Hockey rinks and COVID transmission
An issue for ice hockey players
Outbreaks of Covid-19 were a major concern for many before the re-start-up of sports practices, but thanks to careful planning and adherence to safety measures there have not been as many as were predicted thus far. One exception to that, the spread through hockey teams, has sent scientific researchers scrambling to discover why a hockey rink may pose more risk than other athletic environments.
In an article for the CBC, Natalia Goodwin outlined a major outbreak in Ontario that was traced back to one asymptomatic athlete who attended a team practice. The exposure caused by this single individual was traced by Ottawa Public Health (OPH) and led to 89 other confirmed cases, and 445 high-risk contacts connected to ten sports teams, four schools, and a daycare. OPH produced an infographic picture which can be found in Goodwin’s article that outlines just how many lives are impacted by an outbreak of this size.
Some theorized factors contributing to this outbreak were asymptomatic players, players who carpooled with people from outside their households, inconsistent mask use during practices, and large social bubbles caused by coaches coaching multiple teams and players playing for multiple teams. However, given recent research, those are not the only factors that athletes – specifically hockey players – should be mindful of.
Ariana Eunjung Cha and Karin Brulliard spoke with a variety of scientific experts for their article in the Washington Post in early December and outlined several risk factors that have been given little attention. The overarching theory explains that “Experts speculate that ice rinks may trap the virus around head level in a rink that, by design, restricts airflow, temperature and humidity.” Now let’s dive into the specifics.
Those familiar with hockey rinks know that the area of gameplay is surrounded by plexiglass, both to protect spectators from being hit by flying pucks and to stabilize the airflow and keep the ice at a consistent temperature, normally around 20 degrees Fahrenheit. “The Department of Homeland Security has shown in lab experiments that the virus may live at those temperatures up to two times longer in the air. At 86 degrees, for example, 99 percent of the airborne virus is estimated to decay in 52 minutes. But at 50 degrees, it would take 109 minutes.” The lower the temperature, the longer it takes the contagious, airborne particles to die off, meaning that the particles could pose risk for a much longer period of time when in a hockey rink at 20 degrees.
Jose-Luis Jimenez, an air engineer consulted by Cha and Brulliard, believes the low temperature of rinks to also keep those contagious particles at the perfect height to be inhaled. “Much like in a cold winter night, you have these inversions where the cold air with the virus which is heavier stays closer to the ground. That gives players many more chances to breathe it in.” So the particles not only retain their contagious nature for longer in a hockey rink, they are also more likely to be inhaled because of where they sit once exhaled.
Humidity plays a major role here, as hockey rinks must have low humidity to ensure proper ice conditions. “In higher humidity, the virus attaches to bigger droplets that drop faster to the ground, decreasing the chance that someone will inhale them. The drier the air, the faster droplets will evaporate into smaller-sized particles that stay in the air, increasing concentration.”
While these studies are still fresh and come with limitations, they do provide a much deeper look at why hockey practices and games may pose a higher transmission risk than would be found in other gameplay environments, even when those involved adhere to prescribed safety measures.
Links for referenced sources:
CBC – Natalia Goodwin – A hockey practice led to 89 COVID-19 cases. Ice sports say they’re staying vigilant | CBC News
The Washington Post – Ariana Eunjung Cha and Karin Brulliard – Why does covid thrive in hockey rinks? Scientists are trying to solve the mystery. – The Washington Post
Department of Homeland Security’s study on airborne decay of covid – Estimated Airborne Decay of SARS-CoV-2 | Homeland Security (dhs.gov)