One of the prime motivators for buying organic food is the desire to minimise the intake of dietary pesticides, but new research from the US indicates that 23% of organic fruit and vegetables contains pesticide residues.

This contrasts with nearly 75% of conventionally cultivated produce, revealed a study of government data led by the Consumers Union, publisher of Consumer Reports. Pesticides do not necessarily make any of the produce in question unsafe, particularly since the levels of pesticide residues rarely come anywhere near the limits defined by the Environmental Protection Agency.

Much of the residue found in organic crops was of organochlorine pesticides, chemicals - including DDT and chlordane - that plants can soak up from the soil decades after the products were used. Other chemicals could have been applied to the crops improperly or drifted onto the organic fields from adjacent farms, the scientists leading the study said. Mislabelling and fraud accounted for some of the organic samples that tested positive, but the study downplayed this issue.

The study, which was published in Food Additives and Contaminants journal today [Wednesday], was based on data from the Agriculture Department and the state of California, as well as sampling by the Consumers Union scientific researchers. Researchers looked at test data on residues on more than 94,000 organic and non-organic food samples of around 20 different crops tested over nearly a decade. They said they did not take into account the many special pesticides approved for organic crops, including sulphur and bacteria sprays.

For further information on the study, click here.

For more information on the journal in which the study is published, click here.