On the Haze

1. Why are we affected by smoke haze?
The haze which has been occurring since 1997 and largely within the period of May to October, happen when there are forest fires in the region and the prevailing Southwest Monsoon winds blow the smoke from the fires in our direction.

2. Why do the 3-hour PSI indications appear lower when the visibility is poor?
When a 3-hour PSI reading is released during the smoke haze periods, it is for air quality for the immediate past three hours. It therefore does not correspond to what you may observe at the point when you hear the PSI announcement.

Poor visibility does not necessarily mean higher particles levels in the air . Poor visibility can be due to many reasons e.g. presence of mist, sun reflection etc.

3. What is the meaning of the PSI index?
PSI stands for 'Pollutant Standards Index'. It is an index developed by the United States Environmental Protection Agency (USEPA) to provide accurate, timely and easily understandable information about daily levels of air pollution.

The ambient air in Singapore is monitored through a telemetric network of  air monitoring stations strategically located in different parts of Singapore.

The monitoring stations measure air pollutants such as sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and particulate matter called PM10 (particulate matter of 10 microns or smaller in size). These pollutants are used in the determination of the index.

The PSI value gives an indication of the air quality as shown:

4. What are the general health effects associated with the different air quality categories?
The air quality categories based on PSI and the general health effects associated with the different categories are summarized as follows:

5. Are there any weather conditions that will intensify the effects of the haze?
There is a phenomenon known as the El Nino which tends to produce very dry weather conditions in the region. Its appearance will intensify the effects of the fires in Indonesia.

6. Can the haze affect me even if I stay indoors?
The main pollutant of concern to health during a smoke haze is the fine particulate matter or PM10 (particulate of size 10 micron and below). The health effect depends on the severity of the smoke haze as described by the PSI (Pollutant Standards Index) reading. At a PSI of 101 and above, the air quality is deemed unhealthy.

During a smoke haze, the fine particulates enter an air-conditioned building through the fresh air intake and by infiltration through openings and gaps. The particulate levels indoor can thus build up to unacceptable levels. This could have undesirable health effect on the occupants of the building and adversely affect the efficiency of the air-conditioning system.

7. Would the use of air-cleaning devices be helpful during the haze?
Buildings with central air conditioning systems, can have air cleaning devices fitted so that the particulate level in the indoor air can be kept within acceptable levels during a prolonged smoke haze period. The devices include electrostatic precipitators and media filters.  In homes, portable air cleaners are an option. These are compact, stand-alone appliances designed to keep the particulate levels of an enclosed space low. Several models of air cleaners have been found to be able to reduce the level of fine particles in a typical bedroom to an acceptable level during a smoke haze, such as that experienced in Singapore in 1997.

On Health

1. What are some problems I could face during the haze?
The health effects of haze are mainly caused by the irritant effects of fine dust particles on the nose, throat, airways, skin and eyes. The health effects of haze will depend on its severity as measured by the Pollutants Standards Index (PSI). There is also individual variation regarding the ability to tolerate air pollution. Most people would at most experience sneezing, running nose, eye irritation, dry throat and dry cough from the pollutants. They are mild and pose no danger to the health of the general population.  However, persons with medical problems like asthma, chronic lung disease, chronic sinusitis and allergic skin conditions are likely to be more affected by the haze and they may experience more severe symptoms. Children and the elderly in general are more likely to be affected. For some, symptoms may worsen with physical activities.

2. What are some haze induced health problems that can be expected ?
The current haze related health problems are generally mild and can be treated easily. Eye irritation may be relieved by applying normal saline eye drops which can be purchased from any pharmacy or medicine shop. Persons wearing contact lenses who experience eye irritation are advised to discontinue wearing contact lenses temporarily. Mild sneezing, running nose, dry throat and dry cough can be relieved by cold tablets or cough mixture, obtainable from any pharmacy where the pharmacist's advice can be sought.

3. I am under medication for chronic heart and lung problems, what should I do ?
Persons under medical treatment, it is important that they take their medication regularly. Persons with chronic heart and lung problems are advised not to engage in outdoor sporting activities if the PSI is above 100. There is otherwise no need to take extraordinary precautions.

4. I suffer from asthma, what should I do ?
In the case of breathlessness or asthma, you should seek treatment from your GP or any government polyclinics.