Reminder! I’m still not a doctor. Nor would I want to be one. Nor a nurse. Those people are heroes. Semi-related, but the next time you see a nurse, give them a socially-distanced high-five! They don’t get nearly the love they deserve.
Before I go any further, I want to take a moment and say thank you to everyone that has come to this site – and me – for trusted information. It is humbling to know that you appreciate my judgement to share real, factual information. As well as the occasional estimate based on actual math. There are a lot of outlets to choose from, and it holds a special place in my heart to know that you guys trust me to be real with you.
With both the good and the bead.
Okay, time to get on topic. Kids and masks. I’ve received a few comments and questions over the past few weeks about this. And I’ll be honest, I don’t have a direct answer to offer. And this can be a rather touchy subject. I know a lot of people are for masks for all, and others are masks for none.
The truth – like usual – is somewhere in the middle.
The math of breathing
I want to discuss this from a strictly physics angle first: Children are smaller, and thus the volume of air (CO2) – with the virus – that children can expel in one breath is smaller.
In fact, there was a research paper published way back in the 1960s that looked into this. The paper, titled. “Total lung volume and its subdivisions in children: normal standards” tried to determine the lung capacity of kids. And based on their research, they found that for boys, a formula of (30.71 x Height (in cm)) + (29.35 x Weight (in kg)) – 2545 gave a good idea of lung capacity. And for girls, (30 x Height) + (31.31 x Weight) – 2536.
So, if a boy is 10 years old, is 138cm and 35kg… you just plug and chug! -> (30.7 x 138) + (29.35 x 35) – 2545 = 4236.6 + 1027.25 – 2545 = 2718.85.
So the child’s Vital Capacity = 2718.85 mL = 2.718 L
For adults, it is found a bit differently. It is (27.63 – 0.112 x Age) x Height (in cm)) / 1000.
So, if a guy is 30 and is 182cm tall, more plugging and chugging! ->. ( (27.63 – (.112 x 30) ) x (182) ) / 1000 = (24.27 x 182) x 182 / 1000 = 4.417 L
So a 10 year old is expelling about 60-percent of what a 30-year old adult man would expel.
So, physically speaking… The smaller the child, the lower the risk that the child can infect others by simply breathing.
This gets complicated with coughing, sneezing, singing, yelling, etc.. But with simply breathing. And just looking at the literal volume of air (CO2).
Again, I want to point out that yelling, singing, coughing, sneezing, and everything else can change how far that air is expelled.
But the physics may be the reason that some doctors and researchers have found that the transmission-rate between humans is lower as children get younger than 8-years old. While it isn’t zero, the transmission-rate of the average infected 6-year old is quite a bit lower than, say, a similarly-infected 16-year old. the word “may” carries a lot of weight in that sentence. Because it is important to remember that while some things sound reasonable, it doesn’t make them accurate.
And again, the transmission rate isn’t zero. And we have seen evidence of this plenty of times from the medical community. But evidence has shown the transmission rate to be lower.
Breath less, spread more?
That brings up the question that, “If, physically speaking, children expel less air (CO2) why do any kids have to wear masks?”
The answer may be found in the magnitude of virus and available evidence to support that magnitude.
“Children infected with the coronavirus can transmit it to other kids and adults, but whether they spread the illness more or less than adults is not yet clear,” Aaron Milstone, M.D., M.H.S., a pediatrician at Johns Hopkins Children’s Center and an infectious disease expert at The Johns Hopkins Hospital, said. “Although for the most part, children’s COVID-19 symptoms are milder than those of older people, evidence shows that infected kids carry at least as much of the virus in their mouths and noses as adults.”
In a paper published two weeks ago titled, “Pediatric SARS-CoV-2: Clinical Presentation, Infectivity, and Immune Responses” the researchers found that infected children – even asymptotic ones – could carry more virus in their respiratory system than “hospitalized adults with severe disease.”
That means that while a 10-year old may not expel as much air, that air may be more densely packed with viruses. And according to research done by the National Institute of Health, “There has been no discernible evidence on the minimum infectious viral load for COVID-19 pandemic, but many researchers speculate that a few hundreds of SARS-CoV-2 virus would be enough to cause the disease among susceptible hosts.”
Some of you may recall what I wrote back on March 19th:
According to Johns Hopkins the virus can spread through airborne transmission. Research has shown that tiny droplets remain in the air even after the person with the virus leaves the area. These can remain airborne for up to three hours. This is why it is important to avoid people who are coughing. Even if you are walking 10ft behind them, you may still be at risk for inhaling one of the microscopic airborne droplets. Even hours later.
Those droplets are usually – according to the National Center for Biotechnology Information – under 5 micrometers in size. The Coronavirus itself is about 120 nanometers in size.
So for easy math, let’s say someone sneezes and leaves airborne droplets that at 4 micrometers in size. Those tiny droplets float around – and there could be hundreds – carrying with them about 30 viruses each. And those viruses can start to multiply the second they get into your system.
And because humans don’t have a natural immunity to the infection, each person’s antibodies has to learn how to attack the virus and fight it off. And, due to how the virus multiplies and reproduces itself, that could leave older people more susceptible due to the increased blood sugar (based on research).
So, if that infected 10-year old boy sneezes without a mask on – in public – he could fling thousands of viruses into the air. And if someone walks past that area – say, 10 minutes later – they have a chance to inhale some of the floating viruses. And if it only takes a few hundred to infect someone, that person is at risk for being infected.
Now, the volume of air may be smaller than if an adult sneezed, but the density of virus in the volume of air may actually be higher.
So, should kids wear a mask of not, Nick?
I can’t answer that question. For many reasons. The biggest being: I’m not qualified to answer that question.
But looking at the math, hopefully you can decide for yourself if you want to continue to encourage your kids to wear masks or not. I just wanted to help highlight the evidence about the viral load in children and mathematics regarding the lung capacity.
The only thing I will note is that a lot of the rules and regulations regarding COVID-19 are based on what we know AND based on what we don’t know yet. And I understand that following rules off of an “unknown” can be difficult. But I would encourage everyone to try their best to listen to doctors and medical professionals. They are here for you. They want to keep you safe and healthy. That is their number one priority.
And even if they make a recommendation now that ends up being unnecessary based on evidence in the future, we have to remind ourselves that they are trying their very best to help and be as proactive as possible.
