Share this page!

Enter URL or ID to Unroll

You can paste full URL like: https://x.com/threadreaderapp/status/1644127596119195649
or just the ID like: 1644127596119195649

How to get URL link on X (Twitter) App

  1. On the Twitter thread, click on or icon on the bottom
  2. Click again on or Share Via icon
  3. Click on Copy Link to Tweet
  4. Paste it above and click "Unroll Thread"!
  5. More info at Twitter Help
Al Haddrell Profile picture
@ukhadds
Aug 14 • 8 tweets • 2 min read • Read on X
Huge paper exploring the relationship between exhalation aerosol counts and CO2 has just been published.

Take home message: CO2 and aerosol strongly correlate in silence. Vocalisation causes this relationship to breakdown (way more aerosol than CO2).
pubs.acs.org/doi/10.1021/ac…
This has huge implications on how CO2 can be used to estimate the aerosol counts in a room. Noise matters!!

I've mentioned this work previously, it's great to see it finally published so everyone can have a good look. Image
I mentioned this work in a previous thread where I discussed the many ways in which CO2 is associated with Covid transmission.

One of the lead authors of this work is Justice Archer (@archerjk). I was fortunate enough to share an office with Justice for a few years.

If you have any questions for him, hit him up.
@PrasadKasibhat1 @archerjk You modeller types need to get on this! I'm curious to see how this changes things in terms of risk: gym vs library vs Taylor Swift concert
@archerjk To summarise (there seems to be some confusion): Image
@JOHNJOHNSTONED @linseymarr @jmcrookston @jljcolorado But as you say, it's not exactly inhalation as opposed to being hit in the mouth by a virus loaded droplet. The odds of that will be rarer.
@JOHNJOHNSTONED @linseymarr @jmcrookston @jljcolorado Regarding Jose's claim about it never been proven. I guess my question would be: how does one prove that? To get hit by a ballistic you necessarily need to be in the plume. I'm not sure how you would disentangle one process from another.

• • •

Missing some Tweet in this thread? You can try to force a refresh
　

Keep Current with Al Haddrell

Al Haddrell Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @ukhadds

Al Haddrell Profile picture
Aug 5
"How does humidity affect SARS-CoV-2 transmission?"

Whenever this question comes up, the answer I give is along the lines of “it’s complicated”.

So, what exactly do I mean (a 🧵)?

Context: When considering airborne transmission of a respiratory virus, numerous factors are involved.

They ALL matter.

Moreover, they are all independent. Meaning, a certain parameter may affect each factor differently. Image
Since the dawn of the field (1950s/60s), the airborne survival of viruses has been measured as a function of relative humidity (RH) and temperature. There are numerous reasons for this, such as to understand viral transmission and to inform about why the virus decays. Image
Read 15 tweets
Al Haddrell Profile picture
Aug 3
Given the unusually high number of swimmers catching Covid in the Olympics, many have hypothesized as to why. I’ve seen a few people point to some work we published on how environmental factors affect SARS-CoV-2’s aerostability.

Some thoughts🧵:

Context:

When respiratory aerosol is exhaled, the dissolved CO2 in the fluid (in the form of HCO3) leaves the aerosol over the course of a couple of minutes. When the CO2 leaves, the pH of the aerosol reaches >10.3.

The high pH drives viral decay. Image
We have reported that anything that can limit this increase in aerosol pH, such as nitric acid or CO2, slows the airborne viral decay rate. This, in turn, will increase the risk of transmission. Image
Read 14 tweets
Al Haddrell Profile picture
Jun 26
Given that the COVID numbers are on the rise, I thought I’d it useful to share some our research team’s work looking at the interplay between CO2, aerosol, SARS-CoV-2, and airborne transmission. 🧵 Image
SARSCoV2 is spread primarily through the air via aerosol. Meaning, the amount of aerosol a person produces will to some degree correlate with the amount of virus exhaled. Our group has done of studies into how different activities affect aerosol production
tandfonline.com/doi/full/10.10…
The amount of aerosol a person exhales is correlated with how loud they are talking/singing. Perhaps a reason why there have been no super spreader events reported in a library (?) Image
Read 13 tweets
Al Haddrell Profile picture
May 25
Understanding the rate aerosol particles change phase is critical, from drug delivery to the lung or atmospheric processes, to disease transmission.

Our work looking into the dissolution and crystallization dynamics of aerosol has just been published:
pubs.acs.org/doi/10.1021/ac…
For example, the size of a particle will influence where it is deposited in the airway. Likewise, the rate in which a solid particle dissolves will affect both where the particle is deposited as well as the structure of the particle when it lands: () pubs.acs.org/doi/10.1021/ac…
Image
Previously, we’ve reported that when aerosol containing SARS-CoV-2 are exhaled into dry air, the aerosol changes phase (effloresces). This results in a rapid loss of ~50% of the infectious viral load.

Understanding aerosol phase dynamics is important!

royalsocietypublishing.org/doi/10.1098/rs…
Image
Read 10 tweets
Al Haddrell Profile picture
May 18
@ToshiAkima Great question! The maximum pH respiratory aerosol will reach is highly dependent on CO2. The evaporation of CO2 from the droplet is relatively slow, taking 10s of seconds to minutes. One result of this is at 2 minutes, we saw no effect on aerostability between 500ppm and 0ppm: Image
@ToshiAkima Thus, at 2 minutes the pH of the 500 and 0 ppm droplets were still the same. The result of this is that for short distance transmission, the increase in outdoor CO2 concentration over the past hundred or so years would be expected to have no effect. HOWEVER…
@ToshiAkima After 2 minutes, the pH difference between the 2 would become different. The expected result would be at lower CO2, >99% of the infectious viral load would be gone faster. Much in the same way we show with 3000 ppm vs 500 ppm data: Image
Read 5 tweets
Al Haddrell Profile picture
Apr 26
I’m excited to discuss our latest research on how ambient CO2 affects how long #SARSCoV2 remains infectious in air. We report that even subtle increases in CO2 affects both how long #COVIDisAirborne and transmission risk. Here’s a🧵going over the findings
nature.com/articles/s4146…
Somebroader context: this study is the third part of our SARS-CoV-2 (SARS-Wars(?)) trilogy. Image
In our first paper we reported that the decay dynamics of the original strain. We reported that the viral decay rate is faster than initially reported: 90% of the viral load is inactivated in 20 min. We proposed aerosol pH was playing a role in the decay

pnas.org/doi/full/10.10…
Read 64 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

Send Email!

:(