Chemical and particulate pollutants

Chemical toxicity in buildings is a complicated subject, due to the number of chemicals present in modern houses and their potential interactions. Many of these chemicals are from the outside, and many are imported into the house by occupants in the form of cleaners, hairsprays, furnishings etc. However a large amount of chemicals and particulate pollutants come with the building fabric and the process of construction.

At the beginning of the 20th century there were probably less than a hundred chemically different materials used in common construction. By the end of the century there were over 50,000. However this does not necessarily mean a more toxic environment. Traditional paints and glues were particularly toxic, and we are well rid of them. However we are now in a different situation for two reasons:

• The unknown effect of many of the new chemicals on human health on their own or in combination with each other or with microbiological pollutants
• The effect of airtightness

So long as UK buildings have huge air leakage, there is a reduced danger from chemical and particulate pollution in buildings (and indeed also from microbiological pollutants). This is not only as regards pollutants from the building fabric and process but also from furniture and fittings and from cleaning and body care products (some of which contain chemicals banned altogether in building products such as paints).  However with air tightness being introduced the danger from all toxic materials increases.

The CIBSE TM40 2006 document on Health Issues in Building Services names 25 chemicals and particulate types which are understood to pose a threat at different levels to human health. The most dangerous of these are probably carbon monoxide, formaldehyde, nitrogen oxides and PM10 particulates (particles under 10μm in diameter) . Interestingly these and other chemical pollutants in buildings not only have an effect on their own but are important irritants for allergic reactions as well. Allergic reactions are nearly all caused by protein based materials (sensitizers), but actual allergic incidents can be set off by chemicals and particulates. For example an increase in PM10 particulates of 10μg/m3 has been shown to increase asthmatic incidents by 3%.

Some pollutants such as VOCs are generally found at levels much lower than the present perceived health risk levels (although benzene was found to exceed health guidelines in 50% of dwellings in a recent study) , but can increase hugely during activities such as decorating or cleaning. It is also not certain what the effects of combining VOCs and other chemical such as ozone may be in terms of human health.

This uncertainty calls for a much more precautionary approach than we have taken up until now. It requires that we really look to ensuring proper high quality ventilation and more importantly to removing possible pollutants, microbiological, chemical and particulate at source. Since one of the main sources of these pollutants is the building fabric and the process of construction and maintenance it is critical that non-toxic materials are used in construction wherever possible. This is particularly important if one considers that pollutants from furnishings, appliances, body care products can be removed easily once the source is identified, whereas it is almost impossible to remove a toxin like copper chrome arsenic (as commonly used in treatment of timber) or formaldehyde (from chipboard and plywood) from the structural fabric of the house without actually taking the house down.

Next: Comfort in Buildings