More than two-dozen scientists, including Northwestern Engineering’s Erica Hartmann, have issued a warning about the overuse of antimicrobial chemicals. 

The COVID-19 pandemic boosted the unnecessary use of these products, many of which are linked to health problems, antimicrobial resistance, and environmental harm. In a new critical review, the scientists specifically cite the use of quaternary ammonium compounds (QACs), which are increasingly marketed and used in home, health care, educational, and workplace settings — despite the availability of safer alternatives, including plain soap and water.

The review was published May 9 in the journal Environmental Science & Technology.

In previous human studies, researchers have found associations between QACs and asthma, dermatitis, and inflammation. Laboratory animal studies also raise concerns about potential links to infertility, birth defects, and more. Further, evidence dating back to the 1950s suggests QACs contribute to antimicrobial resistance, making certain bacteria species resistant both to QACs and critical antibiotics.

“It’s ironic that the chemicals we’re deploying in vain for one health crisis are actually fueling another,” said Hartmann, a coauthor and associate professor of civil and environmental engineering at the McCormick School of Engineering. “Antimicrobial resistance was already contributing to millions of deaths per year before the pandemic. Overzealous disinfection, especially with products containing QACs, threaten to make it worse.”

Increasingly used in disinfectant solutions, wipes, hand sanitizers, sprays, and foggers, QACs also are now incorporated into personal care products, textiles, paints, medical instruments and more. Since the pandemic, levels of these chemicals in the environment and our bodies have increased in parallel. 

One of the most common QACs is benzalkonium chloride, but others can be identified on ingredient labels with names that end in “ammonium chloride” or similar. However, disclosure and regulation of QACs varies widely. For example, pesticide labels are required to list QACs, but paint labels are not. Most QACs are not regulated at all, nor are they comprehensively screened for health hazards.  

The scientists recommend eliminating uses of QACs that are either unnecessary or where their effectiveness has not been demonstrated. Disinfection with QACs, for example, often has no benefit over cleaning with plain soap and water. Other recommendations include requiring full disclosure of QACs in all products and closely monitoring their levels in people and the environment. 

“Drastically reducing many uses of QACs won’t spread COVID-19,” said Carol Kwiatkowski, a coauthor and scientist at the Green Science Policy Institute. “In fact, it will make our homes, classrooms, offices, and other shared spaces healthier.”