Frequently Asked Questions (FAQs) on Haze (Updated 28 June 2013)

GENERAL INFORMATION

1.  What is PSI? How is the index measured? What is the meaning of the index?

•  PSI stands for 'Pollutant Standards Index'. It is an index developed by the United States Environmental Protection Agency (USEPA) to provide accurate, timely and easily understandable information about daily levels of air pollution.

•  The USEPA guideline for computation of PSI is based on a 24-hour average of PM10 concentration levels, among other pollutants.  PM10 is the dominant pollutant during haze episodes.

•  The ambient air in Singapore is monitored through a network of air monitoring stations strategically located in different parts of Singapore. 

•  The monitoring stations measure air pollutants such as sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and particulate matter called PM10 (particulate matter of 10 microns or smaller in size, 1 micron is 0.001 mm). These pollutants are used in the determination of the index.

•  The PSI value gives an indication of the air quality as shown:

•  PM 2.5 refers to particulate matter that is smaller than 2.5 microns. PM 2.5 is therefore a subset of PM 10. If the level of particles 2.5 microns or smaller increases, this will be reflected in the level of both PM 2.5 and PM 10. 

•  While PM 2.5 levels do not directly form part of the computation for PSI calculations, as PM 2.5 is a subset of PM 10 which is one component in PSI, a rise in PM 2.5 will also be reflected in the PSI.  PM 2.5 is also reported separately.

•  As the PSI is an index and not a concentration reading, the PSI cannot be compared with the PM2.5 concentration, which is expressed in micrograms per m3.

2.  What is the difference between difference between PSI (3-hour) and PSI (24-hour)?

•  The 24-hour PSI index system adopted by Singapore is based on continuous measurements of five key air pollutants in the air (PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide). The index is based on average values taken over a 24-hour period in accordance with the United States Environmental Protection Agency guidelines. The index is not a composite index and is based on the pollutant that has the highest concentration over a 24-hour period. During haze, the pollutant that records the highest concentration is PM10.

•  The 3-hour PSI is computed based on the 3-hour average PM10 concentrations because PM10 is the pollutant with the highest concentration in the event of haze. We introduced hourly reporting of the 3-hour PSI during the 1997 smoke haze episode to give the public additional information on the current air quality situation as it varies from hour to hour. Since 20 Jun 2013, NEA has been reporting the 3-hour PSI readings round the clock every hour.  The 3-hour PSI is not used to determine the health advisory.

3.  Why are our advisories only based on 24-hour PSI and not 3-hour PSI?

•  Health impacts are related to concentrations as well as duration of exposure, in addition to health status of the individual. The 24-hour measurements are a better reflection of the total exposure of an individual to PM levels. The health advisories adopted by NEA are based on 24-hour PSI and 24-hour PM2.5 measurements as scientific and epidemiological studies on the health effects of particulate matter have been based on these measurements.

•  The 3-hour PSI is only an indicative index. There are currently few studies on the health effects of exposure to short-term spikes in PM levels.

4. The PSI readings only show historical data.  How can I plan for the days ahead?

Since 20 June 2013, NEA has been providing a Pollutant Standards Index (PSI) forecast range for the next day, which will help advise the public what the PSI range is likely to be over the next 24 hours.  NEA will look at all relevant factors, including weather patterns, in determining this forward projection. 

5.  Is forecasting of haze condition possible?

•  Forecasting of haze conditions has not been extensively proven but NEA will be making efforts to project possible haze conditions to better advise the public.

6.   Why is it that the 3-hour PSI released during the smoke haze periods is at times low when the visibility is poor?

•  When a 3-hour PSI reading is released during the smoke haze periods, it is for air quality for the immediate past three hours. It therefore may not correspond to what you may observe at the point when you hear the PSI announcement.

7.    Can we conduct cloud seeding in Singapore to disperse the smoke haze? 

•  Cloud seeding attempts to artificially induce rain by implanting clouds with suitable particles. The seeding particles serve as condensation or ice nuclei to induce formation of more water droplets or ice crystals in the cloud. However, there is still a lack of reliable means to validate the effectiveness of the seeding process.

•  Cloud seeding requires existing clouds as it cannot generate rain out of thin and dry air. During the current dry season, cloud seeding is less effective due to the lack of suitable clouds for seeding. The small size of Singapore and the variability of winds also mean that the induced rain, if any, may not fall directly over our island. In any case, the rain will provide only temporary relief as the smoke haze would continue to be blown toward Singapore by the prevailing winds, should the fires in the region continue to persist. For these reasons, we have no plans to conduct cloud seeding, but we will keep the option open.

IMPACT OF HAZE ON HEALTH

8.  What is the effect of the haze on my health?

•  Haze particles may cause irritation of the eyes, nose, throat in healthy individuals.  Such irritation resolves on its own in most cases.

•  Haze particles can affect the heart and lungs, especially in people who already have chronic heart or lung disease e.g. asthma, chronic obstructive pulmonary disease (COPD), heart failure.

•  There may be up to 1-3 day time lag between exposure to haze and health effects/ symptoms.

9.   What are the long term effects of the haze?

•  Studies have shown that long-term exposure to fine particles (i.e. particulate matter 2.5 (PM2.5); particles smaller than 2.5 micrometers) include (i) cardiovascular effects, such as heart attacks and strokes, (ii) reduced lung development, as well as (iii) the development of chronic respiratory diseases, such as asthma, in children.

•  However, these are the results of long term prolonged exposure, of 7-14 years for persons living in areas with high ambient pollution.  This is not the case here, as we do not get haze throughout the year.

10.    What is MOH’s advice to the public on what to do?

•  Please try to minimise exposure by reducing outdoor activities and physical exertionThis means staying indoors, and reducing the length of exposure and strenuous work if you need to be outside.

•  Drink plenty of water to stay well hydrated

•  Use an N95 mask where appropriate, depending on how healthy you are, the PSI level and the time you need to spend outside.  See http://www.moh.gov.sg/content/moh_web/home/pressRoom/Current_Issues/2014/haze/health-advisory-for-general-public-and-workers.html for advisory.

11.   Should I still follow the daily Health Advisory if the skies look clearer, since these are based on PSI readings from previous hours’?

•  While you need not rigidly adhere to the daily Health Advisory, if the situation changes, following the advice for a higher PSI based on previous day’s level would be prudent.

USE OF MASKS AND AVAILABILITY OF MASKS

12.   Who should use an N95 mask?  When?

•  N95 masks are recommended for individuals who undertake prolonged and strenuous work outdoors when air quality is in the very unhealthy range.  N95 masks are also recommended for individuals who are outdoors when air quality is in the hazardous range.

•  N95 masks are not needed for short exposure, like commuting from home to school or work, travel from bus-stop to shopping mall.

•  N95 masks are also not needed in an indoor environment.

•  Elderly people and people with lung or heart problems should stop using a N95 mask if they feel uncomfortable. Those with severe lung or heart problems who have difficulty breathing at rest or on exertion should not wear N95 masks. They should consult their doctor as to whether they should use the N95 mask.

•  Women in the 2nd and 3rd trimesters of pregnancy should not use the N95 mask for more than a short duration each time.

•  N95 masks are not certified for use in children, so children should try to stay indoors when air quality is poor.

13.   What about children?  Children's N95 masks are not available.

•  The N95 masks that are currently available have not been designed by the manufacturer for use in children.  Further, to be effective, N95 masks need to maintain a well-fitted seal at all times, which may be difficult to achieve in young children. In addition, young children may find it uncomfortable to wear a tight-fitting mask and will very likely adjust the mask that is worn, reducing the effectiveness of the mask. 

•  Although certain types of N95 masks are being offered for sale for young children, their claims of effectiveness have not been verified by the relevant authorities such as the US Food and Drug Administration (US FDA) or Singapore’s Health Sciences Authority (HSA). 

•  While older children (e.g. upper secondary school and above) may be able to fit the smaller sized N95 masks for adults, please note that the mask manufacturers do not certify effectiveness of the mask for this group.  (Based on height and weight data of Singaporean children, an average upper secondary child is similar in size to a small-sized adult.)  Older children with chronic heart and lung disease should not be using N95 masks without medical (paediatric specialist) advice.

•  Children should adhere to the recommendation to minimize outdoor activity at PSI levels above 100, and avoid outdoor activity if PSI levels reach higher than 200. 

14.   Is the N95 mask an adequate protection against the haze? Does it protect against PM2.5?

•  N95 masks are designed to seal to the face of the wearer. This way, most of the air that the wearer breathes in has to go through the filter and not through the gaps between the mask and the wearer’s face. Haze particles are predominantly made up of fine particles that are 2.5 microns or smaller (PM2.5). Studies have shown that N95 masks do provide good protection against the haze as they are at least 95% efficient against fine particles that are about 0.1 – 0.3 microns. It is even more efficient (99.5% efficient) against particles that are 0.75 microns and larger.

15.   What are the effects of wearing a N95 mask?

•  The use of N95 masks increases effort in breathing.  For some people, the use of N95 mask may cause discomfort in breathing, tiredness or headache. This may be due to the mask causing increased resistance to breathing, and a reduction in the volume of air breathed. For most people this is not serious.

•  However, some elderly people, people with lung or heart conditions, and women in the later stages of pregnancy may already have reduced lung volumes or breathing issues.

•  Because of this, elderly people and people with lung or heart problems should stop using a N95 mask if they feel uncomfortable. Those with severe lung or heart problems who have difficulty breathing at rest or on exertion should not wear N95 masks. They should consult their doctor as to whether they should use the N95 mask.

•  Women in the 2nd and 3rd trimesters of pregnancy should not use the N95 mask for more than a short duration each time.

•  N95 masks are not certified for use in children, so children should try to stay indoors when air quality is poor.

16.   How do I get a mask? Is there a shortage of N95 masks?

•  MOH has worked with manufacturers and suppliers to ensure supply of N95 masks in Singapore. Masks are available at major supermarkets, such as NTUC Fairprice, Giant and Cold Storage and pharmacies such as Guardian and Unity. 

•  Employers who have difficulty in purchasing N95 masks for their workers engaged in outdoor work can call MOM at 6438 5122.

•  People should only buy N95 masks for those who need to use them and when required, as per MOH’s health advisory.

17.    Are there different types of N95 masks in the market?

•  There are different brands of N95 masks in the market which have the same functionality. They come in different colours, shapes and sizes.

•  Our national stockpile comprises these three brands : Kimberly-Clark, 3M and Draeger (also known as Dräger).

18.    What are EN-149: 2001 masks?  Are they equivalent to the N95 masks? 

•  EN-149 is one of the European Standard for masks while N95 masks are certified by the US National Institute for Occupational Safety and Health (NIOSH).  Both types of masks are designed to reduce wearer’s respiratory exposure to airborne contaminants such as particles, gases or vapours.

•  The EN-149 masks are classified in 3 classes depending on the ability to separate air-borne particles:  

FFP2 masks that meet the EN-149 standard are the closest to N95 masks in the ability to filter particles.

19.   How would members of public know if the N95 or other types of masks meet safety and quality standards? 

•  A NIOSH-approved mask is certified by the US National Institute for Occupational Safety and Health (NIOSH) to have 95% filter efficiency. A NIOSH-approved respirator has the following information printed on its packaging:

- NIOSH

- the type of approval (e.g. N95)

- the manufacturer’s name

A list of NIOSH certified N95 masks is available on NIOSH’s website: http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/n95list1.html 

•  EN149 is the European Standard for respiratory mask designed to reduce wearer’s respiratory exposure to airborne contaminants such as particles, gases or vapours.  Masks are classified in 3 classes depending on the ability to separate air-borne particles according to the FFP (Filtering Face Pieces). An European standard certified mask will have the following text printed on it:

- the CE mark

- EN 149:2001; the classification of the mask (e.g. FFP2)

- the manufacturer’s name.

20.    How does a consumer choose which mask to purchase?

Both the NIOSH-certified N95 masks or the EN-149 masks are designed to reduce wearer’s respiratory exposure to airborne contaminants such as particles, gases or vapours. Consumers should perform a fit check to ensure a good fit.

21.    How do I learn to fit my N95 mask?

•  For best effect, N95 masks need to be fitted properly for each user. To check for proper fit, please check that the available mask is appropriately sized and covers the nose and mouth comfortably without leak.

•  The HPB website has a step by step guide on how to wear N95 masks properly.  See http://www.hpb.gov.sg/HOPPortal/health-article/HPB051227

•  The use of N95 masks to filter out pollutants in the air is not identical to the use of N95 masks for infection control in a healthcare institution during a disease pandemic situation.  For use during haze, even if the mask is not perfectly fitted, it can still be useful in filtering out pollutants for those need to wear it.

22.   How do I wear a mask?

•  To learn how to put on a mask properly, the HPB has an info graphic on how to wear a mask on their website http://www.hpb.gov.sg/HOPPortal/health-article/HPB051227. Please see also Annex.

23.   Can I reuse my N95 mask?

•  You can reuse your N95 mask. It should be changed when it gets soiled or distorted in shape. It should not be shared.

24.   Are surgical masks useful?

•  Normal surgical masks can protect the wearer’s nose and mouth from irritants in the air but are not effective in filtering fine particles.

•  Individuals with acute respiratory infections may wish to wear a surgical mask to prevent spread of infection.

•  Individuals may feel more comfortable having a surgical mask for short periods of time for unavoidable outdoor exposure e.g. commuting from home to MRT station, and waiting for public transportation. 

•  The N95 mask is only recommended in healthy adults if prolonged and strenuous outdoor activity is unavoidable when the air quality is in the very unhealthy range, and if outdoor activity is unavoidable when the air quality is in the hazardous range.

ACCESS TO CARE IF YOU FALL ILL

25.    What help do I get if I fall ill?

•  Please visit a GP clinic if you feel unwell due to the haze.  MOH is implementing a special scheme for the following groups of patients who are seeking treatment for respiratory problems and conjunctivitis arising from the haze:

–  Young Singaporeans 18 years old and below,

–  Elderly Singaporeans 65 years old and above,

–  Community Health Assist Scheme (CHAS), Public Assistance, Medical Fees Exemption Card (MFEC) and Medical Fees Assistance Card (MFAC) cardholders, and

–   Lower-income Singaporeans earning $1,500 a month and below (by declaration).

•   Most patients visiting the designated GP clinics should expect to pay about $10 after a government subsidy of $30. 

•   All Singaporeans seeking treatment at polyclinics for conditions arising from the haze will also pay not more than $10. 

26.    How many GP clinics do you expect to be on this special scheme?

•  MOH is working with our regular GP partners to operationalize this scheme.  The clinics are listed on http://www.moh.gov.sg/content/moh_web/home/pressRoom/Current_Issues/2013/haze/list-of-gp-clinics-participating-in-haze-subsidy.html and the listed will be updated as more clinics join the scheme.

•  As of 18 July 2013, 3pm, 670 clinics have registered.

IMPACT ON HEALTHCARE INSTITUTIONS

27.    What is the impact on attendances at Healthcare institutions? 

•  So far there is no large spike in polyclinic attendances or attendances at Emergency Departments (ED) for respiratory conditions. Many with respiratory symptoms at ED are treated as outpatients.

•  However, the impact may be more visible in weeks ahead if haze persists.

28.    What has MOH done to help Healthcare Institutions

•  MOH has worked with the restructured hospitals to retrofit suitable spaces to add bed capacity and injected additional bed capacity in wards that still have space. This additional bed capacity is on standby, and can be activated if we have a surge in demand at the hospitals.

•  We have also made manpower deployment plans to staff these beds (if they are deployed).

•  In addition, hospitals can defer non-urgent electives, if necessary to meet the increased demand.

•  We have updated polyclinics on the situation, and informed them to prepare for expected increases in polyclinic attendances. Polyclinics are closely monitoring the situation with regard to attendances for respiratory or eye conditions due to the haze, and patients with serious conditions will be referred to hospitals for further management. MOH and Agency for Integrated Care (AIC) are also working with the GP sector to ensure that they are well supported as front line healthcare providers.

•  AIC has sent a health advisory to all intermediate and long term care providers, e.g. nursing homes, senior activities centres, etc. AIC is working with the aged care providers to render support needed to keep the elderly safe.

29.   How will the haze impact patients in nursing homes and subsidised wards with natural ventilation?

•  These patients are indoors. The healthcare institutions, such as hospitals and nursing homes, will take care to monitor patients closely, and to minimise the impact of the haze, such as closing off the windows when the haze is very heavy, and ensuring ample air circulation indoors.

30.   Where can I get more information on haze?

•  Please refer to the following websites:

www.haze.gov.sg
www.e101.gov.sg/haze

. . . . .

ANNEX

HOW TO WEAR A MASK

Last updated on 31 Aug 2017