HAZE: Are we hazy about the facts.

The country has been enveloped in the haze since July this year. The haze is back and the alarming thing is we are not surprised. It was here in 1991, again in 1994 and now this year. While annually we do see changes in the air quality we have had a triennial love affair with the haze. However this year it is back with a vengeance. While everyone has had something to talk about the haze (like talking about the weather in the United Kingdom), a large number are also beginning to get worried about it. Some have decided to do something about it. However before we start and/or stop worrying about it, it will be useful to increase our understanding about the haze. Although the media has definitely given adequate coverage it still appears the majority area still hazy about the subject.

What is the haze?

The haze can be characterized using two measures : the Air Pollutants Index and the Visibility Index. Some use visibility as a basic indicator of air pollution. While these two measures are interrelated the relationship may not be a simple direct one. The haze phenomenon is due to impairment of visibility as a result of the scattering and absorption of light by particles and gases in the atmosphere. It is called the haze because it obscures the clarity, color, texture and form of what we see. Visibility is usually measured as the furthest distance from which a person can see a landscape. However the same amount of pollution is known to have different effects on visibility and it is useful to know that changes in visual range (a measure of visibility) are not proportional to our perception. A five kilometer change in visual range can either be very apparent or imperceptible depending on the amount of pollution before the change. This means small amounts of air pollution in cleaner areas can have a marked effect on visibility and a much greater reduction in pollution will be needed in heavily polluted areas to make a noticeable difference. Hence visual range may not be the best indicator of visibility. A deciview scale (analogous to the decibel scale for sound) has been developed to address this problem. A change of one deciview is considered perceptible by the average person and a deciview of zero represents pristine conditions. In Malaysia the reports we receive are on visual ranges from the Meteorological Services Department. This in some cases causes confusion among the public who more familiar with the Air Pollutants Index use it alone for assessing the haze (in their minds "polluted air") as opposed to also looking at the visibility index.

What are the conditions that contribute to the haze?

Haze occurs when there is sufficient smoke, dust, moisture and water vapor suspended in air to impair visibility. It is mainly caused by particulate matter from various sources including smoke, road dust and particulate matter formed when gaseous pollutants react in the air. These particles further increase in size with increasing humidity. Pollutants emitted to the atmosphere through forest fires, emissions from vehicles, electric power generation, industrial activity and construction activities can be transported hundreds and even thousands of kilometers. The present scenario has the forest fires in Indonesia affecting the whole ASEAN region (e.g. Indonesia, Malaysia, Thailand, Philippines and Vietnam) with Malaysia bearing the brunt due to wind directions and weather conditions.

It is both the level of air pollutants and a high relative humidity that causes this haze. It is known that sulphates can accumulate water and grow to sizes at which they are more efficient at scattering light. In Malaysia the main pollutant that is contributing to the haze is particulate matter less than 10 microns (PM10). It has however been suggested that it will be useful to measure the particulate matter less than 2.5 microns as it may better reflect the level of air pollution.

How is air quality monitored?

In Malaysia the quality of air is monitored by measuring a number of known air pollutants. The air pollutants measured under the National Air Quality Monitoring Program are respirable particulates (PM10), carbon monoxide, sulphur dioxide, nitrogen dioxide and ozone. These are measured at 29 monitoring stations throughout the country. Lead levels in the air are also measured at some of the monitoring stations. This activity was previously carried out by the Department of Environment before being privatized and since 1995 is carried out by Alam Sekitar Malaysia Sendirian Berhad (ASMA). The Air Pollutant Index and Malaysian Air Quality Index (MAQI) was developed based on the Pollutant Standards Index (PSI) developed by the United States Environmental Protection Agency (USEPA). They have been modified to suit Malaysian Guidelines developed by the Department of Environment (DOE). The Air Pollutants Index (API) provides a uniform system of measuring air pollution levels. The measured level of each of the 5 pollutants (PM10, carbon monoxide, sulphur dioxide, nitrogen dioxide and ozone) is converted to a scale (index) from 0 to 500. The most important number on this index is 100, since this level corresponds to that level at which health effects can occur. The Department of Environment has developed guidelines for each of the air pollutants measured. The recommended level corresponds to an index of 100 for each pollutant. An API level of 100 and above means that a pollutant is in the unhealthy range on a given day. The API is determined for each of the five pollutants, and the highest of the five indices is then reported. More recently the DOE has also begun to report the pollutant with the highest index. From the API is derived an index of air quality, the MAQI, which is characterized as good, moderate, unhealthy, very unhealthy and hazardous. The API and MAQI are used as triggers for action to be taken. While the manner in which the API is calculated is similar to that used in calculating the Pollutant Substances Index (PSI) of the USEPA, the standards set by the USEPA and levels recommended by the Department of Environment in Malaysia differ and the actions recommended at the different levels of the PSI and the API also differ.

What are the effects of the haze?

For some the haze spelt disaster - the 234 passengers who died on board the Indonesian Airbus that crashed on the 26th of September in Sumatra and the 29 sailors who drowned when a cargo vessel collided with an oil tanker off Tanjong Tuan, near Port Dickson the very next day. Whilst for others the haze led to opportunities for selling their products (air conditioners, air purifiers) and some even capitalizing on the current situation to boost sales i.e. by naming a cocktail drink "Haze". Some found driving to be difficult due to the poor visibility whilst others have had to suffer the stress of the uncertainty associated with the "increasing API" and the inconvenience caused by canceled flights. What was the effect of the haze on road safety and motor vehicle accidents?

The health effects are mainly due to the air pollutants. The main pollutant driving the API in the present haze episode is the PM10. Particulate matter less than 10 microns are of concern to us because they are respirable. Scientists have linked particulate matter especially fine particles below 2.5 microns with acute respiratory symptoms, respiratory related hospital admission and emergency room visits, exacerbation of asthma attacks, chronic bronchitis, decreased lung function and work and school absences. Those at increased risk include the elderly, individuals with pre-existing heart disease, chronic bronchitis and emphysema, children and those with bronchial asthma. Sulphur dioxide and ozone have also been reported to be the pollutant with the highest index on some days. These have however not been seen at unhealthy levels. Researchers are also beginning to study the effects of lead in the air especially on the health of children. The health effects (both short and long term) of the haze very much depend on the constituents in the air (which are still being charcterised) of which of .

What are the sources of the air pollutants?

While the exact sources of the pollutants and their contribution to the haze have not been characterized fully, it is known that PM10 is the main pollutant. In the present situation, the forest fires currently raging through Indonesia is the main source of the air pollution causing the haze in the region. Other pollutants contributing to the air pollution are particulate matter from construction activities and unpaved roads, and of other pollutants are burning of gasoline, natural gas, coal and oil for carbon monoxide, burning of coal and oil and industrial processes for sulphur dioxide, vehicle emissions for nitrogen dioxide, ozone as a result of chemical reactions of volatile organic compounds and nitrogen oxides. Lead from leaded gasoline is still an important cause for the presence of lead in the air. It cannot be denied that transboundary pollution we are experiencing currently will need regional/international efforts to eliminate this source of pollution.

Lessons to be learnt from the current haze episode

The issues this haze episode raise include: the uncertainty among the public of what to expect the next day; the manner in which the information on the haze was communicated to the public; the health effects (both short term and long term) and the economic loss as a result of the haze. It is sincerely hoped that the current haze episode (being the worst so far) has provided those involved in studying and managing the haze problem enough information to combat this problem the next time around. My sympathies lie with all those in one way or another affected by the haze especially those in Sarawak where an emergency was declared and the API exceeded 800. The question remains - will we be better prepared the next time around?


Dr Krishna Gopal Rampal

Occupational and Environmental Health Unit

Department of Community Health

Medical Faculty, Universiti Kebangsaan Malaysia.


Air Pollutant Index (API)

Malaysian Air Quality Index (MAQI)

0 - 50


51 - 100


101 - 200


201 - 300

Very Unhealthy

301 - 500


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Last Updated 11 May 2005.

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