The incidence of kidney cancer in the United States rose by an average of 1.2 percent each year between 2011 and 2019 to become the seventh most common cancer. In the meantime, smoking — a well-established risk factor for kidney cancer — has continued to decline.

This led researchers to consider other possible contributing factors, including arsenic, a known cause of various cancers that is naturally occurring in groundwater in Texas and other areas. Unlike previous studies, the Texas A&M study focused on low levels of arsenic exposure (below the regulatory threshold of 10 parts per billion) in both public water systems, which are regulated by various government agencies, and private well systems, which are not regulated.

“Some public water systems are poorly managed and could expose customers to arsenic, but the 40 million people in the United States who rely on private wells are particularly vulnerable,” said Taehyun Roh, with the Department of Epidemiology and Biostatistics.

Others involved with the study were Daikwon Han, Xiaohui Xu, and then-doctoral student Nishat Tasnim Hasan, with the Department of Epidemiology and Biostatistics, and Garett Sansom, with the Department of Environmental and Occupational Health. The project was supported by grants from the Houston Methodist Research Institute, Robert and Janice McNair Foundation and National Institute of Environmental Health Sciences.

Their findings, published in Environmental Pollution, examined the relationship between kidney cancer rates and arsenic levels in drinking water across 240 Texas counties. The team analyzed cancer data from the Surveillance, Epidemiology, and End Results on 28,896 cases of cancer among adults in Texas aged 20 and older, alongside water testing data from the Texas Department of State Health Services and the Texas Water Development Board.

They used a statistical model that accounts for geographic location and adjusted the model for demographic and socioeconomic factors and cancer risk factors such as obesity, smoking and diabetes. They also adjusted for covariates that included pesticide density, social vulnerability, income level, rurality, cardiovascular disease hospitalization rates and the prevalence of chronic kidney disease.

The analysis found that exposure to between 1 and 5 parts per billion raised kidney cancer risk by 6 percent, and exposure above 5 parts per billion raised the risk by 22 percent. In addition, the risk of cancer increased by 4 percent with each doubling of water arsenic levels.

“This suggests that even low-level arsenic exposure in drinking water may be associated with an increased risk of kidney cancer, which aligns with previous research indicating an association between this exposure and lung, bladder and skin cancers,” Roh said.

Hasan noted that their study design can indicate associations between factors but not causality and recommended that future studies focus on individual-level and biometric data — rather than the county-level data used here — to better assess the effects of factors such as lifestyle, family history of kidney cancer and other possible sources of arsenic exposure.

“Still, our findings indicate that reducing arsenic exposure could reduce the incidence of kidney cancer, and this could be achieved through efforts such as enhanced regulatory oversight and targeted public health interventions,” Hasan said.