Core issues are whether there is a safe level of residue and what risks pesticide residue pose.
Pull up to your local farm stand this time of year and consider your choices: fresh strawberries, broccoli, lettuce, rhubarb, peppers. Just lately, native blueberries, raspberries and melons have arrived.
All of it, of course, is good for you, but there is the lingering thought: What about the pesticides?
The presence of more organic products in major supermarkets and at farmers' markets makes you wonder: Would buying organic do more to protect your health? And how much should we worry about the dangers of pesticides?
It all depends on who you talk to. Many a food toxicologist or government official will tell you not to worry. They contend that the federal Environmental Protection Agency has set conservative standards on how much pesticide can remain on foods, and that other federal agencies do a good job of monitoring to ensure these limits are not exceeded.
Critics, including most proponents of organic foods, are more likely to tell you to worry, especially in the case of pregnant women and small children. They argue that not enough is known about the connection between pesticides and various diseases, particularly when pesticides are ingested in combinations.
Two central issues
As Charles Benbrook, chief scientist for the Organic Center for Education and Promotion, explains it, there are two issues. The first is: Are there pesticide residues on food? About this, there is no disagreement, Benbrook says.
If you take conventionally grown soft-skin fruit such as apples, pears, peaches, grapes and strawberries, Benbrook says, 95 percent contain residues of various pesticides.
Usually the pesticides are at low levels and meet government criteria, but not always.
Pesticides are also often present -- though at much lower levels -- on organic produce. This is because certain generally safer pesticides are allowed for use by organic farmers. In addition, a small amount of pesticides used on a neighboring field may blow onto organic produce.
The second issue, which is debatable, is whether there is a safe level of residue, and what risks are associated with residues.
"That's because the science of toxicology is really still in its infancy," Benbrook says.
The medical establishment knows a lot about risk factors, says Benbrook, but can't say that chemical X or pesticide Y has caused an increase in a particular disease, whether breast cancer, leukemia or Alzheimer's.
It may be that even very low exposures to pesticides during critical times -- such as the early months of pregnancy -- may affect development and perhaps ultimately create vulnerability as an adult.
The dose makes the difference
But many experts don't believe that pesticides, as they are used on produce, pose any risk.
Carl Winter, director of the Food Safety Program at the University of California, Davis, says that "toxicologically, it's the dose that makes the poison. It's the dose -- not the presence or absence of pesticide."
From what he has seen over the years, the residues that people are exposed to through produce are very low.
Studies have shown no discernible effects when animals are fed every day of their lives with food that contains pesticides at thousands of times the level ingested by humans.
Washing produce with tap water reduces pesticide residues and protects against bacteria, viruses or fungi. (Not all pesticides can be washed off, however. Some actually penetrate the fruit and become part of it.)
In addition, Winter says, cooking dramatically decreases the level of pesticide residues in food.
If you are concerned about residues in your diet, you can also try to eat less of the foods more likely to be contaminated.
According to the Environmental Working Group, a nonprofit research and advocacy organization, the 12 fruits and vegetables most contaminated by pesticides are apples, bell peppers, celery, cherries, imported grapes, nectarines, peaches, pears, potatoes, red raspberries, spinach and strawberries.
The group recommends buying those fruits and vegetables organically, while others -- asparagus, avocados, bananas, broccoli, cauliflower, sweet corn, kiwi and others -- are among the least contaminated. (For a full listing, see www.foodnews.org/reportcard.php.)