Common bacteria found in classroom dust are associated with reduced lung function in children according to research presented at the European Respiratory Society (ERS) Congress in Barcelona, Spain [1]. The research may show us how to make sure schools are healthy environments for children and their developing lungs.
The study was presented by Dr Soutrik Banerjee from the Department of Environmental and Prevention Sciences, University of Ferrara, Italy and French technology company, Alten S.A.
Dr Banerjee told the Congress: "We know that indoor air quality in schools can be affected by pollutants, humidity, ventilation, temperature, dampness and biological agents like fungi and bacteria. However, much less is known about whether the types of bacteria growing in classroom dust are linked to children's lung function.
"We were particularly interested in two bacterial groups, Streptomyces and Mycobacterium spp., which are found in soil, dust and water systems. We wanted to see whether higher exposure to these bacteria in the classroom is associated with children's lung health across Europe."
The team used data from the SINPHONIE study [2], which covered 22 European countries and almost 300 classrooms, to measure the amount of Streptomyces and Mycobacterium spp. bacteria in classroom dust.
They also tested the lung function of children from each classroom using a standard breathing test called spirometry, where a child takes in a deep breath and then blows out as hard and fast as possible into a measuring device. This calculates the volume of air the lungs can hold and how quickly that volume of air can be exhaled. Reduced lung function is when your lungs can't hold as much air as normal or air cannot flow in and out of your lungs as easily as normal. It limits the amount of oxygen your body takes in and your ability to clear carbon dioxide, which can lead to fatigue and shortness of breath.
The researchers adjusted the data for age, gender, BMI, passive smoking, pet allergens, socio-economic indicators, school building age and region, and local levels of air pollution.
They found that children in classrooms with higher levels of Streptomyces had a 0.08 litres lower forced vital capacity (FVC), a measure of how much air a child can blow out maximally after taking a deep breath.
They also found that children in classrooms with higher levels of Mycobacterium had slightly lower FEV₁ (0.06 litres lower) and PEF (0.13 litres/sec lower). FEV₁ measures how much air a child can blow out in the first second, and PEF is the maximum flow a child can blow out as fast as possible.
Dr Banerjee explains: "Although the reductions we found were modest for each child, they are statistically significant and could be important for the wider population. Children are exposed to school indoor environments every weekday and a mild to moderate reduction in lung function today may be a pre-cursor to preventable lung disease in later life."
Dr Banerjee believes that bacteria in dust may irritate the airways or activate immune and inflammatory pathways. He also believes it possible that these bacteria are markers of broader classroom conditions, such as dampness, ventilation, cleaning practices or outdoor dust entering the building.
"The bacteria may either have a direct biological effect, or they may be indicators of other indoor environmental factors that influence lung function," he adds.
Professor Alexander Möller, Head of the European Respiratory Society's Paediatric Assembly, and Professor of Paediatric Pulmonology at the University Children's Hospital Zurich, Switzerland, who was not involved in the research said: "This large European study shows that children's lungs seem to suffer when two common types of bacteria are growing in dust in their classrooms.
"While not all bacteria are harmful, these findings suggest that the classroom environment is important in children's lung health and they support the idea that healthy school buildings matter. The practical message is not that schools should become sterile environments. Rather, schools should focus on good indoor air quality: adequate ventilation, control of dampness and mould, regular cleaning and proper building maintenance.
"Children spend a lot of their time in the classroom, so it's important that we understand how to keep this environment safe and healthy. This study suggests that investment in indoor air quality, building maintenance and monitoring of environmental conditions in classrooms is money well spent."
