Carl Winter: Hi! My name is Carl Winter. I am a spokesperson for the Institute of Food Technologists and a Food Toxicologist on the faculty at the University of California, Davis.

Today we're discussing food safety issues concerning chemical contaminants in foods that might be potentially hazardous. In previous segments, we've already established that the dose of the chemicals is very important in terms of determining whether there might be any harm. I've also established that for most chemical contaminants our dose as consumers is very, very low.

What I'd like to focus on in this segment is the process by which scientists use to determine what might be acceptable levels of exposure to chemical contaminants. Obviously, we're not allowed to study the effects of these chemicals directly on humans. So what scientists generally will do, will be to study the effects of these chemicals on laboratory animals and then try to extrapolate the results from those studies to predict what might happen in human populations.

This is not a completely precise approach, and in many cases, we make very conservative assumptions that humans maybe much more sensitive than the laboratory animals. For example, if we did a study and we determined that there was a particular dose when given to a laboratory animal on a daily basis throughout the animal's entire lifetime, that didn't cause any effect, we might consider an acceptable level of exposure for humans to be a very small fraction of that often one hundred times lower than that dose or a thousand times lower than that dose to give us a cushion. When we talk about chemicals like pesticide residues, in fact, often we will see that our typical exposures to pesticide residues in the diet are generally levels of 10,000 times or 100,000 times lower than doses that haven't even caused effects in the laboratory animals. This is one key reason why most health professionals consider the potential risk from pesticide residues and foods to be negligible. At the same time there are still a lot of controversies concerning chemicals in foods. In the next segment, we'll talk about some of the reasons that these controversies exist.