Showing posts with label air quality. Show all posts
Showing posts with label air quality. Show all posts

Friday, June 30, 2023

Stay Indoors - But Is That Enough?

 


Any casual reader of this blog might know that I was interested in indoor air quality including airborne viruses – long before it became fashionable. That had various origins including an undergrad focus on ecology, being raised by two heavy smokers, having to manage a coal fired stoker as a kid, working in a HEPA filtered clean room as a research assistant, and routinely getting viral respiratory infections in a hospital staff setting where we were all advised that hand washing was supposed to stop the mini-epidemics. And having asthma through all of that.

The indoor air quality issue has become complicated as our outdoor environment deteriorates. As an undergrad 50 years ago, we studied air pollution scenarios that affected large cities.  That included the concept of how smog was created by photochemical reactions but a lot of the specifics were not known.  More recently the entire Midwest and Northeastern US has been blanketed by wildfire smoke from Canada. Wildfire smoke is chemically complex.  In a lot of areas there are air quality alerts on one day due to wildfire smoke and ozone the next day. Those alerts are graduated to advise people with health conditions like asthma, emphysema, and heart disease on the lower end to limit outdoor activities or stay inside.  At high levels everyone gets the same advice.

The advice to stay inside assumes that your indoor air quality is better than the outdoor air quality that you are being warned about.  But is that a valid assumption?  How do you get measurements on everything and know the critical differences?  A good place to start is the outdoor air quality. The EPA has developed a nationwide network of sensors that detects particulates and ozone in the air and calculates the air quality index.  The AirNow app is available for your smart phone.  It gives you the outdoor reading, particulates, and ozone, as well as the break points from Good (0-50) to Hazardous (301-500). It will give you conservative advice about what to do about health and activity for those break points.

The CDC has a publication on indoor air quality in airports (1) where smoking was allowed. It provides some more intuitive markers of indoor quality. They found that the PM 2.5 (<2.5 micron particles per cubic meter) were 300+ in the smoking areas and 50+ in the areas adjacent to the smoking areas.  300+ levels are considered “very unhealthy”.  Anyone who has ever been in a smoke-filled room can probably sense that the atmosphere is not very good for your health either immediately of after leaving.  In Minnesota when the AQI was greater than 300 due to wildfire smoke – you could smell the wood fired smoke.

With an accurate assessment of the outdoor air – what about your indoor air quality?  I was fortunate enough to have purchased an air cleaner for my office with a PM 2.5 measure built into the machine. It usually reads in the 1-5 range but when the wildfire smoke arrived it was suddenly reading 40+ indoors. I had to figure out why that number was so high.  I had just replaced my furnace and it has a MERV13 filter that should provide some filtering efficiency.  The question mark was how my air exchanger fit into the mix.

My house is about 15 years old and like most modern houses it is considered airtight.  The concern by builders and contractors with modern homes is that they are so airtight that it leads to indoor air pollution from a number of sources including any combustion processes in the home and volatile compounds in the air from various sources like cleaning products.  As a result, air exchangers are installed to vent the indoor air and bring in fresh outdoor air.  These air exchangers are designed to reduce heat exchange and most do not have HEPA ( High Efficiency Particulate Air [filter])  filters.  They have a relatively primitive filtration system to remove mainly insects and very large particles. They can easily bring in outdoor smoke so it is a good idea to have it shut off on days where there is very high particulate matter.

The problem with my new system is that I was not sure that the air exchanger was off.  When my new furnace was installed the air exchanger was integrated into a touch panel with 30 different options and several ventilation settings.  I talked with 5 technicians (3 from the HVAC contractor, 1 from the air exchanger manufacturer, 1 from the smart thermostat manufacturer).  They all agreed shut off the air exchanger was a good idea but they gave me widely varying advice.  I decided to experiment myself over a period of 12 hours and generated the following graph (click to enlarge).

The first section shows the AQI outdoors versus indoors running the MERV 13 filter through the furnace.  There is no difference over that time period.  The next period I shut off the furnace filter and used a free-standing Space Gaard air cleaner with a MERV 8 (MERV = Minimum Efficiency Reporting Values) filter. Notice that during this time period the wind picked up outdoors, blew off some smoke and the PM 2.5 dropped from 160 to about 90.  At that time I talked with a 6th technician and he gave me clear advice on how to shut off the air exchanger.  The last section is with the air exchanger off and all air circulating through the furnace filter MERV 13.  At that point the indoor AQ drops consistently despite a blip upwards in the outdoor PM 2.5 and continued to drop to 10.  To me that illustrates the importance of making sure the air exchanger if off when the outdoor AQ is poor and actively managing it to turn it one when the outdoor AQ is acceptable.

A related indoor AQ related to viral transmission is the carbon dioxide CO2 levels.  Lower levels correlate with less people rebreathing air in the room and that decreases the risk of infection from airborne viruses. Outdoor CO2 is roughly 400-420 ppm. My indoor measure is currently 570 without the air exchanger on.

There are currently PM 2.5 and CO2 monitors available in most home stores and large online retailers.  What we really need is a more comprehensive single device that measures and records all of the parameters. I would suggest PM 2.5, PM 10, CO2, Ozone, and Volatile Organic Compounds (VOC).  The closest I could come to that device was a gadget that required that I purchase a separate weather station and even then the bandwidth to multiple devices was limited.

Home HVAC system design could also use some innovation. Just based on my experience durability is a problem. Should an HVAC system last longer than 14 years?  Probably.  But the design itself does not seem very efficient.  I am not a certified HVAC tech by any means but it appears to me that the air exchanger introduces outdoor air into the system after the air filter so that any particulate matter in the outdoor air does not get at least one pass through the highest efficiency filter.

Outdoor air quality is a little discussed casualty of climate change. As the environment deteriorates, I expect that there will be increasing amounts of wildfire smoke and it will be chemically more complex. I currently wear an N95 mask outdoors during the alerts, but I can envision a time in the not-too-distant future where respirators that can also remove ozone and organic chemicals will also be necessary. Geography is no longer helpful in separating clean air from polluted air. Monitoring your personal indoor air quality and figuring out how to manage it will become the most critical part of home management. I have posted a few things that you can do right now and I am always interested in other ideas about how to address this problem.  Please post any of those ideas in the comments section.

 

George Dawson, MD, DFAPA

 

 

References:

1:  Centers for Disease Control and Prevention (CDC). Indoor air quality at nine large-hub airports with and without designated smoking areas--United States, October-November 2012. MMWR Morb Mortal Wkly Rep. 2012 Nov 23;61(46):948-51. PMID: 23169316.

2:  CDC Health Alert Advisory.   Wildfire Smoke Exposure Poses Threat to At-Risk Populations.  Link


Update 07/06/2023: 

One week after turning off my air exchanger - the PM 2.5 in my house is down to 6 or essentially normal.  I talked with my air conditioning tech who also services the air exchanger and he agreed with the approach.


Image Credit:

Canadian Wildfire Smoke in Minneapolis

Chad Davis from Minneapolis, United States, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons

file URL:  https://upload.wikimedia.org/wikipedia/commons/c/c0/Canadian_Wildfire_Smoke_in_Minneapolis_%2852907984452%29.jpg

page URL:

https://commons.wikimedia.org/wiki/File:Canadian_Wildfire_Smoke_in_Minneapolis_(52907984452).jpg




Sunday, August 28, 2016

The State Fair.....


Grandstands At Minnesota State Fair



It has been a little over a year since I last expanded my horizons and did something I would never do on my own.  That event was going on an Alaskan cruise.  It seems like I am experiencing less and less control of my life because last night I scratched off another activity I would not typically consider and that is going to the state fair.  Not just any fair but the Minnesota State Fair.  In the runup to the event I have listed to Minnesotans apply corrections for total duration and a fairground stadium to the Texas State Fair, in order to say that Texas is not really the largest state fair - Minnesota is.  I will leave that argument up to the fair experts.  I am more focused on why people go to a fair in the first place and the fair in Minnesota is an extravaganza.

I am a fully admitted introvert and as one really do not want to be around large and loud masses of people.  So - consider the source of this review.  My entire life is structured around working and getting home and recovering for the next day.  On Friday - the focus is on recovering all weekend for Monday.  Being around people and in awkward social situations is not the pathway to recovery for introverts.  It seriously delays recovery.  In case you are not an introvert, the recovery that needs to occur is a primarily from a heightened sense of tension and anxiety.  In many cases this spills over into autonomic symptoms like accelerated heart rate, tension, feeling flushed and overheated, and a subtle change in breathing patterns.  It also probably affects the perception of situations.  That might explain why both large state fairs that I have attended (Wisconsin and Minnesota) were experienced like Fellini movies.    I expected the same when I walked through the gate and was face-to-face with a young woman wearing a T-shirt that said: "Satan wants you."  But there were more distressing problems than odd T-shirt slogans.

Minneapolis is a large city by any standard, but it is very easy to avoid the city and stay in the suburbs.  On those occasions where I have ventured downtown, I have never observed the crush of people that I have in New York City, Chicago, or Philadelphia.  The Fair is probably the exception to that rule.  Everywhere I went there was a solid stream of humanity 20-30 people wide, often travelling in opposite directions.  There did not seem to be that many destinations but during this week and a half in August the sheer number of people in foot traffic at the fair is probably the highest density of humanity that occurs anywhere in the state.

Food is a related issue.  Gluttony is probably a more appropriate term.  At some point food at the Fair began to take on absurdist qualities.  How many times could the food be deep fried or put on a stick?  At the Fair that seems to be an open question.  In the last several years bacon as a condiment has also been a popular theme with bacon being added to ice cream and donuts.  A friend I was with at the Fair, purchased a drink and a piece of bacon was added as a swizzle stick.  For my own part I had two bites of Australian Fries that are basically deep fried waffle fried potatoes dipped in batter and refried.  The serving size was 4 of these about the size of a medium pancake - covered in either Ranch dressing or liquefied cheese.  I was too conditioned against deep fried food to really enjoy it.  The average Minnesotan tends to view these forays into horrifically bad food with amusement, but at the same time - tons of the stuff are being consumed at a rapid rate and it makes the usual deep fried fast food seem like a health food by comparison.

One of the health parameters that I have not seen discussed anywhere is the air quality at the Fair.  There are so many deep frying and deep frying again establishments in operation all of that aerosolized material has to be vented somewhere.  Many of these establishments had huge roof vents with an obvious non-smoke exhaust.  Aerosolized particles from cooking is a poorly investigated field in medicine but if that was my field of interest I would be attracted to sampling the Fair.  There was more than aerosolized cooking products to deal with.  Cigarette smoke wafted in from both the designated and non-designated smoking areas.  We also now know that humans all have their own unique microbial cloud and emit up to 106  bacterial particles per hour.  That raises the interesting question about whether or not introversion is more than a brain based property and whether at least part of this behavior could be mediated by the immune system.  A fair also has a large number of animals adding more particles to the environment and some of that dust can have immunogenic properties.  I recognize that all of this is speculative and skeptics will ask if there have been any environmentally based illnesses documented in fairgoers.  But my focus is on more than illness or disease.

The most clearcut health problem that I experience at the Fair was ambient sound levels.  In general the sound levels were not a problem.  I did attend a Grandstand Concert given by the Dixie Chicks as part of their DCX World Tour MMXVI.  I could not be construed as a fan of this group and my demographic was underrepresented. 80% of the crowd were women mostly in the age range of 20-45 years old.  Many of them were wearing cowboy boots, probably more cowboy boots than I have ever seen outside of the state of Texas.  Like most concert crowds there was a significant amount of drinking going on and for the first time in a long time - I caught the scent of Mad Dog 20:20.  Some claim to have smelled cannabis, but I did not detect any.  The predominant demographic and their state of intoxication was relevant to the ambient sound levels but first a digression about the actual sound system.

I have no precise knowledge of the grandstand sound systems and could not find any details online.   Apart from portable stacks of speakers and monitors being wheeled about on the stage, it appeared to be two large inverse parabolic arrangement of 20 or more speakers on each side well off the level of the stage.  The opening acts were useful comparisons.  The first act was Smooth Hound Smith a duet that reminded me of a country version of White Stripes except in this case the guitar player was also the drummer.  In terms of sound, the system seemed to be overdriven leading to some distortion and unintelligibility of the lyrics.  The second opening act Vintage Trouble was more of a traditional rhythm and blues ensemble.  Their sound and distortion levels were much less than the first act.  The psychoacoustics may also have been affected by their very dynamic lead singer.  It is risky for an opening act to ask for a lot of audience participation, but he did and was eventually very successful probably through the power of his high energy personality and vocal talent.  By the time the Dixie Chicks took the stage, the sound levels were less distorted but the intelligibility of the lyrics was still a problem.  I was in the nosebleed section far to the left of stage, so I asked people more centrally located if they noticed this problem.  Her observation was that it was a problem and she was glad to see the lyrics projected at one point.

The typical fan in the crowd had no problem at all with the lyrics because they were singing them at full volume.  Imagine sitting in in a sea of 20 year old sopranos singing at full volume and punctuating the songs and transitions with prolonged screams.  The screams were unworldly at times and befitting an audition for a horror movie.  Of course screaming at concerts is nothing new.  It has been there since the early days of rock and roll.  But was this a rock and roll venue?  Are the Dixie Chicks considered to be a rock act?  I don't think so.  There were definite rock elements including an opening recording of Prince and Let's Go Crazy as well as a tribute to Prince complete with his symbol projected on a purple background by the light show.  Judging from the crowd's memorization of complex country lyrics and synchronized movements - Dixie Chicks have produced art with significant meaning to a large segment of the population.  They have sold tens of millions of albums and had no problem at all selling out this venue of 17,000.  One valuable lesson in presentation and marketing is that country acts are presented as rock and rock events these days.  That includes, the amplification, body language, inflection, and associated light show.  The light show associated with this event was first rate including a highly stylized version of a chase scene of the stars inhabiting unlikely vehicles like old Plymouth Valiants and Mercury Montegos at an interlude for an equipment change.  There was also a stream of consciousness display of various prominent politicians flashing across the screen - a possible homage to their previous political controversy when they criticized George W. Bush  about the invasion of Iraq.  

An interesting technical observation had me thinking about what is lost with the sound system.  It brought to mind  recent story about why Freddie Mercury, the late Queen vocalist is considered one of the all time great rock and roll singers.  A study by acoustic experts point out that his vibrato range was a frequency that exceeded most opera singers.  He was also reported to have a 4 octave range.  Although I am not an audio engineer I am a serious student of high fidelity.  I doubt that a distorted and muddy sound system would allow an appreciation of of those characteristics.  You can check your own emotional response to an a capella rendition by Mercury at this link.  On the other hand - Queen fans could probably have a similarly great time at this venue in a parallel manner to the Dixie Chicks fans.    

Despite not knowing their lyrics, being deafened by their fans, and being put off by the low fidelity of the sound system I was able to relate to their music at a couple of levels.  I am a bluegrass fan.  Bluegrass of the derivations from Will The Circle Be Unbroken.  Some of their music has these origins and at one point they played a bluegrass instrumental on banjo and violin.  They also worked with side musicians who had excellent bluegrass stylings on mandolin, acoustic guitar and electric guitar.

Would I see an act like this at the Fair anytime soon?  Only extraordinary circumstances got me out there this time.  Those circumstances would have to repeat in the future.  If I did go - ear protection would be a must.  I might be tempted to bring along a sound meter and noise cancellation head phones to see if I could block the screaming and hear the act.  I would also opt for seating in the center of the Grandstand and on the same level as the speaker system since high frequencies are directional and that affects both the imaging and clarity of the sound.  



George Dawson, MD, DFAPA


References:


1:   Herbst CT, Hertegard S, Zangger-Borch D, Lindestad PÅ. Freddie Mercury-acoustic analysis of speaking fundamental frequency, vibrato, and subharmonics. Logoped Phoniatr Vocol. 2016 Apr 15:1-10. [Epub ahead of print] PubMed PMID: 27079680. (full text link).


Supplemental:

1.  Yes - I was really there: