Tag Archives: health

aerosols

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A group of academic scientists has put together a long paper with scientific information intended for the public on Covid-19 aerosol transmission. I think this is pretty nice science communication. It is not dumbed down, but it avoids jargon. The graphics they include are mostly helpful. Here are a few takeaways:

  • Secondhand cigarette smoke is a useful analogy to think about. If you are around smokers outside, you are inhaling much less of their poison than if you are around them inside. The amount of time you are around them makes a huge difference – however, this group says the 15 minute CDC guidance is not supported by good evidence. Outside, distance makes a big difference. Inside, being closer is probably worse, but if you are in an enclosed space with them for any period of time you are at pretty high risk. Opening a window should help, but not as much as being outside.
  • Scientists disagree on the relative importance of the three pathways – surfaces, droplets, and aerosols. In the face of uncertainty, it is probably prudent (this is my opinion) to treat them as roughly equal and take precautions against each. Someone coughing or sneezing in your face is a big problem – stay 6 feet away for that reason alone, especially from anyone un-masked.
  • Aerosols probably persist for 1-2 hours. (My thought – this suggests staying in a hotel should be relatively safe. The room has been cleaned, hopefully the maids were wearing masks, and hopefully they cleaned the room in the morning and you are checking in in the afternoon.)
  • Sun and wind tend to reduce risk. All other things being equal, low temperatures and low humidity seem to aid transmission. (Don’t count on the opposite helping you in a sealed room, though. But I am a proponent of humidifying in the winter anyway.)
  • The time it takes air in your house to turn over varies widely – “30 minutes to 10 hours”. For commercial buildings, 12 minutes to 2 hours. Hospitals around 5 minutes!
  • A carbon dioxide concentration of 800-950 ppm is indicative of good ventilation indoors. A carbon dioxide meter costs about $150.
  • Air filters should help, and yes you can tape a furnace filter to a box fan. (I knew it!)
  • “There is no evidence that COVID-19 has been transmitted when people walk past each other outdoors. (But I’m using the bandanna system just because people are scared and confused out there.)
  • Taxis and rideshare are not zero risk, but reasonably probably, maybe reasonably low risk if everyone is masked and windows are open. If it is too cold to open windows, it is better to be drawing in outside air than just recirculating air.
  • Airplanes have very good ventilation, so it is a myth that one infected person on an airplane can infect everyone. If they are sitting right next to you, not wearing a mask, and/or coughing/sneezing, they can infect you. The airport itself is also probably higher risk than the plane. (But let’s remember people are working in all these places.)
  • They say “schools should operate in person only if the levels of infection in the community are low.”
  • Elevators are also actually quite well ventilated, and you are not in there for very long. Again, you don’t want people unmasked and/or coughing/sneezing on you. No singing allowed in elevators.
  • The dental office is suspect. Technology exists to ventilate them safely (but I didn’t see anything obviously new or high tech at my dentist recently.)
  • Masks still help with aerosols. Even though the particles are tiny, they are still inside droplets, which are tiny but not as tiny. Nothing in the air moves around in straight lines, it is turbulent and random, so even if particles are smaller than the openings in the fabric many of them will hit the sides and the risk will be significantly reduced. (Also suggests one reason having multiple layers is better.)
  • Masks work better if they fit well. (I’m a little tired of this, my family has about 100 masks now and not one of them fits well. If there are 1 or 2 I think fit pretty well, they are always in the dirty laundry when I need them. The same gremlins that steal one of each of my favorite socks also steal masks on occasion.)
  • Face shields and plexiglass barriers don’t help a lot with aerosols. You need a mask.

the Oura

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The Oura is a fitness tracker, but unlike others it is a ring you wear on a single finger. See Wired article here and company website here. It seems to focus mostly on measuring your heart beat and temperature – all the time – and coming up with a variety of metrics and feedback for you based on that. The NBA and NASCAR have apparently given them to all their athletes (yes, I maintain that race car drivers are athletes, but we can continue the debate down at the corner bar when and if it reopens.)

I’m curious about fitness trackers, but if I ever invest in something I would like blood pressure and nutrition to somehow be incorporated.

the numbers on maternal mortality

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The site Our World in Data likes to plot various statistics against GDP per capita. The U.S. is almost always below the middle, and sometimes towards the bottom, of the industrialized countries. On maternal mortality, the U.S. is orders of magnitude safer than many poor countries, but like other stats there is a noticeable gap with the leaders in our peer group (Finland, Iceland, France, Japan, Switzerland to name a few). Greece and Poland stand out as middle income countries that do much better than us. Interestingly, Belarus also stands out as a high-performance, lower-income country on this metric. The plot is animated, so you can see the U.S. drifting slightly worse over time even as our wealth grows, and even as other countries tend to make progress over time. I think I’ve said it before – we’re coasting on fumes, drifting behind the middle of the pack, and continuing to lose momentum.

humidity helps reduce coronavirus transmission

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Humidify those schools!

The relationship between climatic factors and COVID‐19 cases in New South Wales, Australia was investigated during both the exponential and declining phases of the epidemic in 2020, and in different regions. Increased relative humidity was associated with decreased cases in both epidemic phases, and a consistent negative relationship was found between relative humidity and cases. Overall, a decrease in relative humidity of 1% was associated with an increase in cases of 7–8%. Overall, we found no relationship with between [sic] cases and temperature, rainfall or wind speed.

Transboundary and Emerging Diseases

Not being a scientist or doctor, I have always assumed that mucous membranes inside your nose help block germs, and that a dried out nose in the winter time is one reasons colds, coughs, and flu spread through schools and offices every winter. It seems like a relatively simple measure to take that would have a clear positive effect. Now, to sit back and wait for my children’s schools and my office building manager to explain why it can’t be done.

teeth: miracle or weakness of evolution?

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I’ve always thought that teeth might be the weakest point of the human body. Why did our teeth evolve to be made of calcium, which dissolves in acid, when pretty much all our food is acidic? Why do we have to strap metal torture devices to children’s teeth for years just for them to be reasonably straight? Why don’t animals seem to have these problems?

This article in Scientific American sings the praises of teeth. It argues that, like many of our other organs and systems, our modern lives just aren’t what they evolved to deal with. It basically comes down to the idea that our food is too sweet and too soft.

The evolutionary history of our teeth explains not only why they are so strong but also why they fall short today. The basic idea is that structures evolve to operate within a specific range of environmental conditions, which in the case of our teeth include the chemicals and bacteria in the mouth, as well as strain and abrasion. It follows that changes to the oral environment can catch our teeth off guard. Such is the case with our modern diets, which are unlike any in the history of life on our planet. The resulting mismatch between our biology and our behavior explains the dental caries (cavities), impacted wisdom teeth and other orthodontic problems that afflict us.

Scientific American

I admit, I don’t like working for my food – I like boneless, seedless, shell-less everything. My teeth may have paid the price.

the goal of social distancing

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Vox has an informative article with some visuals on the goal of social distancing in an epidemic. If you can reduce the total number of infections that is a bonus, but the primary goal is to reduce the peak number of infections happening at any one time. You can do this by delaying cases and spreading them out of time, so that the capacity of the health care system is better able to deal with them. This looks very similar to a stormwater or flood control engineer – often, our goal is also to reduce and delay the peak. Reducing the volume is a bonus if you can manage it. The lesson is not that epidemics are like hydrology, it’s that there are certain fundamental system structures that lead to fundamental behaviors, and they are shared between systems. A couple more that come to mind along the lines of this basic model are congestion pricing to spread traffic out over time, and batteries to store solar and wind energy and trickle them back over time.

the Flynn effect and the reverse Flynn effect

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When IQ tests are taken by each generation, they are always normalized so that the average is a score of 100. However, when people are asked to take tests from older generations, they tend to do better than the older generations did. This is the Flynn effect. It was very consistent throughout the second half of the 20th century and into the 21st, but a number of studies in Scandinavia indicate that it may have reversed more recently. Immigration is one controversial explanation that has been suggested, whether due to genetic or cultural reasons. But the study I link to here tested the effect within families against the effect across unrelated people, and found that it is just as strong within families. This suggests environmental factors such as education and nutrition as the culprits, although the article does still put “migration” in this category. I suppose if you had a society with a high quality of nutrition and education, and you then have an influx of new people with more bad habits (let’s say, a high rate of smoking), that could have an effect.

the stats on Bernie Sanders’s health risks

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Slate has an interesting article on health risks for someone Bernie Sanders’s age with Bernie Sanders’s known health condition. The author points out that these estimates can be done for Bernie because he has released a fair amount of health information (although still not everything the author would like), while the other older candidates have not.

  • His 12-month risk of a heart attack, stroke, or death is about 6%.
  • His risk of being hospitalized for any reason between now and November is about 30-35%.
  • His odds of surviving a first presidential term are about 65%, and his odds of surviving a second about 40%.