Chemical timber treatments carried out in British homes have come under renewed scrutiny as a result of research into Gulf War Syndrome. Recent US research into the Syndrome, published in the Journal of Toxicology and Environmental Health, has suggested that a "cocktail of chemicals", including pesticides and insect repellents, may be responsible. British researchers have now revealed that two of the chemicals under investigation are widely used in Britain - Permethrin is commonly used to treat woodworm in houses, and DEET (Diethyl Toluamide) is a constituent of many insect repellent sprays and creams. So people applying insect repellents to their skin and living in homes treated with permethrin-based timber treatments may be exposing themselves to the same combination of risks experienced by the Gulf War veterans. The extent of the risk is unknown; there has been no specific research undertaken on the potential problems of combining these two chemicals in the home.
The US study investigated the effects of combining permethrin and DEET, and found that mixing the chemicals can have serious side effects; clinical tests on chickens showed that each substance used on its own did not have significant impact, but combinations of both resulted in diarrhoea, weight loss, gait disturbances, body tremors and death.
The findings follow news that the Health and Safety Executive has launched an investigation into health problems attributed to chemical exposure, and come on top of a growing body of evidence that most remedial timber treatment in homes is not needed. Woodworm holes in floorboards, for example, often remain from insect attacks many years old; central heating dries timbers out, below the moisture level needed to support insect life or fungal attack. Dry rot, in particular, requires very high levels of liquid water, and is usually associated with some kind of plumbing leak; when the moisture source is removed the fungus dies, and chemical treatment is not usually necessary.
Building Society surveyors, however, usually recommend further investigation of timbers in older properties, and timber treatment firms called in for a free survey will often point to old woodworm holes as a reason for spraying. Timber treatments are thought to have been carried out in around four million dwellings, or one fifth of the total housing stock. Up to one quarter of the properties being sprayed, around 50,000 per year, are estimated to have been treated already, in some cases two or three times. The annual cost of this unnecessary work has been put at pounds 20m.
Lee Horton, of the Remedial Treatment Research Unit at South Bank University, said: "This unnecessary work is a scandal in itself, but the health implications are even more worrying; it is alarming to realise that large quantities of permethrin are being sprayed in homes which may already contain high levels of dieldrin or lindane, or both." Horton investigates properties in which chemical timber treatments have been specified, usually for the purposes of obtaining guarantees to satisfy mortgage conditions. He has found high residual levels of the pesticide dieldrin in houses where remedial treatment contractors have specified further spraying with permethrin. Dieldrin, an organochlorine, has been banned in the UK since 1989, because of its persistence and high acute toxicity, but no research has been done to investigate the possible health effects of combining existing dieldrin residues in buildings with fresh applications of permethrin. Chemical use within the home is of special significance because it is where people spend a large proportion of their time and, with the environment effectively sealed, people are shut in with their timber treatments for extended periods. Since toxic effects are proportional to the body weight of the recipient, babies and children are known to be especially susceptible to any potential hazards.
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