Nearly a quarter of organic fruits and vegetables contain pesticides, according to a new study by an American consumer group.

Consumers Union studied government data and found pesticide residue on 23 per cent of organic produce. That compares with residue found on 75 per cent of conventionally grown produce.

"Less is better...lower levels of residues are better than higher levels," said Edward Groth, senior scientist of Consumers Union. The group also publishes the magazine Consumer Reports.

The study is published in this month's journal Food Additives and Contaminants.

The report says most of the residue was of organochlorine pesticides, which include DDT and chlordane. These are chemicals plants can soak up from the soil decades after the products were used.

According to Brian Baker, a researcher at the Organic Materials Review Institute who participated in the study, "organic" is not a pesticide-free claim. Besides spray-drift from adjacent farms, there can be soil or irrigation-water contamination.

'Organic production doesn't mean pesticide-free production'

Organic crops are a small percentage of the North American market, less than five per cent, but the industry is growing rapidly. Sales of organic food are expected to grow by 20 to 30 per cent this year.

"Consumers need to recognize that organic production doesn't mean pesticide-free production," says Carl Winter, a food toxicologist at the University of California.

'None of the choices available on the market is completely free of pesticide residues'
Organic farmers tend to use special pesticides approved for their crops such as sulfur and bacteria sprays. But scientists have expressed concerns about the occurence of mycotoxins on organic produce and the use of manure as fertilizer, which could carry harmful bacteria. Mycotoxins are produced by fungi and can be prevented with the use of conventional pesticides.

In Canada, to be "certified organic" the product has to meet a comprehensive set of rules overseen by the Canadian General Standards Board. The standards are voluntary, except in Quebec where there are large fines for noncompliance.

To qualify as certified organic, a field of corn, for example, would have to:

  • be free of commercial fertilizers for three years
  • be free of herbicides for three years
  • use seed that is not from genetically modified seed
  • include a buffer zone between organic plants and non-organic plants