Arsenic. Mercury. Pesticide residues. These toxins make their way into food, but experts continue to disagree over how much of a health threat they pose. A new study from UC Davis and UCLA concludes that people — particularly preschool children — are being exposed to too many of these toxins at concentrations that have been determined to be unhealthy.

The study also offers several ways for concerned people to lower their exposure to these toxins, ranging from the relatively simple strategy of eating less meat and dairy but more fruit and vegetables to buying organically grown milk and produce.

The most disturbing finding was that pre-school children were the age group with the highest exposure to six of the 11 toxic compounds looked at in the study.

Of the eleven toxic compounds studied, benchmarks (exposure levels considered safe) were exceeded by all children for arsenic, dieldrin, DDE and dioxin. And benchmarks were also exceeded by over 95% of preschool-age children for acrylamide and by 10% of preschool-age children for mercury. These compounds have been linked to cancer, developmental disabilities, birth defects and other adverse medical conditions.

While there is some uncertainty about what constitutes a safe exposure level for these toxins, there is broad agreement that they're much more dangerous to children because of their lower body weight and developing brains and nervous systems.

The study used data from a 2007 study called SUPERB, which surveyed households in California about their dietary habits, including 207 pre-school age children (2-4) and 157 school-age children (5-7). The researchers were able to tease out estimates of exposure levels to various toxins by concentrating on consumption of only 44 foods, those known to be extremely high in a particular toxin. For example, when it comes to mercury, you don't need to know dietary information on all mercury containing foods, just major sources such as tuna, to build a good estimate of a person's mercury exposure.

It is notoriously difficult to pinpoint a safe level of exposure for many contaminants that end up in food. For one thing, the experiments that might establish safe levels are almost always unethical and cannot be conducted.

The researchers looked at levels of eleven toxic compounds: three metals (arsenic, lead and mercury); three pesticides (chlorpyrifos, permethrin and endosulfan); four persistent organic pollutants (dioxin, DDE, dieldrin and chlordane); and the neurotoxin and suspected carcinogen acrylamide which is found in cigarette smoke and certain foods cooked at high temperatures, like potato chips.

Perhaps the most disturbing finding was that pre-school children were the age group with the highest exposure to six of the 11 toxic compounds looked at in the study.

It is notoriously difficult to pinpoint a safe level of exposure for many contaminants that end up in food. For one thing, the experiments that might establish safe levels are almost always unethical and cannot be conducted. This is one reason that there's so much bickering among scientists over whether foodborne toxins do or do not present a major health threat.

Avoiding Exposure

For people who are concerned about exposure to toxins in food, the researchers offer several strategies to lower exposure. About the simplest strategy is to eat a varied diet. This helps prevent accumulating too much toxin from a single food group. A much more proactive strategy is to buy organic produce. Even studies that question the usefulness of switching to organic produce agree that organic produce is much less likely to be contaminated with pesticides.

The researchers found particularly high pesticide contamination in thirteen types of produce: tomatoes, peaches, apples, peppers, grapes, lettuce, broccoli, strawberries, spinach, dairy, pears, green beans and celery. Buying organic produce is one way to lower pesticide exposure in a single stroke.

The researchers also suggest lowering meat consumption and switching to organic milk as ways to lower exposure to persistent organic pollutants like DDE, which tend to accumulate in animal fat.

Probably the easiest way to lower acrylamide exposure is to avoid or minimize eating potato chips, tortilla chips and French fries.

The researchers also think their study results should cause both industry and consumers to think long and hard about current food policy — how we grow our food and the approval process for chemicals of questionable toxicity. The persistent organic compound DDE comes from DDT that was sprayed as an insecticide decades ago. DDT use was banned in the U.S. 40 years ago, but we're still dealing today with the consequences of having sprayed so much of it. How many similar compounds are we introducing into the environment now that will continue to keep on giving in decades to come, even if their use were to cease today?

An article on the study was published in Environmental Health and is freely available in PDF format.