Dirty air is invisible, but a real threat to health
Here’s how we can keep the air healthy at home, at work and on public transport
Better ventilation is key to fighting Covid and other diseases, writes the author. Photo: James Stent
If you live in a city, you spend 90% of your time indoors. And 100% of that time breathing. Unless you bring scuba gear, you share the air with everyone else, and you have an interest in that air being clean.
As South Africa officially enters its fifth wave of Covid, dominated by the highly infectious omicron subvariants, the primary threat to health from shared indoor air - but not the only one - is its contamination with the airborne coronavirus.
Covid joins tuberculosis (TB), influenza and many common colds as airborne diseases acquired mainly by breathing the air in crowded indoor settings such as offices, factories, schools, restaurants, clinics and public transport. Not from surfaces.
Covid resulted in 300,000 deaths over the last 24 months, TB caused the death of nearly 60,000 people in 2018, influenza about 10,000. Colds and other viruses lead to less severe illness in most people but the two or three colds we experience each year still cause disruption (millions of days off work) and kill those who are vulnerable (young children, the elderly and those with HIV and other forms of immune suppression). Many of these illnesses and deaths are preventable.
Most South Africans are now protected from severe acute Covid illness or death through previous infection or vaccination. But while omicron is not an inherently less severe version of the coronavirus, it is much more infectious than previous variants. The idea that viruses inevitably progress to more benign incarnations of themselves is a myth. Meanwhile, chronic Covid illness is accumulating, affecting 5 to 10% of those infected, and could cause significant disability and damage a health care system already under severe strain.
The deadliest effects of Covid are hugely reduced by vaccination. But only 40% of South Africans have had the jab, less than 10% get an annual flu shot, and effective TB and cold vaccinations aren’t yet available. Properly worn, high quality masks (such as N95, KN95, KF94) are effective in reducing transmission of airborne disease. But many people are not willing to continue wearing masks at this phase of the pandemic and not enough people are coming forward to get vaccinated.
Outdoor air may be significantly polluted. But outdoor exposure is not, in most cases, how you get Covid or the other airborne diseases, unless you spend prolonged periods up close to someone infected.
Prevention measures should therefore focus on cleaning indoor air. Dirty air is invisible, but a real threat to health, also to the economy. (In South Africa the extent to which shared air contributes to tuberculosis infection has been studied.)
Stale air affects cognition and work performance. In contrast, clean fresh air is a boon to productivity. According to Harvard University’s Healthy Building Program, investment in better air quality yields a 100-fold return on your money .
Clean air is therefore a worthy objective, but for building owners and occupiers two other factors are critical: maintaining thermal comfort, and conserving energy - keeping electricity costs low. Clean, comfort, conservation: we call these the 3 Cs. How can they simultaneously be achieved?
A first step is measurement. The amount of shared air you breathe depends on the number of people in your space and the extent of ventilation. The more crowded an indoor space, the more shared air you breathe. The amount of each other’s air we breathe can be quite easily measured using a handheld or wall-mounted carbon dioxide meter. In Germany, Japan and Belgium these devices are becoming ubiquitous and their use is supported by public health regulations.
In the United States and other countries that routinely experience cold winters and/or hot summers, building standards have focused on sealing off leaks and improving insulation. An airtight, well insulated building is energy-efficient in hot summers or cold winters, reducing the cost of air conditioning or heating.
But an airtight room or building is by definition not well ventilated. HVAC (heating ventilation air conditioning) systems have to provide ventilation and thermal comfort, adjusting the intake of outdoor air, filtering it and the recirculated air as it passes through ducts, heating or cooling it. But these systems consume lots of energy.
Most of South Africa is blessed with a mild climate. During much of the year, good ventilation can be achieved by opening windows and doors to create a flow of outside air through an indoor space (building or vehicle) that dilutes contaminants like coronaviruses, TB bacteria, or your neighbour’s breath. But on a cold highveld morning this is a challenge. The windows of taxis holding 14 occupants on their 6am commute to work are closed to block the cold air and rain.
We can use awareness of local conditions to improve natural ventilation. Where there are prevailing breezes (in Gqeberha or Cape Town for example), meeting near open windows will provide plenty of fresh air. As temperatures change in the morning and evenings, temperature differences encourage air flow through open windows.
We can place window openings to catch and encourage air flow. We can also add simple elements to walls and roofs to catch and amplify air flow, such as galvanised turbines which turn and draw air with the breeze, no energy or maintenance needed.
Perhaps our public transportation can add the solar vents that are used to get additional air flow to ship cabins without letting rain in. All these strategies, and more, can create healthy spaces where we can be together.
The challenge of achieving all three objectives – all three Cs – measurably clean air, comfort and conserving energy – can also be met by new building technologies and designs:
- Sensors can detect occupancy and activity, using signals like CO2, movement and sound. They can regulate heating, ventilation and air conditioning systems, turning them on and adjusting their activity up as occupancy rises, turning them off when the indoor space is empty.
- Because buildings in cold climates are built “tight” to conserve heat, they need systems that ensure indoor air is fresh and clean. Mechanical systems can use and conserve the heat in exhausted air and return it, clean, to the indoor space.
- Filters are old and simple yet remarkably effective technologies. In personal masks, such as N95 ones, and in building systems, filters ensure the air that passes through them is almost completely free of virus and other contaminants, at relatively low cost. Fancy high-tech air purifiers add little other than expense, can generate dangerous by-products and are generally to be avoided.
- Some forms of UV light can kill viruses and bacteria. Newer UV technologies which limit the light to a narrow wavelength do not damage human tissues and could be installed in high risk spaces, perhaps even our taxis.
The 2022 White House Correspondents Dinner was the perfect setting for Covid super-spreading. A poorly ventilated and very crowded indoor space with over 2,000 closely spaced, unmasked guests – including the president of the United States. Several attendees, including Anthony Blinken, the Secretary of State, contracted Covid. Better ventilation – to maintain a CO2 level below 800 parts per million, as opposed to over the 2,300 that was recorded – and the installation of ultraviolet light, offered to the organisers, but rejected – might have averted this.
The failure to take adequate precautions at a high profile event like this one is part of the remarkable failure of authorities throughout this pandemic to use science and technology.
Better outcomes were - and still are - possible by targeting the air through which Covid and other diseases are spread.
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