Indoor Particles – Deadly small
Floating everywhere, too small to notice, indoor particles are not on the spotlight of common knowledge. But they should ! In fact, where do they come from ? What are their consequences on human health and productivity ? How to prevent exposure to indoor particles ? These are the questions that have put the LIMY team (Luc, Iris, Martin, Yorgos) at work. Now is the time for them to share the knowledge.
The team chose this subject not only because we are constantly exposed to it, but also because it is a problem that needs to be solved.
Where does it come from ?
Indoor particulate matter (PM) includes outdoor particles that migrate indoors and particles that originate from indoor sources. The different types of particles are classified by size:
- Coarse particles (PM10), with a diameter under 10 microns.
- Fine particles (PM2.5), with a diameter under 2.5 microns
- Ultrafine particles (UFP), with a diameter under 0.1 micron
Often, they are caused by human activities, but they are also produced by nature, such as volcanic eruptions, natural wind erosion, fires, or advancing deserts.
Coarse particles
PM10 are small particles found in dust or smoke. According to the EPFL’s Human Oriented Build Environment Lab[1], they mostly originate from polluted outdoor air, cooking, smoking, building materials, cleaning products, arranging papers, pets or even humans themselves. As we can see, these sources are mainly anthropogenic. Indeed, coarse particles have also their source in humans’ movements (walking, sitting, …), or even their skin and clothing.
A recent study at Berkeley University [2] measured the emission rates of particles larger than 1µm for a person. The results showed that emissions were 8 million particles per hour when seated and raised as high as 20 million when walking.
Fine particles
Most of the indoor fine particles (PM2.5) take their sources from daily house activities and are very frequently human-associated, like the other sources of particulate matter. The principal source of fine particles is combustion: wood heating, burning candles and incense, or smoking. Fine particles also take their sources in cooking : more precisely when frying, grilling, baking, boiling; or using gas or electric ovens.
Ultrafine Particles
The ultrafine particles take their source mainly in combustion or cooking : for example, gas heating, candle and incense burning (like PM2.5). But UFP are also issued by various electrical appliances, such as lasers, 3D printers, photocopiers, toasters and mechanical sources.
Outdoors air can also be an indoor pollutant source due to the air exchange (caused by ventilation, infiltration and gaps in the building structure). In fact, although the outdoor air is generally less polluted, it has pollutants that are not produced in living spaces, mostly because of factories, construction and traffic.
The impact of daily activities on PM emissions is shown below [3].
As we can see, there are a lot of particulate matter emissions and occupants are exposed to them by doing simple daily activities such as cooking or cleaning.
Impacts on the human health
Particles have more negative impacts on human health as one could imagine, especially for the smaller ones (PM10) since they can infiltrate the lungs and deteriorate one’s health. More precisely, according to the US Environmental Protection Agency [4a] they can cause “irritation of the airways, coughing or difficulty breathing”.
Smaller particles are more dangerous since they can reach the smaller airways of the body [4b]. This causes cardiovascular diseases, severe health problems such as premature death in people with heart or lung disease, decreased lung function or even non fatal heart attacks.
The ultrafine particles are the most dangerous ones. Not only can they deteriorate one’s respiratory system, but they can also penetrate tissues and organs, posing an even greater risk.
Human productivity and PM
Human productivity is also impacted by indoor particles. A Harvard study [5] looked at the link between indoor particles concentration and cognitives capacities. To do so they created in a lab the environmental parameters associated with different buildings types: temperature, CO2, TVOCs, NO2, O3, PM2.5 and measured some cognitive capacities of participants.
It concludes that “Exposure to CO2 and VOCs at levels found in conventional office buildings was associated with lower cognitive scores than [others]”, and that it could have significant impacts on “productivity, learning, and safety”.
You can discover the results below.
Another study on 109 participants published in “Building and environment”, [6] showed that in the US, “Workers in green certified buildings scored 26.4% (95% CI: [12.8%, 39.7%]) higher on cognitive function tests” when taking into account annual earnings, job category and level of schooling. They also had improvements in sleep, asthma and 30% fewer sick building syndrome.
But what is the cost of better air ? Researchers of the universities of Harvard and Syracuse [7] found that doubling the ventilation rate costs 40$/ person and creates an 8% productivity increase, which corresponds to 6500$/ year. It also reduced absenteeism and improved health. The benefits are for: the workers, the company and the society.
Unfortunately, this problem is not only limited to intellectual productivity. A study from the university of Columbia [8] found that fruit pickers in California are less efficient during ozone pollution, even if their pay is proportional to the quantity of fruit they pick.
To conclude, we can highlight the importance of indoor climate for health, comfort and productivity.
Preventing exposure
In order to prevent exposure to indoor particles, a few things have to be considered, especially for civil engineers !
The first solution is to act at the source of the pollution:
- The local environment is a key factor when choosing a buildings’ location because of air exchange.
- Materials and emissions used during the construction should be selected in order to prevent “off-gassing” and indoor particles production. Cooking should be without combustion (use gas or electric ovens) and heating without stoves.
Designing a clean building is also a key element to consider. A good ventilation prevents the accumulation of those harmful particles, mainly where a combustion process takes place. Regarding heating, modern solutions should be considered and the use of certain items should be avoided.
What to do otherwise ?
First of all, “manual” ventilation such as opening windows or using a ventilator can have a positive impact on indoor particle concentration. Obviously, combustion indoors should be avoided (cigarettes, candles, incense).
In conclusion, although indoor particles are small, their impact is huge on our society, and deserves more interest. However, it is obvious that we are not equally impacted by indoor particles. Indeed, low income countries tend to be more affected by indoor particles, simply because the tools they use in their daily life, which are sometimes harmful for its users.
Therefore, there is a real challenge that awaits engineers to find solutions that combine both efficiency and health. According to Dr. Joseph Allan, who is director of the Healthy Buildings program at Harvard’s Center for Health and the Global Environment: “We have been presented with the false choice of energy efficiency or healthy indoor environments for too long. We can- and must- have both”.
How did the LIMY team work for this project ? They started with the course lectures, and then they completed their database with studies from the web that are published by the same research labs.
Iris GIBOURG, Yorgos RUFFY, Luc TEUSCHER, Martin SIMON
Links:
[1] https://www.google.com/url?q=https://www.epfl.ch/labs/hobel/humans-as-sources-of-indoor-particles-and-gases/&sa=D&ust=1606060472092000&usg=AOvVaw0VbkVm1tutJnqBg8HVBdX8
[2] Licina, D., Tian, Y., & Nazaroff, WW. (2017). Emission rates and the personal cloud effect associated with particle release from the perihuman environment. Indoor air, 27(4), 791-802. http://dx.doi.org/10.1111/ina.12365 Retrieved from https://escholarship.org/uc/item/22t072x3
[3] US national library of medicine in 2000
[4a] US Environment Protection Agency (EPA), Indoor Particles Matter https://www.epa.gov/indoor-air-quality-iaq/indoor-particulate-matter
[4b] https://www.who.int/airpollution/household/health-impacts/en/
[5] Allen, Joseph G., Piers MacNaughton, Usha Satish, SureshSantanam, Jose Vallarino, and John D. Spengler. 2015. “Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation,and Volatile Organic Compound Exposures in Office Workers:A Controlled Exposure Study of Green and Conventional OfficeEnvironments.” Environmental Health Perspectives 124 (6): 805-812.doi:10.1289/ehp.1510037. http://dx.doi.org/10.1289/ehp.1510037.https://dash.harvard.edu/bitstream/handle/1/27662232/4892924.pdf?sequence=1
[6] Piers MacNaughtona, Usha Satishb, Jose Guillermo, Cedeno Laurenta, Skye Flanigana, Jose Vallarinoa, Brent Coullc, John D.Spenglera, Joseph G.Allena 2016, “Building and environment” vol 114. “The impact of working in a green certified building on cognitive function and health”
https://www.sciencedirect.com/science/article/abs/pii/S0360132316304723
[7] Piers MacNaughton, James Pegues, Usha Satish, Suresh Santanam, John Spengler and Joseph Allen. “Economic, Environmental and Health Implications of Enhanced Ventilation in Office Buildings” https://www.mdpi.com/1660-4601/12/11/14709/htm
[8] J. S. Graff Zivin, M Neidell: “The impact of pollution on worker productivity”
https://www.nber.org/system/files/working_papers/w17004/w17004.pdf
[9] https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm
Other informations:
Pollution intérieure : de l’air – FUTURE – ARTE https://www.youtube.com/watch?v=Kj7_FaiEx0k
Enjeux de la qualité de l’air des batiments, Placo TV
https://www.youtube.com/watch?v=3JTWP_Lw4xs
The conversation, “research shows if you improve air quality at work, you improve productivity. https://theconversation.com/research-shows-if-you-improve-the-air-quality-at-work-you-improve-productivity-76695. Very good starting point, summing up various studies on productivity.
https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health
https://fr.wikipedia.org/wiki/Particules_en_suspension
https://www.epfl.ch/labs/hobel/category/blog/
https://www.epfl.ch/labs/hobel/humans-as-sources-of-indoor-particles-and-gases/
https://www.epfl.ch/labs/hobel/impact-of-indoor-air-quality-on-human-productivity/
Cover image: courtesy of EPA