Dr Derrick Crump's research includes a survey of air quality in homes in England and developing methods to test chemical emissions from products such as paints and furnishings. We asked him our biggest questions around indoor air quality.

1. How big a problem is indoor air pollution?

We spend a lot of our time indoors; the average person spends about 90% of their time in buildings. Therefore pollutants in the air we breathe indoors are a major contributor to our lifetime exposure to air pollutants. In buildings (and vehicles) we are exposed to pollutants released to the outdoors, such as traffic exhaust fumes, that enter buildings through purposeful ventilation and other air ingress. In addition we are exposed to a wide range of pollutants generated indoors.

Studies of air quality in buildings have found that levels of a number of pollutants are commonly higher indoors than outside. Recent research has highlighted that chemicals released indoors that leave the building by ventilation are a significant source of pollution of the outdoor air in urban areas.

2. What are the most common sources of indoor air pollution at home?

There are a wide range of different pollutants and sources of pollution indoors. Most people are aware of the possibility of carbon monoxide release from faulty gas cookers and boilers, but normal operation of all fuel burning appliances and even candles are a source of gases (e.g. nitrogen dioxide) and particulates that should be appropriately ventilated to the outdoors. Chemicals are released from a wide range of products in our homes including paints and cleaning products where release is often apparent during use. There can also be long term emissions from construction, furnishing and consumer products that may not be perceived yet these are contributing to our exposure to pollutants.

Other sources include smoking or vaping indoors and in some areas of the country radon (radioactive) gas from the ground is significant. Biological pollutants such as dust mites and mould can also be a problem especially where there are issues of dampness indoors.

3. How does indoor air pollution affect our bodies and minds?

Different pollutants affect us in different ways. Carbon monoxide stops your blood from carrying oxygen around the body. At low levels this can cause headaches, dizziness, nausea, and shortness of breath, but at higher levels is fatal. Concerns about the health effects of particulates and nitrogen oxides released into the outdoor air such as from diesel vehicles have been well publicised and some exposure to these will occur indoors in our homes, schools and workplaces particularly in urban areas. This is likely to be particularly important for those suffering from illness and for the elderly and very young who may spend all their time indoors.

The indoor sources themselves may generate the same type of pollutants as outdoors (e.g. nitrogen dioxide) thereby having a similar health concern, but also generate different pollutants with different concerns. This includes chemicals with potential to cause effects such as sensitisation of our airways, provocation of asthma, and an increased risk of cancer. Dust mites and mould can be a particular problem for allergic individuals.

4. What are some simple changes that we can make that can reduce our exposure to indoor air pollution?

Check your gas appliances at least once a year. When they are well maintained the risk of carbon monoxide is much lower. Carbon monoxide alarms are readily available, and can be a life saver.

Make sure that you’re providing good ventilation for your home: check your bathroom and kitchen extractor fans regularly to make sure they are working well and that any filters are clear. Use trickle vents and opening windows to ensure the air is not stuffy and condensation is minimised.

If you’re purchasing products for the home, particularly when decorating, look for those that are labelled with regard to the emission of chemicals into the indoor air. Unfortunately there is no UK label (or pan European one) at this time but there are labels in France, Denmark, Finland and Germany for example. Increasingly products in UK stores carry these labels. Recently I purchased a flat pack bedroom wardrobe from a major DIY store and that had the Danish Indoor Climate Label giving me confidence it had been tested for emissions to indoor air. For some product types such as paints there are low VOC (volatile organic compounds) and zero VOC products available. Also if you're concerned, consider selecting fragrance free cleaning products and toiletries.

5. Is it better to have windows shut to keep the outside air out, or open them up to let the fresh air in?

Ventilation is really important to control damp that can contribute to mould, and to remove pollutants from your home.

If you live near busy roads or in an air pollution hot spot, it can be sensible to keep your windows shut at the highest risk times, such as around the morning rush hour. You may also be able to limit the opening of windows to rooms not facing a busy road. It can also be useful to be aware of when especially bad periods of air pollution occur and adjust your behaviour accordingly. There are a number of web sites and apps that can send you alerts when high pollution days are expected, including Defra.

6. Is indoor air pollution a concern in workplaces?

Workplaces have a lot of similar air quality issues to homes, although the exact pollutant mix will depend on the building characteristics and the nature of the work being carried out. There are legal standards for a range of chemicals and dusts in workplace air but these largely address industrial rather than office environments.

For all situations, good ventilation and good maintenance of equipment are really important to keeping levels of indoor air pollution as low as possible. Of growing interest is the impact of the indoor environment (including air quality) on the well-being and performance of the work force. As worker salaries dominate the cost of most businesses, the potential benefits for achieving an indoor environment that is both good for people and profits are increasingly a topic of board level discussion.

Dr Derrick Crump's career spans government, academia and the private sector. He has worked for 35 years as a consultant and researcher into provision of good indoor air quality, and published 175 scientific papers.

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