Do people respond to air pollution forecasts?

What is it about?

In a report entitled "Every breath we take - The lifelong impact of air pollution", the Royal College of Physicians and the Royal College of Paediatrics and Child Health recommend developing technology such as smart monitors that empower individuals “to check their exposure and to take action to protect their health”. But do people actually do that? Do people respond to information about air pollution and show avoidance behaviour? I address this question in this paper. I investigate responses to air pollution warnings in England. First, I looked for indirect evidence of avoidance behaviour by investigating the relationship between air pollution warnings and hospital emergency admissions for respiratory diseases in children aged 5 to 19 years. Using regression analysis, I essentially compared days with a certain level of air pollution for which an air pollution warning was issued with days with the same level of air pollution for which no air pollution warning was issued. If parents and children do respond to air pollution warnings by reducing their exposure or taking other preventive measures, we expect fewer emergency hospital admissions on days for which an air pollution warning was issued compared to days with the same level of air pollution but no warning. Looking at all respiratory admissions I found no effect. Looking at a subset of respiratory admissions - admissions for acute respiratory infections such as pneumonia and bronchitis – I also found no effect. Only when I examined another subset of respiratory admissions, namely admissions for asthma, did I find that air pollution warnings reduce hospital emergency admissions, by about 8%. It is less costly for asthmatics to respond to an air pollution warning. Standard advice for asthmatics is to adjust the dose of their reliever medicine and to make sure they carry their inhaler with them. Other types of respiratory disease require far more disruptive preventive measures such as staying indoors, making the cost of responding to air pollution warnings larger than the perceived gains. Looking for direct evidence of avoidance behaviour, I examined daily visitor counts to Bristol Zoo Gardens. Most people will consider a zoo visit to be an outdoor activity and therefore susceptible individuals might adjust their plans to the air pollution forecast. I found that lower temperature, more rain and higher wind speed reduced visitor numbers but found no effect of air pollution warnings on visitor numbers. Only when I looked at members – visitors who have an annual membership that entitles them to unlimited visits for a year – did I find that air pollution warnings reduce visits by about 6%. For members it is less costly to respond to air pollution warnings as they tend to be local residents who can just drop in for a quick visit. Thus, the perceived gains from postponing a visit are more likely to exceed the cost of postponing than for day visitors.

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Why is it important?

My results show that whether individuals respond to air quality information depends on the costs and benefits of doing so: where costs are low and the benefits clear, responses are higher. Empowering people to check their exposure as recommended by the Royal Colleges may not bring about the desired prevention of adverse health effects from air pollution. The report's other recommendations aimed at lowering air pollution levels are more likely to succeed in preventing ill health.