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Air pollution can make mould allergies worse and also increase the risks for COVID-19 transmission

Uncategorized Apr 26, 2020

Hello and welcome to this week's live stream. My name is Dr. Cameron Jones and I'm an environmental microbiologist and today I have some very exciting research to bring to you. Yes, again, we're going to be focusing on mould and importantly, we're going to be focusing on one of the primary ways that all of us, if we are allergic to mould, come into contact with this - and that is by simply breathing [see for example the WHO Guidelines for Indoor Air Quality - Dampness and Mould] .

I'm going to be focusing on something in the air called particulate matter, PM. Particulate matter, again, for anyone who watches these live streams knows that we can measure the particulate matter in the air and we can actually measure it and measuring it puts it into these different size classes called particulate matter.

I'm going to demonstrate how this is being used to not only show that there is a strong connection between exposure to particulate matter and inducing an adverse immune response, but some really interesting emerging research is coming out showing that the particulate matter in the air is also connected with the rate of COVID-19 cases that we're seeing worldwide. And this is really interesting because there are a lot of engineering interventions that certainly we can consider putting into our homes that can reduce the exposure to particulate matter. And that's really the topic that I'm going to be focusing on today. Fort example, you could consider using a HEPA air extractor to filter your indoor air and remove cells and other airborne debris.

I want to get onto this now. So I'm going to be talking about pollution and how this increases the risk for mould allergy and COVID-19 infections. And I want to put this in context now because it's all very well that I can hold up a particle size analyzer, but what actually is in the air? What do we find outside of our homes in the built environment? Basically, the little schematic that I've put up on screen shows you the relationship to these two things called particulate matter.

In order to index this, we use this term, PM or particulate manner, and they come in really two size classes. But particulate matter represents the aggregate of all of the solid and liquid materials in the air. And of course, this includes all the dirt and dust debris, the pollens, all the microbes, the fragments of cells, the fragments of plastics, for example. The soot and all those sort of chemical elements that are produced in the classic smokestack analogy and picture visualization to index air pollution. But there is a whole host of biological material and microbiological material present in particulate matter as well and that's particularly what I want to focus on today.

Again, the schematic shows you some of this size in relationships between beach sand, for example at 19 microns in diameter, right down to the width of a human hair and then on down to what we're talking about, PM 2.5 and 10. As I already said that they come in two size classes. Obviously, when we're measuring this using an instrument, we get these in different groupings. So they're really just different thresholds that are used to classify the air or what's in the air into these different sizes. And these types of instruments are absolutely fundamental to measuring particulate matter.

Think of PM 2.5, these are all those the material which is less than 2.5 microns whereas the PM 10 is the course in high-level particle fraction and these are your 10 micron-sized particles.

Now, to give you an idea, especially for those who can't easily visualize what's in the air, I've pulled up a scanning electron micrograph from this particular paper and I've got the URL up on screen and you can see that at high resolution. This is well beyond what you can see with a light microscope. You can see that dusts and bacteria and pollen all obviously have a size. We can even see salt crystals, which are these long ones in the middle of the schematic. So this is what's actually in the air. This is what we are breathing in all the time. We really can't do a lot about it other than filter out our area and really this concept of air pollution is highly significant because this is exactly what we are being exposed to, especially in dense urban environments.

Now, you might be thinking, well, okay, my lungs are pretty good, my nose hairs might filter this out. Surely, this can't be a severe problem. Well, it is, unfortunately. It's just something which our bodies are in a sense capable of filtering out to some extent, but even the US EPA lists a whole lot of problems associated with exposure to particulate matter in the air, and I'm just going to list some of these here.

  • For example, early death is one of the dominant ones. Obviously, no one wants that.
  • Non-fatal heart attacks, so there is great evidence showing that exposure to particulate matter puts a huge stress on your cardiovascular system.
  • It can be connected with irregular heartbeat and the worsening of asthma. This is something that we talk about a lot on this show and again, there's great epidemiological data making a connection between exposure to fine and coarse particulate matter and asthma symptoms being exacerbated. And we're going to drill into this soon in this live broadcast to talk about what's actually in this particulate matter because, as I said, it's not just the dust and debris but
  • particulate matter is also shown to worsen lung function in many people and of course
  • it's a respiratory irritant.

Now, I want to make the point that it's not just dirt and debris from urbanization. There is a lot of biological material as well in this particular matter soup and a lot of this is fungal in origin. Now, if I pull up a paper from a journal, a recent journal article, what I've been able to do is pull out one of their figures and this is a heat map diagram and this shows the whole different range of fungal genera that are found in three types of air issues, and they are the PM 2.5 that we've talked about, the PM 10 size class. Remember, they are sizes: small and large and then the total suspended solids, TSS and that is the whole aggregate of what we're being exposed to because if you don't have one of these then you just have to look at smog and urban haze as the total suspended solid.

And what you can see from this heat map is that there is a range of different fungi that are present, ubiquitously and also selectively, in certain size classes. And so I really want to make the point that air pollution contains a huge amount of fungal particles and discrete fungal cells that can be classified using molecular and classic microbiological methods to work out what's in the air.

We're also able, in this particular paper, to show that there was a relationship between temperature and relative humidity and various other chemicals as well. And this was called a canonical correspondence analysis. And this is an excellent paper. I've got the URL up there. I suggest that all of you read this paper if you're interested in the connection between the different fungi and these other chemical types.

But the point of me putting this slide up is just to emphasize that air quality and when we measure particulate matter to 2.5 and 10, we're actually measuring a huge contribution of fungi, intact fungi, and also the cell wall fragments and debris as they break down. And how do the scientists actually do it? Well, they use molecular methods and I've put up one of the PCR analyzers on here because they use an Illumina platform to determine what the species distribution was in these different size fractions.

Again, I've taken one of their tables out to show that the combination of fungi found in the PM 2.5 and PM 10 samples. You can actually see that there is some overlap with the different types of fungi but also some selectivity as well. And so certain fungi spores particularly have different sizes and you would expect them to be present in the different size fractions. But again, this has a huge impact on how long they remain suspended in the air and whether or not they are being distributed and other people potentially outside of water damaged areas are being exposed to this particulate matter. Really, this is just a fascinating table within the paper that was on the previous page.

But again, because I'm all about takeaway messages in these live streams, that if we look at just hazy days versus non-hazy days. So imagine you don't have access to a particle size analyzer nor do you have access to the city-based particle analysis equipment, which is really distributed all over the world, and there's a lot of organizations that are mapping the PM 2.5 and 10 concentrations throughout the world. But if we just look at hazy versus non-hazy days, you can see that there is a breakdown in the distribution or concentration of different fungi present. And again, the dominant fungi that we see ubiquitously across the size classes and the really interesting thing about this table is that they are looking at those situations of non-haze.

So in a sense, that's the control. That's just when we can't do anything about what is already present in the air, but we have some ability to, as I said, implement engineering controls to reduce emissions for example. The first column is looking at the combination or the control plus a very light haze. And then the second column is looking at more heavy haze and then again with the control in there as well. And then the third column is looking at light haze and heavy haze. And then in a sense, you can subtract that to find out what the most dominant concentration of microbes is, or fungal microbes are. And we find that the dominant genus or genera are Cladosporium, Alternaria, Fusarium, Penicillium, Sporisorium, which is essentially a plant fungus, and of course, Aspergillus.

Now, I hope I've made the point that there are a lot of different fungal types in the air space. But now I want to take you and walk you through the evidence for pro-inflammatory problems being caused by these fungal microorganisms. In order to do this, I have to define a few things here. The first one is something called an inflammatory cytokine. Now for those who don't have a strong biology background and certainly for all the lay people watching this, it's very instructive to look up on Wikipedia what is the definition of a cytokine.

And we find that an inflammatory cytokine is a type of signaling molecule that is secreted from your immune system, something called T cells and that this promotes inflammation. And the whole issue about exposure to particulate matter and fungi and can they cause us harm, well, obviously there is the direct infection pathway where microbes can be inhaled and they can cause an illness. But this issue of inflammation is much more interesting because it definitely explains why many people have such an extreme reaction to problems in the built environment such as water damage and mould. And this is related to this concept of inflammation. Inflammation can be thought of essentially as a pain response.

Think of inflammation, if you bang yourself and you end up with a reddening, that is inflammation. And so this concept of localized physiological reaction somewhere in the body, this is mediated by these things called inflammatory cytokines. And to make this even clearer, there are these, as I said, cytokines and they can act either directly or indirectly, but in all cases, they can end up with a pain response.

Again, there are some indirect ways as well where pain may not be registered, but at the level of the cells there is in a sense like a swelling reaction or some other phenomena. And this is the cytokine inflammatory response and it is quite serious and it is considered to be the dominant pathway in which exposure to pollutants causes adverse human health.

Now, there is an excellent paper that has come out in the journal Indoor Air recently on the pro-inflammatory potential of mould. Again, I've got the DOI URL up here, so you can download this paper yourself and read it. And this is looking at the human exposure pathway to spores and hyphal fragments that act as allergens and pro-inflammatory mediators to the human body. And again, we know, this is revision for many of you, that fungi can damage the airways by producing toxins. They release enzymes and also if they have sufficient concentration, they release these microbial volatile organic compounds or these VOC's which you can actually smell in a severely water-damaged building because it is the alcohol-based odor that you can smell.

These damage the airways as well and continuous exposure to mould may result in chronic low-grade pro-inflammatory responses which then contribute to respiratory disease. Now, the data in all of these papers and a lot of the references replete through preprint service and the peer-reviewed literature suggests that it is the fungal hyphal fragments in indoor air, which may well be missed with classical microbiology looking for viable growth, colony growth on petri plates or spore traps, which are also looking for intact spores.

What about when things break down or are sheared? As you can imagine, under window air currents, you've got all of that complex mixture of organic and inorganic material which comes up against each other and shears and creates these fragments which go right down past the micron into the nanoscale size range. And these literatures (see below) demonstrate very conclusively that it is the very small particles that again are causing this pro-inflammatory problem for people.

  • Seo S, Choung JT, Chen BT, Lindsley WG, Kim KY. The level of submicron fungal fragments in homes with asthmatic children. Environ Res. 2014;131:71–76. doi:10.1016/j.envres.2014.02.015
  • Seo, S., Ji, Y., Yoo, Y., Kwon, M., & Choung, J. (2015). Submicron fungal fragments as another indoor biocontaminant in elementary schools. Environmental Science: Processes & Impacts, 17(6), 1164-1172. doi: 10.1039/c4em00702f

To make this very clear, I've extracted a couple of the tables from this publication showing the comparison between the inflammatory response for spores on the right-hand side versus the hyphal fragments. These, in a sense, can only be identified potentially using molecular methods in order to determine that they're causing the problems. And you can see that Aspergillus fumigatus, a very common mould found in water-damaged buildings but also ubiquitously in these low and high haze environments, this has a huge inflammatory reaction. In fact, much higher than the intact spores.

Similarly, Penicillium chrysogenum also has a very high inflammatory response relative to the intact spore. You can see that if we drill into the immune system, how the immune system is reacting to hyphal fragments versus intact spores, we can look at interleukin levels. We can see that in a sense, macrophages are a type of immune cell which is responsible for engulfing or eating or destroying pathogens, and you can see that the hyphal fragments induce a much higher level of inflammation than the intact spores.

So you must remember this when you are looking at or interpreting the data from water damage or occupational hydrogenous or environmental air professionals who go into water-damaged buildings or suspect water damage buildings to assess them, that a lot of the methods that we all use that relies on intact spores, for example, spore traps or viable testing, may in fact severely underestimate the potential of that water-damaged building to cause severe harm to people. And that's something I really want to make a very clear point about in today's live stream.

Now, what about the connection between airborne particles and COVID-19? Well, in a sense, all of us are living through a worldwide pandemic of epic proportions. Obviously, the academic research literature is pumping out academic articles all over the place on various different aspects of SARS-CoV-2 or the disease of COVID-19. And I want to review a couple of papers that have appeared in the last couple of weeks, predominantly from April, 2020 that is reviewing and summarizing data from China and also from Italy because they were the two first countries with the worst number of cases of COVID-19.

And these four papers, I'm going to put the URLs at the end of this live stream so you can look at them up yourself. The first one came out on April 14th, the next one came out on April 16th, the next one on April 17th, the next one on April 19th and in fact I've got a few more recent ones for the United Kingdom and also another one on China in April 21 from one of the preprint service.

But why I'm putting up these four papers, and these are the titles of the papers. Again, screenshot this or wait till the end and then get the references from the caption to this live stream. What I want to cover is each one in turn because they're saying something about particulate matter and this is absolutely fundamental because they have found some really wonderful epidemiological data linking particulate matter exposure and the right of COVID-19 cases and also, unfortunately, mortality and this has a lot to say about this whole issue of indoor air quality, outdoor air pollution and its relationship to human health.

We're going to go through each one of these papers quickly in turn. And the first paper from April 14th was looking at what are the effects of particulate matter pollution on COVID-19 across China? And one of their figure one trends, they're just showing what the relationship is between the large particles, the PM 10, and the fine particles across different dates in early January right through to late February, 2020. And you can see that there is some variation but also a decline in the amount of PM 2.5 and 10.

I'm going to talk about this a little bit later about why there is a decline. But in a sense, a difference is shown on different days, as you would expect for normal fluctuations in the amount of particulate matter, but also the impact of lockdown reduced the amount of pollution and this is to some extent being measured as well in this particular curve. But the more important point in this curve is something that they've done with regard to the RR or the relative risk of contracting COVID-19. That is actually being exposed to the virus and going on to have the illness or the disease.

What they were able to do is they looked at the two size classes, the PM 10 and the PM 2.5, and they looked at something called the lag. And in the first left-hand side to the graph, you'll see that there's a graph at the top and the bottom, they represent the coarse fraction. The graph at the bottom is the fine particle fraction and the lags represent the time from initial exposure to when there was a problem. And a problem, in this case, is relative risk which is succumbing and actually getting COVID-19. They found that with a one-off exposure, there was a lag of three days.

But again, people don't just suddenly drop out of the air and be exposed to particle pollution once. But remember that if you're exposed to it once, it takes about three days, at least where this study was undertaken, before there'd be increased relative risk. But what about the cumulative risk? And that's shown on the right hand side of both of these graphs and you can see that it takes approximately 14 days of continuous exposure to the adverse PM 2.5 and 10 levels before there would be a serious episode or COVID-19 episode. And this is really dynamite research because it is linking the problem of air pollution with an increased susceptibility of getting the illness caused by the virus.

Now, what else were these authors able to conclude? That aerosol transmission of the virus was confirmed and in their paper, they repeated some often-quoted statistics that the virus can remain viable for up to three hours in the air. There is some competing evidence for this suggesting that the duration of viability is much longer than three hours, but we'll get to that in other live streams. But the point of this paper was that nearly 25,000 cases were examined across 72 different cities and this positive correlation was found between PM 2.5 and 10 and the COVID-19 diagnosed cases.

These results are quite similar to the literature for other coronaviruses, other SARS viruses. The PM pollution, the particulate matter pollution is a definite health hazard and the authors conclude that it could impair immune function. This is related to the receptive binding and something called ACE2 and this is quite a complex topic, I really don't have time to delve into this as part of today's live stream, but essentially, this ACE2 is related to the secretory cells in the bronchial tree and this is considered to be the pathway of mediation why many COVID-19 patients have such severe lung problems associated with the infection. So again, their conclusion is that particulate matter pollution increases the potential or possibility of SARS-CoV-2 lung invasion primarily through this ACE2 pathway.

Now, let's move on to the next publication from the 16th of April, 2020. These academics reviewed not so much the particle counts that were measured on the ground, but they reviewed the satellite-based imagery, which is an alternative way of looking or indexing pollution. And again, I've shown the satellite to give you an idea of the type of research which was undertaken and again, I've pulled from another publication satellite imagery showing two examples of the map of France showing the amount of nitrogen dioxide because that, in a sense now, is how they are measuring particulate manner. This is an index or a marker, think of it like a biomarker or a chemical marker for this particular particulate matter index.

Again, you can see that as the lockdown in France progress's over two separate time periods, there is a significant reduction in the amount, red or orange, areas in France. This type of information is what they did in the April 16th paper. What they did is they did this and they mapped the death rate in China back to the nitrogen dioxide levels. I'm going to show the companion maps for China, but I want to make the point that higher PM 2.5 carbon monoxide and nitrogen dioxide, these are the markers that we use to compare the death rate in China to, look at it, the nitrogen dioxide concentration. You can see that there is a good correspondence between the death rate, unfortunately, and the amount of pollution present in certain areas or regions of China.

Now, what about Italy? Well, we can do, or they can do, what these scientists using the imagery data from the satellite mapped out the number of COVID-19 cases. Look at it now, that's the number of cases and now look at the nitrogen dioxide concentration. You can see that there is a very strong connection between exposure to pollution and the number of cases of COVID-19.

Now, what about America? This image schematic of these countries, you can see now again we compare the number of COVID cases to the contamination level. This is a little bit harder to visualize, probably because all the states are marked out on here, but no doubt some other publications are going to drill into the US experience even further. But suffice to say that this is a landmark paper because it demonstrates using satellite imagery, which of course can be performed easily throughout the world in a sense to predict those areas from existing data on contamination level in the air, what the potential is for COVID-19 caseload. And that's pretty powerful information, again from image processing and image analysis, I might say.

Now, I want to move on to the last publications from September 18 and 17 and these are by the same principal author, and I've put the URLs up here because these are really fascinating papers and they go into another aspect of air pollution. And again, we've talked about the fact that PM 2.5 and 10 elicits an immune reaction. We know that particulate matter contains a lot of microbiological debris and intact cells. We know that that influences immunity. We know that there is a connection between exposure to particulate matter and the COVID-19 caseload, but now these authors are looking at whether or not the particles themselves are transmitting the virus. That is, is the pollution acting as a vector? And these papers are very, very important. How they started doing this research, again, this is from Italy and they were talking about a particular province in Italy called Bergamo.

And again, the evolution of the cases there. You can see that on the 25th of February, there are only 18 cases. By the 4th of March, there were 423 cases. By the 12th of March, there were over 2000 cases and on the 21st of this month, there were 10,788 cases. So this particular area in Italy is a fascinating petri plate in a sense for studying the impact of pollution. And that's exactly what these authors have done. Again, I'm going to summarize their results. And again, I'm just putting up that scanning electron micrograph, not from their paper, I might add, but just to emphasize that this is the types of material that are present in the air space when it is polluted.

And so what these scientists did, because of course you can measure the size or the cumulative size distribution using these types of instruments or you can suck in using an air pump, the air from Bergamo and collect it onto filters. And you can index the amount of pollution, for example, measuring it, which is called a gravimetric analysis, or you can apply molecular tools such as PCR to analyze what is collected on these filters. And that's what these scientists have done. Their aim was to confirm or refute the potential that SARS-CoV-2 is actually present on particulate matter. Because imagine what the implications are if the particles themselves can transmit the virus from one location to another, and of course the more densely populated areas with more pollution are necessarily then going to probably see higher levels of COVID-19 cases.

These scientists looked for particular markers and they looked at something called E gene, which is defined in their methods paper, but they say that 15 out of 16 filters were positive for the presence of SARS-CoV-2. And then when they looked at another molecular marker even more connected or correlated with SARS, they found that five out of five or a hundred percent of the filters containing this particulate matter have SARS-CoV-2.

The conclusion and the takeaway from this live stream is that this April 18 result is preliminary evidence that SARS-CoV-2 RNA can definitely be present on outdoor particulate matter. This is a landmark paper and I suggest that you reread and consider the implications of this final conclusion on what is this nearly final slide to today's talk. But again, there is more literature which has emerged since I even collated these papers together this week to prepare this talk.

And again I mentioned that on the 21st of April, another paper came out this time from China and they stated that within weeks of imposing the lockdown in China, there was a decrease of 25% in the PM 2.5 concentration in the air. And I'm going to read verbatim their conclusion here. They say that: "We estimate that such improvements would avert 24,000 to 36,000 premature deaths from air pollution per month."

So between 24 and 36,000 people can be saved simply by reducing the exposure risk from these particles in the air. This must surely demonstrate to you that indoor air quality and outdoor air quality are very strongly linked. There are a range of things that individuals can do to reduce their exposure to particulate matter. Obviously, urbanization and engineering controls to minimize pollution and emission of pollution needs to be tackled at a policy and government level.

But from an individual and family perspective, what are you to do? Well, if you can afford it, go out and get an indoor air purifying filter, something that uses a [Harper-righted 00:00:34:27] filter to reduce your exposure. Consider if you have ducted heating to even use a MERV-rated filter to reduce the amount of particles in your home. Obviously, there are a whole range of different things that can be implemented in a domestic living environment. We know from previous live streams and from the academic research that the presence of carpets increases the amount of particulate matter in the air versus hard flooring, but similarly, hard flooring can expose us also to particulate matters.

So at the end of the day, our overwhelming objective is to just be mindful and aware about the impact of particulate matter, not just to induce fungal allergies and inflammatory responses, but nowadays we need to consider the exposure to the air space as potentially able to cause us severe infections such as bringing us into contact with unwanted viruses like SARS-CoV-2.

In any case, my name is Dr. Cameron Jones. Each one of these live streams is turned into a podcast. Myself and my team spend a lot of time each week preparing the content and producing this content for you. I'd encourage you, if you can, going on to our dedicated webpage for the podcasts ( and subscribing to the podcast on iTunes or on your favorite podcast player, or simply just tuning into these live streams live each week on Thursday or watching them after the fact. In any case, my name is Dr. Cameron Jones. Stay safe, and next week I will bring you more interesting research on indoor air quality, mould and water damage. Bye for now.

YouTube Link:


SARS-Cov-2 RNA Found on Particulate Matter of Bergamo in Northern Italy: First Preliminary Evidence
Leonardo Setti, Fabrizio Passarini, Gianluigi De Gennaro, Pierluigi Baribieri, Maria Grazia Perrone, Massimo Borelli, Jolanda Palmisani, Alessia Di Gilio, Valentina Torboli, Alberto Pallavicini, Maurizio Ruscio, PRISCO PISCITELLI, Alessandro Miani
medRxiv 2020.04.15.20065995; doi:
Posted April 18, 2020

The Potential role of Particulate Matter in the Spreading of COVID-19 in Northern Italy: First Evidence-based Research Hypotheses
Leonardo Setti, Fabrizio Passarini, Gianluigi De Gennaro, Pierluigi Barbieri, Maria Grazia Perrone, Andrea Piazzalunga, Massimo Borelli, Jolanda Palmisani, Alessia Di Gilio, PRISCO PISCITELLI, Alessandro Miani
medRxiv 2020.04.11.20061713; doi:
Posted April 17, 2020.

Initial evidence of higher morbidity and mortality due to SARS-CoV-2 in regions with lower air quality
Riccardo Pansini, Davide Fornacca
medRxiv 2020.04.04.20053595; doi:
Posted April 16, 2020.

An effect assessment of Airborne particulate matter pollution on COVID-19: A multi-city Study in China
Bo Wang, Jiangtao Liu, Shihua Fu, Xiaocheng Xu, Lanyu Li, Yueling Ma, Ji Zhou, Jinxi Yao, Xingrong Liu, Xiuxia Zhang, Xiaotao He, Jun Yan, Yanjun Shi, Xiaowei Ren, Jingping Niu, Bin Luo, Kai zhang
medRxiv 2020.04.09.20060137; doi:
Posted April 14, 2020

Holme JA, Øya E, Afanou AKJ, Øvrevik J, Eduard W. Characterization and pro-inflammatory potential of indoor mold particles [published online ahead of print, 2020 Feb 20]. Indoor Air. 2020;10.1111/ina.12656. doi:10.1111/ina.12656,

Yan D, Zhang T, Su J et al. Diversity and Composition of Airborne Fungal Community Associated with Particulate Matters in Beijing during Haze and Non-haze Days. Front Microbiol. 2016;7. doi:10.3389/fmicb.2016.00487

Li, C.Y., Ding, M.S., Yang, Y., Zhang, P.C., Li, Y., Wang, Y.C., Huang, L.C., Yang, P.J., Wang, M., Sha, X., Xu, Y.M., Guo, C.W. and Shan, Z.W. (2016) Portrait and Classification of Individual Haze Particulates. Journal of Environmental Protection, 7, 1355-1379.

Schaible, H. Nociceptive neurons detect cytokines in arthritis. Arthritis Res Ther 16, 470 (2014).



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