Epidemiology, the who, what, when and where of health and disease in a population, derives from the Greek epi upon, demos, people or district and logos, meaning study. The study of what is upon the people. It is the cornerstone of public health and is critical in shaping health policy, identifying risk factors for disease and providing guidelines for preventative care.
Hippocrates was the first person who studied how the environment influences disease and coined the terms endemic (for diseases found in some populations to the exclusion of others) and epidemic (diseases seen at some periods of time but not others).
However, it is John Snow who is considered the father of modern epidemiology when he mapped an outbreak of cholera tracing it to a contaminated water pump on Broad Street in the mid nineteenth century. His detailed map of the pattern of disease convinced the local council to disable the contaminated well pump by removing the handle. This simple action resulted in containment of the outbreak to the area. Snow did not know how the disease was transmitted but evidence suggested it was related to sewage from a nearby cesspit contaminating the water.
Snow went on to show that The Lambeth Water Company and Southwark and Vauxhall Water Company supplied pumped water to South London and were using sewage contaminated water from the Thames. His theory was disputed and not accepted at the time. However, it did eventually lead to changes in public health policy with improvement in sanitation.
In the developed world, we take clean water for granted. However, just as there was a poor understanding about how cholera was transmitted in Snow’s time, for two years, there was a misconception about how the SARS-CoV-2 virus was transmitted. It was widely thought that Covid-19 was spread primarily via small droplets from the nose and mouth that quickly landed on surfaces. This error caused confusion and resulted in inaccurate health advice. The debate about transmission revolved around the extent to which transmission occurs indirectly via surfaces or directly through the air we breathe. More than two hundred scientists from thirty-two countries wrote an open letter to the United Nations outlining evidence of respiratory spread of the virus, with smaller exhaled particles lingering in the air where people could breathe them in. They called for a change in guidelines, but it was not until the 23 December 2021 that the World Health Organisation used the word airborne when discussing the SARS-CoV-2 virus.
During the horrific bushfires of 2019 air quality was so poor that masks were introduced, and people were advised to stay indoors. This was followed by the pandemic where we were required to wear masks, with the recommendation to open windows to allow air to circulate. Despite these experiences where air quality was demonstrated to have a direct impact on health, there are still no standards for indoor air quality.
There will no doubt be a time in the future when a generation will look back in horror at the filthy air we were breathing when indoors. Most of our buildings are poorly ventilated and high in carbon dioxide levels (the gas we breathe out) resulting in higher levels of airborne pathogens and increasing the risk of respiratory illness. In countries like Australia, we spend ninety per cent of our time indoors, and yet there has been little research done on the quality of the air we are breathing.
'It is easy to ignore the things you cannot see, in the same way authorities dragged their heels on improving sanitation and providing clean water to the poorer residents in nineteenth century London.'
The leading expert in this field is physicist Professor Lidia Morawksa who established and runs the International Laboratory for Air Quality and Health at the Queensland University of Technology and advises WHO on air quality. She won a Planetary Health Award and holds numerous international positions. She was prominent in forcing WHO to change their stance and to acknowledge that transmission of SARS-CoV-2 is airborne rather than via droplet spread. She was identified as one of the one hundred Most Influential People in the World in 2021 by Time magazine.
Morawksa said, ‘In the future…buildings will be designed such that clean air will be provided like clean water is provided, but it will be some time yet.’
This sentiment is echoed by Professor Bronwyn King, a radiation oncologist who has turned her attention to air quality and believes that as part of the response to the catastrophic effects of smoke from the 2019-20 bushfires and the pandemic, attention had to revolve around ensuring the air in our indoor environments is safe to breathe.
Poor indoor air quality is considered one of the five top environmental risks to public health. While we wait for a government response ensuring that public buildings like hospitals, offices, classrooms, shopping centres, theatres, hotels, and homes are designed to meet minimum air quality requirements, there are simple interventions that can be implemented to both raise awareness of air quality and encourage individual action.
The more people are in an enclosed space, the higher the carbon dioxide levels which in turn increases the emission of pathogens. More people exhaling means dirtier air, often exacerbated by windows that can’t be opened or poor ventilation. Carbon dioxide (CO2 concentration can be used as a proxy for air quality. The outdoor concentration of CO2 is four hundred to five hundred parts per million but inside the concentration is higher, depending on the number of people, ventilation, and size of the room. Once the concentration is higher than eight hundred parts per million, the risk of infection is high.
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Both Morawska and King carry small CO2 monitors which cost about three hundred dollars and fit into the palm of your hand. In buildings with poor air quality, it can prompt you to open windows, or as an interim solution, say for a classroom, buy an air purifier that filters not only pathogens but also particulate matter during bushfires. These are imperfect but are beneficial provided they are the right fit for the size of a room, and the number of people in it.
It is interesting to know what Hippocrates and Snow would make of our reluctance to apply epidemiological knowledge about air quality to enforce changes to building regulations and retrofit older buildings with mechanical ventilators. It is easy to ignore the things you cannot see, in the same way authorities dragged their heels on improving sanitation and providing clean water to the poorer residents in nineteenth century London.
The bushfires and the pandemic have each prompted research into the importance of fresh, clean air. There will no doubt be cries of alarm at the increased cost of making our indoor environments safer. Let us hope that human health and wellbeing prevail over economic expediency.
Jo Skinner is a Brisbane-based GP, women’s fiction author, freelance health writer and distance runner.
Main image: (Getty Images)