Soil Pollution May Contribute to Antibiotic Resistance, Study Finds

A new study indicates that soil pollution might be contributing to the rising rates of antibiotic resistance. While the problem has long been attributed to the overuse of antibiotics, recent research suggests that heavy metals could also be a threat.

Researchers from the University of Georgia found soils that contained heavy metals had a higher level of bacteria with antibiotic-resistant genes (ARGs) for vancomycin, bacitracin, and polymyxin—three antibiotics commonly used to treat infections in humans. Their results were published in the July issue of Microbial Biotechnology.

“This is an increasingly important problem, and we hear of several types of bacterial infections that are getting harder and harder to treat because they become 'resistant' to available antibiotics," Daniel A. Monti, MD, chair of integrative medicine and nutritional sciences at Thomas Jefferson University who was not involved with the study, tells Verywell. "Antibiotic resistance leads to higher healthcare costs, longer hospital stays, and increased mortality."

What is Antibiotic Resistance?

Antibiotic resistance accounts for 700,000 deaths globally every year. It occurs when bacteria develop defense mechanisms to the antibiotics that usually kill them.

These bacteria, nicknamed "superbugs," can cause difficult-to-treat infections that require emergency hospital interventions and extended hospital stays. In the U.S., 2.8 million people are infected with antibiotic-resistant bacteria each year.

In addition to soil pollution, there are several other factors known to contribute to antibiotic resistance.

• Inappropriate and/or overuse of antibiotics
• Bacterial mutation and gene transfer
• The use of antibiotics in agricultural feed

How Soil Contamination Happens

For the study, researchers collected soil samples from four locations along the Savannah River in South Carolina, three of which were known contaminated sites, and one which served as a control. They then used a process called genomic analysis to test the levels of heavy metals in the soil and the characteristics of the bacteria present in the soil.

"The bacteria living in these contaminated soils have to adapt to survive," Samantha Radford, Phd, a chemist with a background in public health who is unaffiliated with the researchers, tells Verywell. "The adaptations they make to survive in soils with high concentrations of metals seem to also increase antibiotic resistance. If these bacteria later infect humans, it could be very difficult to treat them with antibiotics, as the bacteria are already resistant to some of our strongest drugs."

Radford says that soil contamination comes from both agriculture and industrial processes. It affects air and water quality as well as soil quality.

"The soils tested [in the study] came from a river that is known to be contaminated with metals," Radford says. "However, a similar phenomenon could potentially happen in farmland. It's not uncommon for heavy metals to build up in farmland, as they are sometimes found in fertilizers or pesticides, particularly in developing countries."

Is Food Grown In This Soil Safe?

This study may make you concerned about what your produce has been exposed to. But Monti says most bacteria are heat-sensitive and will die when cooked.

"While more research is needed to better understand to what degree these organisms penetrate the food grown in these soils, it makes sense to be extra careful about washing and sanitizing vegetables and fruits, and even to peel the skin from root vegetables," he says.

It's not just about the food you eat; antibiotic-resistant bacteria have the potential to cause problems on a larger scale.

"I think the bigger issue is ecology and biodiversity," Radford says. "There were fewer types of bacteria in the more contaminated soils, and this reduction can affect plant life, groundwater health, and animal life. While these concerns don't affect human life quite as directly, it will certainly make an impact in the long run."