What is haze?
Haze is a form of trans-boundary air pollution which affects Singapore seasonally. The haze refers to the loss of visibility experienced due to the smoke which is blown over the island of Singapore from forest fires mainly on the island of Sumatra in Indonesia.
Forest fires are started deliberately in Indonesia every year to clear land for palm oil plantations, despite being illegal. Singapore, Malaysia and Indonesia work together to try and limit the effects of the trans-boundary pollution, mainly with success since 2015 when Singapore experienced one of the most prolonged periods of unhealthy levels of air pollution on record. In 2019 a prolonged dry spell exacerbated the number and spread of burning hot spots and led to a return of unhealthy levels of haze pollution.
Pollution Standards Index
In Singapore the air quality index used is called the Pollution Standards Index (PSI). It is calculated from a combination of air quality data from monitoring stations which read levels of sulphur dioxide (SO2), particulate matter (PM10), fine particulate matter (PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3). A 24hr-PM10 reading is provided by the National Environment Agency along with a 1hr PM2.5 reading, a 24-hr PSI forecast to help the public plan activities and accompanying health advice.
Fire hot spots in South East Asia resulting in haze pollution in Singapore in 2019
The Main Pollutants: PM10 and PM2.5
PM10 is particulate matter 10 micrometers or less in diameter, PM2.5 is particulate matter 2.5 micrometers or less in diameter. PM2.5 is generally described as fine particles. By way of comparison, a human hair is about 100 micrometres, so roughly 40 fine particles could be placed on its width.
PM2.5 is more harmful to human health than PM10 because the fine particles are so small they are not filtered as effectively by the body's natural filters. PM10 particles are most often filtered within the nose, mouth and throat before they reach the lungs. There is a greater chance with the deep breathing resulting from physical exertion that these particles can lodge deep into the lung tissue and over time and exposure contribute to chronic health issues.
Other regular sources of these pollutants occur daily in Singapore without the addition of the pollution from forest fires. Anyone spending time waiting at bus stops or running or cycling along busy roads, or exposed to cigarette smoke is regularly experiencing elevated concentrations of particulate matter,
Particulate Matter 2.5 is the most serious pollutant and therefore attention to the 1-hr PM2.5 reading (µg/m3) which is provided separately (and almost uniquely in Singapore) to the overall PSI is the most important indicator influencing Wildings' haze policy and decision making. The NEA describe this index as the most important factor for 'deciding whether or not to go for a jog' so it is also the most relevant for deciding whether or not to go ahead with a forest school session.
Factors affecting the severity of the haze event
Direction of the wind
Amount of rainfall
Levels of ground moisture
Number of fires set (hotspots)
Actions taken by the authorities to put out the fires
Factors affecting the effect of the Singapore haze on health
Only you know what your level, and your child's level of exposure to the Haze is. This is determined by:
How much time you and your child are spending indoors in air conditioned or air purified environments
How much time you or your child is spending outdoors physically active
The status of you or your child's respiratory health
Your personal tolerance for haze, which may be lower or higher, even when the health advisory is for normal or minimised outdoor activities to continue
It is standard Forest Schools procedure to weigh the benefits of an activity against its risks before making a decision to go ahead or not. Wildlings follows the Health Advisory issued by the Singapore authorities when considering the acceptable pollution level to continue with Forest School activities and when activities should be adapted or postponed. The health advisory states:
"Air quality indicators and health advisories during periods of transboundary haze refer primarily to the 24-hour PSI. There are no accompanying health advisories for any other air quality indicators. In addition, the main air pollutant during the haze season is PM2.5. Hence, the 1-hour PM2.5 concentration readings are a good indicator of the current air quality."
Careful consideration of the information provided by the National Environment Agency has led to the following table setting out Wildlings' Haze Policy:
The 1-hr PM2.5 reading (µg/m3) is read 2-hrs before a session starts from www.haze.gov.sg.
The 24-hr PSI is read 2-hrs before a session starts from www.haze.gov.sg and will influence decision making if the haze has persisted for two or more days and the PM2.5 (µg/m3) is in the elevated level.
An early warning alert is sent to parents via WhatsApp if the 1-hr PM2.5 reading is in or nearing the high elevated level.
The 1-hr PM2.5 reading (µg/m3) is read 1-hr before a session starts from www.haze.gov.sg
The air quality trend will also be considered when decision making. A trend of rapid deterioration combined with an unfavourable 24-hr PSI forecast could also result in a session cancellation.
If levels are below 100 PM2.5 (µg/m3) and improving then the normal operating procedure applies and parents are updated if they were alerted earlier.
If levels are between 100-150 PM2.5 (µg/m3) and not worsening then the session will start on time but will finish 30 minutes early and physical activity will be limited. Parents will be alerted via WhatsApp and asked if they will be attending the session.
If levels have risen above 151 PM2.5 (µg/m3) then the session will be postponed and Wildlings' make-up session policy applies.
Levels of PM2.5 (µg/m3) will be monitored during any session which started in the high-elevated PM2.5 (µg/m3) zone. If levels increase into the high zone the session will be drawn to a close and no make-up session will be possible.
DATE: 14th September 2019
AUTHOR: Claire Seabrook
REVIEW: 14th September 2020