15 PA counties in cancer cluster linked to ag. Researchers say more study needed
Authors of a new Penn State study published this month showing a correlation between herbicide-treated cropland and melanoma rates in Central Pennsylvania say more research is required to determine whether pesticides or something else is responsible for heightened rates of the deadly cancer among older residents in farm-rich counties.
The new study, published Nov. 14, found a correlation between agriculture and skin cancer rates in residents older than 50 in 15 counties, including Centre County. Melanoma is the deadliest form of skin cancer.
The study was “kind of like a nudge that this is something to look into,” said Benjamin Marks, a Penn State medical student who authored the paper with four other researchers. “And so without that, people may not be aware of, there’s a possible correlation.”
The researchers determined 15 rural counties in Central Pennsylvania constituted a melanoma “hotspot,” with a county labeled a part of the hotspot if it and its neighbors had unusually high melanoma rates. Some counties, like Lancaster, Wyoming and Huntingdon, had high rates but weren’t included since they didn’t satisfy both criteria.
The 15 counties, where researchers concluded melanoma rates were 57% higher than the rest of Pennsylvania, account for about 15% of the commonwealth’s population. Counties with more cultivated land and more herbicide-treated property were associated with higher melanoma rates.
“This whole study was started by an observation from our dermatologists,” said Eugene Lengerich, an epidemiologist and co-author. Penn State’s dermatologists, he said, saw “a lot of melanoma cases, and some of them associated with agriculture.”
The study “is sort of the next step after that, to be able to document where those are, and what is the rate and background” of the cases, he added.
The research piggybacked off other papers that suggest a link between pesticide exposure and skin cancer, with Marks noting the literature stretches back to the Vietnam War era.
The U.S. Environmental Protection Agency regulates pesticide use to account for risks, including by setting pesticide “buffer zones” and certification standards. Pennsylvania requires certifications beyond what is set by the federal government, according to Edward Crow, a pesticide regulatory education specialist at Penn State Extension.
“There’s some products that, by their nature, there may be some issues with them, but if they’re used according to label directions, there shouldn’t be any problems,” Crow said. He added that farmers are “pretty responsible and try to do the best job they can” when applying pesticides and generally follow the law.
Marks stressed the goal of the study was to support farmers by identifying ways to reduce risk.
“Agriculture workers are the experts in farming,” Marks said. “We’re not dictating how to farm.”
Chris Hoffman, the president of the Pennsylvania Farm Bureau, the commonwealth’s top farm lobby, said he interpreted the study as “more of a question mark.”
“I reached out to Penn State, and I talked to the College of Ag, saying, ‘This is pretty interesting, what do you guys think?’” said Hoffman, a Penn State trustee. He said the response amounted to “We’re curious, looking into this and seeing if we could sometime, maybe do some studies for correlations.”
Hoffman, who noted he lost his father to melanoma, said farmers “trust the science” and are “willing to move forward and to make sure we’re using” new products as they become available, but the study hasn’t moved the needle that far yet.
Lengerich, the epidemiologist, said the study is “not only part of a bigger science-wide study effort, but also much bigger effort at Penn State to get to the bottom of the issue.
“Ben and I have been to farms trying to understand what’s going on there so that we can develop more and more targeted preventive efforts in that area,” he said. Charlene Lam, another co-author, “is a dermatologist, so she does see the melanoma patients, so she has been planning additional follow-up studies.”
Marks said he conducted the study as part of his graduate studies, using publicly available data and no outside funding. The study states pesticide exposure may increase sensitivity to sunlight, suppress the immune system and damage DNA, making skin cancer more likely. But it looked at broader countywide trends and did not account for individual behavior, like sunscreen use or receiving cancer screenings.
Pennsylvania farmers, the study notes, skew older, meaning they are more prone to cancer.
Lam said in a news release the findings nonetheless suggest melanoma risk in ag-heavy areas extends beyond farmers.
“This is relevant for people living near farmland,” she said. “You don’t have to be a farmer to face environmental exposure.”
State Rep. Emily Kinkead, No. 2 Democrat on the House Agriculture Committee, said more research would need to be done for regulations to change.
“Let’s let the scientists do what scientists do, and figure out if there is an actual causation connection here,” she said.
