Emergency visits rise with higher PM2.5 levels: S’pore Study

But during periods of haze such as that experienced in Singapore from September, PM2.5 readings have reached over 100. On Sept 29, PM2.5 concentrations in eastern Singapore was 70 mcg per cubic m as at 1pm.

Researchers found that for each 10 mcg per cubic m increase in PM2.5 above the 15 mcg per cubic m reference level, emergency department visits for asthma and chronic obstructive pulmonary disease increased by 3.2 per cent over the following two days.

For the study, the researchers compiled the asthma and chronic obstructive pulmonary disease-related emergency department visits from February 2016 to December 2022.

A total of 74,839 visits were analysed, of which 43,446 resulted in hospital admissions, and 1,369 patients died within 30 days.

The data was extracted from all public hospitals via a government administrative and health data platform.

They also retrieved data on PM2.5 levels and other environmental parameters, such as temperature, humidity and rainfall, from the website of the National Environment Agency.

Statistical analyses were performed to see if there was any correlation in the data.

They found that asthma-related emergency department visits specifically rose by 4.4 per cent over the two-day window between an increase in PM2.5 concentration and emergency room visits.

Chronic obstructive pulmonary disease-related visits also tended to increase, though the association was less clear at these lower PM2.5 concentrations.

The researchers observed stronger evidence of an increase in such visits at higher pollution levels, which suggested that the respiratory effects of PM2.5 could become more apparent with increased exposure.

While the researchers also analysed subsequent hospital admissions and 30-day mortality, they observed no statistically significant associations with the pollution spikes.

Of the data collected, nearly 60 per cent of these patients were male and more than 75 per cent had a monthly household income of less than $2,000.

However, the study found no evidence that the pollution-related risk differed significantly based on sex, age, income, or other existing diseases.

The researchers noted several limitations. While the data had captured most of Singapore’s emergency care, it excluded visits to clinics, polyclinics and urgent care centres.

They also acknowledged that their analysis of only one pollutant, consistent with standard practice, meant that the effects of other ambient pollutants cannot be ruled out.

They noted that lingering effects of the Covid-19 pandemic could have affected the study as they had only adjusted the data for the period of 2020 to 2021.

The authors concluded that the findings support integrating real-time air quality data into alerts for patients and using the information to plan for respiratory case surges in emergency departments.

Said Professor Marcus Ong, Director of the Health Services Research and Population Health programme at Duke-NUS Medical School, said: “Haze is not only an environmental issue; poorer air quality can translate into additional demand on emergency healthcare within days.”

The NEA provides one-hour PM2.5 reading on its website, which shows the average concentration of such particles measured in the air over the past hour.

Readings are considered high when they reach between 151 mcg per cubic m and 250 mcg per cubic m. When readings are high, people are advised to avoid strenuous outdoor activity for the next hour.