Haze in Singapore: Who Is at Risk and How to Manage Patients in Primary Care

During haze, the patients most likely to need you are those with asthma, COPD or cardiovascular disease, children, older adults, smokers and outdoor workers. Singapore data show mostly mild effects overall, but respiratory morbidity clearly rises with the PSI. This summary combines Singapore-specific studies with international wildfire-smoke guidance where local evidence is limited.

Who is at risk?

• Patients with pre-existing cardiopulmonary disease. Asthma, COPD and cardiovascular disease patients show significantly more emergency department visits and admissions as the PSI rises. Asthma exacerbations track closely with same-day PSI elevation.[1][2][3]
• Children and older adults. These are consistently the most vulnerable groups for haze-related respiratory illness across ASEAN studies, and adults aged 65 and above have a higher risk of emergency admission as pollutant levels rise.[3][4]
• Pregnant women, smokers and those with lower health literacy. In a Singapore population study, smokers and less-educated individuals had lower haze knowledge and took up fewer protective behaviours.[5]
• Outdoor workers and people with prolonged outdoor exposure. They have higher inhaled particulate deposition and cumulative exposure.[6]

What symptoms should you expect?

• Upper respiratory and irritant symptoms: eye, nose and throat irritation, cough and rhinitis. These were the most consistently reported symptoms in ASEAN haze studies, with throat discomfort the most reproducible. During Singapore’s 1997 haze, a PM10 rise from 50 to 150 µg/m³ was associated with a 12% increase in upper respiratory tract illness and a 26% increase in rhinitis presentations.[4][7]
• Lower respiratory and exacerbation symptoms: wheeze, dyspnoea, chest tightness and increased cough, particularly in asthma and COPD, where PM2.5 triggers exacerbations through oxidative stress and airway inflammation. Asthma presentations rose by about 19% in the 1997 haze, and a 30-unit rise in PSI was associated with significant increases in respiratory-related ED visits and admissions in a nationwide Singapore study.[1][7][8][9]
• Cardiovascular and systemic effects: haze has been linked to cardiovascular morbidity and, in some studies, to acute psychological and neurological effects, but the cardiovascular association is less consistent than the respiratory one.[4][10]
• Overall picture: health effects of Singapore haze episodes have generally been mild, with no significant rise in mortality or overall admissions in the largest surveillance periods, although respiratory-specific morbidity is clearly elevated.[1][7]

How should you manage haze-related problems in primary care?

• History and risk stratification: ask about asthma, COPD and cardiac disease, smoking status, age extremes and outdoor occupational exposure. These define who needs closer monitoring and pre-emptive counselling.[1][3][8][9]
• Irritant symptoms (eye, nose, throat, rhinitis): supportive care with saline eye and nasal irrigation, antihistamines for allergic-type rhinitis, and advice to minimise outdoor exposure when the PSI is high.[4][7]
• Asthma or COPD exacerbation: step up bronchodilator use according to the action plan, make sure rescue and controller inhalers are in adequate supply, and consider a short course of oral corticosteroids for moderate to severe exacerbations as per usual protocols. Advise patients to increase bronchodilator use proactively during smoke events.[8][11]
• Exposure-reduction counselling for all at-risk patients: stay indoors with windows and doors closed, avoid outdoor exertion, and use a portable HEPA air cleaner or MERV-13 filtration (more effective and cost-efficient than standard air conditioning alone in Singapore haze conditions). If going outdoors, use a well-fitted N95 respirator. N95 use has been associated with an estimated 30% reduction in smoke-related respiratory hospitalisations and with wider adoption of other protective behaviours.[5][11][12]
• Preparedness planning: for asthma and COPD patients, agree a written action plan with adequate medication supply, home PSI monitoring, and a plan to relocate if severe symptoms develop despite home measures. Escalate to acute care for red flags: chest pain, palpitations, significant dyspnoea, or wheeze unresponsive to rescue bronchodilator.[9][11]
• Targeted education: because lower education level and smoking were associated with weaker haze knowledge and protective behaviour, counsel these groups proactively on masks and indoor air quality during clinic visits.[5]

Related reading: Do surgical masks protect against haze?

This article summarises published evidence for healthcare professionals. It is not a substitute for clinical judgement or current MOH and NEA guidance. Written by Dr Seah, a locum doctor who built Locum Radar for other locum healthcare professionals.

References

1. Chan SL, Ho AF, Ding H, et al. Impact of air pollution and trans-boundary haze on nation-wide emergency department visits and hospital admissions in Singapore. Ann Acad Med Singap. 2020;49(2):78-87.
2. Toh MR, Wen X, Ng GXZ, et al. Association between weather, air quality and asthma-related emergency department visits: a retrospective time-series study in Singapore. BMJ Open. 2025;15(12):e108426. doi:10.1136/bmjopen-2025-108426
3. Ho AFW, Hu Z, Woo TZC, et al. Ambient air quality and emergency hospital admissions in Singapore: a time-series analysis. Int J Environ Res Public Health. 2022;19(20):13336. doi:10.3390/ijerph192013336
4. Ramakreshnan L, Aghamohammadi N, Fong CS, et al. Haze and health impacts in ASEAN countries: a systematic review. Environ Sci Pollut Res Int. 2018;25(3):2096-2111. doi:10.1007/s11356-017-0860-y
5. Ng KYY, Yeung W, Sou KL, et al. Factors influencing protective behaviours during haze episodes in Singapore: a population-based study. Ann Acad Med Singap. 2021;50(7):514-526. doi:10.47102/annals-acadmedsg.2020614
6. Othman M, Latif MT, Hamid HHA, et al. Spatial-temporal variability and health impact of particulate matter during a 2019-2020 biomass burning event in Southeast Asia. Sci Rep. 2022;12(1):7630. doi:10.1038/s41598-022-11409-z
7. Emmanuel SC. Impact to lung health of haze from forest fires: the Singapore experience. Respirology. 2000;5(2):175-182. doi:10.1046/j.1440-1843.2000.00247.x
8. Ren J, Li B, Yu D, Liu J, Ma Z. Approaches to prevent the patients with chronic airway diseases from exacerbation in the haze weather. J Thorac Dis. 2016;8(1):E1-7. doi:10.3978/j.issn.2072-1439.2015.11.61
9. Balmes JR. Where there’s wildfire, there’s smoke. N Engl J Med. 2018;378(10):881-883. doi:10.1056/NEJMp1716846
10. Cheong KH, Ngiam NJ, Morgan GG, et al. Acute health impacts of the Southeast Asian transboundary haze problem: a review. Int J Environ Res Public Health. 2019;16(18):3286. doi:10.3390/ijerph16183286
11. Fadadu RP, Solomon G, Balmes JR. Wildfires and human health. JAMA. 2024;332(12):1011-1012. doi:10.1001/jama.2024.13600
12. Tran PTM, Adam MG, Balasubramanian R. Mitigation of indoor human exposure to airborne particles of outdoor origin in an urban environment during haze and non-haze periods. J Hazard Mater. 2021;403:123555. doi:10.1016/j.jhazmat.2020.123555