Children in many countries have had a hard time over the last two years. They have been put under enormous pressure during lockdowns — most having to work from home while trying to keep up with their studies in isolation from their teachers and fellow students.

By the time schools opened up again, the emphasis on measures to protect from Covid-19 had changed from surface hygiene and regular deep cleaning to air hygiene. Numerous aerosol, engineering, atmospheric and respiratory disease specialists presented evidence that Covid-19 is primarily an airborne disease. This showed the importance of mask-wearing and ensuring there is good indoor air quality to reduce the risk of infection.

In several countries there have been high numbers of infections in schools during the delta variant wave, resulting in children passing on infections to adults in their homes. Recent research (Dec 2021) by the Swiss Federal Laboratories for Materials Science and Technology (EMPA) has shown a clear link between poor ventilation in classrooms and high numbers of infections. This shows poorly ventilated classrooms (measured by CO2 sensors) had six times the number of cases of Covid-19.

The dirty truth about indoor air quality in schools

The issue of keeping children safe from infection when schools opened up also highlighted a problem that has affected schools. Poor air quality in school classrooms has been impacting children’s learning for decades. This is despite the large amounts of research showing poor ventilation and pollution, which is highly prevalent around urban schools, have major effects on children’s health, performance and well-being. School staff is also affected and they have a right to a safe working environment.

The Lancet COVID-19 Commission Task Force on Safe Work, Safe School, and Safe Travel found that most schools in the US do not meet even the minimum ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) ventilation design standard – which is aimed at comfort, not disease control, so it is much lower than what is needed to remove infectious aerosols adequately.

Funds are being provided in many countries for schools to take measures to stay open safely. The Lancet report highlighted that this provides a once-in-a-generation opportunity to make health-based improvements to school buildings, including indoor air quality. Preventing the spread of airborne diseases and reducing pollution in schools are part of the same problem. Indoor air quality improvements will both reduce indoor air pollution and the risk of children and staff catching airborne diseases. Both of which will provide the benefits of improved health and academic performance. Below we discuss why clean air is particularly important for schools.

Why classroom air quality is important for children


As our bodies develop, different individuals from different populations react differently to toxins and allergens in the air. Some people are hypersensitive to low levels of indoor air pollution or sick building syndrome – the specific causes of which have still not been fully clarified by research. It is thought to be caused by exposure to low levels of multiple pollutants. This strengthens the case for good quality indoor air, keeping pollutant levels as low as possible.

“Cash-strapped authorities have routinely placed schools on the cheapest available land, which is often beside busy roads, factories or on previously contaminated sites.” A study by Dr. Sara Grineski, published in the Environmental Research Journal, showed that one-third of schools in New York and New Jersey are at the highest risk for air pollutants. Those states are not alone — counties in Pennsylvania, Idaho, Ohio, Illinois, and Oregon ranked in the top ten worst US counties for air pollution near public schools.

Pollutants coming from both outdoor and indoor sources contribute to poor indoor air quality. These include volatile organic compounds (VOCs) such as formaldehyde, benzenes, nitrous oxide, carbon dioxide, radon, particulate matter (PM1.0, PM2.5, PM10), fungi (including mold spores), bacteria and viruses (carried in dust and respiratory aerosols), and even human skin particles. Vehicles congregate in front of the building at certain times of the day. Schools also use many types of products in teaching, such as art and science materials, that are sources of pollution.

Children are particularly vulnerable to air pollution because their bodies are still developing. Younger children, especially, have an underdeveloped or compromised immune system. While children are still growing, their lungs are larger in proportion to their body size. Children also breathe more rapidly than adults. So relative to their blood volume and body size, they intake more toxins and a greater concentration of pollutants.

There is a relationship between exposure to indoor pollutants and the development of respiratory symptoms and asthma among people who have not been sensitized or who are prone to allergies. Children are more likely to be susceptible while they are young and growing. Children who have been exposed to high levels of air pollution are also susceptible to chronic diseases later in life.

Small children spend more time close to the floor because of their height and activities, making them more exposed to pollutants in dust settled on the floor and disturbed by classroom activities –  especially their own. These pollutants can include dust mites, pet allergens, fungal spores, pollen and plant debris, soil and industrial and vehicular particulates brought in from outdoors. A range of synthetic organic compounds, including pesticides, can accumulate in dust. Small children ingest around 100–200 mg/day of dust, about 2-4 times the quantity of adults.

The effects of air quality on academic performance


Research shows that poor indoor air quality in schools has a variety of effects on children’s health, learning ability and academic performance. The wide-ranging and well-known long-term health effects of pollution include lung diseases, cardiovascular disease, myocardial infarction, heart failure, neurological disorders, diabetes and cancer.

The effects of poor air quality are not always obvious and include headache, fatigue, coughing, sneezing, dizziness, nausea, and irritation of the eyes, nose, throat, or skin. These have a direct effect on the academic performance of children and teachers and attendance at school.

The US EPA reviewed the scientific evidence on the impact of air quality on academic performance and classified studies according to their findings.

  • Higher outdoor ventilation (by HVAC or opening windows) in classrooms gave higher scores on standardized tests in math and reading.
  • Improved indoor air quality (IAQ), either by removal of pollution or higher ventilation rates, is linked to faster and improved performance of children.
  • Poor building condition is linked to higher absenteeism and dropout rates.
  • A survey of teachers in two areas in the US found that the most frequently cited problem affecting teaching quality was poor IAQ.
  • Causes of pollution most frequently associated with respiratory problems such as asthma, include moisture damage, animal and biological allergens, NO2, moisture or dirt in HVAC systems, low ventilation rate, formaldehyde, cleaning products, outdoor pollutants and vehicle exhaust. In the US, nearly one in thirteen children has asthma, which is the leading cause of school absenteeism caused by a chronic illness.
  • Higher ventilation rates reduce the transmission of infectious diseases and reduce rates of respiratory diseases.
  • Control of temperature and relative humidity to keep children in a comfort zone has the most positive impact on mental tasks requiring concentration.
  • Airborne or surface dust affects health in schools.

How can schools improve air quality?


Schools have some unique aspects that can make managing air quality more difficult than buildings such as offices. A typical school can have four times as many people as office buildings per area, requiring higher rates of ventilation. School budgets have been under strain in many countries, often with maintenance facing the largest cuts.

Multiple factors make managing air quality in schools a high priority for ensuring the health, and well-being of students and staff and the educational performance of the students. The pandemic has given a rare opportunity to solve the problem of chronic underventilation in schools and focus on improving air quality. Many countries are now taking action by allocating significant budgets to improve indoor air quality.

There are several measures schools can take to improve indoor air quality.

  • Mechanical ventilation with an HVAC system. Often these have not been designed to have sufficient ventilation or filtration rates for airborne diseases. They may need to be supplemented with portable air cleaners in rooms. HVAC systems also need regular maintenance to perform adequately.
  • Natural ventilation, by opening windows where outdoor pollution levels are not going to negatively impact the air indoors and the outdoor air temperature difference won’t affect comfort indoors.
  • Portable air cleaners with HEPA 13 filters. These filter particulates, including respiratory aerosols, and VOCs from the air (but not CO2, which will require ventilation). They should have a clean air delivery rate (CADR) of at least five air changes per hour in the room.