‘Global Dimming’ Was Caused by Human Pollution, Study Confirms


Quats, or quaternary ammonium compounds, are charged molecules that can kill bacteria, fungi, and viruses. Quats are effective disinfectants, but some researchers are raising alarm given recent research on the compounds’ possible human health and environmental effects, including fertility issues, endocrine disruption, occupational asthma, marine toxicity, and potential to spur antibiotic-resistant bacteria.

And, while industry defends quats as safe, some states are taking notice and looking into regulations.

Bacterial Resistance

The pandemic has increased demand for products like Lysol wipes that use quats as active ingredients: sales of Lysol wipes were up nearly 50 percent in spring of 2020 compared to 2019. Other cleaning products are also in high demand — aerosol disinfectant sales as a whole have doubled in 2020 in the U.S., a large fraction of which also contain quats.

All those additional sales mean quats are becoming more present in the environment. “We’re in an era now where the concentration [of quats] is certainly higher than ever before,” William Arnold, an environmental engineer at the University of Minnesota, told EHN. He published a paper in June that revealed an increased load of quats may be ending up in wastewater plants, with some worrisome implications. Quats can end up in wastewater plants after they’re flushed down the drain — at the levels of use during the pandemic, some plants can’t keep up, so quats have the potential to pollute waterways. There, they might disrupt marine food chains, as quats have been found to be toxic to small invertebrates like plankton in lakes.

The ingredients also may be spurring antibiotic-resistant germs, Arnold said.

Bacteria are constantly working to shore up their defenses against the antiseptics we use. “We’ve had an 80- or 90-year head start, but we really need to keep innovating” to stay ahead of microbial evolution, Kevin Minbiole, a Villanova University chemist who studies how quats affect bacteria and viruses, told EHN.

Quats work like spears, penetrating the shell on the outside of a bacteria or virus. But some bacteria are getting better at recognizing quats and getting rid of them, or becoming resistant, said Minbiole. He and his collaborator, Emory University chemist William Wuest, are experimenting with new antimicrobial ingredients and recently patented their own quats that can mount multiple attacks on a single microbe. These quats are likely even more effective antiseptics than current quats on the market, but the new chemicals haven’t yet been tested for safety, so it’s not clear how their health or environmental impacts might differ, or not, from current quats, according to Wuest.

But the germs may be one step ahead. As they encounter quats and other antiseptics, bacteria can develop broad, rather than specific, resistance. These new bacterial shields, which evolved to block attacks by antiseptics, might also protect them against other threats, including the antibiotic medications doctors prescribe to help fight serious infections.

It’s called cross resistance: when changes bacteria make to get around one threat make them better suited to survive other threats, too. “Those changes make bacteria capable of surviving different compounds, different chemicals that it hasn’t seen before,” Beatriz Pereira, a recent graduate student in microbiology from University of California, Davis, told EHN.

In lab experiments, Pereira has seen bacteria develop resistance to certain quats, even when she only exposes them to low concentrations of the chemicals. The bacteria shore up their defenses, strengthening their outer membrane — a good way to develop cross resistance to other chemicals as well. It’s not clear whether bacteria are yet developing resistance in the wild in response to current levels of quat pollution, or even how much quat pollution currently exists. But to Pereira, these lab experiments alongside a growing body…

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