Why does the haze look worse than the PSI reading? How does it compare to 2013 levels when the PSI hit a record high? We put your burning questions to the authorities.
Diane Leow, Channel NewsAsia 16 Sep 15;
SINGAPORE: Singapore is grappling with its worst bout of transboundary haze pollution in two years, with the 24-hour Pollutant Standards Index rooted in the Unhealthy range for several days since Saturday (Sep 12).
We put some of your frequently asked questions to the authorities.
The haze outside my window looks worse than the PSI reading. Why?
According to officials from the National Environment Agency and the Ministry of Environment and Water Resources (MEWR), there is no 100 per cent correlation between smell, visibility and the PSI reading, or the 1-hour PM2.5 reading posted on the NEA website.
"PM2.5 particles are measured in a very scientific way, based on the mass of particles as collected in a volume of air. This is accurate as far as the weight of particles in a particular area. Visibility and smell are affected by other factors, other than the mass and the weight of the particles. Visibility could be affected by humidity, and smell could be affected by other types of compounds in the air," MEWR said.
At what point should I wear an N95 mask?
For healthy individuals, the Ministry of Health (MOH) recommends putting on an N95 mask when air quality reaches Hazardous levels, when the 24-hour PSI has surpassed 300.
Authorities also say that those who worry about overexposure to the haze should check the 1-hour PM2.5 reading on the NEA website or app. If the figure is high, it would be advisable to minimise outdoor activities.
MOH says the best way to limit exposure to the haze is to stay indoors, adding that the haze could affect individual people's health differently. Elderly, pregnant women and children should minimise prolonged or strenuous outdoor activity amidst the haze and those with chronic lung or heart diseases should avoid any outdoor activity.
How does this haze episode compare to the one in 2013?
During the 2013 Southeast Asian haze crisis, a typhoon in the Philippines acted as a low pressure zone, causing westerly winds to blow haze from hotspots in Indonesia to Singapore. It propelled the 3-hour PSI to a record reading of 401 on Jun 21, 2013.
This year, Minister for the Environment and Water Resources Vivian Balakrishnan says authorities are watching a typhoon off the coast of Vietnam. Once it has made landfall, that could result in less westerly or south-westerly winds, which bring haze to Singapore.
MEWR also notes that sudden spikes in PM2.5 readings this year are "very possible", if dense haze clouds are blown towards Singapore by prevailing winds. Looking at 1-hour PM2.5 concentrations, MEWR said sharper spikes were seen in 2013. As such, there could still be sharp spikes from time to time this year.
I've seen social media accounts saying they have the "real haze levels". Are they the real deal?
NEA says there are members of the public who use handheld devices to measure air quality in Singapore, which may not be accurate.
It adds that there are many ways of calculating air quality around the world, as there is no singular international air quality index. Hence, it is best to check NEA's website, Twitter account or refer to the myENV app for accurate PSI and PM2.5 readings, the agency says.
How will the Transboundary Haze Pollution Act help?
The Transboundary Haze Pollution Act enables authorities to prosecute individuals or companies in neighbouring countries that cause severe air pollution in Singapore through slash-and-burn agricultural practices. Errant companies can be fined up to S$2 million if they contribute to the 24-hour PSI remaining at 101 or higher for 24 hours or longer.
NEA says Singapore has been in the Unhealthy zone for close to 70 hours, which has crossed a threshold in the Act.
"In order for us to be able to use some of the provisions in the Act we need to be able to identify where this haze is coming from. This requires some investigation. We would have to have satellite pictures of places where they may be fires and fumes. We are still in the process of doing this investigation for this period that we've been in the unhealthy zone," says NEA.
- CNA/dl
Rain or shine, keep N95 masks on during severe haze: Expert
Rain helps to remove haze particles but it does not do too much to remove toxic gases, says research scientist Dr Erik Velasco.
Chan Luo Er Channel NewsAsia 16 Sep 15;
SINGAPORE: Heavy rain on Tuesday may have provided respite from the haze, but an expert has cautioned that although the air may seem clearer after the showers, toxic gases are still present.
Dr Erik Velasco, research scientist at the Singapore-MIT Alliance for Research and Technology said the public should still keep their N95 masks on, especially when the Pollutant Standards Index enters the Hazardous range.
“Haze is a mix of particles and toxic gases, and the rain helps to remove particles but it doesn't do too much to remove toxic gases, that is why after this rain, we are still smelling that acrid smell,” he said at an Urban Air Quality and Public Health symposium at Nanyang Polytechnic on Tuesday (Sep 15).
"In previous days we saw the pollution level drop after showers. Yesterday, there was a huge strong shower from 6 to 7pm but it was not capable of reducing the pollution level. In general, rain, strong showers help to clean the air but there are other parameters we need to consider to, meterological winds, the atmosphere, turbulence," added Dr Velasco.
He said this can be attributed to the dense concentration of particles in the air.
On air quality information released by authorities, Dr Velasco urged the public to also pay attention to the PM2.5, which measures particle concentration.
The PM2.5, like the PSI, is available on the National Environment Agency's (NEA) website. On an average day, Singapore's PM2.5 reading ranges between 20 and 40 µg/m³. A reading above 50µg/m³ indicates slight pollution.
"When concentrations go above 150µg/m³, the situation is very bad. More than 200 microgrammes is terrible – that means we have to take drastic measures like closing the schools, avoiding all type of outdoor activities, maybe industry refineries should reduce their activities, traffic should be reduced too. Last night, we reached 341µg/m³ at 8pm in the south sector of the city,” said Dr Velasco.
NTU DEVELOPS HAZE APP
Another expert noted that the haze may be on everyone's mind, but this does not mean that they are responding appropriately.
Said Dr Christopher L Cummings, from Nanyang Technological University’s Wee Kim Wee School of Communication and Information: "We need to be able to get people to react effectively during this time. It's more about people taking their own initiative now and making sure they have ownership over their own actions to protect their own behaviour."
To help Singaporeans do just that, Dr Cummings, along with a team at Nanyang Technological University, is developing an application.
Called Haze Analytics Tools (HATS), this prototype builds on information by authorities to dish out advice, as well as suggest activities best suited to the wearer's health profile. It will also be able to sync with smart watches to monitor a person's heart rate, and in turn, respiratory symptoms.
The team hopes that the app, which will be available in a year or two, will help Singaporeans to alter their daily behaviour when haze levels are high.
- CNA/dl
