New study identifies the human growth factor PDGF-BB as a biomarker for low-level arsenic exposure

Arsenic-contaminated drinking water is a known health hazard and a daily reality for millions of Americans. Consuming water with high levels of arsenic—described by the U.S. Environmental Protection Agency (EPA) as 10 micrograms per liter or more—is associated with increased risk of cancer, especially bladder cancer.

Although many studies have looked into the effects of high arsenic concentrations, far fewer have focused on lower exposures.

Now, a new study by environmental health experts from the Texas A&M University School of Public Health gives new insight into exposure to low levels of arsenic through drinking water.

The study was supported by the Houston Methodist Cancer Center, the Robert and Janice McNair Foundation and the National Institute of Environmental Health Sciences and was published in Toxicology and Applied Pharmacology.

Environmental epidemiologist Taehyun Roh, PhD, and colleagues conducted a study of private well water users in South Texas and an in vitro experiment to determine how certain biomarkers change when exposed to arsenic.

Roughly 10 percent of private wells in Texas have arsenic levels higher than the EPA limit, but the problem is especially pronounced in South Texas, where wells drawing from the Gulf Coast Aquifer often contain elevated arsenic levels due to naturally occurring arsenic in the region’s soil and geologic formations.

“Private wells are not regularly regulated or monitored, and their water quality is entirely the responsibility of the owners. No studies have assessed exposure to arsenic through biomonitoring and the resulting health risks in this area,” Roh said.

The research team recruited 74 users of private water wells in the South Texas counties of Bee, Goliad, Refugio, San Patricio and Victoria. They collected samples of tap water and urine from participants and measured concentrations of arsenic in both water and urine as well as multiple cytokines and other potential biomarkers in urine. Cytokines are proteins that play a key role in the immune system and can cause inflammation and other health conditions in excess amounts.

Additionally, the researchers developed a parallel model based on human bladder cells to measure arsenic responses. They exposed bladder cells to arsenic concentrations equivalent to those found in the study area for five weeks and analyzed levels of biomarkers.

The wells measured had an average arsenic concentration of around 7.5 micrograms per liter. Water from 22 of the 74 wells had arsenic levels above the EPA standard of 10 micrograms per liter.

“There is a clear association between arsenic concentrations in water and those in urine,” Roh said.

The team also found a significant association between levels of arsenic and Platelet-Derived Growth Factor-BB (PDGF-BB), a human cytokine involved in tissue growth and repair. Similarly, the cell-based model showed increases in PDGF-BB with exposure to arsenic. Prior research has found elevated levels of PDGF-BB in bladder cancer patients.

The researchers note a few limitations to their study, such as an inability to measure changes over time, the relatively high age of the study subjects and relying solely on residential water sources. Further studies that investigate water from workplaces and restaurants and use a more diverse population would likely give more detail.

“While further research is needed, these findings suggest that PDGF-BB is a biomarker for lower-level arsenic exposure and indicate a way to measure bladder cancer risk in communities relying on private wells,” Roh said.

The study is ongoing to assess arsenic levels in private well drinking water and to increase public awareness to reduce exposure across additional counties in South Texas.

Others involved with the study were Natalie M. Johnson, PhD, Nishat Tasnim Hasan, DrPH, doctoral students Alexandra E. Svetlik and Nusrat Fahmida Trisha, Raj Satkunasivam at Houston Methodist and Daniel White at University of Houston-Victoria.