The Mersey is the area most heavily polluted with mercury, discharging three tons of the toxic metal each year, the meeting was told, while the pesticide gamma- HCH, used as a wood preservative, is discharged mainly in the South-east.
The results come from the first comprehensive study of the quantity and origins of dangerous substances entering the seas around England and Wales. The pounds 1m survey was carried out by the National Rivers Authority.
Dr Jan Pentreath, chief scientist with the authority, warned that large quantities of 'organic tin' were being carried down rivers to estuaries, despite the 1988 ban on the use of a tin-based anti-fouling paint on small boats.
Tributyltin (TBT), the active ingredient in the paint, had leached into the waters around yachting marinas, killing oyster beds and causing female whelks to grow penises. Dr Pentreath expressed particular concern that nearly 20 tons of organic tin compounds from other sources found their way into coastal waters each year.
He warned that the principal source of most of the toxic chemicals was not industrial outfalls, but the collective input from sewage works and run-off from agricultural land into rivers. 'Controlling industrial discharges is only half the job, because the diffuse sources have a greater cumulative impact.'
Nothing could better demonstrate the wisdom of the Government's moves to amalgamate the rivers authority with the inspectorate, to form an environmental protection agency, than the data on sources of toxic chemical pollution, he said.
While the inspectorate's policy of integrated pollution control was effective in reducing pollution at source, the authority's focus on managing the catchment areas of rivers forced it to look at all the other, non-industrial sources of pollution.
A union of the two approaches could not come fast enough, Dr Pentreath added.Reuse content