Classroom Dust Bacteria Linked to Lower Lung Function in Children, European Study Finds

Common bacteria lurking in the dust of school classrooms are associated with measurable reductions in children’s lung function, according to new research presented at the European Respiratory Society (ERS) Congress in Barcelona, Spain. The findings, drawn from one of the largest studies of school indoor environments ever conducted in Europe, suggest that the microscopic ecology of classroom dust may play a previously underappreciated role in shaping the respiratory health of children during the years when their lungs are still developing. The work could ultimately help guide how schools are designed, cleaned, and ventilated to protect the health of the pupils who spend thousands of hours inside them.

The study was presented by Dr Soutrik Banerjee of the Department of Environmental and Prevention Sciences at the University of Ferrara in Italy, working with the French technology company Alten S.A. Speaking at the Congress, Dr Banerjee explained the motivation behind the research. Scientists already know that indoor air quality in schools can be influenced by a wide range of factors, including pollutants, humidity, ventilation, temperature, dampness, and biological agents such as fungi and bacteria. What has remained far less clear is whether the specific types of bacteria growing in classroom dust are linked to the lung function of the children who breathe that dust every day.

To answer that question, the research team focused on two bacterial groups with a particular ecological profile: Streptomyces and Mycobacterium species. Both are found naturally in soil, dust, and water systems, which means they can make their way into buildings through tracked-in dirt, airborne particles, and moisture. Streptomyces are filamentous bacteria famous for producing antibiotics, while certain Mycobacterium species are known to trigger immune responses in the airways. The researchers wanted to determine whether higher exposure to these microorganisms in the classroom environment was associated with differences in children’s lung health across Europe.

The investigation drew on data from the SINPHONIE study, a large European project covering 22 countries and almost 300 classrooms. This breadth gave the team an unusually rich picture of school environments across different climates, building types, and regions. From each classroom, the researchers measured the amount of Streptomyces and Mycobacterium species present in the dust, creating a quantitative profile of the bacterial burden in the rooms where children spent their school days.

Lung function was assessed using spirometry, the standard breathing test used in respiratory medicine worldwide. In a spirometry test, a child takes a deep breath and then blows out as hard and as fast as possible into a measuring device. The test calculates the total volume of air the lungs can hold and the speed at which that air can be exhaled. Reduced lung function means the lungs cannot hold as much air as normal, or that air cannot flow in and out of the lungs as easily as it should. This limits the amount of oxygen the body takes in and impairs the ability to clear carbon dioxide, which can lead to fatigue and shortness of breath.

Because many factors can influence a child’s lung capacity, the researchers carefully adjusted their analysis for a wide range of potential confounders. These included age, gender, body mass index, passive smoking exposure, pet allergens, socio-economic indicators, the age and region of the school building, and local levels of outdoor air pollution. This statistical rigor is essential in observational research, where associations can easily be distorted by differences between schools and populations. Even after accounting for all of these variables, the link between bacterial levels in classroom dust and reduced lung function persisted.

The results revealed two distinct patterns. Children in classrooms with higher levels of Streptomyces had a forced vital capacity (FVC) that was 0.08 litres lower than average. FVC measures how much air a child can blow out maximally after taking a deep breath, essentially reflecting the total capacity of the lungs. Meanwhile, children in classrooms with higher levels of Mycobacterium showed slightly lower values on two other spirometry measures: their forced expiratory volume in one second (FEV1) was 0.06 litres lower, and their peak expiratory flow (PEF) was 0.13 litres per second lower. FEV1 captures how much air a child can blow out in the first second of exhalation, while PEF records the maximum flow rate achievable.

Dr Banerjee was careful to put the size of the effect in context. Although the reductions found for each individual child were modest, he noted that they were statistically significant and could matter at the level of the wider population. Children are exposed to their school’s indoor environment every weekday, often for years of their lives, and a mild to moderate reduction in lung function during childhood may serve as a precursor to preventable lung disease later in life. In public health terms, small shifts across an entire population of schoolchildren can translate into a substantial burden of respiratory illness in adulthood.

What remains uncertain is the precise mechanism behind the association. Dr Banerjee suggested that bacteria in dust may irritate the airways directly or activate immune and inflammatory pathways within the lungs. He also raised an alternative possibility: that these bacteria may function as markers of broader classroom conditions, such as dampness, inadequate ventilation, poor cleaning practices, or outdoor dust entering the building. In other words, the bacteria may either exert a direct biological effect on children’s lungs, or they may simply be indicators of other indoor environmental factors that influence lung function. Distinguishing between these explanations will require further research, but either interpretation points toward the same practical conclusion: the physical condition of school buildings matters for respiratory health.

Independent experts welcomed the findings while cautioning against overreaction. Professor Alexander Möller, Head of the European Respiratory Society’s Paediatric Assembly and Professor of Paediatric Pulmonology at the University Children’s Hospital Zurich in Switzerland, who was not involved in the research, said the large European study shows that children’s lungs seem to suffer when two common types of bacteria are growing in classroom dust. He emphasized that not all bacteria are harmful, but the findings suggest the classroom environment is important in children’s lung health and support the idea that healthy school buildings matter. The practical message, he stressed, is not that schools should become sterile environments. Rather, schools should focus on good indoor air quality through adequate ventilation, control of dampness and mould, regular cleaning, and proper building maintenance. Because children spend so much of their time in the classroom, he argued that investment in indoor air quality, building maintenance, and monitoring of environmental conditions is money well spent, and that understanding how to keep this environment safe and healthy is essential for protecting the next generation’s lungs.

Subject of Research: Association between bacterial content of classroom dust and lung function in schoolchildren

Article Title: Bacteria in classroom dust associated with reduced lung function in children

Article References: Bacteria in classroom dust associated with reduced lung function in children. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: classroom dust, children's lung health, Streptomyces, Mycobacterium, spirometry, indoor air quality, SINPHONIE study, European Respiratory Society, school buildings, ventilation, respiratory health, public health