Sir, - Senator Mairin Quill's concerned response (July 21st) to the continuing deterioration in the quality of Ireland's waters is welcome but misleading. While there is no doubt that the ecological quality of many of the country's lakes and rivers has declined as a result of increased phosphorous loads, it is simply incorrect to lay blame for this solely on phosphate-based detergents.
Phosphorus from detergents will play its part in fuelling increases in biological production that underlie the ecological changes caused by nutrient enrichment of aquatic environments, but it is almost certainly a small part compared with the amount of phosphorus that enters waterways from application onto land of inorganic fertiliser, as well as animal manure and other organic wastes.
It is generally accepted among both independent researchers and government agencies that so-called diffuse run-off from land contributes the majority of nutrients to our inland waters. With increasing installation of phosphorus removal at sewage treatment works, the proportional contribution of phosphorus from diffuse sources can only become greater unless there is serious progress in measures to improve agricultural nutrient management practices.
Like the impact from phosphorus-based detergents, the effect on water quality of the recent rural environment protection scheme (REPS) to reduce nutrient run-off remains unquantified.
Nutrient enrichment of Ireland's freshwaters is a major, but multi-dimensional problem. The banning of phosphate-based detergents may be part of the solution, but these substances should not be a scapegoat in an environmental issue that requires a wider perspective, and perhaps difficult political decisions about how our landscape is managed. - Yours, etc.,
Dr Kenneth Irvine, Department of Zoology, Trinity College, Dublin 2.