Chapter 10

AIR QUALITY DURING HAZE EPISODES AND ITS IMPACT ON HEALTH

Kathryn Ostermann

Atmospheric Sciences Program, The University of British Columbia,

and

Michael Brauer

School of Occupational and Environmental Hygiene, The University of British Columbia, 2206 East Mall, Vancouver BC, Canada V6T 1Z3

E-mail:

Introduction

There are only a limited number of studies directly evaluating the community health impacts of air pollution from vegetation fires, such as those that affected Southeast Asia in 1997 and 1998. In this chapter we describe the available information regarding air pollutant concentrations during “haze” episodes in Southeast Asia and use available data from the literature to discuss the potential population health impacts of the resulting exposures. Several recent review papers have discussed the health impacts and pollutants associated with wood smoke air pollution (Larson and Koenig, 1994; Pierson et al., 1989; Vedal, 1993). Although the emphasis of these reviews was on North American community exposures, many of the conclusions are relevant to the broader understanding of vegetation fire air pollution. This chapter will also discuss the health impacts of exposures to biomass air pollution encountered by forest firefighters and by individuals in developing countries who use biomass for cooking and heating as these exposures demonstrate the plausibility of health impacts associated with exposures to smoke from vegetation fires. In the context of public health impacts associated with haze we also discuss management strategies and efforts to mitigate health effects.

Exposures to air pollution from vegetation fires

Air pollution from vegetation fires, referred to here as biomass smoke, contains a large and diverse number of chemicals, many of which have been associated with adverse health impacts. The major chemicals present in biomass smoke and their sources are listed in Table 1. These chemicals include both particulates and gaseous compounds. Although little is known about the toxicology of biomass smoke as a complex mixture, review of the exposure and health impacts literature, as well as evaluation of the available air monitoring data from the 1997-98 Southeast Asian episodes (Radojevic and Hassan, 1999), indicates that the pollutant variable most consistently elevated in association with biomass smoke is particulate matter.

Particles in biomass smoke consist of solid and liquid compounds of small diameter composed predominantly of organic and elemental carbon (Pinto et al., 1998). This type of pollution can be classified as particulate matter, which can be divided into several categories. Suspended particulate matter (SPM), total suspended particulate (TSP) and total particulate matter (TPM) represent the sum of all the suspended particles in the atmosphere at a given time. The fraction of particulate matter consisting of particles less than 10 micrometers (µm) in aerodynamic diameter are termed PM10. PM10 can be broken down into coarse particulate, comprising particles between 2.5 to 10 µm in aerodynamic diameter, and fine particulate, which is less than 2.5 µm in aerodynamic diameter (PM2.5).

The size of particulates produced in vegetation fires is an important factor in understanding potential health risks. Only smaller particles (PM10) are inhaled and have the potential to cause adverse health impacts. Respirable particles (PM2.5) penetrate into the lower respiratory tract and may present increased risk. Due to the size distribution of biomass particulates, essentially all will be contained in the PM2.5 fraction, while the PM10 fraction will include additional particulates from resuspension of soil and ash. Biomass combustion particulate is typically smaller than 1 µm, with a peak in the size distribution between 0.15 and 0.4 µm (Hueglin et al., 1997; Sandberg and Martin, 1975).

Monitoring air quality in SE Asia

Many countries develop a network of air quality monitoring stations as a means of overseeing pollution levels. A typical air quality monitoring station will routinely measure the concentrations of the major air pollutants: ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2) and particulates ( usually measured as PM10). Currently there are 22 stations in Malaysia, of which 17 are located in peninsular Malaysia and 5 are located in Sabah and Sarawak ( while Singapore has 15 stations (Radojevic, 1997, 1998). Brunei has one fully equipped air quality station monitoring the five major pollutants, as well as 7 other stations for measuring PM10 concentrations, with plans for further expansion (Radojevic, 1997). In Indonesia, different government ministries conduct air pollution measurements independently of one another, in nearly all the capital cities of the 27 provinces (Heil, 1998). Table 2 gives a breakdown of the monitoring that takes place in the countries affected by haze. Partially because of the problem with haze, there has been an increase in the numbers of monitoring stations in the past decade. Specifically, the focus has been on the measurement of particulates, as vegetation fires release these in much higher concentrations than other pollutants. Therefore, better data are available for the more recent haze episodes.

Air quality standards and guidelines

Air quality guidelines and standards have been adopted to protect public health from the negative effects of environmental pollutants ( airindex.htm). These guidelines encompass the routinely measured pollutants, including CO, NO2, O3, SO2 and sometimes PM10. The values given by the United States Environmental Protection Agency (US EPA), as their primary (to protect public health) National Ambient Air Quality Standards (NAAQS), and the World Health Organization (WHO), as well as those of several Southeast Asian countries, are given in Table 3. Averaging times vary depending on the pollutant.

As discussed previously, the particulate matter standards and guidelines are of greatest relevance for air pollution from vegetation fires. Currently, the US EPA has a standard for PM10 of 50 µg/m3 (annual average) and 150 µg/m3 for a 24-hour average. For PM2.5 the annual and 24-hour standards are 15 and 65 µg/m3, respectively. In its most recent revision of Air Quality Guidelines, the WHO elected not to set a threshold value, but instead has derived a linear relationship between PM10 or PM2.5 concentrations and various health impacts ( This revision is based upon the absence of scientific evidence to support a no-effects threshold concentration for airborne particulate matter. These relationships allow each country to manage particulate air pollution by assessing the health effects associated with different levels of particulate matter.

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Air quality indices

Air quality indices have been developed as a simple way to inform the general public about pollution conditions. There is currently no standardised air pollutant index for Southeast Asia. In Malaysia, the Air Pollution Index (API) is used. The API is based on the Pollutant Standards Index (PSI) developed by the United States Environmental Protection Agency (Pinto et al., 1998). The PSI is used in Singapore and Brunei, while Thailand reports the concentration of each pollutant. Indonesia relies on visibility readings as a means to monitor haze (Radojevic, 1997). Table 2 lists a summary of the means of reporting air quality in the countries of Southeast Asia.

The PSI and API are based on the measurement of five pollutants: carbon monoxide, sulphur dioxide, nitrogen dioxide, ozone and PM10. The values for each pollutant are converted to a scale from 0 to 500, with only the highest value being reported. A value of 100 represents the air quality standard for each country. It is important to note that the PSI and API do not take into account the effects of the combination of pollutants. The main difference between the PSI and API comes from the fact that the standards set by the US EPA and the Malaysian Department of Environment differ. The main criteria pollutant during haze events is PM10, as concentrations far exceed those of the other pollutants. Table 4 gives the range of index values for the API and PSI with the corresponding PM10 value and cautionary statements.

Air quality during haze episodes

During the 1990s, five separate haze episodes (1990, 1991, 1994, 1997 and 1998) occurred in Southeast Asia. Although not a new phenomenon, as haze in the area dates back to at least the early 1980s and even 1960s (Rindam, 1995), the increasing frequency is of great concern. Figure 1 depicts estimated PM10 levels in Sarawak for the period of 1978 to 1997. The haze episodes of 1991, 1994 and 1997 are clearly evidenced by the increases in PM10. This figure is based upon PM10 estimated from visibility. A quantitative relationship exists between visibility and the amount of particles in the air, though it is confounded by moisture. An equation for predicting the amount of PM10 in the atmosphere can be developed by using this association (Brook, 1998). Data on visibility, humidity and PM10 at stations in Sarawak, Malaysia were used to determine a linear equation for PM10 (Brook, 1998). Potential sources of error in these estimates are that the correction factors were not derived for particles from vegetation fires, and the subjective nature of visibility measurements. Nonetheless, the equation is useful for identifying peak PM10 concentrations. All of the haze episodes discussed are the result of biomass burning.

Many of the air quality concentrations reported in the literature for haze episodes are based on measurements of total particulate. In order to standardise the data, TPM, SPM and TSP are converted to PM10. The ratio of PM10 to total particulate varies depending on the stage of combustion, but the United States Environmental Protection Agency estimates that 92.8% of particulates from agricultural burning are less than 10 µm ( pm_vol1.htm). Also, Ward (1990) suggests that up to 95% of particulate matter is less than 2.5 µm. Therefore, we assume that 90% of total particulate matter is smaller than 10 µm and use this to convert all measured TPM, TSP and SPM values to estimated PM10 concentrations. Original measurement values are reported in parentheses.

1990

For a period of two weeks during 1990, haze affected areas of peninsular Malaysia resulting in reduced visibility and an increase in particulate concentrations. The episode began around the middle of August and lasted until the end of that month. A sudden decrease in visibility occurred on 21 August, with values as low as 1 km over the central states of peninsular Malaysia (Tussin, 1995). Levels of particulates increased starting from 15 August. Peak 24-hour values of PM10 were equivalent to 426 µg/m3 (TSP=473.8 µg/m3) in Petaling Jaya (Tussin, 1995) and 464 µg/m3 (TSP=516 µg/m3) in the Klang Valley (Rindam, 1995). These quantities were up to four times the mean levels measured during non-haze periods (Tussin, 1995).

1991

Two separate haze episodes occurred in Malaysia during 1991. The first, which will not be discussed further, took place in June as the result of the injection of ash from the volcanic eruption of Mt Pinatubo (Tussin, 1995; Hassan et al, 1995). The second, at the end of September and lasting through most of October, was more severe and was the result of biomass burning from forest fires (Tussin, 1995). The latter episode included two phases separated by a rainy period: from September 27 until October 11, and a less severe event from 22 to 31 October (Tussin, 1995; Hassan et al, 1995). The impact of the haze was most evident in Malaysia (Hassan et al, 1995). Locations in western Borneo reported visibility of less than 2 km after 2 October (Tussin, 1995). Days of low visibility corresponded to high concentrations of particulate matter (Hassan et al, 1995). 24-hour PM10 values in Kuala Lampur, Malaysia ranged from 102 µg/m3 to 254 µg/m3 (SPM=113 µg/m3 to 282 µg/m3) for the first period of 4 to 11 October and 95 µg/m3 to 153 µg/m3 (SPM=105 to 170 µg/m3) for 23 to 30 October (Hassan et al, 1995). These values were significantly higher, up to three times the normal mean (Tussin, 1995), than those for the rest of the month (Hassan et al, 1995). In Petaling Jaya, peak 24-hour averages were 445 µg/m3 (SPM=494.5 µg/m3) on 30 September and 441 µg/m3 (SPM=489.8 µg/m3) on 8 October (Tussin, 1995).

1994

After two years of relatively haze-free air quality in 1992 and 1993, fires in 1994 brought haze again to the Singapore-Malaysia-Indonesia region (Nichol, 1997). The area affected by the smoke spanned approximately 3 million square kilometers (Nichol, 1997). The haze lasted from August to October in Indonesia, Malaysia (Hassan et al, 1995), Brunei (Radojevic and Hassan, 1999) and Singapore (Chia et al, 1995; Nichol, 1997). Most of the available information comes from Malaysia. Visibility was reduced to 1 km in Malaysia with a minimum of 0.3 km in Petaling Jaya, as compared to 30 km under normal conditions (Rindam, 1995). Some measurements also suggest that the haze in 1994 was worse than in previous years in Malaysia (Rindam, 1995). The highest 24-hour average PM10 reading reported in Petaling Jaya was 410 µg/m3 (TSP=454.5 µg/m3) on 30 September (Tussin, 1995), while in Kuala Lampur, PM10 reached 409 µg/m3 on 5 October (Hassan et al, 1995). In Singapore, 24-hour average PM10 concentrations peaked above 250 µg/m3 (PSI>150) on 13 and 27 September and 29 October (Nichol, 1997). Concentrations of other particulate constituents such as sulphur, potassium, titanium, vanadium, manganese, nickel, arsenic and lead were 3-6 times higher than average during the haze period in late October (Orlic et al, 1997). The forest fires, though, did not have a significant influence on the levels of PAHs in Singapore (Chee et al, 1997).

1997

The 1997 fires in Indonesia drew worldwide attention as the haze impacted Malaysia, Singapore, southern Thailand and the Philippines and lasted from June through until November. As early as the beginning of May, air quality began to deteriorate in Singapore (Nichol, 1998). 24-hour average concentrations in Singapore peaked at approximately 230 µg/m3 (PSI=140) on 19 and 29 September (Nichol, 1998). These particulate levels in Singapore were not any more severe than those associated with the 1994 forest fires (Nichol, 1998). In Sarawak, however, 24-hour average PM10 peaked as high as 930 µg/m3 on 23 September (Nichol, 1998), which represents a value more than 15 times the normal levels (Brauer and Hashim-Hisham, 1998). Due to the location of fires and direction of the wind, Sumatra and Kalimantan in Indonesia were the most severely affected areas (Pinto et al., 1998). Daily averaged concentrations of PM10 reached as high as 3546 µg/m3 (TPM=3940 µg/m3) in Sumatra at the end of September (Heil, 1998). The concentrations were even higher in Kalimantan, on the island of Borneo, with a 24-hour maximum of 3645 µg/m3 (TPM=4050 µg/m3) (Heil, 1998). Even at the beginning of November in Palembang when the air quality was improving, daily PM10 and PM2.5 still exceeded the US NAAQS (Pinto et al., 1998). Aircraft measurements performed during this episode indicated that the smoke plume reached an altitude of 4 km and included high concentrations of O3, NOx and CO along with aerosols. In the lower layer of the plume, visibility was less than 500m (Tsutsumi et al, 1999).

1998

With the persistence of the El Niño that started in 1997 and an abnormally short wet season (Levine et al, 1999), forest fires raged again in 1998 and resulted in another, more localized, haze event (Radojevic and Hassan, 1999). In this case, the episode was most acute on Borneo and particularly in Brunei. The haze first emerged on 1 February and remained until 30 April, with especially severe conditions at the beginning of April. Daily average concentrations in the capital, Bandar Seri Begawan, reached nearly 450 µg/m3 and the 24 hour guideline for PM10 of 70 µg/m3 was exceeded 54 times during the period of 1 February to 30 April (Radojevic and Hassan, 1999). The "warning stage," which is associated with a PSI value of 300 (24-hour average PM10 concentrations of 420 µg/m3), was exceeded on 15 April (Radojevic and Hassan, 1999). During the 1998 episode in Brunei, PM10 was the only significant pollutant contributing to the haze (Radojevic and Hassan, 1999). Other gaseous pollutants such as SO2, O3 and NO2 were within acceptable limits, and only the 8 hr guideline for CO was exceeded on several occasions (Radojevic and Hassan, 1999). In Miri, Sarawak, Malaysia, 24-hour average PM10 concentrations rose above 600 µg/m3 (API=649) on March 30 (WHO, 1998).

Table 5 summarises the available information from the haze events described above.

Acute health effects of haze

Indoor air pollution in developing countries

To understand the potential for health effects resulting from exposure to “haze” we first review the available information regarding exposure in indoor air in developing countries where wood and other biomass is used as a cooking and heating fuel. Respirable particulate levels measured in these settings are typically 1000-2000 µg/m3 depending upon the specific fuel, ventilation, cooking duration and measurement interval (Smith and Liu, 1993; Wafula et al., 1990; Smith, 1993; Brauer et al., 1996). These levels are 10 – 50 times above those observed in urban areas. In terms of exposure, domestic cooking and heating with biomass clearly presents the highest exposures since individuals are exposed to high levels of smoke on a daily basis for many years. Exposures of this group are typically 70-85 hour-years of exposure.

The health effects of biomass smoke inhalation have been documented in developing countries where women, and in some cases, children spend many hours cooking over unvented indoor stoves. A number of studies have reported associations of health impacts with use of biomass fuels, and a few have directly measured exposure. These studies have been reviewed in detail by Smith (1993) and Chen et al. (1990). Exposure to biomass combustion products has been identified as a major risk factor for acute respiratory infections, the leading cause of infant mortality in the developing countries. In addition to the risks of infants, the women who are cooking are also at risk from chronic respiratory diseases as well as adverse pregnancy outcomes (Perez-Padilla et al., 1996). As these exposures (in terms of both concentration and duration) are much higher than would occur as a result of short-term exposure to biomass air pollution associated with forest fires, direct comparisons are difficult to make. For example, individuals who are particularly susceptible may avoid indoor exposures, whereas this is not usually possible for ambient air pollution resulting from vegetation fires. The studies conducted in developing countries indicate the serious consequences of exposure to high levels of biomass air pollution. Increased acute respiratory illness in children associated with biomass smoke exposure is a likely cause of infant mortality while the development of chronic lung disease in adults is associated with premature mortality and substantial morbidity.

Wildland firefighters

Several studies have evaluated impacts of biomass smoke to another group with high exposures, wildland (forest) firefighters. Exposures of this population are seasonal (4-5 months per year) and highly variable depending upon the number of fires per season, the intensity of the fires and specific job tasks. Exposures of wildland firefighters were recently reviewed by Reinhardt and Ottmar (1997) and appear to be dominated by high particulate (500 – 7000 µg/m3) and more variable CO exposures (4 – 40 ppmv). Limited monitoring of PAHs has measured low levels (mean exposures <100 ng/m3 except for phenanthrene at 380 ng/m3) (Materna et al., 1992). In summary, the exposure measurements of firefighters, while variable, indicate the potential for exposure to carbon monoxide and respirable particulates at levels (above 35 ppmv CO and above 5 mg/m3 respirable particulate) which have been associated with adverse health impacts.