About 20 per cent of the food we eat is contaminated with trace amounts of pesticides, even though most of them have been banned for decades, a new report says.

A typical diet features between 60-70 hits daily of toxic chemicals such as DDT, dieldrin and dioxin, according to the study published in today's edition of the Journal of Epidemiology and Community Health.

The San Francisco-based Pesticide Action Network, which conducted the analysis based on U.S. government data, said that finding up to five chemicals in popular foods such as salmon, cheese and cucumbers is routine.

The group said that adults who eat a well-rounded diet may be ingesting up to 90 times the acceptable limit for exposure to a group of chemicals known as persistent organic pollutants. POPs are described as a class of chemicals that are "among the most insidiously dangerous compounds ever produced" because they persist in the environment for years and can build up in the body's fatty tissues.

The POPs most likely to be found in food, DDT and dieldrin, are pesticides that have both been banned in North America since the early 1970s.

The Pesticide Action Network identified the Top 10 foods contaminated with POPs, in alphabetical order: butter, cantaloupe, cucumbers, meat loaf, peanuts, popcorn, radishes, spinach, summer squash and winter squash.

The group said the typical Thanksgiving dinner consumed by Canadians over the long weekend was likely high in chemical content.

The authors calculated that a typical holiday meal consisting of 11 ingredients -- notably turkey, stuffing, gravy, potatoes, green beans, squash, pickles and pumpkin pie -- featured 38 "hits" of POPs.

A second report, published in the same edition of the journal, found that three-quarters of conventionally grown produce and one-quarter of organically grown produce contain chemical residues.

The analyses focused on 12 chemical compounds targeted to be phased out in the Stockholm Convention on POPs. Canada is one of only 22 countries in the world to have ratified the convention.

"Prevention of further food contamination must be a national health policy priority in every country," said PAN's Kristin Schafer, the principal author of the report. "Early ratification and rapid implementation of this treaty should be an urgent priority for all governments."

In a related commentary in the same edition of the journal, Tim Meredith of the World Health Organization's chemical safety program agrees that it is important for all countries to ratify the convention on POPs.

At the same time, however, he accuses the environment group that prepared the report of fear-mongering, saying that while 20 per cent of foods may contain extremely low levels of these chemicals, "there is no scientific consensus that such levels are hazardous to most humans."