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    Research as long ago as 1991 found that households with dogs that developed malignant lymphoma applied 2,4-D herbicides (weedkillers) to their lawns more frequently than households where the dogs did not develop malignant lymphoma. In addition, the risk of canine malignant lymphoma rose much higher with four or more yearly applications of 2,4-D. This finding that exposure to certain lawn chemicals by dogs increases the risk of the dogs developing canine malignant lymphoma was confirmed in a 2012 study .

The following excerpts from an article geared toward students nicely explains a recent study that looked at the exposure that dogs have to lawn pesticides, specifically looking at 2,4-D, MCPP, and dicamba (commonly used weed-killers or herbicides). The study looked at exposure of pet dogs to 2.4-D by measuring it in the dog's urine, and also looked at how long the herbicides come off the grass where it had been applied. They found widespread detection of lawn chemicals in the urine of pet dogs, that lawn chemicals were commonly detected on both treated and "untreated" lawns (probably due to "drift"), that the lawn chemicals persisted on grass for at least 48 hours after application, and that the chemicals can persist longer on grass under certain environmental conditions (e.g., dry brown grass).

Finally, the researchers said that dogs may serve as sentinels for human exposures (think of them as canaries in the mine) - if they are exposed to this degree, then humans must also be highly exposed. Dogs get malignant lymphomas after a short latency period, while for humans it is years longer to develop cancer. NOTE: weed-killers are herbicides, a type of pesticide. My question is: why are people still applying pesticides to their lawns when there are links between pesticides and cancers? Is the weed-free lawn more important than health? From Science News for Students:

Weed killers may go from plant to pooch

Many people treat their lawns with weed killers — also known as herbicides — to rid themselves of unwanted plants, such as dandelions. Most people know to keep small children away from the grass after it’s been sprayed. That’s because these chemicals can be dangerous if children touched the treated lawn and then put their hands to their mouths. New data show that herbicides also can end up in dogs. The evidence: It comes out the other end in the animals’ urine.  ...continue reading "Dogs, Weed Killers, and Malignant Lymphoma"