Disinfectant Sprays May Cause Greater Lung Damage When Inhaled

Spray disinfectants are used almost everywhere, from kitchens and bathrooms to schools and hospitals, often with little thought given to their use.

However, fresh research indicates that how these products are applied could be more important than previously recognised. Laboratory experiments found that inhaling widely used cleaning chemicals caused substantially greater lung injury than ingesting identical substances.

The results are not a call to abandon disinfection. They do, though, highlight a significant weakness in existing safety assumptions, particularly concerning chemicals that are released into the air as sprays.

What happens after spraying

In experiments involving mice, injury occurred at doses well below those connected with ingestion studies.

Gino Cortopassi of the University of California, Davis (UC Davis) linked this harm to ingredients found in commonly used disinfectants.

Chemical concentrations in the blood reached a broadly similar range to levels previously documented in people, connecting lung exposure with the chemical load already observed beyond laboratory settings.

This similarity does not establish the risk to humans, but it makes the exposure route the central issue that needs to be addressed.

More than surface cleaners

These disinfectants are part of a chemical group known as quaternary ammonium compounds, or QACs, which are widely incorporated into cleaning products.

By themselves, they do not readily become gases. Once sprayed, however, they form minute droplets that can be inhaled and travel deep into the lungs.

QACs also occur outside cleaning products. They can be found in herbicides, nasal sprays, mouthwashes, dryer sheets and fabric softeners, so people may encounter them more frequently than they realise.

Their extensive use has prompted concern. One study detected QACs in 80 percent of those tested, and higher concentrations were associated with lower energy production within cells.

Tracking exposure in blood

The latest study showed that blood levels of these chemicals fell rapidly following exposure. This indicates that they can move quickly, entering through the lungs before circulating into the bloodstream.

As a result, the timing of blood tests is important. Testing too long after exposure could indicate low exposure, despite levels having been considerably higher soon after inhalation.

Mouse research cannot fully forecast risk in humans, but it can help show how sprayed cleaning products pass from the air into the body.

Some disinfectant sprays are more harmful

The research also identified meaningful variations between the chemicals and between individuals.

At equal doses reaching the lungs, one ingredient, didecyl dimethylammonium chloride, was more damaging than benzalkonium chloride.

It resulted in more mouse deaths and produced greater quantities of protein and debris in lung fluid, which are clear indicators of more severe damage to the air sacs. Immune cells arrived sooner as well, while tissue samples taken later revealed greater swelling and disruption.

These contrasts indicate that similarly labelled products may not present identical risks. Researchers further observed that male mice were more likely than females to die at the same exposure levels.

The blood findings provided one possible reason. Female mice seemed to transfer benzalkonium chloride from their lungs into the bloodstream more rapidly, potentially reducing the time the chemical remains in lung tissue and causes injury.

Yet this trend did not completely account for the effects of the second chemical, so differences linked to sex remain incompletely understood.

How QAC disinfectant sprays damage the lungs

When these compounds are swallowed, much of them remains outside the body, whereas inhalation produces a markedly different outcome. Sprayed droplets that enter the lungs make direct contact with fragile tissue designed for fast gas exchange, leaving the lungs particularly susceptible.

Scientists suspect mitochondria, the cell structures responsible for producing energy, are involved in the damage. These disinfectants seem to interfere with those systems.

Without sufficient energy, cells find it difficult to preserve protective barriers. Fluid and immune cells may then enter lung tissue, worsening inflammation and injury.

Although this mechanism has not been fully verified in humans, it offers an explanation for why inhaled exposure differs so greatly from ingestion.

Evidence from real-world settings points in a similar direction. In healthcare environments, exposure to QACs has been associated with a 7.5-fold rise in physician-diagnosed asthma.

A separate study involving 73,262 U.S. nurses linked high disinfectant exposure with chronic obstructive pulmonary disease (COPD).

These findings do not demonstrate that the same effects occur in homes, but they indicate that repeated inhalation could involve genuine respiratory hazards.

Questions still remain

In people, exposure generally consists of repeated low-level contact over months or years, rather than one acute dose administered to mice.

Timing is also significant, since chemical levels declined quickly in mouse blood and may have appeared lower if samples were collected late.

Only two ingredients were examined by the researchers, meaning other chemicals within this family could act differently in the lungs.

These limitations mean the study cannot resolve human risk, but they also clarify which experiments are now most needed.

The risk of airborne cleaners

Airborne droplets represent the crucial change: the same disinfectant may create a very different risk when sprayed rather than poured or applied by wiping.

This difference is especially relevant in homes, schools, hospitals and transport systems, where frequent cleaning may allow droplets to remain in shared indoor air.

“We have to question whether we really want to have all of these QAC-based disinfectant sprays in the environment,” said Cortopassi.

The findings do not argue for ending disinfection completely, but they challenge the long-standing belief that inhaled exposure is insignificant.

Instead, cleaning chemistry appears less like a straightforward issue of surface treatment and more like an airway-exposure concern caused by airborne droplets.

Future research will need to examine chronic exposure levels relevant to humans. Even so, this mouse study already makes the risks linked with spraying harder to dismiss.