shower-water-aerosol-infection

As an Amazon Associate we earn from qualifying purchases.

Readers searching for shower water aerosol infection usually ask whether the mist from a shower can carry bacteria into the lungs. Two studies in this guide sampled the air during showers in people’s homes. One compared homes of people with Mycobacterium avium complex lung disease with matched control homes. The other sampled homes of patients with nontuberculous mycobacterial (NTM) lung disease in Brisbane, Australia. Both describe aerosol as a possible route. Neither shows how often infection happens.

Quick answer

• Shower aerosol was sampled with an air impactor placed near the shower, with the hot tap running. In the 2013 Brisbane study, NTM grew from aerosols in several homes.
• In the 2020 case-control study, NTM were isolated from shower aerosols in case homes more often than in control homes. The adjusted odds ratio was 4.0, with a 95% confidence interval of 1.2 to 13.
• An earlier analysis by the same 2020 team found no link between the disease and aerosol-generating behavior. The later study found a link with what the aerosols contained.
• The studies do not show how much aerosol exposure, if any, leads to infection.

How the studies sampled shower aerosol

Both studies collected shower aerosol with a cascade impactor, a device that draws air onto a culture plate. The 2013 team describes its method in detail. The impactors were “Andersen six-stage cascade impactors”, and “The impactor was placed as close as practicable to the shower recess, and the shower hot tap was run.” The paper adds that “Windows were left as the patient would normally have them during showering, and exhaust fans were left off.” The collection time was 20 minutes.

The 2020 study took its aerosol sample from the bathroom people used most for showering. The paper says that “Shower aerosols were collected from the bathroom most often used by the subject for showering or bathing.” That choice reflects a hypothesis: the authors say the sites were “selected on the hypothesis that aerosol generation during routine hygiene, cooking, and gardening is an important step in disease acquisition.”

The method has one clear effect on what the results mean. The papers report whether mycobacteria grew from the air samples on culture plates. Neither paper reports how much a person breathed in, and neither reports a dose. Both studies are about the presence of mycobacteria in aerosol, not about the number of organisms a person inhales.

Why researchers focus on aerosol

The 2013 introduction gives the basic logic. It says that “Aerosols generated during these activities can be inhaled, and water can be aspirated when swallowed”, where “these activities” include drinking, swimming and bathing. The same paper states that “There is some evidence that susceptible individuals may acquire infection from potable water in their own homes.”

The 2020 paper adds a lab observation about how mycobacteria behave. It cites work showing that “Mycobacterium species preferentially partitioned into aerosols compared with other bacteria species”. From this, the authors suggest that “mycobacteria in premise plumbing can detach from biofilms and aerosolize at showerheads, effectively seeding the airways of users.” The word “conceivably” in that passage marks it as a proposed mechanism. The 2020 study set out to test that connection in people’s homes.

The 2013 Brisbane study

Thomson and colleagues studied 20 patients with NTM pulmonary disease in Brisbane, Australia. The study included patients who had lived in the same home for more than five years before diagnosis. The eligibility wording is direct: “Prevalent patients who had been resident in the same dwelling for greater than 5 years prior to the diagnosis of NTM disease were eligible for home sampling.”

The team found pathogenic mycobacteria in 19 homes. The paper reports that the species found in the home matched the species in the patient in “seven (35%) cases”. Aerosols were collected in 18 homes, and several NTM species grew from them, including M. abscessus, M. gordonae, M. kansasii, members of the M. fortuitum complex, M. mucogenicum and M. wolinskyi. The study therefore shows that these organisms can be grown from shower aerosol in homes of people with NTM disease. It does not show that the aerosol caused any of those diseases.

The authors state the main finding in plain terms: “NTM causing human disease can be isolated from household water and aerosols.” They also report an important negative result. Despite a predominance of disease caused by M. intracellulare, “we found no evidence for acquisition of infection from household water” for that species. That is a useful reminder that not every species in the water is linked to disease.

The abstract describes samples from 20 patients and does not describe a comparison group. That design can show that a species is present in a home. It cannot show how often a home without disease would have the same species.

The 2020 case-control study

Tzou and colleagues compared homes of Washington and Oregon residents diagnosed with MAC pulmonary disease with homes of matched population controls. Controls were matched on age, sex and geography. The authors sampled bathroom faucets, kitchen faucets, shower aerosols, indoor soil and outdoor soil. The study had 56 case homes and 51 control homes.

The main result concerns shower aerosol. The abstract states that “NTM were isolated from shower aerosols collected in case homes more often than in control homes.” After adjustment, NTM isolation from shower aerosols “had a high odds ratio associated with disease (odds ratio, 4.0; 95% confidence interval, 1.2–13)”. The confidence interval is wide, so the size of the association is uncertain, even though every estimate points the same way.

The other sampling sites did not show the same pattern. The abstract says that “Other home environmental samples (tap water, soils) did not exhibit this association.” The authors conclude that “The results implicate shower aerosols as uniquely significant sources of NTM exposure in homes”. That is their interpretation of a study with 107 homes in total, and it does not settle how much exposure matters.

The authors also state the study’s limits. “Additional limitations were that the study was not powered to divide results into high, low, and no colonization”, and they note that “A larger study may have detected weaker associations between NTM and disease in point-of-use sources other than shower aerosols.” They also say that “Limitations in our microbiologic techniques would have applied to both case and control samples and therefore were unlikely to explain the association” in shower aerosol. That is an argument about lab method, not a proof that the association is causal.

Behavior did not explain the aerosol result

The 2020 team had published an earlier report on the same case-control study. It “did not find evidence of association between MAC-PD and behaviors believed to increase aerosolization of water and soil in the residential environment”. The current paper contrasts its result with that finding: the earlier report did not observe an association with aerosol-generating behavior, while “the current study observed an association between MAC-PD and the microbiological content of aerosols.”

This matters for a reader who wants to know whether shower habits change risk. The sources do not show that longer showers, hotter showers or more frequent showers raise the chance of infection. They show that the organisms in shower aerosol differed between the two groups of homes.

Who the studies describe as at risk

The 2020 paper says that NTM pulmonary disease “has known host risk factors that include advanced age, thoracic structural anomalies, preexisting pulmonary disease, and autoimmune disease”. The authors also say that their earlier analysis found “MAC-PD is strongly associated with host risk factors”. Their interpretation was that there was “more evidence that MAC-PD is a disease that affects” susceptible persons than evidence of an unusual dose of organisms.

The 2013 study describes the same pattern. Its introduction says that “It has been postulated that susceptible individuals may acquire infection with nontuberculous mycobacteria (NTM) from water and aerosol exposure.” It also notes that “this is often a disease of the elderly” when it explains why NTM disease is becoming more common. The authors of the 2020 study recommend further work on “residential exposures, including but not limited to shower aerosols, in the homes of individuals with compromised immune or pulmonary systems”.

For healthy readers, the sources do not describe a serious risk from shower water aerosol. They describe possible exposure, and they describe disease in people who already had lung problems or risk factors. Readers with weakened immune systems, chronic lung disease or a history of lung infection should talk with a doctor about their own situation.

The time between exposure and disease

The 2013 authors name a basic limit of this kind of research. “A major limitation of home water and soil sampling studies relates to the long lag time between exposure and infection that can occur with NTM disease.” Because of that lag, a sample taken in a home today may not reflect the exposure that led to a disease diagnosed years earlier. The 2013 study also states that “We have demonstrated that a variety of species can be aerosolized and cultured from droplets of a respirable size.” That shows the organisms can be aerosolized and cultured. It does not show that a person breathed enough of them to become ill.

How we chose

This guide uses two sources, both opened and checked for quotes on 2026-10-28. Both are peer-reviewed journal articles about NTM in home water or shower aerosol. The 2020 paper gives the clearest comparison with control homes. The 2013 paper gives the most detail on how shower aerosol was sampled and what species grew from it. Between them, they cover the sampling method, the comparison result and the study limits.

The sources are about people in the United States and Australia, in homes sampled in Washington, Oregon and Queensland. This guide does not assume that the same results would hold in other countries or in other kinds of buildings.

What we could not verify

• How much mycobacteria a person breathes in during a shower. Neither source reports an inhaled dose.
• Whether the shower aerosol result in the 2020 study would appear in homes in other regions. The study covers Washington and Oregon.
• Whether the 2013 patients’ homes differed from other homes in ways that were not sampled.
• How often the same species from the home matches the species in a patient. The 2013 paper reports seven matches among its 20 patients.

What the sources do not say

The sources do not give a cleaning method, a filter, or a showerhead design that reduces aerosol or infection, and this guide does not offer one. They do not compare shower aerosol with aerosol from other sources, such as hospitals, workplaces or pools, in a way that would rank the risks. The 2013 paper notes that aerosol sampling for NTM has been done for hot tubs and indoor pools, but it does not report a comparison with showers.

The sources also do not describe how long an infection takes to appear after exposure, or whether a shorter shower, a cooler setting, or a change in bathroom ventilation would change anything. The 2013 paper says the exhaust fans were off during its sampling, but it does not test what the fans do.

FAQ

Can shower water aerosol carry mycobacteria?

Yes, the studies show that NTM can be grown from shower aerosol. In the 2013 study, several species were isolated from aerosols in homes of patients with NTM disease. The studies do not show how often this leads to infection.

Did the 2020 study prove that showers cause lung disease?

No. It found that NTM were isolated from shower aerosols in case homes more often than in control homes, with an adjusted odds ratio of 4.0 and a wide confidence interval. The authors state that a larger study may detect weaker associations, and the sources do not show causation.

Do shower habits change the risk?

The earlier analysis by the 2020 team did not find an association between the disease and aerosol-generating behavior. The sources do not measure how long or how hot the showers were in relation to infection.

Is shower aerosol a risk for healthy people?

The sources do not describe a serious risk for healthy people. They describe host risk factors such as advanced age, lung disease and immune problems, and the authors call for more research on people with compromised immune or pulmonary systems.

What should I do about shower aerosol?

The sources do not give a practical protocol, so this guide does not provide one. If you have a health condition that affects your lungs or immune system, talk with a doctor before making changes based on this topic.

Talk to a doctor

Readers with weakened immune systems, chronic lung disease, or a history of NTM infection should talk with a doctor. A doctor can review symptoms, test results and medical history. These studies were not designed to assess any one person’s risk.

Bottom line

The studies support a narrow point: mycobacteria can be grown from shower aerosol in some homes, and in one case-control study NTM isolation from shower aerosol was more frequent in homes of people with MAC lung disease. They do not measure a dose, they do not show how often showering leads to infection, and they do not give a cleaning method. Treat them as evidence that the question is worth studying, not as proof of risk for any one shower.

Sources

• Thomson R, Tolson C, Carter R, et al. “Isolation of Nontuberculous Mycobacteria (NTM) from Household Water and Shower Aerosols in Patients with Pulmonary Disease Caused by NTM.” Journal of Clinical Microbiology. 2013;51(9):3006-3011. https://pmc.ncbi.nlm.nih.gov/articles/PMC3754680/ (opened 2026-10-28)
• Tzou CL, Dirac MA, Becker AL, et al. “Association between Mycobacterium avium Complex Pulmonary Disease and Mycobacteria in Home Water and Soil: A Case-Control Study.” Annals of the American Thoracic Society. 2020;17(1):57-62. https://pmc.ncbi.nlm.nih.gov/articles/PMC6944351/ (opened 2026-10-28)