Bacteria in school dust linked to decreased lung function in children

School dust may contain bacteria, the presence of which is associated with a slight decrease in lung function in children. The researchers came to this conclusion after analyzing data from almost 300 classrooms in 22 European countries. What microorganisms have scientists discovered and does this mean that school premises are dangerous for children? — in the Izvestia article.

What scientists have found in school dust

The researchers drew attention to two types of bacterial groups — Streptomyces and Mycobacterium. They are found in soil, dust, and water systems and may be present indoors. The scientists decided to check whether there is a connection between their amount in school dust and the condition of children's lungs. The results are published on the Medical Xpress portal.

The question turned out to be especially important because of the length of the contact. Schoolchildren spend a significant part of every weekday in classrooms, so the peculiarities of the air and the environment inside the building can regularly affect their respiratory system. At the same time, school dust is not only a mixture of visible particles. It can contain various biological components, including bacteria and fungi. Their quantity and composition can be affected by humidity, ventilation, building condition, cleaning and ingress of particles from the street.

The researchers emphasized that so far much less is known about the possible relationship between the composition of bacteria in school dust and the lung function of children. The new work was supposed to help understand whether the microbial composition of classrooms could be one of the factors related to the state of the respiratory system.

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How the lung health of schoolchildren was checked

For the analysis, the researchers used data from the SINPHONIE study, which covered 22 European countries and almost 300 school classes. The amount of Streptomyces and Mycobacterium in the dust samples was determined, after which these indicators were compared with the results of the examination of children.

Lung function was assessed using spirometry. During this test, the child first takes a deep breath, and then exhales the air as strongly and quickly as possible into a special device. This way, experts can determine how much air the respiratory system can hold and how quickly it leaves the lungs.

One of the indicators was forced vital capacity, or FVC. It reflects the maximum amount of air that a person can exhale after taking a deep breath. Another indicator is FEV₁: the volume of air exhaled in the first second of forced exhalation. The scientists also took into account PEF— the maximum speed at which a person is able to exhale air.

To prevent the results from being explained by other characteristics of children and schools, the researchers adjusted the analysis to take into account age, gender, body mass index, secondhand smoke, pet allergens, socio-economic factors, age of the school building, region, and local air pollution.

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What changes were found in children

A higher concentration of Streptomyces in school dust was associated with a slightly lower forced lung capacity. On average, the FVC index in children from such classes was lower by 0.08 liters. For Mycobacterium, scientists have obtained a different picture. With a higher number of these bacteria , the FEV₁ index was lower by 0.06 liters . In addition, the peak exhalation rate (PEF) decreased: the difference was 0.13 l/s.

At the level of one child, these changes were small. However, the authors of the study note that the differences were statistically significant. Since children are regularly in school premises, even relatively small changes in lung function can be significant when considering large populations.

However, the results cannot be interpreted as evidence that it is these bacteria that cause lung function to deteriorate. The study found a statistical relationship between the composition of school dust and spirometry indicators, but did not establish a direct cause-and-effect relationship.

Are bacteria or conditions in classrooms to blame?

Scientists are considering several possible explanations for the connection. One option is that the bacteria themselves or the components associated with them can irritate the respiratory tract. In addition, they can potentially affect immune and inflammatory processes in the body.

But there is another version. An increased number of certain bacteria may not be the cause of changes in lung function, but a kind of marker of the general condition of the room. For example, the microbial composition of school dust can be affected by dampness, ventilation, the quality of cleaning, or the ingress of street dust into a building. The same factors can simultaneously affect the state of the respiratory system. Therefore, it cannot yet be said that the presence of Streptomyces or Mycobacterium is the main factor in the decline.

For a more accurate answer, further research will be needed to separate the influence of various components of the school environment. In particular, scientists will have to understand whether the detected bacteria have an independent biological effect or whether their presence only reflects other features of the premises.

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How to make schools safer to breathe

The results do not mean that schools need to be turned into sterile facilities. The experts who commented on the study separately emphasized that not all bacteria are harmful, so the task is not to completely destroy the microorganisms.

It is much more important to maintain normal air quality inside buildings. Among the main measures, experts name adequate ventilation, humidity and mold control, regular cleaning and timely maintenance of school premises. This is especially important for children, as their respiratory system continues to develop. If the school environment regularly exposes the body to adverse factors, this can potentially have more serious consequences than short-term contact with a pollutant.

At the same time, the authors of the work do not yet propose to change the sanitary rules solely because of the discovered connection. Rather, the study shows that the microbial composition of school dust may be another indicator of indoor conditions that should be taken into account when studying air quality.

Thus, we are not talking about "harmful bacteria in every school," but about a broader issue — how well the conditions inside the buildings meet the requirements for children's health. Further study of bacteria, humidity, ventilation and other factors together can help to better understand which characteristics of the school environment affect the developing lungs.