For instance, the Drinking Water Inspectorate could have calculated that in 1992, supplies to around 14 million customers at times exceeded the legal limits on pesticides - but they didn't. Using the inspectorate's data, Friends of the Earth did.
Although the UK agreed in 1980 that water should be virtually free from pesticides, supplies to millions of people still exceed the legal limit at times. The water industry is spending pounds 1bn to sort this out - but remember it is the customers' money, so the polluted, rather than the polluters, are paying for this clean-up. A tax on pesticide manufacture or use might be a fairer way of funding this water treatment.
Of course, prevention is always better than cure; and pesticides that pollute drinking water sources should be banned. A recent study commissioned by the Drinking Water Inspectorate has shown that restrictions on pesticide use in the vicinity of water sources could well be cheaper by millions of pounds than treating the water, even taking into account extra costs to farmers.
The Government has powers to enforce restrictions on pesticide use near water sources, but these powers have never been used. Instead the Government is lobbying hard in Europe to relax the limits on pesticides in drinking water, based on World Health Organisation guidelines.
But consumers don't want pesticides in their drinking water, whatever the scientific assessment. And the WHO's definitions are not comprehensive.
Curiously enough, while the Government is happy enough to promote higher levels of pesticides in drinking water based on WHO recommendations, there is a rather different attitude to the problem of lead in drinking water. Lead is almost universally acknowledged as toxic at any level, but the UK is still sticking firmly to the current legal standard for lead - despite recommendations three years ago from the WHO for new limits some 5 times more stringent. This really is trying to have it both ways.
To add insult to injury, the consumer can do little about the supply of sub-standard water as long as agreements have been reached between the Secretary of State for Environment and the water company. Water legislation prevents customers from taking action in court - only the secretary of state can do that, a move which neatly protects the privatised water companies from legal action.
Friends of the Earth has been successful in speeding up the removal of pesticides by challenging some of these agreements in court, and has sought leave to appeal to the House of Lords over the legislation. But the real thrust of our campaign has been to protect water sources in the first place.
In response to constant campaigning pressure, two of the most commonly occurring weedkillers, atrazine and simazine, were partially banned in 1993. But the piecemeal strategy has a drawback: it seems likely that users are switching to other pesticides with potential for water contamination. It underlines the point that there is no substitute for a fully comprehensive ban.
The author is water campaigner for Friends of the Earth.Reuse content