Delhi chokes on pollution: Will masks protect you?

Can masks protect you from pollution?

Doctors say although “impractical”, the N-95 masks when worn properly may offer some protection from the small particulate matter. “The pollution levels are so high at present that people would need to wear an N-95 mask 24*7. This is impossible and impractical. But, yes, when worn properly with no leaks from the sides, it does offer some protection,” says Dr Arvind Kumar, chest surgeon from Sir Ganga Ram Hospital.

It aligns with the World Health Organisation advisory that says: “Face masks are generally not regarded as a suitable measure for the protection of health but may be indicated in certain special circumstances, for example, during prolonged commuting and outdoor activities in situations of hazardous air quality.”

A 2021 study from the USA shows that an N-95 mask may reduce exposure to particulate matter by a factor of 14. Another study from Vietnam where exposure of a manikin wearing different types of masks was measured shows that N95 reduced exposure to ultra-fine particles by 60%.

These results, however, depend on proper fit and minimum leakage of air from the sides. However, a study from China that tested commercially available masks with volunteers showed that there was 3% to 68% inward leakage of air during sedentary tests.

Do masks protect against gaseous pollutants?

While N-95 masks can protect against particulate matter, they cannot prevent exposure to gaseous pollutants such as sulphur dioxide, nitrogen dioxide, and ozone. Dr Kumar said: “Gases will pass through even an N95 mask. There are some activated carbon filters that have been developed, but they are impossible to keep on.”

A recent study by AIIMS, Delhi shows that exposure to nitrogen dioxide (NO2), even for a short duration, between zero and seven days, leads to an increase in the number of emergency room visits by 53%. This is alarming because an increase in the levels of the more familiar pollutant PM 2.5 pushed up the patient load by 19.5% in comparison.

Which masks should you choose?

Surgical and cloth masks should be avoided as they do not offer protection against pollutants.

N-95 or N-99 masks that offer a good fit around your face should be selected.

The masks must have a clip over the nose to offer a proper seal.
The masks should have adjustable straps, with one that goes over your head providing the best seal.

How can you ensure that your mask is effective?

When wearing a mask, ensure that your nose and mouth are properly covered and pinch the metal pin on the nose to create a seal. Make sure to change the mask frequently and avoid ones that have cracked.

“You can repeatedly use the N-95 masks as long as they have not cracked. However, if you keep removing it frequently you will notice that it cracks quickly. A cracked or creased mask does not offer proper seal,” says Dr Kumar.

It should also not be wet, he adds.