Skin cancer cluster found in 15 Pennsylvania counties with or near farmland

November 14, 2025 - By Adrienne Berard

UNIVERSTIY PARK, Pa. — Counties in Pennsylvania that contained or were near cultivated cropland had significantly higher melanoma rates compared to other regions, according to a new study led by scientists at Penn State.

Researchers at Penn State Cancer Institute analyzed five years of cancer registry data, 2017 through 2021, and found that adults over the age of 50 living in a 15-county stretch of South Central Pennsylvania were 57% more likely to develop melanoma, the deadliest form of skin cancer, than residents elsewhere in the state. They published their findings today (Nov. 14) in the journal JCO Clinical Cancer Informatics.

The cancer cluster includes both rural and metropolitan counties, meaning risks are not confined to remote areas or reserved for those most exposed to the outdoors, explained Charlene Lam, associate professor of dermatology at Penn State Health and co-author on the paper.

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The usual suspect — sunlight — was considered as a part of the study. But even after adjusting for ultraviolet radiation in Pennsylvania and socioeconomic factors, two patterns stood out: Counties with more cultivated cropland and those with higher herbicide use had significantly higher melanoma rates.

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