Pink Floyd may have said it best:
Breathe, breathe in the air.
Don't be afraid to care.
These days, this lyric takes on an even greater meaning as we aspire to have a clean, healthy environment. Yet, our worries continue to be manifested as we witness rises in air pollution related chronic diseases such as lung function deficits, cardiovascular problems and cancers. Even more troubling is the importance of air in the spread of infectious diseases. For over 50 years, the air has been recognized as a mode of transmission for bacterial, viral and fungal pathogens. Yet, much like controlling air pollution, stopping this mode of spread has been a significant challenge.
Airborne transmission of infection is usually related to human traffic. In essence, the greater the density of people, the more likely infection will spread. This is especially important in enclosed spaces such as the home, work, schools, travel vessels such as airplanes and health care facilities, the latter of which has been the focus of most studies. Based on studies dating back almost 40 years pathogens can become airborne in almost every environment. Once there, they can spread to unsuspecting victims leaving them vulnerable to illness.
To reduce the levels of airborne spread, the majority of work has focused on ventilation design. Factors such as temperature, relative humidity, air flow, and how air is exchanged have been modified, tested and remodified. Despite all the efforts, no perfect option has been found, leaving some to look at adding a new factor: disinfection.
For years, two general models have been regarded as the gold standards, filtration and ultraviolet light. Both have been used extensively in the microbiology laboratory environment and are critical to keep the air in these environments safe. However, labs are confined and controlled spaces; when it comes to more open spaces, these technologies may not fare so well.
There may be a more natural option based on a rather antiquated idea: opening the windows. Back in 2007, an international team of researchers discovered natural ventilation led to a decrease in airborne transmission. While factors such as increased air flow and more exchanges helped, a chemical component in natural air not found in its artificially ventilated counterpart most certainly played a role.
The molecule is known as the atmospheric hydroxyl radical (•OH) and is known as an atmospheric cleaner. Its chemical structure is similar to water (H2O); it has one oxygen atom (O) but is missing one of the two hydrogens (H). But while the chemical structure may be easy to understand, how it may help us from becoming ill is rather complex.
To get a better sense of the potential for hydroxyl radicals in preventing airborne infections, I reached out to Tom Charlton, the CEO of a company called HGI Industries, which specializes in disinfection of air using this very intriguing molecule. As he suggests, hydroxyl radicals are not difficult to make indoors and can offer significant benefits.
"Hydroxyl radicals are generated from water vapor and oxygen by the action of a range of ultraviolet frequencies. There are several pathways to generating hydroxyls that involve water, oxygen and ultraviolet radiation. Outside, this happens naturally, thanks to the sun. We've taken this process and brought it inside using our Odorox® technology so we can keep the environment just as safe."
When hydroxyl radicals are made, they are highly reactive and can interact with almost any other molecule rapidly. As Charlton points out, if that molecule happens to be a on the surface of a pathogen, the consequences can be dire. "The cellular membranes of microorganisms are comprised of many organic molecules like lipids, proteins and carbohydrates. They can be easily damaged by hydroxyls much like an enemy attack. If enough of these attacks occur, the membrane becomes so damaged that the cell dies. For humans, this happens without any health concerns but for microbes such as bacteria, viruses and fungi, it is a death sentence."
The process of microbial control using hydroxyls is not entirely new. For over a century, researchers have known sunlight is toxic to bacteria due in part to ultraviolet light. But it wasn't until the 1990s that researchers realized oxygen was also part of the process. As Charlton points out, this is why it may be difficult to regain the benefits of natural air once indoors.
"On a sunny day, there are over two million hydroxyls in each cubic centimeter of outdoor air. Natural levels can be as high as 17 million molecules per cubic centimeter. Indoors, the levels are almost negligible. To mimic the outdoors, these hydroxyls need to be re-established by generating them in the same way as in nature so that it is safe."
The chemistry may be solid, but the question as to whether hydroxyls are effective when used indoors may still be asked. This is where Charlton smiles and explains he's been there and done that. "We've done several studies not only in the lab, but also in large facilities, and we've seen the same thing over and over again. Before you use hydroxyl radicals, it's a stinky, pathogenic mess. After installation, it smells nice, feels nice and there are fewer infections." As a result, he has some big names to support him. "We've applied for FDA approval in the United States although we are further here in Canada. The Minister of Health, Rona Ambrose, likes the technology and the government has given us a green light for food processing facilities."
In light of the potential risks from airborne infections, there may be hope not in advancing human technologies but instead through mimesis of those of nature. Charlton states his company has the Odorox technology available and is committed to making it more available to the majority over the months and years to come.
"I've heard more concern about airborne infection this year than any other. It doesn't matter where you are -- home, work, school and healthcare -- there is worry. Maybe it's due to Ebola, enterovirus, pandemic flu or some other infectious agent. What is clear to me is the need to calm fears going forward. If I can do that using what Mother Nature already gave us, I'll be able to breathe the difference."
In the context of the Endless River of airborne infection control, Pink Floyd may very well agree.