MOM issues new guidelines for employers to adjust outdoor work based on hourly PM2.5 readings

MOM issued additional guidance for employers to adjust outdoor work according to 1-hour PM2.5 readings. This complements existing guidance based on the 24-hour PSI forecast. The aim is to help employers respond when air quality changes during the day, protecting workers without unnecessarily stopping all operations.

Employers should use the 24-hour PSI forecast to plan outdoor work for the following day. During that day, they should monitor hourly PM2.5 readings and progressively reduce outdoor work as readings rise. For example, a worksite may revise strenuous tasks, move breaks indoors, or reschedule activities after readings become elevated.

The hourly readings provide a more current view of air quality. MOM also urges employers to review haze plans, identify vulnerable workers, and set limits as conditions worsen. The guidance supports faster decisions while maintaining business continuity and worker safety.

PM2.5 means fine particulate matter with a diameter of 2.5 micrometres or shorter. During haze, these particles are the dominant pollutant affecting health. Their size is important because they are much finer than visible dust and can be inhaled into the respiratory system.

The article does not detail the biological mechanism. Established health knowledge shows that fine particles can travel deep into the lungs, where they may trigger irritation and inflammation. Some particles or their effects can contribute to strain on the heart and blood vessels, increasing health risks, particularly during heavy exposure.

That is why MOM links work arrangements to hourly PM2.5 readings. As readings rise, employers should reduce strenuous outdoor work and add protective measures. The ministry specifically highlights elderly people, pregnant women, and people with chronic heart or lung diseases as more vulnerable.

The two measures serve different purposes. A 1-hour PM2.5 reading gives a more current indication of air quality. The 24-hour PSI is an indicator of daily air quality and forms the basis of the National Environment Agency’s daily health advisories.

For example, employers can use the 24-hour PSI forecast to decide whether tomorrow’s outdoor schedule should be reduced or rescheduled. If conditions worsen or improve during the working day, they can use the latest hourly PM2.5 reading to change tasks, breaks, or outdoor exposure. This makes the response more immediate.

The distinction matters because daily averages or forecasts may not show short-term changes quickly enough for worksite decisions. MOM therefore says employers should use both measures, but at different times. The PSI supports advance planning, while hourly PM2.5 readings support timely adjustments during the day.

Employers should progressively reduce outdoor work as hourly PM2.5 readings rise. The rules become stricter for vulnerable employees, including elderly people, pregnant women, and those with chronic heart or lung diseases. This recognises that the same haze exposure may pose greater risks to them.

When readings are elevated, employers should avoid strenuous outdoor work for vulnerable workers and reduce strenuous outdoor work for healthy workers. When readings are high, outdoor work should be avoided for vulnerable workers, while healthy employees should avoid strenuous outdoor work. If readings become very high, outdoor work for vulnerable workers is prohibited.

For healthy workers, employers should minimise all outdoor work when readings are very high. If strenuous work cannot be avoided at high readings, N95 or equivalent masks should be provided. At very high readings, workers need masks or suitable respirators and indoor hourly rest breaks where outdoor work continues.

When outdoor work cannot be avoided, employers should use measures that reduce exposure and physical strain. MOM lists mechanical aids, job rotation, indoor rest breaks, and adequate hydration as appropriate risk-mitigating measures. These steps can reduce the amount of time workers spend doing strenuous tasks outdoors.

For example, a worksite might rotate workers through outdoor and indoor duties, use equipment instead of manual lifting, and schedule regular indoor recovery periods. If strenuous outdoor work cannot be avoided when readings are high, employers should provide N95 or equivalent masks. The mask requirement adds respiratory protection to changes in work organisation.

At very high readings, employers should provide masks or appropriate respirators if outdoor work remains unavoidable. Workers should also receive indoor hourly rest breaks. Employers must assess reduced visibility risks, especially during tower-crane and mobile-crane lifting, and maintain at least a one-week mask supply when outdoor work is required.

MOM carried out more than 400 worksite inspections since September, according to Acting Minister for Manpower Jasmin Lau. About a quarter of the inspections found sites that fell short. This indicates that shortcomings were not widespread across every inspected site, but they affected a substantial minority of workplaces.

Most employers had done the right thing with haze management plans, N95 masks, and regular worker updates. For sites that fell short, MOM directed employers to correct the problems and said it would check again. The article does not give a detailed breakdown of the exact reasons for each failure.

Inspections were set to continue while the haze lasted. The ministry described the reasons for shortcomings across sectors as extremely varied. The response combines enforcement with prevention: employers must improve plans, provide protection, identify vulnerable workers, and adjust outdoor work as readings worsen.

PM2.5 particles are small enough to travel deep into the lungs rather than being stopped mainly in the upper airways. Established health knowledge indicates that they can irritate lung tissue and trigger inflammation. Inflammatory effects and particles entering the bloodstream can also place stress on the heart and blood vessels, especially during substantial or repeated exposure.

The article identifies elderly people, pregnant women, and people with chronic heart or lung diseases as vulnerable, but it does not explain the biological reasons. In general, older adults and people with existing heart or lung conditions may have less physiological reserve. Pregnancy changes the body’s demands, so air pollution can create additional concern for the pregnant person and developing fetus.

These differences explain MOM’s stronger limits for vulnerable employees. Employers should avoid strenuous outdoor work for them when readings are elevated, avoid outdoor work when readings are high, and prohibit it when hourly readings reach the very high band.