KUALA LUMPUR, Aug 17 — Malaysians are once again experiencing the unwelcome return of a familiar foe — the haze.

Residents in several states, including Selangor, Negri Sembilan and Sarawak, are grappling with deteriorating air quality.

As of Thursday (Aug 13) morning, air quality in 11 areas across the country was at unhealthy levels, with Sarawak the worst-affected state.

According to data from the Malaysian Air Pollutant Index Management System portal, Samarahan recorded the highest Air Pollutant Index (API) reading at 183, followed by Serian (182), Kuching (176), Sarikei and Sri Aman (158), while Mukah and Sibu each recorded readings of 152.

In Peninsular Malaysia, four areas recorded unhealthy readings: Johan Setia (154) and Shah Alam (101) in Selangor, as well as Kuala Lumpur (131) and Putrajaya (104).

Reports indicate that the current haze is largely caused by forest and land fires, primarily in neighbouring Indonesia, where extensive land-clearing practices are common.

Meteorologists have warned that without significant rainfall, the haze may persist, affecting air quality and public health across Malaysia.

What causes the haze?

Haze is a form of air pollution characterised by fine particulate matter suspended in the atmosphere.

These particles comprise various pollutants, particularly smoke, dust and industrial emissions, which combine with water vapour.

Malaysia is susceptible to haze due to its geographical location and tropical climate, which contributes to high humidity and temperature fluctuations.

Land-clearing practices, particularly for palm oil plantations and agricultural purposes, can also result in significant emissions when fires occur.

Smoke generated by these fires can drift across borders, severely affecting air quality in Malaysia, particularly in states closer to the source of the fires.

Haze has been a recurring environmental issue in Malaysia since the late 1990s, often linked to land-clearing methods and changing weather patterns, particularly during El Niño years.

Significant haze events were recorded in October 1997, lasting for several months and triggering international outcry and the mobilisation of resources to address the crisis.

In 2005 and 2015, severe transboundary haze from Indonesian agricultural fires forced widespread school closures across Malaysia.

In August 2005, a state of emergency was declared in Kuala Selangor and Port Klang after API readings exceeded 500, resulting in the closure of schools in the affected areas.

In October 2015, nearly 7,000 schools were closed nationwide as API readings reached hazardous levels.

How is haze measured?

In Malaysia, air quality is assessed using the API, which measures the concentration of various pollutants, including particulate matter.

The API is divided into several categories indicating the level of air quality:

Good (0-50): Air quality is satisfactory, posing little or no risk. 

Moderate (51-100): Air quality is acceptable, although some people, particularly those unusually sensitive to air pollution, may be affected. 

Unhealthy (101-200): Everyone may begin to experience health effects, while members of sensitive groups may experience more serious effects. 

Very unhealthy (201-300): A health alert level at which everyone may experience more serious health effects. 

Hazardous (301 and above): Health warnings of emergency conditions, with the entire population more likely to be affected. 

As API levels rise, authorities typically issue health advisories and take measures such as closing schools or limiting outdoor activities.

At-risk groups and protective measures

Certain groups are particularly vulnerable during haze episodes, including children, the elderly, people with pre-existing respiratory or cardiovascular conditions, and pregnant women.

To reduce the risks associated with haze, those in at-risk groups should stay indoors as much as possible, use air purifiers, stay hydrated and limit strenuous outdoor activities.

Health authorities often recommend face masks, particularly N95 respirators, which can effectively filter fine particulate matter.

How effective are masks?

Masks can help reduce exposure to haze, but not all masks provide the same level of protection.

N95 masks are designed to filter out at least 95 per cent of airborne particles.

However, during extremely high levels of pollution, even these masks may not provide complete protection against all harmful particles.

Haze can also infiltrate homes, further affecting indoor air quality. It is therefore important to monitor air quality levels and take additional measures where necessary.

Impact of El Niño on haze conditions

The El Niño phenomenon can significantly alter weather patterns, often resulting in prolonged dry spells that increase the likelihood of forest and land fires.

During El Niño years, higher temperatures and reduced rainfall can make it easier for fires to start and spread.

In Malaysia, stagnant air caused by limited wind movement can exacerbate haze, allowing it to linger for longer and creating a hazardous environment for residents.

The combination of adverse weather conditions and reduced air circulation can result in an extended period of poor air quality if the dry season persists.