Tuesday, August 12, 2008

Risks and pesticides

the pesticide label is a legally binding document
I was reading a new product label this morning and came across a phrase that caught my attention. The label stated that "It is impossible to eliminate all risks inherentlyassociated with the use of this product."

This phrase, undoubtedly drafted by a lawyer and--I suspect--ignored by most users of the product, reminded me of a profound principles of pesticide toxicology and safety testing--one that I think few of us fully understand or appreciate: "It's impossible to prove that a pesticide is absolutely safe."

Science is a wonderful process. It allows us to discover useful things about our world. It forms the basis for new technology, answers our deepest questions about the universe, and brings wonder into our lives. Science, however, has it's limits. One of its limits is that it cannot prove absence of harm with complete certainty. It's the old "you can't prove a negative" argument.

Let me give an example. If my job is to test the safety of a new pesticide, I may expose a variety of organisms to my product to see if anything bad happens. Toxicologists routinely do this in laboratories with mice and rats and bacteria. Some tests are designed to measure acute toxicity, others look for evidence of mutations, others for cancer or other chronic disease. Suppose in the course of my testing all the rats develop cancer. This would be alarming evidence that my pesticide might be a human carcinogen. Evidence is strengthened if there are epidemiological studies that show a pattern of elevated cancer rates in humans exposed to the pesticide during its manufacture or use.

Now suppose there are no signs of cancer or other illness in my animals. Have I proved that my pesticide is safe? No. Science, because of physical and economic limitations, cannot prove safety with absolute certainty. For example, pesticide toxicology studies are not generally performed on people for ethical reasons. And people, despite our many occasional similarities, are not rats. Also, we cannot rule out all possible genetic, environmental or health factors that might influence carcinogenicity.

We know of cases, for example, where pesticides have proved exceptionally toxic to people taking certain prescription drugs. In these cases the drugs interfered with the user's ability to detoxify the pesticides, making them more toxic.

If we insisted that science provide absolute proof of safety, the science would become almost infinitely expensive. The best we can do is require a robust set of testing requirements, and base our decisions on the best available science. In addition, there should be a system of reporting suspicious patterns of health complaints associated with pesticide manufacture and use.

This is exactly what we do in the United States. The U.S. has, arguably, one of the best pesticide registration and approval processes in the world. New pesticides are incredibly expensive to register, in large part because of the safety testing required by the U.S. Environmental Protection Agency. The biggest beneficiaries of this regulatory process are those of us who work with pesticides on a daily basis.

So what's a pesticide applicator to do? Follow the label. The answer is so obvious that we often forget to do it. Labels are written to provide wise protection from the admitted limitations of our science when it comes to safety testing. From the precautionary statements, to the requirements for protective clothing, pesticide labels provide uncertainty protection.

Though they can be extremely uncomfortable in heat (especially in our part of the country), gloves, respirators and chemical resistant clothing, when required on the label, are essential to our safety. It may be necessary to explain this to a customer who balks at an applicator wearing gloves or breathing filters. They can be told that the extra protection is required by law (the label is the law) because, unlike them, applicators are exposed on a daily basis to our pesticide tools. It's not an admission of toxicity; it's a common sense precaution. It's an acknowledgement that we don't take unecessary chances with ours or our customer's health.

We should remember that there will always be risks working with pesticides, as with nearly any other consumer chemical product. That's the surprisingly wise message of the pesticide label.

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