2/ The air pollution that we breathe during our lifetime, even pollution of outdoor origin, is dominated by the air we breathe INDOORS.
3/ We can dramatically reduce our exposure to air pollution by reducing emissions from indoor sources, removing pollutants of indoor origin (ventilation & good engineering controls), & designing/operating buildings to reduce outdoor pollution from penetrating indoors.
Highest % of courses with a hands-on component in the entire CSU system.
3rd highest % of students in natural resources and STEM programs in CSU.
CSU’s highest % of STEM grads who go on to earn doctoral degrees, ranking 8th nationally among 660 master’s level institutions.
It's always had a robust Environmental (Resources) Engineering degree program, among the largest and oldest in the US. That program has graduated a large number of highly-qualified engineers who have served the State of California & beyond.
1/ I agree with @Don_Milton. It is important to distinguish between near- and far-field aerosol particles. In the near field (close contact) there is potential for much higher concentration of aerosol particles in the breathing zone of a receptor.
2/ The actual concentration depends on extent of emissions from infector, body positioning of infector and receptor, mixing conditions between infector and receptor (which depends on a number of other factors), and DISTANCE between infector and receptor.
3/ Aerosol particles do not vanish beyond the near field. They exist in the far field and will accumulate until an approximate steady-state is achieved (more on this later) as long as the infector(s) stay in the space.
Sad that we have come to this point. We are here because throughout this mess political leaders, health authorities, and the general public were irresponsible, stubborn, & impatient. Will we learn from this that "fits and starts" is the worst possible policy?
We did not invoke the precautionary principle early on this pandemic, deciding (without any scientific evidence) that only three of four transmission routes were relevant and downplaying transmission by aerosol particles.
Across the board, there was a lack of unified effort to starve this virus of its hosts & manage it. We did not need major investments. What needed to be done was obvious to many scientists from the start, but lacked acceptance by leaders, unified messaging, & public commitment.
1/ Most important thing at the moment is to starve this virus of hosts. Need political leaders, business owners, bldg managers, school officials & public all acting in concert to substantially reduce inhaled dose of virus-laden aerosol particles in indoor near- & far-fields.
2/ We will find ourselves w/ similar challenges again. So, we also need to reflect on all of the things done wrong to get us into this horrific mess, learn from mistakes, and be prepared to do the right things next time.
3/ There have been unconscionable failures of leadership that fueled this mess. But there have also been many other failures, from general public to academia, media to businesses, medical profession to much more.
1/ Reviewing data from past school study in Texas. On average ventilation rates are considerably higher in portable than in permanent classrooms, but with much greater variability.
2/ Portables are much more connected to outdoor environment - greater infiltration and opportunity for natural ventilation (open door/windows).
3/ But interestingly, portables (on average) appear to have higher rebreathed fraction of air (fraction of inhaled air that was exhaled by others in the indoor space) than permanent classrooms due to higher density (occupants per classroom volume).
1/ As a senior in high school I ran for Mayor of @TorranceCA, Calif, against a sitting Councilmember (James Armstrong). At the time I believe I was the youngest candidate to ever run (& lose!) in California. Gr8 experience and learned a new meaning for the term "landslide".
2/ I conceded immediately after the votes were counted. Within a couple of days my "opponent" and I had lunch together at the Good Earth in the Del Amo Mall. We kept in touch over the years until Jim's passing & would occasionally discuss our campaign and debates.
3/ We had several public debates, including one on the radio that I wish I could find. To this day, I am haunted by a question regarding my views on binding arbitration.
1/ As inferno of infection kills & drives nation to the abyss, many governors starting to take stricter action. Many waited too long, frozen in headlights, or in denial. Need strong leadership (courage) to reduce inhalation dose (& so cases & deaths). Just Do It!
2/ "Fits & starts" has been a HORRIBLE approach & only added to suffering, deaths, economic crisis, lost jobs, detriment to education of children. The correct approach was all-out assault on reducing inhalation dose to "starve" virus of hosts and then manage it like others did.
3/ Much more difficult to do this now because of lack of leadership & long delay in listening to experts related to transmission by and control of aerosol particles that are ride share for virus. Need an all-out assault to reduce inhalation dose now to save lives. Let's do it!
1/ Much of US is on fire w/ COVID-19 infection & the flames are only getting hotter. Politicians & the general public who continue to be cavalier about, or blind to, this inferno are adding fuel to fire. People are burning. People are dying.1st responders are exhausted & dying.
2/ We know what to do. Wear a mask in indoor spaces outside of own home w/ immediate family, avoid non-essential indoor spaces, limit time in indoor spaces where you must go, physically distance. Just do it!
3/ Business or building owners/building managers: Require masks, design for physical distancing, reduce density, increase ventilation, improve filtration and/or employ UV. Just do it!
1/ Heading to 200K/day this month & 300K/day in Dec. Increased death rates to follow. What got us here is obvious. Failed leadership. Ill preparedness. Stubbornness. Failed communication. Irresponsible behavior. Water under bridge now. Learn from it, but move on w/ urgency.
2/ Do we act now to save hundreds of thousands more from gasping for breath & dying without family around them, the heartache of losing loved ones, the struggles of those who survive, the horrific impacts on our economy? Acting now is responsible, empathetic, and patriotic.
3/ Please be a patriot. Act. Wear a mask in any indoor space other than your own home w/ immediate family present. Visit only essential indoor spaces where everyone wears a mask. Reduce time in those spaces. Distance. Ventilate. Filter. Sanitize hands. Help to educate others.
Inhaled deposited dose of aerosol particles via close contact is difficult to model, even if two people stay facing each other at 4 - 6 feet apart, due to huge variations in emissions as well as dispersion of the plume between them.
2/ If the indoor space is a crowded event (e.g., wedding reception, bar, etc.) in which people move around, the complexity becomes even greater. How often does a person come in close contact with one or more infectors? What is the average contact time?
3/ I have been thinking back to my PhD dissertation (way back in the day) when I studied and applied surface renewal theory for gas transfer at interfaces where liquid-phase mass transfer dominates.
1/ Gr8 that @cdc has discovered the dual (lower emissions & less inhalation dose) benefits of masks. A 5 min Sci Citation Index search leads to several past papers of relevance. Here is one by researchers @cdc's very own @NIOSH from 2010.
2/ This paper was cited in tweets by several researchers earlier in the pandemic & shows 40% to 60% removal efficiency (100% - penetration%) for 1 um particles at receptor end (& so even better for > 1 um) for some materials (much worse for others).
3/ More recent results reported by @linseymarr, @Smogdr, & their colleagues/teams significantly increase knowledge of different materials, layered materials, particle size effects, etc.
My previous tweet illustrating dual benefits. 40+40 = 64%, 50+40 = 70%, 60+60=84%, etc.
2/ Simulation I did for background aerosol particles in the cab of a typical-sized vehicle and realistic ventilation. The vertical axis is inhaled deposited dose in ride share normalized by that of those infected in Restaurant X in China with same infector emissions.
3/ That red bar with windows closed and no outdoor intake underscores high risk. Simulation is without masks, so bars lower if driver and passenger(s) wear masks. Opening windows (even a small amount) dramatically reduces dose. Avoiding busy commutes (shorter time) also helps.
2/ But we could use more than limits (or recommendations) on social gatherings. Responsible businesses, gov agencies, school districts, etc., should require & enforce masks, employ strict physical distancing, increase outdoor air supply rates, & employ advanced filtration.
3/ If we are relentlessly committed to actions that dramatically reduce inhaled dose (whether from close contact or far field) of SARS-CoV-2 (it's wholly possible to reduce dose by 90 to 95% in most buildings), we can stop the frustrating cycle of starting & stopping in fits.
2/ “It is very important to understand that portable air cleaners, improved filtration in HVAC systems, and increased outdoor air supply can significantly reduce inhaled dose of aerosol particle concentrations in classrooms for those away from an infector”
3/ “They do not appreciably reduce the dose of aerosol particles for someone standing near an infector who is speaking or coughing. For this close contact case physical distancing and required mask wearing by everyone is critical.”
1/ Just had a wonderful interview that took a tangent into terpenes and terpene alcohols associated with air "fresheners" (plug in, heated essential oils, etc.). They do NOT remove pollutants from indoor air. Period. Period. Period.
2/ They can be oxidized to form secondary organic aerosols and a wide range of oxygen-containing reaction products. Tox data on a large fraction of these reaction products do not exist (could be benign or not).
3/ Terpenes and terpene alcohols can mask (overwhelm) objectionable odors, but do not rid of the source of the odors. I suspect based on their popularity that many people also find these scenting agents to relieve stress.
Ventilation & filtration are important, but so is source reduction.
"If there is a pile of manure in a space, do not try to remove the odor by ventilation. Remove the pile of manure." (Max von Pettenkofer, 1858)
2/ Humans who are infected are not manure, but we should do everything possible to reduce the emissions of infectors indoors (in addition to grater ventilation and improved filtration). So, how do we do that?
3/ First, anyone who has had contact w/ an infector should quarantine and not go to work, school, and other indoor environments other than their homes. They need to be removed from the playing field. Testing is also valuable for keeping positive cases in isolation & off field.
1/ I have left my blog up on Inhaled Deposited Dose at corsiaq.com. IMO we should discuss this concept more & use it as a guide for how to effectively reduce dose, risk of infection, and infection outcomes.
2/ Without knowing what the actual dose-response relationship is we should assume that any level of inhaled deposited dose leads to some risk (precautionary principle). The higher the dose the higher the risk of infection.
3/ It is also likely that the higher the dose the worse the outcome (on average) from an infection. There is certainly individual variability (elderly, diabetics, etc.) wrt dose-response.
1/ Previous analysis by my team of occupied-day average & peak CO2 concentrations in K-8 classrooms in Central Texas and Rio Grande Valley. Results shown as cumulative distribution plots. So, 35% of classrooms w/ CO2 less than 1,000 ppm & 65% greater (note ref on absenteeism).
2/ 20% of classrooms with average CO2 concentrations greater than 2,000 ppm and peak concentrations greater than 3,000 ppm! Sadly, conditions in the Rio Grande Valley were far worse than in Central Texas (an indoor socio-environmental justice issue). next ....
3/ Mean occupied day CO2 concentration in Central Texas = 1,300 ppm and in RGV = 1,800 ppm with similar disparity for peak values. Also compared portables versus traditional classrooms. more ...
1/ Why universal mask wearing in buildings is important
First, the persons infected are unknown. So, if everyone wears a mask the infectors are also wearing masks. Second, everyone else (receptors) get an extra layer of protection for also wearing a mask.
2/ The % reduction in volume (or mass) of aerosol particles inhaled by a receptor is given by the following equation: Z = A + 0.01 x B x (100 – A)
3/ Where Z = combined % reduction in inhaled particle volume by receptors, A = % reduction in emissions by virtue of infector(s) wearing masks, B = % reduction in inhaled volume by virtue of receptors wearing masks.
1/ Not surprising & consistent w/ comments I made in a recent article by @RobertRoyBritt. Exposure time is NOT the only factor that determines risk, whether in close contact or indoor far field. We should focus on inhaled deposited dose (IDD) & not just on distance or time.
2/ IDD = Concentration (C) (#/L) x Respiratory minute volume (B) (L/min) x Time of exposure (t) (min) x Fraction deposited in respiratory system (f) (-). C & f are taken for specific particle sizes and the resultant size-specific IDD values summed (integrated) for total IDD.
3/ Concentration (C) depends on a number of factors, including distance, emission mode and strength, air flow conditions (e.g., cross-flow, mixing/TKE) & whether the receptor is wearing a mask (as concentration is in breathing zone inside mask), quality of mask, etc.