By: Jessica Hefes

Date: 9/8/10

Extrapolation from current trends in pollutant levels indicates that air pollution will significantly affect the health of the entire Hong Kong population in the near future. [1]

Pollution directly impacts on health spending. It is estimated that the annual direct health care cost for all four pollutants is HK$839 million. [2] It is a cause of the increase in hospitalizations and doctors’ visits.

In scientific studies four criteria pollutants are used to estimate the impact of air pollution on population health: particulate matter (PM10 and PM2.5), nitrogen dioxide (NO2), sulphur dioxide (SO2) and ozone (O3). All four criteria pollutants are associated with adverse health effects in terms of hospital admissions and death risk. Estimates are higher for nitrogen dioxide and sulphur dioxide. [1]

PM10, PM2.5, SO2, NO2, O3 are associated with increased hospital admissions for chronic obstructive pulmonary disease. For every 10mg/m3 increase in these pollutants the risk of hospitalization increased significantly. [3] Concentrations of PM10, SO2, NO2 and O3 have been significantly associated with mortality from respiratory disease and ischemic heart disease. [4]

Long-term exposure to nitrogen dioxide and sulfur dioxide, both found in motor vehicle emissions, and fine particulate matter, found in industrial air pollution, increases the risk of hospitalization for pneumonia in older adults by interfering with lung immune defenses designed to protect the lung from pathogens. [5] Similarly exposure for more than a year to higher levels of nitrogen dioxide and fine particulate matter of less than 2.5 micrometres, more than doubled the risk of hospitalization for pneumonia in adults aged 65 and older. Pneumonia is a leading cause of illness and death in older adults. [6]

A joint Hong Kong – United Kingdom study showed links between hospital admissions for respiratory disease and PM10, NO2, SO2 and O3 in both London and Hong Kong. It also showed links between these pollutants and cardiac disease. It appears that the problem of NO2 and O3 is unique to Hong Kong as the link between these pollutants and health was negative in London but positive in Hong Kong. [7]

Overall a concentration of pollutants has been associated with an increase in hospital admissions for a number of illnesses. Concentrations of PM10, SO2, NO2 and O3 have been significantly associated with hospital admissions for respiratory disease, cardiovascular disease, pulmonary disease and heart failure. Concentrations of PM10, NO2 and O3 have been associated with hospital admissions for asthma, pneumonia and influenza [8] and concentrations of SO2, NO2 and O3 have been linked with mortality from all non-accidental causes such as cardiovascular and respiratory diseases during the cool season [9]. Significant positive interactions were found between PM10, NO2 and O3, and between O3 and winter months. [8]

Asthma is also linked with air pollution. Hospital admissions for asthma have increased significantly with the augmentation in ambient SO2, NO2 and inhalable particles. [10] Additionally daily hospital admissions for all causes of circulatory disease were associated with increased O3 concentrations. The strongest effect O3 had on daily hospital admissions was on patients with arrhythmias and heart failure. [11] PM10 is linked with mortality from respiratory disease only. [9] Similar associations were observed between other respiratory diseases and the four pollutants. [12]

Finally, an increase in air pollution also increases the number of doctors’ visits. A study found that there was a significant association between visits to general-practice clinics in eight districts for upper respiratory tract infections and an increases in NO2, O3, PM2.5 and PM10 concentrations in the same area. The risk of visits to GP clinics was 3.0% when there was an increase in NO2, 2.5% for an increase in O3, and over 2% for an increase in PM2.5 or PM10. [12] For each 10-mg/m3 increase in PM10, the relative risk of general-practice visits for all respiratory illnesses and upper respiratory tract infections were 1.030 and 1.033 respectively. Relative risk for O3, NO2 and SO2 were statistically non-significant. [13]


  1. 1.0 1.1 The impact of air pollution on population health, health care and community costs, Department of Community Medicine, HKU, 27 November 2006 - last accessed 7/8/10
  2. A Price Too High: The Health Impacts of Air Pollution in Southern China, Civic Exchange, HKU Medical Centre, Department of Community and Family Medicine, CUHK, Institute for the Environment, HKUST, June 2008 - last accessed 5/8/10
  3. The temporal relationship between air pollutants and hospital admissions for chronic obstructive pulmonary disease in Hong Kong, Ko FW, Tam WW, Wong T. et al, 2007, Thorax 62:780–785
  4. Associations between daily mortalities from respiratory and cardiovascular diseases and air pollution in Hong Kong, Wong TW, Tam WS, Yu TS et al, 2002, Occup Environ Med 59:30–35
  5. Loeb, a physician, is a professor in the Department of Pathology and Molecular Medicine and the Department of Clinical Epidemiology and Biostatistics of the Michael G. DeGroote School of Medicine
  6. Air pollution linked to hospitalizations for pneumonia in seniors, 30 Dec 2009 - last accessed 9/8/10
  7. A tale of two cities: effects of air pollution on hospital admissions in Hong Kong and London compared, Wong CM, Atkinson RW, Anderson HR et al, 2002, Environ Health Perspect 110:67–77
  8. 8.0 8.1 Does ozone have any effect on daily hospital admissions for circulatory diseases?,Wong CM, Ma S, Hedley AJ et al, 1999, J Epidemiol Community Health 53:580–581
  9. 9.0 9.1 Effect of air pollution on daily mortality in Hong Kong, Wong CM, Ma S, Hedley AJ et al, 2001, Environ Health Perspect 109:335–340
  10. Temporal relationship between air pollution and hospital admissions for asthmatic children in Hong Kong, Wong GWK, Ko FWS, Lau TS et al, 2001, Clin Exp Allergy 31:565–569
  11. Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong, Wong TW, Lau TS, Yu TS et al, 1999, Occup Environ Med 56:679–683
  12. 12.0 12.1 Association between air pollution and general practitioner visits for respiratory diseases in Hong Kong, Wong TW, Tam W, Tak Sun Yu I et al, 2006, Thorax 61:585–591
  13. Air pollution and general practice consultations for respiratory illnesses, Wong TW, Wun YT, Yu TS et al, 2002, J Epidemiol Community Health 56:949–950