The 2006 Southeast Asian haze event was caused by continued uncontrolled burning from "slash and burn" cultivation in Indonesia, and affected several countries in the Southeast Asian region and beyond, such as Malaysia, Singapore, southern Thailand, and as far as Saipan;[1] the effects of the haze may have spread to South Korea.[2] Local sources of pollution partly contributed to the increased toxicity, particularly in high-pollution areas such as ports, oil refineries, and dense urban areas. In the highly urbanised and industrialised Klang Valley of Malaysia in particular, the surrounding terrain acted as a natural retainer of polluted air, aggravating the situation when the haze set in.

There is also a link to El Niño.[3] The haze was made worse than during previous occurrences by the El Niño-Southern Oscillation which delayed the year's monsoon season. Fires in Kalimantan produce great amounts of smoke, burn a long time and are difficult to extinguish because they are on peatland, and once lit the fires can burn for months and release gases that produce sulfuric acid.[4]

Air quality across the region appeared to improve in late October as heavy rainfall doused fires in Indonesia.[5]


While the haze largely spared Singapore with 24-hour Pollutant Standards Index readings within the "Good" range for 15 days in September and the rest in the "Moderate" range and no higher than a reading of 66,[6] its harmful effects became more prevalent in October.

On 7 October 2006, the 3-hour PSI reading breached the 100 mark at 8 a.m. and entered unhealthy levels for the first time in the year, as winds from neighbouring Sumatra blew the haze to Singapore.[7] At 10 a.m., it hit 130, the highest in three years, before subsiding to 80 at 4 p.m. and climbing rapidly to 150 at 9 p.m.,[8] the worst since 1997, before ending the day at 136, still in the unhealthy range.[9]

Although the air quality was set to improve with the arrival of the Northeast monsoon rains in mid-October, southeasterly winds extended the hazy season.[10] A mild El Niño effect delayed the starting of the showers to late October or early November,[11] or even until the end of November. The prolonged haze could be attributed to the extended dry season, which put the rains on hold and affected wind patterns which brought the haze to Singapore. Intermittent showers could occur in the pre-monsoon period, but these would do little in increasing air quality. The unpredictable winds in the pre-monsoon period could bring haze from either Sumatra or Kalimantan.[12]

Air quality remained in the moderate range for the next week[6] until 14 October, when the 3-hour PSI readings gradually increased from 53 at 6 a.m. to peak at an unhealthy 116 at 10 p.m.[13] This time, majority of the haze came from Kalimantan.[14]

Similarly, on 15 October, the PSI readings increased from 69 at 6 a.m. to 98 at 3 p.m. and 4 p.m.,[15] 3 points short of reaching the unhealthy range. This eased to 82 by midnight.[16] As winds remained southeasterly, haze from Kalimantan blew across the South China Sea to Singapore.[17]

The next day, on 16 October, the PSI stayed in the 80s in the morning, before shooting up once again into the unhealthy range, hitting a high of 130 at 4 p.m. and 5 p.m. The 3-hour PSI remained in unhealthy levels for 8 consecutive hours, between 2 p.m. and 9 p.m.[18] The haze obscured the sun, and symptoms of exposure to haze resurfaced in the general population.[19] The 24-hour PSI for 16 October reached 98,[6] just 3 points short of unhealthy. Visibility dropped to as low as 1 km in some areas, compared to the usual 20 km.[18]

The PSI on 17 October gradually increased from the moderate range in the morning to slip into the unhealthy range at 4 p.m., reaching 106,[20] before declining back to 100 in the moderate range at 10 p.m.[21] The hazy conditions were expected to persist.[20]

On 19 October, the PSI crept into the unhealthy range at 106 at 2 p.m.,[22] peaking at 113 at 4 p.m. The National Environment Agency reported that the situation would not improve the next day.[23]

Throughout the early morning on 20 October, the PSI kept in the 90s, before reaching a high of 103 at 8 a.m.[12] This dropped to 74 by 7 p.m., although the PSI remained in the 90s in the afternoon.[24] Even though rain fell in some areas, this was not enough to "alleviate the haze situation". The NEA forecast thunderstorms over the weekend, but the southeasterly winds would continue to prevail.[25] The 24-hour PSI on 20 October also reached the unhealthy range at 102.[6]

Later in October, though, the situation began to improve, with the PSI hitting a low of 11 at 2 p.m. on 26 October.

However, in early November, intermonsoonal winds brought slight haze back to Singapore, with the 3-hour PSI in the moderate range most of the time.

The highest 3-hour average PSI recorded prior to that point 226 in September 1997.[26]


While some Singaporeans began donning face masks, others frequented shopping malls and public places like VivoCity, with many shopping before Deepavali at Little India,[27] and going to Geylang Serai's annual Hari Raya bazaar. Stallholders said that the haze had not affected their business.[28] However, Singaporeans generally kept indoors,[16] with some staying away from East Coast Park.[27]

The government announced plans for a haze action plan if the situation became "extremely dangerous", which included priority treatment for haze-related illnesses.[29] Health Minister Khaw Boon Wan said that there was "very little that (could) be done to stop the haze", and advised people to remain indoors, especially those with prior respiratory conditions.[30]

Some minor haze-related illness began to surface, but free clinics across the island did not report any increase in patients with this symptoms.[13] However, attendance figures at polyclinics islandwide increased by 600 cases to about 15,000 cases of haze-related conditions in the first week of October as compared to the same period last month.[29] This is despite the National Healthcare Group reporting that the number of people "complaining of the same ailments" has decreased from the same period last year.[31]

Air purifier sales shot up during the hazy period. Best Denki, an electronic store, sold S$350,000 worth of air purifiers and related items in 4 days, a 300 percent increase. However, experts from the Institute of Environmental Science & Engineering at the Nanyang Technological University said that only some of these products, like High Efficiency Particulate air filters, would effectively remove small particles from air. Other kinds of air purifiers like ionizing purifiers gave off ozone which could cause symptoms similar to those caused by the haze. The experts recommended regularly cleaning the filter media and opening windows to get some fresh air at night.[32]

The western region, which includes Boon Lay, Choa Chu Kang and Jurong, seemed to be the "epicentre" of the haze. Residents there complained of the worse conditions in their area, saying that it felt "hotter than usual", and health problems were more widespread. The air quality levels in the west have consistently been the worst, but only by several points. Some speculated that the more polluted air was caused by the many construction sites and industrial parks in Jurong and Tuas, but NEA refuted this, claiming that they did not contribute to the haze. Polyclinics in Jurong and Bukit Batok have an increase of 20 percent for patients with respiratory problems and asthma.[31]

Schools islandwide restricted outdoor activities and had to rethink post-examination activities and training or revert to wet-weather programmes. The Singapore Sports School's swim team had to cut back on training when the haze reached unhealthy levels even though they were in the midst of various international competitions.[33] The Ministry of Education recommended that schools suspend all outdoor activities when the PSI reading passes 100, but some schools chose to move indoors regardless of the PSI.[34]

Many Singaporean "fitness buffs" have also made the move indoors. Fitness clubs reported increases in turn-outs and check-ins, utilizing gym facilities rather than outdoor activities. Rock climbers were also affected, and began to move activities indoors instead.[35]

The haze has also caused increased sales and rental of entertainment VCD and DVD titles, but cinema attendance is unchanged.[36]

The National Environment Agency website received about 170,000 hits on 14 October, as compared to the usual 60,000, and caused the server to temporarily go down due to the sheer volume of traffic.[11]

According to economists, Singapore suffered a US$50 million economic loss due to the onset of the haze in 2006.[37]

PSI readingsEdit

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File:Jurong East, Singapore, Oct 15.JPG
File:SG haze-merlion.JPG
24-hour PSI readings in October 2006[38]

  0–50  Good  51–100 Moderate 101–200 Unhealthy 201–300 Very unhealthy 301- Hazardous

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