The effects of haze on health in Singapore

By: Osler Health International
Posted on: 17 Aug 2022

According to a recent news report, transboundary haze may return to Singapore this year. Fortunately, it is unlikely to reach levels seen in 2019, when the Pollutant Standard Index (PSI) reached levels deemed unhealthy by the National Environment Agency (NEA).

Is that haze or mist outside my window?

Mist, fog and haze can all be observed by the naked eye. However, while mist and fog are caused by the suspension of water droplets in the air, haze is an airborne mixture of pollutants such as soot particles, carbon dioxide and other toxic gases. This is why haze can also be potentially harmful for your health, or exacerbate existing health issues.

Between June and October in Singapore, forest fires in the Southeast Asian region sometimes result in transboundary haze, causing the distinct smell of ashes to appear. The highest PSI reading to date over a 24-hour period is 401, which was recorded in June 2013.

What are some haze-related health issues?

According to the NEA, haze reaches unhealthy levels once the PSI reading is above 100. 

NEA has guidelines in place to help people in Singapore reduce the likelihood of developing haze-related health issues. The general public is advised to reduce “strenuous outdoor physical exertion”. Elderly people, pregnant women and children are advised to minimise said activities, while people with chronic lung and heart disease are advised to avoid such activities overall. As pregnant women in their second or third trimesters may already have reduced lung volumes, they should take extra care and stop wearing masks and stay indoors if they feel unwell.

For healthy individuals, this is to decrease the chances of irritation to the eyes, nose and throat, which may occur if exposed to high levels of haze over a few days. For individuals with health conditions such as asthma or chronic obstructive pulmonary disease, the effects of haze may be more serious. 

24-hr PSI

Healthy persons

Elderly, pregnant women, children

Persons with chronic lung disease, heart disease


Normal activities

Normal activities

Normal activities

101- 200


Reduce prolonged or strenuous outdoor physical exertion

Minimise prolonged or strenuous outdoor physical exertion

Avoid prolonged or strenuous outdoor physical exertion

201 – 300

(Very Unhealthy)

Avoid prolonged or strenuous outdoor physical exertion

Minimise outdoor activity

Avoid outdoor activity



Minimise outdoor activity

Avoid outdoor activity

Avoid outdoor activity

The Ministry of Health (MOH) notes that although long-term studies on the effects of haze on health show that constant haze exposure makes it more likely for people to develop health complications such as cardiovascular effects, there is currently no data available for long-term exposure to episodic haze. 

N95 masks are commonly used in Singapore during the haze season as it is able to filter out fine particles, unlike surgical masks. However, the MOH does not recommend wearing N95 masks for short-term exposure. 

When to see a doctor

According to the MOH, each person’s reaction to the pollutants found in haze may be different. If you find that you are experiencing breathing difficulties or persistent health issues during the haze season in Singapore, you’ll want to consult a doctor. 

Vulnerable people, such as pregnant women, children and the elderly should also take more effort to monitor their health. People with existing heart and lung conditions are also advised to have their medication at hand, for easy access. 

Help is available at Osler Health

At Osler Health, we have dedicated doctors who are ready to assist you with any concerns you may have during the haze season. If you’re looking for a doctor in private practice here in Singapore, Osler Health has conveniently located clinics in Star Vista as well as Raffles Hotel Arcade. Easily accessible by public transportation with plenty of places to park, we stand ready to take care of you and your family. 

To book an appointment, contact us via phone or email and one of our friendly reception staff will be glad to help.

Raffles Hotel Arcade Star Vista