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Kimberly Prather, Ph.D. Profile picture
@kprather88
Aug 9, 2021 • 29 tweets • 11 min read • Read on X
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0. Decided to make a thread on what we have done @UCSanDiego to create a safe University environment during COVID-19. I was also involved in opening @sdschools. In both cases, we were able to open and remain open. (1/)
1. Vaccines are required for all (this is key tool for Fall since Delta is here). Having this more transmissible variant sets a higher bar for all other mitigations...i.e. need better/more filtration and ventilation, aerosol masks, etc.) (2/)
2a. Masks indoors at all times. Eat outside, if possible. Note that taking mask off after people leave the room is HIGH RISK--the virus can hang in the air for HOURS. Note that masks are key-they block the virus from getting into the air in the first place. (3/)
2b. Once airborne, it becomes much harder to control. Breathing produces aerosols. Speaking makes even more. Yelling and singing even more. Coughing and sneezing produce bursts--but many times the people producing the virus do not know they are sick and have no symptoms. (4/)
2c. Important that the masks fit well--surgical masks leak (designed for droplet protection) and are not as good for blocking aerosols. There is lots of info on this on the web and Twitter on the best masks for people of all ages. (5/)
3a. Air ventilation-bring in as much outside air as you can thru the HVAC system. Avoid re-circulating air. Important to measure CO2 levels when classes are running-w/ people present. Levels need to be <800 ppm. ARANET4 is a great sensor that can be used to assess. (6/)
3b. Fresh outdoor air is 415 ppm so this is as low as possible and suggests one is breathing fresh air. Higher levels mean you are breathing other people's breath which can contain virus. This virus released in the breath of infectious people. 1000x more released w/ Delta (7/)
4a. Air filtration: Two types: 1) upgrade HVAC filters to MERV13. Make sure they fit well and there are no gaps/leaks. 2) supplement and add standalone HEPA filters (simple filtration--no ionizers or other bells and whistles) throughout big rooms. (8/)
4b. Reduces concentration of all aerosols and provides overall cleaner air (good!). Best to run 2 or 3 on lower speeds so they are more quiet. There are tests for quietness -- see Marwa Zaatari on Twitter.



(9/)
4c. To build inexpensive air filters-see Rich Corsi @CorsIAQ, Jim Rosenthal @JimRosenthal4, David Elfstrom @DavidElfstrom--all are on Twitter-great info-some below including cost estimate.





(10/)
5. Wastewater testing. We tested wastewater in all buildings @UCSanDiego -- other Universities did this too. This gives you a heads up before big outbreaks occur. When a building tests positive, everyone is alerted in that building and told to be tested. (11/)
6. Testing is key--PCR most common. There are really cheap rapid antigen tests that only cost $5 per test and only come up positive when the individual is infectious! Attached is article on the rapid/cheap tests developed by @michaelmina_lab

insidemedicine.bulletin.com/378975113857960

(12/)
7. @UCSanDiego hired student "ambassadors" to help insure people were adhering to "rules"--wearing masks, avoiding crowds, etc. Enlisting a peer cohort (who wore bright yellow T-shirts) to help spread the word helped get important buy-in. (13/)
Items 8-10.

8. When spread was really high in community--we only allowed one student per dorm room. In Fall, we will have two per room.

9. Tracing -- when someone tested positive, we did tracing/testing of contacts.

10. Post signs reminding people to wear masks, etc.

(14/)
11. Here is @UCSanDiego dashboard with lots of info-open and transparent sharing of info as you will see.

returntolearn.ucsd.edu

Here is a video you can show them on how aerosols spread and fill a room....



(15/)
12. Note the riskiest places to be are crowded indoor locations with poor ventilation and people talking/yelling without masks.

FAQs on protecting yourself that we created:

tinyurl.com/FAQ-aerosols

(16/)
13. I also attached a list of items for protecting yourself from 1918--Do's and Don'ts showing we have known what to do for a very long time!



(17/)
14a. Final points-Also, please share the Greenhalgh paper I co-authored-this provides evidence for how we know the main mode of transmission is in aerosols through the air -- sharing air needs to be avoided.

(18/)
14b. If you can't, then masks and cleaning the air are critical. People say ventilation and filtration are expensive--they don't have to be. Can simply open the windows and doors (for free).

(19/)
14c. Build cheap filtration devices (see above). This will have health benefits beyond COVID-19!! It will reduce respiratory disease of all kinds (flu too) and cognitive issues in kids related to high CO2 levels and add extra protection until everyone can be vaccinated.

(20/)
15. Multiple layers of protection are critical especially to protect those that are unvaccinated still.



(21/)
16. Key point....we need vaccines as well as controls to clean indoor air to reduce the spread of this virus and protect everyone. See tweet below for more.

17. I am sure I am forgetting something. I just wrote this off the top of my head this morning based on an email I sent to help others at another University. Feel free to add helpful info. Hope it helps!
18. One on masks...excellent thread by Dr. @trishgreenhalgh superstar MD at Oxford.

19. Great info on kid masks by @masknerd.

High efficiency masks that filter aerosols are critical. Surgical masks are designed to block big droplets-aerosols leak out/in. There is a simple brace you can add to improve them or there are other options.

20. One more good thread on masks by @CPita3. Her threads are incredibly informative--if you don't follow her, you should!

21. More details on our wastewater surveillance program @UCSanDiego. Our group helped build a way to automate them so more samples could be easily collected. Before this, it required a massive amount of time.

health.ucsd.edu/news/releases/…
22. One more on our paper in @TheLancet which gives the evidence on this virus mainly being transported through the air and inhaled just in case your school district of leaders do not know. You can buy many filtration systems in place of hand sanitizer.

23. Almost forgot one of the best aspects @UCSanDiego makes testing as easy as possible. All staff/students/faculty can be tested as much as they want--FOR FREE. It is easy too--self test kits are in vending machines located all over campus!! Thank you:

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More from @kprather88

Kimberly Prather, Ph.D. Profile picture
Mar 8
(1/23) More on the largest ongoing environmental health crisis in the United States. Many of you asked for more details on our Tijuana River research after my thread yesterday []. Here's what we (@airborne_ucsd) have found so far — and why no one should be forced to breathe this toxic air for another day. 🧵
(2/23) When ~240 million gallons of sewage recently leaked into the Potomac River near DC, it was declared a state of emergency within days. The @NYTimes incorrectly labelled it as the largest sewage leak in U.S. history. The Tijuana River releases that amount every few days continuously — and has for years. No emergency declaration. No national outcry. This is environmental injustice, plain and simple.
(3/23) See @nbc7sandiego story on the frustrated reactions of local residents to the @NYTimes erroneously labelling the Potomac River () spill the worst in U.S. history:. They've been living through something far worse — for years — with only a tiny fraction of the attention.
Read 23 tweets
Kimberly Prather, Ph.D. Profile picture
Mar 7
🧵Right now, 40–80 MILLION gallons of raw sewage and wastewater flow through San Diego's South Bay region EVERY DAY — poisoning the air, water, and people in some of California's most socio-economically challenged communities. This is the largest ongoing environmental crisis in the U.S. Most Americans have no idea. A thread. (1/10) 👇
My team's study in @ScienceMagazine (Rico et al., 2025) established for the first time a direct link between contaminated water and hazardous AIR quality. We measured hydrogen sulfide — a gas that attacks the respiratory and nervous systems — at 4,500x typical urban levels. (2/10)
But H₂S is just the beginning. We're detecting massive levels of heavy metals, thousands of other gases, PFAS (forever chemicals), pharmaceutical compounds, and drugs in polluted river foam — and airborne pathogens carried from the contaminated waterway directly into neighborhoods where families live and children go to school. (3/10)
Read 10 tweets
Kimberly Prather, Ph.D. Profile picture
Mar 3
1/ If I hear one more public official call indoor air filters a "band-aid," I'm going to explode! It's so logical, yet so readily dismissed. Filtering indoor air should be as standard as filtering water. Full stop. 🧵
2/ Measles, flu, COVID-19, norovirus—most infectious diseases spread through the air we breathe. We just accept that everyone gets sick indoors. It doesn't have to be this way.
3/ And it's not just pathogens. Wildfire smoke, heavy metals, toxic gases, soot—all flowing into your lungs, heart, and even your brain with every single breath you take.
Read 9 tweets
Kimberly Prather, Ph.D. Profile picture
Jan 26, 2025
The science/research landscape (at least in the US) has evolved so much since I began. It used to be about forming a hypothesis and exploring it—you might be right, you might be wrong. You'd design the best experiment to test it. Often in science, being "wrong" (1/)
helps us end up learning so much more and possibly changing a longstanding "belief"-referred to as a paradigm shift. Now you get called out for being wrong and called all kinds of names by those (non-scientists) who your hypothesis/finding feel inconvenienced. (2/)
It's a really sad time as it has become difficult to talk to anyone about our best ideas/thoughts because there are "two sides" now even in science. If you say you are trying to understand the reason for the differences, people will immediately classify you as the problem. (3/)
Read 6 tweets
Kimberly Prather, Ph.D. Profile picture
Jan 13, 2025
Getting questions about LA -- the air looks really clean right now. That is because the PM levels (which scatter light) are very low (the air is being pushed out to sea). However, air toxins are still present from the burning of structures and synthetic materials. More...(1/2)
The AQ index being reported says "Good"--that is based on a handful of criteria pollutants like ozone and NOx (and PM). There are literally thousands of other gases present in the air right now which will react away and become more dilute over time. Stay safe. (2/2)
Current AQI readings with areas of fires marked in red: Image
Read 5 tweets
Kimberly Prather, Ph.D. Profile picture
Oct 28, 2024
Sad to see a few surfers and couple of weak writers saying I was alarmist during Covid and now again w/ high H2S levels in air. Alarmist? Really? How about thank you for helping you and your family stay safe. Yes I still would not go in the ocean with raw sewage. Not a chance.
Further..yes we have since shown that bacteria from the polluted ocean/river water can become airborne. No that dumb woman was not wrong then or now.

pubs.acs.org/doi/full/10.10…
It is a battle between just ignoring idiots who clearly don't read the scientific literature versus speaking up because you're concerned their idiocy confuses others. I care a lot about the public--and these dudes clearly do not. Yes, a reporter from the LA Times (1/2)
Read 4 tweets

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