Lawn fertilizers and pesticides not only pollute streams that feed the Chesapeake Bay. They might also increase the risk of cancer for dogs, according to a study in the scientific journal Environmental Research.
Research by Biki Takashima-Uebelhoer (above) of the University of Massachusetts Amhurst School of Public Health and colleagues concluded that dogs have a 70 percent greater risk of developing a canine malignant lymphoma when their owners treat their lawns with pesticides and fertilizers, compared to owners who do not spray their lawns with chemicals.
"We looked at dogs because of the close interaction in the household environment we share with our dogs," said Takashima-Uebelhoer. "It may give us a unique insight on how exposure to pesticides and herbicides may contribute to human non-Hodgkin's lymphoma."
Dr. Amir Sapkota, an assistant professor at the University of Maryland School of Public Health, said Takashima-Uebelhoer's conclusions echoed those of human health studies funded by the National Institutes of Health.
Scientists studied almost 90,000 farmers and pesticide applicators in Iowa and North Carolina, and found higher risks of not only lymphoma from pesticide exposure, but also of lung and pancreatic cancer, according to a summary of the federally funded Agricultural Health Study published in 2010 in the journal Environmental Health Perspectives.
"What they have found is increased risk of cancer associated with many of the pesticides," said Dr. Sapkota. "There is very strong evidence in humans, actually."
Ruth Berlin, director of a health advocacy group called the Maryland Pesticide Network, said Takashima-Uebelhoer's research provides further evidence that people should think twice before treating their lawns with pesticides and fertilizers. She noted that both children and dogs roll and play in lawns sprayed with chemicals.
"There is no need for it, really," Berlin said. "You can have a beautiful lawn that's pesticide free.”
Takashima-Uebelhoer’s decision to devote herself to exploring the subject of lawn chemicals and cancer sprouted from a childhood mystery. She was haunted by the death of one of her best friends, who happened to be a dog.
"Being an only child, dogs were not only my best friends, but my siblings," she recalled. "I was fortunate to have my boxer, Bucci, live to be 16 years. But I was not as lucky with Kuma."
"Kuma" means "bear," in Japanese, her mothers' native language.
"Kuma was a Rottweiler. He was the sweetest, smartest, and most gentle of them," she said. “He was approaching his ninth birthday, when one day we found him hiding at the back of our home, out of everyone's sight. This was not typical of Kuma, who was so social and loved to be with people."
The family rushed the dog to the vet.
"The vet told us that it was probably an infection, and that with medication, he would improve," said Takashima-Uebelhoer. "Unfortunately, he was wrong, and Kuma died that weekend."
Later she discovered that her dog had canine malignant lymphoma, a form of cancer. Looking for a cause, she examined their home, which was in Honduras.
"In Honduras, once a month, I mean, the plants were drenched with pesticide and herbicide –- including the lawn and garden," said Takashima-Uebelhoer. "We also had an inside garden in our house, and that, too, was sprayed."
Then Takashima-Uebelhoer's father developed kidney cancer. Her mother previously had breast cancer. And so when Takashima-Uebelhoer went off to study at Boston University and Harvard, she decided to examine if there is any possible relationship between cancer and lawn chemicals.
Her conclusions were published earlier this year in paper in Environmental Research. "Results suggest that use of some lawn care chemicals may increase the risk of CML (canine malignant lymphoma)," the paper says. "Additional analyses are needed to evaluate whether speciﬁc chemicals in these products may be related to risk of CML, and perhaps to human (non-Hodgkin’s lymphoma) as well."
Her report notes that incidence of non-Hodgkin’s lymphoma -– which is similar to canine malignant lymphoma -- has doubled in humans since the 1970s, making it the sixth most common cancer. In 2010, an estimated 65,540 men and women were diagnosed with non-Hodgkin's lymphoma in the U.S., according to Takashima-Uebelhoer's report.
Biki Takashima-Uebelhoer is determined to keep digging -- and get to the bottom of the still unanswered questions of precisely which pesticides, in what amounts around the home, could potentially cause cancer.
By Tom Pelton
Chesapeake Bay Foundation