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linseymarr's profile
Linsey Marr
Linsey Marr
Linsey Marr
Verified account
@linseymarr

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Linsey MarrVerified account

@linseymarr

Engineering prof at VT with expertise in airborne transmission of viruses, air quality, nanotechnology. Intellectual omnivore and avid recreational athlete.

Blacksburg, VA
cee.vt.edu/people/lmarr.h…
Joined February 2009

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    Linsey Marr‏Verified account @linseymarr 11 Mar 2021

    Here's a 🧵summarizing my testimony on airborne transmission of COVID-19. Full version at https://edlabor.house.gov/hearings/clearing-the-air-science-based-strategies-to-protect-workers-from-covid-19-infections … /0

    9:19 AM - 11 Mar 2021
    • 846 Retweets
    • 1,737 Likes
    • Posie Boggs Nick Eliopulos Dezmonroe🦍🚀 Megan Lynch Doug Day Tomás Sherwen Alvin Pahlevi (fully vax’d) kaldu jamur udah vaksin Shannon (😷💉X3 )
    40 replies 846 retweets 1,737 likes
      1. New conversation
      2. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        COVID-19 is transmitted mainly by breathing in aerosol particles carrying the virus. Two other possible routes are 1) touching a sick person or contaminated object and 2) being sprayed by large respiratory droplets. These other routes are rarer. /1

        14 replies 124 retweets 365 likes
        Show this thread
      3. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Many cases of COVID-19 have been traced to “close contacts,” and this was incorrectly interpreted to mean that large droplets were responsible for transmitting the disease. /2

        3 replies 57 retweets 288 likes
        Show this thread
      4. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        When people breathe, talk, sing, laugh, cough, or sneeze, they release far more aerosols than large droplets. These aerosols are most concentrated close to the sick person, and they don’t fall quickly to the ground. /3

        1 reply 83 retweets 318 likes
        Show this thread
      5. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        When people talk in close proximity, it is much more likely that they will breathe in each other’s respiratory aerosols than shower each other with large droplets of spittle. /4

        1 reply 57 retweets 255 likes
        Show this thread
      6. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Aerosols remain floating in the air and follow air currents like cigarette smoke. Aerosols can easily travel more than 6 feet, filling a room and building up over time if the space does not have good ventilation. /5

        5 replies 116 retweets 382 likes
        Show this thread
      7. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Evidence for the importance of aerosol transmission includes superspreading events, transmission by people who are infected and don’t have symptoms (no coughing), much more indoor transmission and almost no outdoor transmission, various scientific studies. /6

        2 replies 67 retweets 303 likes
        Show this thread
      8. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        If you spend a long time around other people indoors and do not wear a good mask, you could breathe in enough virus-containing aerosols to become sick with COVID-19. To limit exposure, avoid crowded indoor spaces and limiting time indoors with others. /7

        1 reply 67 retweets 293 likes
        Show this thread
      9. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        If contact with others cannot be avoided (e.g., essential workers), it is critical to reduce exposure to virus in the air by ensuring good ventilation—this reduces the amount of virus in the air—and wearing high-performance masks or respirators. /8

        2 replies 57 retweets 272 likes
        Show this thread
      10. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        A worker who spends 8-12 hours in a poorly ventilated workplace where they share the air with other people is at much greater risk for transmission than a customer who passes through the space for a short period of time. /9

        2 replies 85 retweets 392 likes
        Show this thread
      11. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Face coverings work in both directions. They reduce the amount of virus that an infected person spreads into the air = “source control.” They can also reduce the amount of virus that the wearer breathes in from the air around them. /10

        2 replies 63 retweets 275 likes
        Show this thread
      12. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Some types of face coverings are much more effective than others against aerosols. The performance of a face covering depends on the filtration efficiency of the material and the fit. /11

        1 reply 33 retweets 206 likes
        Show this thread
      13. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Cloth masks have wildly varying filtration efficiencies of <10% to >90%. The actual performance also depends on fit. Leaks seriously degrade performance. /12

        3 replies 41 retweets 227 likes
        Show this thread
      14. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Surgical masks are good at filtration efficiency because they’re made out of meltblown, non-woven polypropylene, but bad at fit. /13

        3 replies 37 retweets 220 likes
        Show this thread
      15. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Respirators are designed to be tight fitting and to filter out aerosols with very high efficiency. Examples include N95s, KN95s, KF94s, elastomeric respirators. /14

        3 replies 38 retweets 232 likes
        Show this thread
      16. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        For workers and others in high-risk settings, the hierarchy of controls calls for control of source (i.e., masking), engineering controls (i.e., ventilation and filtration), and PPE (i.e., high-performance masks or respirators). /15

        2 replies 45 retweets 214 likes
        Show this thread
      17. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Most CDC guidance and recommendations have not been updated or strengthened to address and limit inhalation exposure to aerosols. CDC downplays aerosols and airborne transmission, a position that is exactly opposite the best scientific evidence. /16

        2 replies 124 retweets 460 likes
        Show this thread
      18. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        CDC’s FAQ on “How does the virus spread?”, emphasizes close contact and says nothing about inhaling the virus. /17

        2 replies 51 retweets 297 likes
        Show this thread
      19. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        The Scientific Brief “SARS-CoV-2 and Potential for Airborne transmission” obfuscates by incorrectly equating all transmission at close proximity with droplets. This is wrong because transmission in close contact is dominated by inhalation of aerosols. /18

        1 reply 57 retweets 285 likes
        Show this thread
      20. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Why the reluctance? 1) Incorrect understanding of aerosols, 2) “airborne” has special meaning in hospitals, 3) concerns about limited supplies of N95s. /19

        5 replies 43 retweets 303 likes
        Show this thread
      21. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        CDC must update and strengthen its guidelines to fully address transmission via inhalation of aerosols at both close distances and farther away. /20

        3 replies 54 retweets 316 likes
        Show this thread
      22. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Most CDC guidance and recommendations continue to emphasize distancing and surface cleaning, which are important, but less important than using high-performance masks and sufficient ventilation to clean the air. /21

        6 replies 94 retweets 371 likes
        Show this thread
      23. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Our letter (https://drive.google.com/file/d/1O5zd_JO-D98iY4DpzwVVfPQFoRIFHpQ5/view …) calls for CDC and OSHA to issue recommendations and requirements that address transmission of COVID-19 by inhalation of aerosols. /22

        7 replies 82 retweets 325 likes
        Show this thread
      24. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        Calling the virus “airborne” is the clearest way to convey how it is transmitted. /23

        7 replies 85 retweets 438 likes
        Show this thread
      25. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        This testimony is based on my 12+ years of studying viruses in the air and 30+ scientific papers on the subject, along with many discussions with colleagues (next tweet). Thanks to @jljcolorado @kprather88 for providing feedback on my testimony. /24

        7 replies 62 retweets 453 likes
        Show this thread
      26. Linsey Marr‏Verified account @linseymarr 11 Mar 2021

        At the risk of overlooking some, especially newer ones: @Don_Milton Yuguo Li, Julian Tang, Lidia Morawska @Lakdawala_Lab @j_g_allen @ShellyMBoulder @CorsIAQ @CathNoakes Lydia Bourouiba @ProfCharlesHaas and all my students and post-docs! /25

        10 replies 21 retweets 233 likes
        Show this thread
      27. End of conversation

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