Two hundred years ago, drinking water from a water pump could have been lethal. The water might have appeared clean but could be contaminated with sewage, causing a serious and often deadly diarrhoeal disease owing to cholera. Luckily, societal norms and regulations around water and sanitation have shifted. We now expect the water from our taps to be clean and safe.
Although we now have safer drinking water, we have a challenge ahead to do the same for the indoor air that we breathe and share.
The COVID-19 pandemic has had a devastating impact on tuberculosis (TB) care in South Africa and globally, with TB-related deaths increasing for the first time in a decade. However, since COVID-19 and TB are both airborne infections, the attention surrounding mitigation measures could provide a glimmer of hope for the TB response.
Much of this synergy has focused on mask-wearing, which can reduce the risks of transmission of both COVID-19 and TB that result from exposure to shared air. Mask-wearing has gained traction and some level of acceptance during the ongoing COVID-19 pandemic.
Yet there has been inadequate prioritisation of the need to improve the safety of our shared air. This is particularly important in crowded indoor settings that pose the highest risk of transmission and requires dedicated efforts, resources, and policy changes to improve indoor ventilation.
We have known for years that increasing natural ventilation by opening doors and windows is an effective strategy to increase the volume of fresh air that enters from the outdoors. In South Africa, we are fortunate to have weather that allowed us to use natural ventilation frequently. However, the COVID-19 pandemic has brought attention to settings that are difficult to ventilate - due to building infrastructure or when the weather becomes colder.
Many tools available
Yet there are many tools to improve ventilation that we have not used optimally. This includes high-efficiency particulate air (HEPA) filtrations, Carbon Dioxide (CO2) monitors, and Germicidal Ultraviolet disinfection technology. During the COVID-19 pandemic, a do-it-yourself (DIY) cost-effective air filter, known as the Corsi-Rosenthal Box, has gained traction both as school project and a convenient solution to improve indoor air quality, with research showing it can be an effective tool to reduce aerosol hazards in indoor spaces. This DIY air filter takes about 45-minutes to make and only requires a box fan, duct tape, four HEPA air filters, and cardboard.
While the world of HEPA filters can offer a dizzying array of options (some that fall firmly in the snake oil category) - a non-profit public service known as Clean Air Stars has developed an air filter recommendation tool that evaluates the acceptable noise level, Wi-Fi requirements, room volume, and filter requirements to ensure that an adequate number of HEPA filters are provided to ensure effective filtration and to reduce the transmission of airborne diseases. They have also developed a repository for businesses that have taken steps to make their shared air safer.
CO2 monitors could also be an important tool to help evaluate the ventilation quality of indoor facilities and spur further action to improve ventilation. Higher CO2 levels, particularly if they reach over 1000-1500 parts per million (ppm), show that there is likely a build-up of rebreathed air that indicates poor ventilation.
A study conducted in South Africa using CO2 monitors demonstrated the important point that air conditioners, unlike other strategies to cool the air such as opening a window, do not provide outdoor air exchange and lead to a build-up of CO2 indoors when doors and windows are closed, thereby decreasing ventilation.
Increased use of measures such as germicidal ultraviolet (GUV) disinfection holds promise to clear the air of potential pathogens. Guidelines have been developed for the use of GUV, based on key studies conducted in South Africa, but they have not been released and there is still a moratorium on the implementation of GUV fixtures in healthcare facilities after previous unregulated use did not have adequate maintenance and oversight.
Healthcare workers at risk
Even prior to the COVID-19 pandemic, we have known that there is an urgent need to improve ventilation in healthcare settings as healthcare workers are three times more likely than the general population to develop drug-sensitive TB and six times more likely to develop drug-resistant TB. Poor ventilation in overcrowded indoor spaces such as health facilities is recognised as an important risk factor for TB transmission. A recent study conducted in South Africa using small, portable CO2 monitors worn by health workers during their work shifts showed that health workers who experienced higher average CO2 levels had a higher risk of developing TB infection. Yet, the Occupational Health Policy for Health Workers regarding TB and HIV, drafted in 2016, that has far-reaching recommendations for addressing this occupational risk has still not been released.
Some might argue that making indoor ventilation improvements will be too costly for the South African context, both in health facilities and for businesses. But improving indoor air quality will make a difference in our preparedness to manage new variants of the current COVID-19 pandemic, our co-existent TB crisis, and help us respond to future respiratory disease outbreaks. Improving indoor air quality has other far-reaching benefits, such as improving the productivity of workers along with improved cognitive performance, reduced work stress and absenteeism, and increased job satisfaction.
A recent study evaluated the estimated costs of TB prevention and control interventions in South Africa and found that the most inexpensive intervention was to retrofit buildings to improve ventilation. A scientific review also revealed that improvements to indoor air quality are cost-effective as they can ensure three to six times the return on investment for increased ventilation.
Other countries have started to take this seriously. An initiative by the Australian government provides businesses with grants to improve indoor ventilation and the United States White House has recently launched a 'Let's Clear the Air' initiative that makes improving indoor air quality a major political priority.
COVID-19 has already triggered big societal changes, but we have been too slow to use all the available tools to improve indoor ventilation. Improvements in ventilation represent a cross-cutting measure that could help reduce the impact of COVID-19, flu, TB, and other respiratory epidemics. The 1854 cholera epidemic triggered a cascade of responses that led us to expect clean water in our taps. We need to use this opportunity in a similar way to address the invisible dangers in our shared air.
*The authors are all affiliated with TB Proof.