Pesticides and the Environment

The use of pesticides that are POPs led to not only to contamination of the local environment but also to regions remote from their source. Their volatile nature meant they were transported for very long distances on air currents. As a result, substantial levels of POPs even contaminate the Arctic where they have never been used.

The presence of pesticides in groundwater, surface water and drinking water is problematic and costly. For instance, in the EU, many groundwater supplies exceed the maximum admissible concentration for individual products and total pesticides. In the US, many pesticides are found in groundwater. Between 1971 and 1991, 68,800 wells were tested and 9,900 had pesticide contamination which exceeded Environmental Protection Agency (EPA) standards for drinking water.

Pesticides and Wildlife

The use of pesticides has undoubtedly lead to adverse impacts on many species of wildlife although it has often taken years to reach an understanding of the impacts. Adverse impacts can occur in a variety of ways such as direct contact causing death or injury, contamination of food sources or removal of food sources. Effects of pesticides on wildlife have been reported in most classes of animals including bees and other beneficial insects, birds, fish, amphibians, reptiles and mammals.

Some organochlorine pesticides which are POPs are known to have caused dramatic population declines of birds of prey in Europe and the US in the 1950s to the 1970s. DDE, a breakdown product of DDT was implicated in egg shell thinning and this effect resulted in crushed eggs and breeding failure of many sensitive birds of prey and fish-eating birds. The bioaccumulation of the pesticides aldrin and dieldrin in birds of prey also caused deaths and population declines. Since the use of these pesticides was banned, the affected species have gradually undergone recovery although in some species recovery has been slow.

Other bird species continue to be affected by industrialised farming practices in Europe, particularly the UK. The abundance and diversity of many species of birds have fallen over recent decades. The problem is that pesticides have led to the reduction of weeds from arable fields and margins with an adverse impact on the birds that rely on the weeds for seeds or insects. Declines in the grey partridge were clearly shown to be linked with herbicide use. Subsequently, the declines of a further 20 or so species have been associated with changes in the abundance of food in intensively farmed regions.

In the UK, cypermethrin, a synthetic pyrethroid insecticide, has been used in sheep dips but was recently banned because of adverse effects on wildlife. Many incidences of the pollution of watercourses as a consequence of use in sheep dips occurred and this resulted in the killing of vast numbers of aquatic invertebrates.