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Is Outside Air COVID-Safe? Are Masks Needed Outdoors?

Is Outside Air COVID-Safe? Are Masks Needed Outdoors?

Via Cliff Mass Weather Blog,

When I visit parks in Seattle and the region, bike along the Burke Gilman Trail, cross-country ski at WA snowparks, or go hiking in the Cascades, I note that.

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Is Outside Air COVID-Safe? Are Masks Needed Outdoors?

Via Cliff Mass Weather Blog,

When I visit parks in Seattle and the region, bike along the Burke Gilman Trail, cross-country ski at WA snowparks, or go hiking in the Cascades, I note that many people are wearing masks outdoors to avoid COVID-19.  A lot of people.

Some folks are clearly afraid and fearful of COVID exposure outdoors.  For example, I often see individuals making a point to avoid unmasked bikers or joggers on the Burke-Gilman trail...moving 5-10 feet off the trail and sometimes turning away. Occasionally it gets tense, as when one local scientist (not me) was angrily called a "Republican" when he was walking in a park without a mask.  

The fear of outdoor spread even hit the management of Seattle Parks last year, when several parks and their parking lots were closed because of COVID fears.

Photo by Nate Loper Through a Creative Commons License

It is time to bring science to this issue and to relieve the worries of many who wish to enjoy outdoor recreation.

In this blog, I will tell you about measurements of carbon dioxide (CO2) I took around Seattle this weekend, measurements that suggest little threat of COVID transmission outdoors. I will also review some of the latest scientific literature, which again does not indicate a significant threat of COVID transmission in the outside air.

The message of this information is obvious: wearing masks outdoors does not appear to be necessary.

My Field Experiment Around Seattle

In my experiment, I used a sensitive CO2 sensor that makes use of proven measurement technology (see below).  Human breathing puts out a lot of CO2, roughly 4 percent by volume or roughly 40,000 parts per million (ppm).  The background level of CO2 in the free atmosphere is currently approximately 415 ppm.... a concentration much, much less than coming out of our mouths.

Thus, CO2 can act as a tracer of the air coming out of our respiratory systems, something mosquitoes know all about since they use the plume of CO2 we exhale to find us.  By measuring CO2 levels, it is possible to determine the relative concentration of air coming from humans and the degree of dilution by the surrounding air.

There have been a number of peer-reviewed scientific papers that have shown that CO2 concentrations are a potent tool for evaluating the potential for disease spread by viruses and other agents, with higher concentrations of CO2 associated with more transmission of disease (some examples of relevant scientific papers found here and here).  

Most of these papers use CO2 to measure the potential for transmission in indoor spaces, so why not take it one step further and evaluate potential disease transmission in the outside environment? That is what I did around Seattle on Saturday, a very nice day (high around 63F) with lots of people in the parks and outdoor locations.

My CO2 unit reported about 400-405 ppm away from roads and people, and this value represents the background level of carbon dioxide.

The Burke-Gilman Trail

My first stop was the crowded Burke Gilman trail, with folks walking, running, and whizzing by continuously.  There was no increase in CO2 concentrations compared to the background at any time (around 400).  Clearly, the diffusion/dispersion/dilution of CO2 by outside environmental air was very large.  And the same would be true of any COVID virus breathed out by anyone on the trail.

Magnuson Park

I then traveled to Magnuson Park, one of the most popular parks in Seattle.  First, I walked about a half-mile, back and forth, on a crowded path.  No increase in CO2 values above background (still around 400 ppm).  

Then I decided to really push things and walked around crowded picnic shelters, some with as many as 15-20 peoples without masks. (I suspect they thought I was being a bit odd as I circled around the groups, but this was for science!)   I could find no enhancement of CO2 above the background levels....natural movement of air diffused their CO2 emissions completely.    I did find a weak signal downstream of a raging barbecue fire...but even that was muted (about a 10 ppm increase 40 feet downwind).

So the bottom line so far:  natural ventilation and mixing in the outside air was effective in diffusing the CO2 emitted by people in an outside park environment, even when there was a high density of people.  And if CO2 enhancement by all the people was undetectable, the same would be true of COVID-19 virus emission by any infected individuals.  Parks appear to be entirely safe locations and masks are not necessary.

University Village Shopping Center:  Outside and Inside

Next, I went to the University Village shopping center.  There is a nice little urban park adjacent to the Apple Store.  It was packed with people enjoying the nice weather.  If there was going to be a place where human CO2 would be evident, this would be it, particularly with nearby structures lessening the wind flow.

I walked all around the park, even close to groups of people.  Only background levels of CO2 were observed.  No hint of people's CO2.  Atmospheric mixing was still large, and thus there was little threat of catching COVID-19 from the general environment.  And I found similar results near lines of individuals waiting to enter some U. Village stores.

Supermarkets and Indoor Restaurants

As a little side test, I then went into a busy local supermarket.  The CO2 concentration zoomed up to 830 ppm.  A warning, perhaps, about food stores.  

Then I went into a restaurant, one that was well ventilated (I could feel the breeze) and with reasonable spacing between tables.   The CO2 level was a very modest 520.  Turns out the restaurant had a CO2 meter, which read 530.   Good confirmation of my calibration and a positive note about the restaurant providing a safe environment for its patrons.

A Visit to A Gym

Then I stopped in a local gym, a major one located in northeast Seattle.  Lots of ventilation and the CO2 level was a very modest 465.   A safe place for one's workout and less than the value in my home (which is about 530).   People are required to wear masks in the gym, but quite honestly they probably aren't needed.

Reality Check

I shared my results with some local air quality experts and a well-known epidemiologist.  They thought my results were reasonable and not surprising.   They acknowledged that COVID transmission is far less problematic outdoors. 

One suggested that the risk outside was not zero:  imagine if you had a conversation with a highly infectious individual for an extended time at close proximity (within a foot or two), with little wind and the person was upstream of you.  Perhaps.  But you can imagine how unlikely this situation would be.  And easily avoided.

The epidemiologist, although generally agreeing about the safety of outdoor air, suggested the potential for a very short (transient) exposure to the long-distance breath of a COVID-infected person.

He noted the example of smelling cigar or pot smoke at a distance--might one get exposed to COVID the same way?  I suspect this is highly unlikely. First, large virus-containing droplets tend to fall out close to the infected (that is why there is a six-foot "rule" for separation).  And smaller particles tend to get diluted with distance. But just as important is that current best science suggests that extended or prolonged exposure to a COVID-infected individual is necessary, with the Centers for Disease Control indicating 30 minutes or longer (see here).  That is simply not going to happen outside if you and the source are moving around.

This never made any sense and prevent people from enjoying a healthful environment

Finally, what does the current scientific literature indicate about outdoor transmission?  The scientific literature is very thin on this topic, but here are some examples:

  • Qian et al., 2020:   Examined 1245 confirmed cases in 120 cities in China and identified only a single outbreak in an outdoor environment, which involved two cases. 

  • Nishiura et al., 2020:  Transmission of COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval). (they could not exclude the possibility that the few "outdoor" transmission might have occurred by undocumented indoor transmission)

  • Bulfone et al., 2021:  A review of all the literature on outdoor transmission.  They found only five studies, two of which are above.  They noted the poor quality and inconsistent approaches of most of the studies so far.

Quite honestly, one can only be disappointed in the quality of the "studies"  on outdoor transmission, which is surprising at this point in time.  Importantly, there is no compelling published research that demonstrates significant outdoor transmission. 

The Key Message

My observations of CO2 concentrations suggest that the diffusion, dilution, and dispersion of human exhalations are very large outdoors, making the threat of outdoor COVID-19 transmission very, very low.  This is consistent with the (limited) scientific literature on the topic.

Outside air is very safe, and it gets even safer during the summer since ultraviolet radiation rapidly kills airborne virus.  The logical conclusion from these results is that wearing a mask outdoors is probably unnecessary. Closing outdoor parks makes no sense at all.

If any of you see some weaknesses in the above logic, let me know.  That is how science works.

Tyler Durden Mon, 04/05/2021 - 19:00

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There will soon be one million seats on this popular Amtrak route

“More people are taking the train than ever before,” says Amtrak’s Executive Vice President.

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While the size of the United States makes it hard for it to compete with the inter-city train access available in places like Japan and many European countries, Amtrak trains are a very popular transportation option in certain pockets of the country — so much so that the country’s national railway company is expanding its Northeast Corridor by more than one million seats.

Related: This is what it's like to take a 19-hour train from New York to Chicago

Running from Boston all the way south to Washington, D.C., the route is one of the most popular as it passes through the most densely populated part of the country and serves as a commuter train for those who need to go between East Coast cities such as New York and Philadelphia for business.

Veronika Bondarenko captured this photo of New York’s Moynihan Train Hall. 

Veronika Bondarenko

Amtrak launches new routes, promises travelers ‘additional travel options’

Earlier this month, Amtrak announced that it was adding four additional Northeastern routes to its schedule — two more routes between New York’s Penn Station and Union Station in Washington, D.C. on the weekend, a new early-morning weekday route between New York and Philadelphia’s William H. Gray III 30th Street Station and a weekend route between Philadelphia and Boston’s South Station.

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According to Amtrak, these additions will increase Northeast Corridor’s service by 20% on the weekdays and 10% on the weekends for a total of one million additional seats when counted by how many will ride the corridor over the year.

“More people are taking the train than ever before and we’re proud to offer our customers additional travel options when they ride with us on the Northeast Regional,” Amtrak Executive Vice President and Chief Commercial Officer Eliot Hamlisch said in a statement on the new routes. “The Northeast Regional gets you where you want to go comfortably, conveniently and sustainably as you breeze past traffic on I-95 for a more enjoyable travel experience.”

Here are some of the other Amtrak changes you can expect to see

Amtrak also said that, in the 2023 financial year, the Northeast Corridor had nearly 9.2 million riders — 8% more than it had pre-pandemic and a 29% increase from 2022. The higher demand, particularly during both off-peak hours and the time when many business travelers use to get to work, is pushing Amtrak to invest into this corridor in particular.

To reach more customers, Amtrak has also made several changes to both its routes and pricing system. In the fall of 2023, it introduced a type of new “Night Owl Fare” — if traveling during very late or very early hours, one can go between cities like New York and Philadelphia or Philadelphia and Washington. D.C. for $5 to $15.

As travel on the same routes during peak hours can reach as much as $300, this was a deliberate move to reach those who have the flexibility of time and might have otherwise preferred more affordable methods of transportation such as the bus. After seeing strong uptake, Amtrak added this type of fare to more Boston routes.

The largest distances, such as the ones between Boston and New York or New York and Washington, are available at the lowest rate for $20.

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The next pandemic? It’s already here for Earth’s wildlife

Bird flu is decimating species already threatened by climate change and habitat loss.

I am a conservation biologist who studies emerging infectious diseases. When people ask me what I think the next pandemic will be I often say that we are in the midst of one – it’s just afflicting a great many species more than ours.

I am referring to the highly pathogenic strain of avian influenza H5N1 (HPAI H5N1), otherwise known as bird flu, which has killed millions of birds and unknown numbers of mammals, particularly during the past three years.

This is the strain that emerged in domestic geese in China in 1997 and quickly jumped to humans in south-east Asia with a mortality rate of around 40-50%. My research group encountered the virus when it killed a mammal, an endangered Owston’s palm civet, in a captive breeding programme in Cuc Phuong National Park Vietnam in 2005.

How these animals caught bird flu was never confirmed. Their diet is mainly earthworms, so they had not been infected by eating diseased poultry like many captive tigers in the region.

This discovery prompted us to collate all confirmed reports of fatal infection with bird flu to assess just how broad a threat to wildlife this virus might pose.

This is how a newly discovered virus in Chinese poultry came to threaten so much of the world’s biodiversity.

H5N1 originated on a Chinese poultry farm in 1997. ChameleonsEye/Shutterstock

The first signs

Until December 2005, most confirmed infections had been found in a few zoos and rescue centres in Thailand and Cambodia. Our analysis in 2006 showed that nearly half (48%) of all the different groups of birds (known to taxonomists as “orders”) contained a species in which a fatal infection of bird flu had been reported. These 13 orders comprised 84% of all bird species.

We reasoned 20 years ago that the strains of H5N1 circulating were probably highly pathogenic to all bird orders. We also showed that the list of confirmed infected species included those that were globally threatened and that important habitats, such as Vietnam’s Mekong delta, lay close to reported poultry outbreaks.

Mammals known to be susceptible to bird flu during the early 2000s included primates, rodents, pigs and rabbits. Large carnivores such as Bengal tigers and clouded leopards were reported to have been killed, as well as domestic cats.

Our 2006 paper showed the ease with which this virus crossed species barriers and suggested it might one day produce a pandemic-scale threat to global biodiversity.

Unfortunately, our warnings were correct.

A roving sickness

Two decades on, bird flu is killing species from the high Arctic to mainland Antarctica.

In the past couple of years, bird flu has spread rapidly across Europe and infiltrated North and South America, killing millions of poultry and a variety of bird and mammal species. A recent paper found that 26 countries have reported at least 48 mammal species that have died from the virus since 2020, when the latest increase in reported infections started.

Not even the ocean is safe. Since 2020, 13 species of aquatic mammal have succumbed, including American sea lions, porpoises and dolphins, often dying in their thousands in South America. A wide range of scavenging and predatory mammals that live on land are now also confirmed to be susceptible, including mountain lions, lynx, brown, black and polar bears.

The UK alone has lost over 75% of its great skuas and seen a 25% decline in northern gannets. Recent declines in sandwich terns (35%) and common terns (42%) were also largely driven by the virus.

Scientists haven’t managed to completely sequence the virus in all affected species. Research and continuous surveillance could tell us how adaptable it ultimately becomes, and whether it can jump to even more species. We know it can already infect humans – one or more genetic mutations may make it more infectious.

At the crossroads

Between January 1 2003 and December 21 2023, 882 cases of human infection with the H5N1 virus were reported from 23 countries, of which 461 (52%) were fatal.

Of these fatal cases, more than half were in Vietnam, China, Cambodia and Laos. Poultry-to-human infections were first recorded in Cambodia in December 2003. Intermittent cases were reported until 2014, followed by a gap until 2023, yielding 41 deaths from 64 cases. The subtype of H5N1 virus responsible has been detected in poultry in Cambodia since 2014. In the early 2000s, the H5N1 virus circulating had a high human mortality rate, so it is worrying that we are now starting to see people dying after contact with poultry again.

It’s not just H5 subtypes of bird flu that concern humans. The H10N1 virus was originally isolated from wild birds in South Korea, but has also been reported in samples from China and Mongolia.

Recent research found that these particular virus subtypes may be able to jump to humans after they were found to be pathogenic in laboratory mice and ferrets. The first person who was confirmed to be infected with H10N5 died in China on January 27 2024, but this patient was also suffering from seasonal flu (H3N2). They had been exposed to live poultry which also tested positive for H10N5.

Species already threatened with extinction are among those which have died due to bird flu in the past three years. The first deaths from the virus in mainland Antarctica have just been confirmed in skuas, highlighting a looming threat to penguin colonies whose eggs and chicks skuas prey on. Humboldt penguins have already been killed by the virus in Chile.

A colony of king penguins.
Remote penguin colonies are already threatened by climate change. AndreAnita/Shutterstock

How can we stem this tsunami of H5N1 and other avian influenzas? Completely overhaul poultry production on a global scale. Make farms self-sufficient in rearing eggs and chicks instead of exporting them internationally. The trend towards megafarms containing over a million birds must be stopped in its tracks.

To prevent the worst outcomes for this virus, we must revisit its primary source: the incubator of intensive poultry farms.

Diana Bell does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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This is the biggest money mistake you’re making during travel

A retail expert talks of some common money mistakes travelers make on their trips.

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Travel is expensive. Despite the explosion of travel demand in the two years since the world opened up from the pandemic, survey after survey shows that financial reasons are the biggest factor keeping some from taking their desired trips.

Airfare, accommodation as well as food and entertainment during the trip have all outpaced inflation over the last four years.

Related: This is why we're still spending an insane amount of money on travel

But while there are multiple tricks and “travel hacks” for finding cheaper plane tickets and accommodation, the biggest financial mistake that leads to blown travel budgets is much smaller and more insidious.

A traveler watches a plane takeoff at an airport gate.

Jeshoots on Unsplash

This is what you should (and shouldn’t) spend your money on while abroad

“When it comes to traveling, it's hard to resist buying items so you can have a piece of that memory at home,” Kristen Gall, a retail expert who heads the financial planning section at points-back platform Rakuten, told Travel + Leisure in an interview. “However, it's important to remember that you don't need every souvenir that catches your eye.”

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According to Gall, souvenirs not only have a tendency to add up in price but also weight which can in turn require one to pay for extra weight or even another suitcase at the airport — over the last two months, airlines like Delta  (DAL) , American Airlines  (AAL)  and JetBlue Airways  (JBLU)  have all followed each other in increasing baggage prices to in some cases as much as $60 for a first bag and $100 for a second one.

While such extras may not seem like a lot compared to the thousands one might have spent on the hotel and ticket, they all have what is sometimes known as a “coffee” or “takeout effect” in which small expenses can lead one to overspend by a large amount.

‘Save up for one special thing rather than a bunch of trinkets…’

“When traveling abroad, I recommend only purchasing items that you can't get back at home, or that are small enough to not impact your luggage weight,” Gall said. “If you’re set on bringing home a souvenir, save up for one special thing, rather than wasting your money on a bunch of trinkets you may not think twice about once you return home.”

Along with the immediate costs, there is also the risk of purchasing things that go to waste when returning home from an international vacation. Alcohol is subject to airlines’ liquid rules while certain types of foods, particularly meat and other animal products, can be confiscated by customs. 

While one incident of losing an expensive bottle of liquor or cheese brought back from a country like France will often make travelers forever careful, those who travel internationally less frequently will often be unaware of specific rules and be forced to part with something they spent money on at the airport.

“It's important to keep in mind that you're going to have to travel back with everything you purchased,” Gall continued. “[…] Be careful when buying food or wine, as it may not make it through customs. Foods like chocolate are typically fine, but items like meat and produce are likely prohibited to come back into the country.

Related: Veteran fund manager picks favorite stocks for 2024

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