La qualité de l’air à Singapour s’est améliorée avec le retour de la région centrale dans la fourchette modérée à 97, bien que la persistance des feux et de la brume transfrontalière en Indonésie maintienne les risques de fluctuation de la pollution selon les données publiées le 18 septembre.
L’amélioration de la qualité de l’air et l’indice PSI dans la région centrale
La qualité de l’air à Singapour s’est améliorée, l’indice standard des polluants (PSI) sur 24 heures dans la région centrale de l’île étant revenu dans la fourchette modérée selon les données de l’agence nationale pour l’environnement (National Environment Agency, ou NEA). At 7am on Sept 18, the 24-hour PSI reading in the area was 97, within the moderate range of 51 to 100. The central region includes the Thomson, Marymount, Sin Ming, Ang Mo Kio, Bishan, Serangoon Gardens, MacRitchie and Toa Payoh areas, according to the National Environment Agency’s (NEA) website. The region’s 24-hour PSI dropped to 100 at 1am after hovering in the unhealthy range in the previous few hours. The reading for that area hit 102 at 9pm, before inching up to 103 at 10pm, after a reprieve a day earlier, when readings across Singapore fell into the moderate range from 11am onwards. The PSI for the central region stood at 102 at midnight. Readings in the north, south, east and west have remained in the moderate range since Sept 16. The PSI readings were 90 for the west, 80 for the east, 73 for the north and 69 for the south at 7am on Sept 18, unchanged from those at 6am.
Cette embellie intervient après une période d’instabilité où la brume a provoqué des hausses intermittentes. La veille au soir, la qualité de l’air dans cette même zone centrale s’était dégradée pour atteindre un niveau classé comme malsain, avec une valeur de 102 à 21h (hit 102 at 9pm, crossing into the unhealthy band), grimpant ensuite à 103 à 23h (standing at 103 as of 11pm). Air quality remained in the moderate range for the other regions of the country. PSI readings have dipped in and out of the unhealthy range over the past two weeks. On Tuesday, all five regions of Singapore recorded unhealthy air quality levels, marking the first time this has happened since September 2019.
Les foyers d’incendie en Indonésie et la dérive de la brume transfrontalière
Singapore’s air quality has slipped back into the unhealthy range after four days of moderate readings, with haze from Indonesia continuing to affect parts of the region. The 24-hour Pollutant Standards Index (PSI) in Singapore’s central region crossed into the unhealthy band at noon on Monday, September 14, reaching 102. The reading climbed further to 105 by 1 pm, while PSI levels across the other four regions remained in the moderate range, between 81 and 93. L’origine de ces épisodes répétés réside dans les conditions climatiques et les incendies observés dans la région voisine. Les autorités ont enregistré la présence de nombreux foyers d’incendie et de fumées denses dans les régions de Sumatra et du Kalimantan, specifying that hotspots were detected in southern Sumatra, as well as western, central and southern Kalimantan. These areas have been among the sources of smoke affecting air quality across parts of Southeast Asia. According to the NEA, dry conditions were observed across much of the southern Association of Southeast Asian Nations (ASEAN) region on Monday morning, although showers were recorded over parts of Sumatra.
Les observations satellitaires menées par les services compétents ont confirmé que les panaches de fumée ont été transportés par les vents dominants en direction de Singapour. L’agence environnementale a indiqué que l’agence a précisé que quelques foyers d’incendie avaient également été détectés dans la péninsule Malaise et à Java, selon ses déclarations rapportées par CNA, soulignant l’ampleur régionale du phénomène de brume transfrontalière. The agency also reported moderate to dense haze over central and southern Sumatra, along with western and central Kalimantan. The haze has not been confined to Indonesia. Transboundary haze was observed in parts of Sarawak, peninsular Malaysia and southern Vietnam, with monitoring stations in affected areas recording air quality ranging from moderate to unhealthy levels. Showers over parts of Kalimantan, where hotspots have been detected, contributed to improvements to Singapore’s air quality on Wednesday (Sept 16), although haze risks remain.
Les recommandations sanitaires et les prévisions météorologiques
Face à la volatilité de la situation, les autorités locales recommandent à la population de moduler ses activités extérieures en fonction des indicateurs en temps réel. Pour les déplacements immédiats, les citoyens sont invités à consulter les concentrations de particules fines PM2.5 (hourly PM2.5 readings, which indicate the current concentrations of fine particulate matter, were in the normal band for all regions), tandis que le PSI sur 24 heures sert à l’organisation des journées à venir pour anticiper les risques sanitaires. At at 7am on Sept 18, the hourly PM2.5 readings stood at 11 in the south, 12 in the north, 17 in the east, 20 in central and 23 in the west. The previous readings were eight in the south, 11 in the north, 18 in central, 20 in the east and 23 in the west at 6am. The NEA has advised the public to refer to the hourly PM2.5 readings for immediate activities and 24-hour PSI ones to plan for the day ahead.
Les consignes officielles distinguent les personnes en bonne santé, qui doivent limiter les efforts physiques prolongés en plein air lorsque l’air se dégrade, et les populations vulnérables. Air quality is considered unhealthy when the 24-hour PSI is in the range of 101 to 200, while an hourly PM2.5 reading between 56 and 150 indicates an elevated concentration of fine particles. NEA has advised that during such periods, those who are healthy should reduce prolonged or strenuous outdoor activities, while vulnerable groups like the elderly, children and pregnant women, as well as people with chronic lung or heart disease, should minimise or avoid such outdoor activities altogether. Members of the public should note that the health impact of haze depends on one’s health status, the PSI level, and the length and intensity of outdoor activity.
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