Past and current uses of chemical treatments to control or eradicate fungal and insect infestations in buildings have led to a number of reported cases where occupants and users of these buildings have suffered various physical symptoms. The role of chemical treatments, whether as biocides, fungicides or insecticides, has therefore come under scrutiny, and various countries are now reviewing their use in favour of a more benign approach to the management of decay in buildings.
Growing concern for the environment and the health of those treating, or living in treated, buildings has also led to changes in the way we perceive and deal with buildings and building defects. The conventional approach to survey, defect diagnosis and remediation has to be re-thought and placed in the context of a wider environmental agenda.
This presentation provides evidence for how historic chemical treatments may have harmful effects on the health of the building and its occupants, and considers the implications of such treatments for those charged with specifying or undertaking works to the fabric of affected buildings.
There is a clear link between healthy buildings and healthy people. The use of chemicals raises the following issues.
Chemical treatments are used for the control or eradication of fungal infections and insect infestations in homes or the contents of buildings including museums and galleries.
The residues from these treatments are not widely considered or reported, and dealing with them is not normally part of the service provided by the building remedial industry. But they have wide implications for both home-owners and property professionals, whose responsibilities include inspecting and refurbishing existing buildings, duties of care, maintaining professional indemnity insurance and the necessity of identifying previous chemical treatments. Currently growing environmental awareness have raised concerns about the use of harmful materials in the construction industry, and how effectively these problems are addressed by health and safety legislation.
The following statistics give some indication of the extent of chemical treatments used. In the United States, 75 per cent of households used at least one pesticide product indoors during one year, and there were measurable levels of up to a dozen pesticides found in air inside homes.
Of buildings in the UK, approximately 100,000 remedial treatments are conducted annually (1983). 150,000 premises undergo in situ remedial timber preservation treatment per annum (1989). An estimated four million dwellings, or a fifth of the total housing stock has been treated in the last 25 years, with 20-25 per cent of treated properties receiving multiple treatments.
However, the total number of buildings that have been, and are being, chemically treated, whether professionally or otherwise, is probably unknown, as are the potential risks to health of chemical treatment residues.
It must be asked whether the good practice guides drawn up by the Health & Safety Executive and the British Wood Preserving and Damp-proofing Association, intended to protect the building and people's health, are, in fact, implemented.
According to BWPA, when remedial treatment is being carried out, floor coverings, furniture and soft furnishings should be removed, water tanks should be protected, the thermal insulation in roof voids should be removed or protected, the electrical circuits within the treatment area should be isolated, and rubber-covered cable, cable ends and junctions should be protected against the ingress of treatment fluids. People not carrying out the treatment should be excluded from the immediate vicinity should be kept out during and immediately after the spraying.
According to the HSE's 1989 guidelines, to avoid the potential hazards to health, safety and the environment arising from in situ remedial treatment of timber, everybody should be informed about the products to be used and the risks involved; the possible need to evacuate the building, or to isolate the affected areas, should be investigated.
In their 1991 guide to good practice, the HSE go further. They give details of the special precautions needed and evacuation procedures of occupied buildings, and advance evacuation periods. There are special precautions for people with respiratory problems or for the very old or very young. Specialist advice from a medical practitioner may be needed for occupants before the work is carried out. The supervisor of the work is charged with checking whether other occupants of the building, or in nearby properties, suffer from respiratory conditions or allergies that might be triggered by the work. If, despite all the safeguards, a potential health risk remains, and an appropriate evacuation is impracticable, the supervisor is to seek non-pesticidal alternatives for the remedial work.
But how often are these questions asked and the checks made? And how often are non-pesticidal treatments preferred in practice?
There are a number of factors influencing subsequent treatment residue levels. If the building has a traditional form, there is greater air movement through natural leakage and infiltration. There may already be a build-up of earlier chemicals. Loft insulation, carpets and furnishings may provide reservoirs and sinks of chemicals, and the building materials and finishes may be more or less absorbent.
The environment within the building also influences residue levels: ambient temperatures, levels of dust, the air exchange rates with the outdoors, and those caused by the diaphragm action of suspended floors and ceilings.
According to the World Health Organisation's European Charter on Environment and Health every individual is entitled to 'an environment conducive to the highest attainable level of health and wellbeing'; public policy that 'the health of every individual, especially those in vulnerable and high-risk groups, must be protected'.
A holistic approach should be adopted to building conservation. Ideally, buildings should work by themselves, and prevention is better than cure. Greater understanding of the mechanisms of deterioration and decay is needed, and better information on past and present chemical treatments and associated treatment residues.
[As published in PEX Newsletter No.4, September 1999]