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Veterinary Forum May 2008 (Vol 25, No 5)

Editor's Note: Cause, effect and coincidence

by Marie Rosenthal

    When Bogart, my weimeraner, was about 6 months old, he started vomiting about 2 days after I spread a seasonal lawn chemical on my yard. The vomiting was so severe that he required an overnight hospital stay and rehydration therapy. I don't know if he caught a bug, ate something he should not have or got an overdose of toxic chemicals when he licked his paws, but I stopped using that brand of lawn chemical.

    Even though the new brand I use now claims to be safer for animals, if I spread it on the lawn, I wash off Bo's paws when he comes into the house until we've had the first good rainfall. He hasn't had severe vomiting requiring rehydration therapy since then, and he's 9 years old now.

    I thought of this episode because the Environmental Working Group (EWG) recently issued a study (see article) about the number of toxic chemicals that were found in 20 dogs and 37 cats in Virginia.

    It is an important study because it sheds light on a potentially serious problem — not only in our pets but in our children and ourselves — that our environmental exposure to toxic chemicals may be too high.

    But the EWG makes a giant leap when the researchers conclude that this exposure is leading to an increase in cancers, thyroid disease and other problems in our pets. Dr. Lawrence McGill, a pathologist on our Editorial Board, told me that to prove that claim will take a lot more study and a lot more samples.

    There is nothing wrong with making an educated guess, as I did for Bogart, and taking prudent steps, but we do need data to draw conclusions, such as the EWG has made.

    Sometimes there is a cause and effect, but sometimes it is just a coincidence. Scientists, owners, politicians and many others often make giant leaps without scientific evidence.

    They forget that coincidences happen, and that a coincidence is not a cause and effect — just because I forgot my umbrella doesn't mean I made it rain.

    I'm not saying that these chemical exposures don't cause disease; they probably do, but a lot more data are needed before we can conclusively say that. I will never know if the lawn chemicals caused Bo's vomiting.

    We live in frightening times, but that should not erode our scientific standards. In fact, that should reinforce the need for rigorous data.

    I hope that veterinarians begin to study dogs and cats to learn whether any of these toxins do lead to more disease. If they do, I hope legislators pass laws restricting their use.

    In the meantime, as Dr. McGill points out in the article, owners can take prudent steps to help reduce their pet's exposure. In addition to those steps, you might recommend that they use safer and less-toxic products in their homes and gardens.

    NEXT: FORUM Fast Stat (May 2008)
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