Author: Antonio Da Roza

Date: 12/8/10

Child Welfare Scheme commissioned from the Chinese University Hong Kong a review of medical research from 1980 – 2009 on measures that individuals can take to reduce their exposure to air pollution. [1]

Of the 414 papers found through the literature search, only 13 were of relevance. Furthermore, given the ways in which air pollution concentrations may differ in various micro-environments (such as the home, classroom, at roadside, inside different forms of transport, shopping centers etc) in different cities [2], recommendations that may be made from studies based outside Hong Kong may not be all that helpful.

Protective measures that were evaluated include: facemasks, air cleaners, various types of dust filters (including vacuum cleaner bags and HEPA filters [3]). Air cleaners and filters were evaluated for their effectiveness on allergic respiratory diseases in children. [4]

Outdoor air pollution

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Woman wearing facemask at roadside in Hong Kong - Alex Hofford (

As there is little an individual can do in terms of protection from air pollution, reduction of exposure to outdoor air pollution is the most practical measure to take.

Of particular interest are suggestions from one academic journal that air pollutants may lurk inside vehicles, and the recommendations on avoiding in-vehicle pollution include driving in less congested areas and avoiding trailing polluting vehicles. [5] Several studies show high levels of air pollutants inside school buses. [6] These findings may be compared with a local study which found that the lung function of 129 drivers of non-air-conditioned buses was lower than those of 358 in air-conditioned buses. The drivers of non-air- conditioned buses reported frequent productive cough, dry cough and sore throat. [7]

It also appeared from one study that facemasks offer limited protection against outdoor air pollutants. Whilst some facemasks may prevent penetration from particulate matter, facemasks that are equipped with activated charcoal as filters may exclude even gaseous air pollutants, though such filters may be too cumbersome and impractical for common use. [8]

Indoor air pollution

Sources of toxic air pollution can be kept to a low level indoors if rooms are well-ventilated with outdoor fresh air – unventilated or poorly ventilated rooms can allow air pollutant concentration to build up.

The effectiveness of indoor devices such as air cleaners and air filters is equivocal. Some of the studies reviewed suggested that they offer limited protection to individuals with allergic respiratory illnesses, and of the studies reviewed there was no clear demonstration of effectiveness in terms of reducing respiratory symptoms among those with such illnesses. [3]

One study demonstrated the effectiveness of HEPA filters among asthmatic children who kept pets [9], whilst another suggested the effectiveness of a control programme against indoor air pollutants and allergens that included several strategies, including pest extermination, mattress and pillow encasings and the use of HEPA air cleaners [10].


  1. ‘Air pollution control strategies for the individual: a literature review’, 18/1/10, Professor T.W. Wong, Chinese University Hong Kong (published by Child Welfare Scheme) – last accessed 12/8/10
  2. See Guo H, Lee SC, Chan LY, et al, 2004. Risk assessment of exposure to volatile organic compounds in different indoor environments. Environ Res 94:57-66 for an example of a local study on air pollution and micro-environments
  3. 3.0 3.1 Sulser C, Schulz G, Wagner P, et al. Can the use of HEPA cleaners in homes of asthmatic children and adolescents sensitized to cat and dog allergens decrease bronchia hyperresponsiveness and allergen contents in solid dust? Int Arch Allergy Immunol 2009;148:23-30
  4. Reisman. Do air cleaners make a difference in treating allergic disease in homes? Ann Allergy Asthma Immunol 2001;87 (Suppl):41-43
  5. Weinhold B. Don’t breathe and drive? Environmental Health Perspectives 2001; 109(9):A423-7
  6. Zhang Q, Zhu Y. Measurements of ultrafine particles and other vehicular pollutants inside school buses in South Texas. Atmospheric Environment 2010; 44:251-61; Marshall J, Behrentz E. Vehicle self-pollution intake fraction: children’s exposure to school bus emissions. Environmental Science and Technology2005; 39:2559-63; Rim D, Siegel J, Spinhirne J, et al. Characteristics of cabin air quality in school buses in Central Texas. Atmospheric Environment 2008; 42:6453-64
  7. Respiratory health of bus drivers in Hong Kong, Jones AY, Lam PK, Dean E, 2006 Int Arch Occup Environ Health 79:414–418
  8. Langrish JP, Mills NL, Chan JKK, et al. Beneficial cardiovascular effects of reducing exposure to particulate air pollution with a simple facemask. Particle and Fibre Toxicology 2009; 6:8 – last accessed 12/8/10
  9. Vaughan JW, Woodfolk JA, Platts-Mills TAE. Assessment of vacuum cleaners and vacuum cleaner bags recommended for allergic subjects. J Allergy Clin Immunol; 104(5)1079-83
  10. Eggleston, PA, Butz A, Rand C, et al. Home environmental intervention in inner-city asthma: a randomized controlled clinical trial. Ann Allergy Asthma Immunol 2005; 95:518-24