Fiona Prismall explains the often over-looked risk of indoor air pollutants and why we may see a shift in the influence this has on planning decisions in the future.
I recently wrote about the implications of air quality improvements attributed to reduced activity during lockdown. In that article I focused on changes in outdoor air quality and what the headlines really mean; but now as we move in to our new normal, carrying with us a range of lifestyle changes, we need to consider the flip side of that coin – the risk of exposure to harmful indoor air pollutants instead.
For many of us, our ‘pre-COVID’ lives involved leaving our homes and commuting to work each day to spend time in another indoor space, such as an office, workshop, factory, shop, café or restaurant. During the evenings and at weekends, we might have spent time in a variety of other indoor spaces, such a gym, restaurant, pub, theatre or a cinema.
Except for key workers, the Government required us to stay at home during the height of the lockdown with only one hour outside allowed for exercise. Even as the lock down eases, the Government is still advocating that people work at home wherever this is an option. For many of us, this means we will have spent more time at home than ever before. The sources of outdoor air pollution are relatively well known, and most people are now aware of the health-impacts associated with ambient (or outdoor) air pollutants. But fewer people will be aware that even when we are inside, we can be affected by air pollutants.
This shouldn’t really be a surprise if we think about it: we don’t generate air inside our buildings; it is brought in from the outside by one means or another and that may be by natural ventilation (e.g. windows, air-bricks) or mechanical ventilation. If the whole area has high outdoor air pollution levels, this will permeate the interiors of naturally ventilated buildings. For mechanically ventilated buildings, steps can be taken to try to place the air intakes away from places where outdoor pollution is highest, or filters can be used. Our air quality assessments help with the design of these mitigation measures by forecasting the pollution concentration levels at the different building façades to guide developers in understanding the best location for air intakes.
On top of whatever quality air is brought in from outside, is the air pollution created within our indoor spaces. These pollution sources include heating and cooking appliances but can also include paints, coatings, cleaning products, carpets and upholstery. Often not widely known, the air pollutants generated by indoor sources can be just as harmful as those created outside by traffic. Their effects can be magnified in buildings with poor ventilation because these pollutants are trapped within a confined indoor space. For example, when a scented candle is lit, indoor levels of highly harmful fine particulates can be seen to rise to thousands of microgrammes per cubic metre; compared to levels outdoors that are mostly in single figures.
The Department for Environment Food and Rural Affairs’ Clean Air Strategy 2019 dedicated an entire chapter to actions to reduce emissions at home, stating that “Awareness of the exposure that takes place in the home is currently very low. The government’s objective is to raise awareness of the potential impacts of air pollution at home and ensure that consumers are armed with reliable information enabling them to make informed choices to protect themselves, their families and their neighbours.” At present though, the World Health Organisation and Public Health England both set guidelines for pollutants that apply in any indoor space (i.e. in workplaces and in homes) but they do not provide assessment levels for all the substances that can be found in an indoor environment. The Control of Substances Hazardous to Health Occupational/Workplace Exposure Limits provide assessment levels for a wider range of pollutants but these are generally set at higher levels as they apply to healthy individuals working in industrial settings. In other words, these levels might not be appropriate for everyone.
Our way of living has changed since March 2020 and may continue to be very different for some time to come. This change in lifestyle brings a change in the way that we are exposed to air pollutants. We may have been less exposed to outdoor air pollution (due both to a reduction in emissions and because we have been spending less time outside) but this will have been balanced against an increased exposure to indoor air pollution. Whether this has resulted in a net benefit, or a net worsening of exposure will be very dependent on the location, the home and the lifestyle choices of the occupiers. However, we may want to bear in mind that poor air quality in our homes – identified as a problem in the government’s Clean Air Strategy – is likely to become rather more important with the population likely to work from home more in the future. We may see a shift in the concerns of planning decision-makers to reflect this greater influence of indoor air on residents’ health.
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