Living near a busy road can kill you

Early April saw some unusually smoggy days across much of Western Europe, resulting in widespread media attention to air pollution.
(See, for example, here, here and here.) On one day, air quality in some parts of London was worse than in Beijing. Further attention has been drawn to the issue by a number of recent official reports, including one from the World Health Organisation, which has declared that air pollution is now the world’s biggest single environmental threat to health.

As has been noted, media coverage can give a misleading picture of the health risks of air pollution. Coverage tends to focus on short-term peaks, such as those seen recently in Western Europe, but the health risks of air pollution are primarily related to long term exposure, and show no ’safe threshold’ effect. Elevated baseline levels of pollution are thus more of a problem than occasional peaks.

There’s another important aspect of air pollution that often goes unnoticed; small geographical differences can have a marked effect on exposure to air pollution and thus on risk of adverse health effects. For example, living near a busy road appears to substantially increase air pollution-related mortality. A study published last year in the Lancet (press summary here) investigated the effects of very local differences in air quality on mortality by pooling 22 European cohort studies. The investigators found that an increase in average annual fine particulate (PM2.5) exposure of 5 µg/m3 was associated with a 7% increase in the risk of dying from all natural causes. This is approximately the difference between living on a busy urban road and living in a traffic-free area. The finding was robust in the face of correction for various possible confounding factors.

Given the ubiquity of busy roads and the reported magnitude of the effect, this is an important issue. These findings suggest that, not only is air pollution a serious health threat in terms of the amount of morbidity and morality it causes, there is also substantial inequality in the distribution of these health costs – more inequality than is apparent from city-wide data. This plausibly strengthens the general case for seeking ways of  reducing air pollution, particularly since inequality in exposure to air pollution probably maps on to socio-economic inequality. (In many places, one has to be well-off to live in a less polluted area.) Air-related ill-health may thus tend to compound other forms of disadvantage.

The findings also raise at least three ethical questions.

The first concerns information. Should more be done to bring the possible health effects of living near a busy road to public attention? My admittedly anecdotal observation is that people who can afford to avoid living near a busy road tend to do so, but they do so not because of concern about the health effects of air pollution, but because of concern about noise or aesthetic considerations. Many people seem to be unaware of the health costs of living near a busy road or intersection, or at least, these considerations aren’t near the forefront of their mind when deciding where to rent or buy accommodation. If this is correct, then, given the substantial harmful effect, there may be a case for public health campaigns in this area.

Second, these findings raise the question of whether specific steps should be taken to protect those who live by busy thoroughfares. It’s now fairly widely accepted that wider society should be seeking to develop less polluting forms of transportation, and many would argue that individuals should also be constraining their driving behaviour in the name of improving air quality. But perhaps those who use or benefit from roads should also be supporting more specific initiatives to help protect those who have to live beside them. For example, lower urban speed limits (or voluntarily driving more slowly) could help to solve the problem, and there may also be ways of reducing the extent to which pollution enters homes and workplaces. It might, for instance, be possible to design houses which harness principles of fluid mechanics to ensure that airflow tends to be in a streetward direction. Or perhaps industrial strength air purifiers could be used to mitigate indoor air pollution. Of course, these home-modification options could be pursued by inhabitants themselves, but they’re likely to be expensive, and it’s not clear why inhabitants, rather than those who produce and benefit most from the pollution, should bear the cost.

It could be argued that those who live near busy roads have voluntarily accepted the health risks that come with this. This may be true in some cases, but in others it seems a stretch. I noted above that, in some places, homes in unpolluted areas come at a premium and are thus beyond the reach of many. In such circumstances, living on a busy road is not always a choice. But even if it is a choice, it’s not clear that it’s a choice that excuses others from taking preventive measures. I’ve speculated that many people seem to be unaware of the heath effects of living near a busy road. Given that there is not a large amount of public information on the issue, this ignorance seems blameless. If people are blamelessly ignorant of the health effects of living near a busy road, it’s difficult to see how their choice to do so could absolve others of any responsibility for helping to improve the situation.

Finally, there’s the question of how knowledge about the health effects of traffic should be taken into account in urban planning. A fairly common practice in city planning is to pick out one of a number of similarly sized roads to serve as an arterial route, while steps (e.g. judder bars) are taken to ensure that the others become quieter routes for local residents. This strikes me as frequently unfair to those whose road happens to be picked for ‘arterialisation’, who will typically suffer an increase in noise and, if house owners, a fall in property value. This unfairness becomes much more acute if there’s also a substantial health risk attached to one’s road becoming busier. Perhaps, to combat such unfairness, an effort should be made to compensate for the health effects of such planning-induced traffic changes. Or perhaps urban planners should pick, as new arterial routes, roads that run through areas that are otherwise relatively safe from an environmental health point of view.

Of course, all of these questions would become less urgent were it possible to generally reduce the polluting effects of transportation, and small-scale geographical variations in air quality probably strengthen the case for seeking to do just that.

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