The range of various pollutants in the ambient air of these cities is summarized in Table 4.

In 2000, a survey of ambient air quality in Lahore, Rawalpindi and Islamabad was conducted under a joint project of the Japan International Cooperation Agency and Pakistan Environmental Protection Agency. The ranges of air pollutant concentrations in ambient air based on hourly averages are presented in Table 5 [22].

The concentration ranges of various pollutants in the ambient air of urban centres of Pakistan are presented in Tables 4 and 5. The upper ranges of SO2, NOx, PM10 and Pb concentrations are higher than WHO limits [3].

The reported concentrations of pollutants in these surveys only give a general idea about the prevailing situation. A true picture of ambient air quality can only be obtained through well-defined long-term monitoring programmes. The situation calls for the establishment of a comprehensive countrywide air quality monitoring programme in Pakistan.

Proposed air quality guidelines for Pakistan

Taking account of WHO and regional standards, together with the prevailing levels of ambient pollutants in Pakistan, the proposed air quality guidelines for the 6 most common pollutants, along with averaging times for reporting, are summarized below and on Table 6.

Carbon dioxide

The CO concentration ranges given in Tables 4 and 5 correspond to 24-hour and 1-hour averaging times respectively. WHO provides guidelines for 1-hour and 8-hour averaging times as 30 000 μg/m3 and 10 000 μg/m3 respectively [4]. Most countries in the Regions have employed similar standards and the same levels for CO are therefore proposed for Pakistan.

Ozone

As given in Table 5, ambient concentrations of O3 range from 0.2 to 119 μg/m3 based on 1-hour averages. Keeping in view the averaging times adopted in Indonesia, Sri Lanka and Thailand and the prevailing local conditions, the suggested O3 level for Pakistan over 1-hour is 200 μg/m3.

Nitrogen dioxide

Local data in Table 5 indicate a concentration range for NO2 of 45.6–056 μg/m3 on 1-hour averages. Most countries in the Region have standards for 1-hour and 24-hour concentrations. To keep in line with the standards enforced in these countries, the following guidelines are proposed for NO2: 1-hour and 24-hour averages of 300 μg/m3 and 150 μg/m3 respectively.

Sulfur dioxide

Ambient concentrations of SO2 are reported to be in the range of 0.8–553 μg/m3 for 1-hour averages. As SO2 may also exist in particulate form, WHO and many other countries have also specified guidelines on an annual average basis, in addition to 1-hour and 24-hour averages. Therefore, the suggested guidelines for SO2 levels for Pakistan are 1-hour, 24-hour and annual levels of 350 μg/m3, 125 μg/m3 and 80 μg/m3 respectively.

Lead

WHO and some countries including India, Sri Lanka and Iraq specify ambient lead concentration values on the basis of annual averages. Lead concentrations, as indicated in Table 4, are well above WHO guidelines. Under the present conditions, it would therefore be appropriate to adopt WHO guidelines for Pakistan for lead of an annual average of 1.0 μg/m3.

Total suspended particulate matter

WHO guidelines do not suggest any value for TSP levels. Despite having a high TSP content in ambient air, Saudi Arabia does not specify TSP standards. Monitoring data reported in Table 4 show a high value for TSP in Pakistan of 180–1375 μg/m3. The major cause of this is the arid nature of the land and there is little hope of any major reduction in ambient TSP levels in the near future. Therefore, the following guidelines for TSP are proposed for Pakistan: 24-hour levels of 500 μg/m3 (excluding duststorm days) and annual levels of 300 μg/m3. The guideline values are in line with the values adopted by countries with conditions similar to Pakistan.

Particulate matter

Many countries in the Regions employ PM10 standard. The data presented in Table 5 indicate a PM10 range of 80–535 μg/m3 for a 1-hour averaging time. In order to place the emphasis on improvement measures, the following values for PM10 levels are suggested: 24-hour average of 200 μg/m3 (excluding duststorm days) and annual average of 120 μg/m3.

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