There are millions of tons of pesticides and fertilisers used to grow crops across the world. Pesticides aim to kill pests, particularly insects (insecticides) and weeds (herbicides). But most of these chemicals miss their targets, and end up in air, water, land - and food. Some of these pesticides build up in concentration down the food chain, ending up harming other organisms many miles away.

Concerns were raised in the 1960s when it was found that organochlorine pesticides, like DDT, were very persistant. Instead of degrading they accumulated in the food chains of animals, building up in birds of prey. They weakened the shells of their eggs resulting in a serious decline in their numbers. Similar fears are being raised now in relation to the second generation of rat poisons (secondary anti-coagulants or 'super warfarins'). While there is no evidence of damage, there is evidence that they are accumulating in the food chain as they are more persistant than their predecessors. (more from English Nature)

The UK was criticised by the Organisation for Economic Co-operation and Development (OECD) in its Environmental Performance Review (2002) (pdf). The UK uses about 0.6 tonnes of pesticide for every square kilometer of land - about twice the EU average.

In the UK the water industry spends £120 million cleaning pesticides from water. For full report (pdf) from UK Gov visit defra.

Pests develop immunity to the chemical pesticides and so greater quantities of chemical poisons are needed, at the same time many of the pesticides persist in the environment. Imported foods may have been produced using chemicals now banned in the EU owing to their toxicity.