Outdoor air quality: A primer for BC physicians

Two new information tools are available to assist physicians in responding to patient concerns about air pollution and to help interpret public air-quality health messaging. The primer offers essential background on air pollution and its effects on health and provides a series of tips on how to decrease vulnerability to those effects. An appendix provides a guide to interpreting BC air-quality advisories and the new Air Quality Health Index. The primer, with its many web-accessible references, can be downloaded at www.bc.lung.ca or www.bccdc.ca. It was mailed to BC physicians this summer. Here are some highlights.

The health effects of air pollution
Air pollution affects the health of British Columbians. Health effects have been demonstrated even in areas with relatively low levels of air pollution.

Epidemiologic studies of long-term (months to years) exposure to air pollution show increases in risk of death from lung cancer and cardiopulmonary diseases. Health effects associated with long-term exposure include:

• Accelerated development of atherosclerosis.
• Increase in systemic inflammatory markers.
• Impaired lung development in children.
• Increased incidence of asthma and asthma exacerbations.
• More frequent preterm births and low birth weight babies.
• Increased rates of otitis media.

Short-term exposure (hours and days to weeks) to air pollution has been associated with increased hospitalizations and deaths due to cardiovascular and respiratory causes. Generally, respiratory effects have been associated with exposure to ozone and cardiovascular effects with exposure to fine airborne particles. Health effects associated with short-term exposure include:

• Increased rates of myocardial infarction in those with risk factors for cardiovascular disease.
• Increased incidence of cardiac arrhythmia.
• Exacerbation of obstructive respiratory illness (e.g., asthma and COPD)
• Respiratory inflammation and irritation.
• Reduced lung function.

For most people air pollution may be a relatively minor risk, especially over the short term. However, studies of large populations indicate measurable health effects on susceptible individuals and substantial public health impacts. Controlling underlying cardiac and pulmonary diseases decreases the effects of air pollutants.

Health burden for BC residents
A 2008 Canadian Medical Association estimate for BC projected 306 premature deaths, 1158 hospital admissions, 8763 emergency department visits, and 2 526 900 minor illnesses related to air pollution during 2008. The majority of these are attributable to long-term exposure to air pollutants.

Ways to lower exposure outdoors
Commuting is a significant contributor to air pollution exposure; reducing time spent in traffic can reduce exposure. When considering where to live and work, people should ideally choose a location that is more than 150 metres away from major roads. 

High pollutant concentrations can be found up to 750 metres from truck routes. Walking or exercising away from busy roads or smoky areas can reduce exposure to particulate matter. In the summer, engaging in outdoor activity in the early morning or later evening may reduce ozone exposure.

Pollutants and staying indoors
Some outdoor pollutants efficiently penetrate indoors. Installing HEPA filters in forced-air furnaces may reduce indoor exposure to particles. Ozone concentrations are usually lower indoors. Stand-alone air cleaners can reduce particulate levels, but it is important to select non-ozone-generating models. See www.arb.ca.gov/ research/indoor/o3g-list.htm.

Air pollution, medication, and diet
Optimal use of cardiac and respiratory medications can offer some protection against air pollution related effects on health. Omega-3 fatty acids and vitamins C and E, taken as supplements, may limit the effects of exposure to high levels of air pollution. However, there are currently no established recommendations for the routine use of specific dietary supplements to prevent the effects of air pollution.

Air-quality messaging
The Air Quality Health Index (AQHI) is a tool recently introduced to indicate the immediate risk to health of current and near-future levels of three monitored air pollutants.

Acknowledgments
This primer was prepared with the assistance of Dr Michael Brauer, Dr Chris Carlsten, and Ms Nina Clark (UBC School of Environmental Health and Centre for Health and Environment Research); Drs Tom Kosatsky, Ray Copes, and Deena Hinshaw (BCCDC); Dr Menn Biagtan (BC Lung Association); and Ms Natalie Suzuki (Ministry of Healthy Living and Sport).