tag:theconversation.com,2011:/id/topics/fine-particles-41415/articlesFine particles – The Conversation2018-12-13T19:17:23Ztag:theconversation.com,2011:article/1087272018-12-13T19:17:23Z2018-12-13T19:17:23ZThe contest for the worst air pollutant<p>In its report published on June 28, 2018, the French <a href="https://www.anses.fr/en/content/ambient-air-quality-anses-recommends-surveillance-13-butadiene-and-enhanced-monitoring">Agency for Health Safety</a> (ANSES) presented a list of 13 new priority air pollutants to monitor.</p>
<p>Several air pollutants that are harmful to human health are already regulated and closely monitored at the European level (in accordance with the guidelines from <a href="http://extwprlegs1.fao.org/docs/pdf/eur49733.pdf">2004</a> and <a href="https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32008L0050&from=fr">2008</a>): NO2, NO, SO<sub>2</sub>, PM10, PM2,5, CO, benzene, ozone, benzo(a)pyrene, lead, arsenic, cadmium, nickel, gaseous mercury, benzo(a)anthracene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, indeno(1,2,3,c,d)pyrene and dibenzo(a,h)anthracene.</p>
<p>While some pollutants like ozone and PM10 and PM2.5 particles are famous and often cited in the media, others remain much less known. It should also be noted that this list is still limited, considering the significant number of substances emitted into the atmosphere.</p>
<p>So, how were these 13 new pollutants identified by ANSES? What were the criteria? Let’s take a closer look.</p>
<h2>The selection of candidates</h2>
<p>Identifying new priority substances to monitor in the ambient air is a long but exciting process. It’s a little like choosing the right candidate in a beauty contest. First, independent judges and experts in the field must be chosen. Next, the rules must be determined for selecting the best candidates from among the competition.</p>
<p>Over the past two years, the working group of experts developed a specific method for considering the physical and chemical diversity of the candidates present in ambient air.</p>
<p>To gather all the participants at this “beauty contest”, the experts first created a core list of chemical pollutants of interest that were not yet regulated. The experts did not include certain candidates, such as pesticides, pollen and mould, greenhouse gases and radioelements, because they were being assessed in other studies or were outside their scope of expertise.</p>
<p>This core list is based on information provided by Certified Associations of Air Quality Monitoring (AASQA) and French research laboratories like the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) and the Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA). It is also informed by consultation with experts from national and international organizations like the European Environment Agency (EEA) and from Canada and the United States (US-EPA), as well as by inventories established by international organisations like WHO.</p>
<p>Finally, this list was supplemented by an in-depth study of recent international and national scientific publications on what are considered “emerging” pollutants.</p>
<p>This final list included 557 candidates – just imagine the stampede.</p>
<h2>Ranking the finalists</h2>
<p>The candidates are then divided into four categories, based on the data available on atmospheric measurements and their intrinsic danger.</p>
<p>Category 1 includes substances that present potential health risks. Then there are categories 2a and 2b for candidates on which more data must be acquired from air measurements and studies on health impacts. Non-priority substances – with concentrations in the ambient air and health effects that do not reveal any health risks – are placed in category 3.</p>
<p>Certain exceptional candidates were reclassified, such as ultrafine particles (with diameters of less than 0,1 µm) and carbon soot, due to their potential health impacts on the population.</p>
<p>Finally, the experts prioritised the identified pollutants in category 1 to select the indisputable winner of this unusual beauty contest.</p>
<h2>And the winner is…</h2>
<p>Gas 1,3-Butadiene ranked number one out of the 13 new air pollutants to monitor, according to ANSES. It is followed by ultrafine particles and carbon soot, for which increased monitoring is recommended.</p>
<p>1,3-Butadiene is a toxic gas that originates from several combustion sources including exhaust-pipe emissions from motor vehicles, heating, and industrial activities (plastic and rubber). Several temporary measurement campaigns in France revealed that the pollutant frequently exceeded its toxicological reference value (<a href="https://www.anses.fr/en/content/toxicity-reference-values-trvs">TRV</a>)–a value that establishes a relationship between a dose and the effect.</p>
<p>Its top spot on the podium comes as no surprise: it had already won a trophy in the United Kingdom and Hungary, two countries that have reference values for its concentration in the air. In addition, the <a href="https://monographs.iarc.fr/wp-content/uploads/2018/06/mono100F-26.pdf">International Agency for Research on Cancer</a> (IARC) classified 1,3-butadiene as a known carcinogen for humans as early as 2012.</p>
<p>As for the ten other pollutants on the ANSES list, increased monitoring is recommended. These ten pollutants, with exceedances in TRV observed in specific (especially industrial) contexts are, in decreasing order of risk, manganese, hydrogen sulfide, acrylonitrile, 1,1,2-trichloroethane, copper, trichloroethylene, vanadium, cobalt, antimony and naphthalene.</p>
<p>This selection is a first step toward 1,3-butadiene being added to a list of substances that are <a href="https://www.airparif.asso.fr/en/pollution/differents-polluants">currently regulated in France</a>. If the French government forwards this proposal to the European Commission, by the end of 2019 it could be included in the ongoing revision of the 2008 directive on monitoring air quality.</p>
<p>Since this classification method is adaptive, there is a good chance that new competitions will be organised in the coming years to identify other candidates.</p>
<hr>
<p><em>This article was published from the French by the <a href="https://blogrecherche.wp.imt.fr/en/2018/11/28/contest-worst-air-pollutant/">Institut Mines Télécom</a>.</em></p><img src="https://counter.theconversation.com/content/108727/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laurent Alleman received funding from ANSES, INCA-INSERM and the Haut de France region</span></em></p>The number of substances emitted into the atmosphere is immense and growing, but some are particularly harmful to health and are subject to increased monitoring.Laurent Alleman, Associate professor, IMT Nord Europe – Institut Mines-TélécomLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/966252018-06-11T10:42:58Z2018-06-11T10:42:58ZIncreased deaths and illnesses from inhaling airborne dust: An understudied impact of climate change<figure><img src="https://images.theconversation.com/files/222434/original/file-20180608-191971-1tlb4is.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A large dust storm, or haboob, sweeps across downtown Phoenix on July 21, 2012.</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Dry-Southwest/8ddce44e44b345d09d6e4c7bfce0e86e/2/0">AP Photo/Ross D. Franklin, File</a></span></figcaption></figure><p>The Dust Bowl in the 1930s was one of the worst environmental disasters of the 20th century. Intense dust storms relentlessly pounded the southern Great Plains of the United States, wreaking severe ecological damage, forcing <a href="https://migration.ucdavis.edu/rmn/more.php?id=1355">2.5 million people to leave the region</a> and claiming unnumbered lives, mainly from <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1996313/pdf/pubhealthreporig01958-0004.pdf">“dust pneumonia.”</a></p>
<p>Research has <a href="https://doi.org/10.1175/2007JCLI2134.1">shown</a> that this disaster was fueled by a combination of severe droughts and over-cultivated lands. Today, climate change driven by human actions is <a href="https://doi.org/10.1002/wcc.81">enhancing the occurrence of droughts</a> in multiple regions around the world. </p>
<p>As researchers working at the intersection of environmental health, air pollution and climate change, we wanted to know how increasing drought conditions and population growth in the U.S. Southwest could affect airborne dust levels and public health. </p>
<p>In a recently published <a href="https://doi.org/10.1088/1748-9326/aabf20">study</a>, we estimate that if the world stays on its current greenhouse gas emissions path, rising fine dust levels could increase premature deaths by 130 percent and triple hospitalizations due to fine dust exposure in this region.</p>
<h2>Harmful effects of inhaling dust</h2>
<p>If global greenhouse gas emissions are not sharply reduced, scientists project that the U.S. Southwest – already the nation’s hottest and driest region – will experience unprecedented multi-decade “<a href="https://www.theatlantic.com/science/archive/2016/10/megadroughts-arizona-new-mexico/503531/">mega-droughts</a>” in the coming decades. </p>
<p>It is now well understood that short- and long-term exposures to airborne particles, including dust, pose major <a href="https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm">health risks</a>. Effects range from increased hospital admissions to higher risk of premature death, primarily due to cardiovascular and respiratory disorders. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/1OdDieuD1OA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The ‘Black Sunday’ dust storm on April 14, 1935, was one of the most dramatic of hundreds of “black blizzards” that struck the Great Plains in the 1930s.</span></figcaption>
</figure>
<p>In our study, “dust” refers to soil-derived airborne particles generated by wind erosion or human activities, such as farming operations or travel on unpaved roads. Any soil particles smaller than 0.05 millimeters – roughly the width of a human hair – can be uplifted into the air. We focused on particles smaller than 0.0025 millimeters (2.5 microns), which are collectively known as “fine” particulate matter (PM). Particles this small stay in the air longer and cause the greatest harm to human health, since they can penetrate deep into the lungs.</p>
<p>Decades of epidemiological research have firmly established a link between exposure to fine PM and adverse health effects. Although more research is needed to differentiate between the potency and effects of various materials that make up fine PM, which also include emissions from fossil fuel combustion and other industrial sources, <a href="http://dx.doi.org/10.3390/atmos7120158">evidence</a> <a href="http://dx.doi.org/10.1016/j.envint.2013.10.011">suggests</a> that dust is a significant contributor. </p>
<p>For example, silica, which makes up around 60 percent of windblown desert dust, is <a href="http://dx.doi.org/10.3390/ijerph7031205">known to cause</a> chronic lung inflammation, lung cancer and autoimmune diseases. Dust can also transport soil-borne pathogens and toxic contaminants over large areas. In the U.S. Southwest, dust episodes have been linked to outbreaks of <a href="https://www.pbs.org/newshour/science/dust-storms-valley-fever-blanketing-southwest">valley fever</a> and <a href="https://www.scientificamerican.com/article/how-global-warming-is-spreading-toxic-dust/">arsenic poisoning</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222435/original/file-20180608-191954-1lwqjfg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fine particulates are much smaller than a human hair.</span>
<span class="attribution"><a class="source" href="https://www.epa.gov/pm-pollution/particulate-matter-pm-basics#PM">USEPA</a></span>
</figcaption>
</figure>
<h2>Dust and droughts in the U.S. Southwest</h2>
<p>The southwestern United States, much of which consists of deserts and drylands, has the nation’s highest levels of airborne dust. The first question we investigated was how drought conditions occurring in different hydrologic systems, such as surface soils, river discharge areas and groundwater storage, have been influencing levels of airborne fine dust in recent years. </p>
<p>By analyzing data collected between 2000-2015 at 35 monitoring sites in Arizona, Colorado, New Mexico and Utah, we found that year-to-year changes in fine dust levels observed at each monitoring site tended to occur in sync. This pattern suggests that there is one or more common cause of large-scale changes in fine dust levels. </p>
<p>Indeed, we found that these changes were significantly correlated with soil moisture conditions across southwestern North America. Years with higher-than-normal fine dust levels were also marked by drier-than-normal soil moisture in areas spanning the Chihuahuan, Mojave and Sonoran deserts, the southern Great Plains and the Colorado Plateau. </p>
<p><a href="https://doi.org/10.1016/j.atmosenv.2010.03.019">Studies</a> have shown that dust emissions within these regions primarily come from desert areas, dry lake beds, previously burned areas and lands disturbed by <a href="https://doi.org/10.1002/hyp.10569">agricultural activities and fossil fuel development</a>. Our findings are consistent with previous field studies showing that soil moisture can control dust emissions by modulating vegetation cover and soil stability.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222436/original/file-20180608-191940-1n5t0zp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In early June 2018, drought affected 27 percent of the lower 48 states.</span>
<span class="attribution"><a class="source" href="https://www.drought.gov/drought/">NIDIS</a></span>
</figcaption>
</figure>
<h2>Airborne dust and health risks under future climate change</h2>
<p>In our next step, we quantified potential future changes in fine dust levels and associated public health impacts under two different climate change scenarios used in the <a href="https://www.ipcc.ch/report/ar5/">Fifth Assessment Report</a> of the <a href="https://www.ipcc.ch/index.htm">Intergovernmental Panel on Climate Change</a>. The so-called “worst-case” <a href="https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/drafts/fgd/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter12.pdf">scenario</a> in the report is characterized by unabated, increasing greenhouse gas emissions over time. In the “best-case” scenario, dramatic cuts in emissions are required to hold global warming below two degrees Celsius. </p>
<p>First, we used projections of temperature and precipitation for the years 2076-2095 from an ensemble of 22 climate models in conjunction with our derived dust-soil moisture relationships to quantify future changes in dust due to changing drought conditions under the two climate scenarios. Since there is variation among climate model projections, using a large group of them allows us to gauge the robustness of the results. </p>
<p>We then estimated the resulting public health impacts by applying relationships drawn from studies that have quantified increases in risk of premature deaths and hospitalizations in representative U.S. populations due to exposure to fine PM. In these calculations, we also took into account projections of population growth for the Southwest and changing vulnerability to disease.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222509/original/file-20180610-191974-ofuq3f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On March 31, 2017, thick plumes of dust stretched hundreds of kilometers from northern Mexico into Texas and New Mexico. The source appeared to mainly be farmland near the Mexican town of Janos.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/NaturalHazards/view.php?id=89960">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<p>Under the worst-case scenario – the path we’re currently on – fine dust levels in the Southwest could increase by 30 percent by the end of this century compared to present-day values. This would result in a 130 percent increase in premature deaths and a 300 percent increase in hospital admissions attributable to fine dust exposure.</p>
<p>Even under the best-case climate mitigation scenario, we project that fine dust levels in the region could increase by 10 percent. This rise would increase premature deaths and hospital admissions due to fine dust exposure by 20 percent and 60 percent respectively, compared to present-day values. </p>
<p>It is worth noting here that we only looked at the isolated effect of future drought conditions. Changes in other factors, such as wind speed and human land use, may enhance or dampen our results.</p>
<h2>Dust and droughts are a global threat</h2>
<p>Other researchers have found results similar to our study in other parts of the world. For example, researchers have shown that the occurrence of dust storms in <a href="https://doi.org/10.1029/2004JD004615">China</a> and <a href="https://doi.org/10.1002/2014JD022611">Saudi Arabia</a> is modulated by rainfall or soil moisture in surrounding regions, which include remote deserts and drylands. </p>
<p>Today, <a href="http://www.un.org/en/events/desertification_decade/whynow.shtml">drylands</a> compose 41 percent of the world’s total land area and are home to around 2.1 billion people. On the world’s current greenhouse gas emissions trajectory, droughts will intensify and drylands will expand in <a href="https://doi.org/10.5194/acp-13-10081-2013">parts of South America, Africa, Australia and the Mediterranean</a>. Our findings highlight the potential for climate change to worsen air quality problems in many populated arid regions around the world – one of the many <a href="https://doi.org/10.1016/S0140-6736(15)60854-6">threats</a> posed by climate change to human health and well-being.</p><img src="https://counter.theconversation.com/content/96625/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ploy Achakulwisut received funding from the US Environmental Protection Agency (EPA) under Assistance Agreement 83587501 to conduct the research discussed in this article. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the EPA.</span></em></p><p class="fine-print"><em><span>Loretta Mickley receives funding from the US Environmental Protection Agency (EPA) under Assistance Agreement 83587501. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the EPA.</span></em></p><p class="fine-print"><em><span>Susan Anenberg did not receive funding for this article. She receives funding on a related project from US EPA and Industrial Economics Inc. She consults for Environmental Health Analytics, LLC. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the EPA or any other organization. </span></em></p>New research projects that climate change could greatly increase airborne dust levels in the southwestern US, causing higher hospital admissions and premature deaths from heart and lung ailments.Ploy Pattanun Achakulwisut, Postdoctoral Scientist, George Washington UniversityLoretta Mickley, Senior Research Fellow in Chemistry-Climate Interactions, Harvard UniversitySusan Anenberg, Associate Professor of Environmental and Occupational Health and Global Health, George Washington UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/844062017-09-26T22:00:48Z2017-09-26T22:00:48ZFine-particulate pollution: can we trust microsensor readings?<p>Last May, Paris City Hall launched “Pollutrack”, a fleet of micro-sensors placed on the roofs of vehicles traveling throughout the capital to measure the level of fine particles present in the air in real time. A year early, <a href="http://metropole.rennes.fr/actualites/education-vie-sociale-sante/sante/citoyens-a-vos-capteurs/">Rennes</a> proposed that residents participate in assessing the air quality via individual sensors.</p>
<p>For several years, high concentrations of fine particles in France have been regularly observed, and air pollution has become a major health concern. Each year in France, 48,000 premature deaths are linked to air pollution.</p>
<p>The <a href="https://blogrecherche.wp.imt.fr/2017/02/07/pics-pollution-particules-fines-detecter-prevenir/">winter of 2017</a> was a prime example of this phenomenon, with daily levels reaching up to 100µg/m<sup>3</sup> in certain areas, and with conditions stagnating for several days due to the cold and anticyclonic weather patterns.</p>
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<h2>A police sketch of the fine particle</h2>
<p>A fine particle (particulate matter, abbreviated PM) is characterized by three main factors: its size, nature and concentration.</p>
<p>Its size, or rather its diameter, is one of the factors that affects our health: the PM10 have a diameter ranging from 2.5 to 10μm; PM2.5, a diameter less than 2.5μm. By way of comparison, one particle is approximately 10 to 100 times finer than a hair. And this is the problem: the smaller the particles we inhale, the more deeply they penetrate the lungs, leading to an inflammation of the lung alveoli, as well as the <a href="http://invs.santepubliquefrance.fr/publications/extrapol/32/Extrapol%2032%20bd.pdf">cardiovascular system</a>.</p>
<p>The nature of these fine particles is also problematic. They are made up of a mixture of organic and mineral substances with varying degrees of danger: water and carbon form the base around which condense sulphates, nitrates, allergens, heavy metals and other hydrocarbons with <a href="http://www.who.int/mediacentre/factsheets/fs313/en/">proven carcinogenic properties</a>.</p>
<p>As for their concentration, the greater it is in terms of mass, the greater the health risk. The World Health Organization recommends not to exceed personal exposure of 25 μg/m<sup>3</sup> for the PM2.5 as a 24-hour average and 50 μg/m<sup>3</sup> for the PM10. <a href="http://www.statistiques.developpement-durable.gouv.fr/fileadmin/documents/Produits_editoriaux/Publications/Datalab_essentiel/2017/datalab-essentiel-88-particules-atmospheriques-fevrier-2017.pdf">In recent years</a>, thresholds have been constantly exceeded, especially large cities.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/177329/original/file-20170707-2984-1a9rbna.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The website for the WHO’s BreatheLife campaign, where you can enter the name of a city and find out its air quality. Here, the example of Grenoble is given.</span>
</figcaption>
</figure>
<p>Humans are not the only ones affected by the danger of these fine particles: when they are deposited, they contribute to the enrichment of natural environments, which can also lead to <a href="https://www.airparif.asso.fr/etat-air/air-et-climat-bilan-emissions">eutrophication</a>, a phenomena in which excess amounts of nutriments, such as the nitrogen carried by the particles, are deposited in the soil or water. This can lead to algal blooms that can suffocate local ecosystems. In addition, due to the chemical reaction of the nitrogen with the surrounding environment, the eutrophication generally leads to soil acidification. Soil that is more acidic becomes drastically less fertile: vegetation becomes depleted, and slowly but inexorably, species die off.</p>
<h2>Where do they come from?</h2>
<p>Fine particle emissions primarily originate from human activities: 60% of PM10 and 40% of PM2.5 are generated from wood combustion, especially from fireplace or stove heating, 20% to 30% originate from automotive fuel (diesel is the number one). Finally, nearly 19% of national PM10 emissions, and 10% PM2.5 emissions result from agricultural activities.</p>
<p>To help public authorities limit and control these emissions, the scientific community must improve the identification and quantification of these sources of emissions, and must gain a better understanding of their spatial and temporal variability.</p>
<h2>Complex and costly readings</h2>
<p>Today, fine particle readings are primarily based on two techniques.</p>
<p>First, samples are taken from filters; these are taken after an entire day and are then analysed in a laboratory. Aside from the fact that the data is delayed, the analytical equipment used is costly and complicated to use; a certain level of expertise is required to interpret the results.</p>
<p>The other technique involves making measurements in real time, using tools like the Multi-wavelength Aethalometer AE33, a device that is relatively expensive, at over €30,000, but has the advantage of providing measurements every minute or even under a minute. It is also able to monitor black carbon (BC): it can identify the particles that originate specifically from combustion reactions. The aerosol chemical speciation monitor (ACSM) is also worth mentioning, as it makes it possible to identify the nature of the particles, and takes measurements every 30 minutes. However, its cost of 150,000 euros means that access to this type of tool is limited to laboratory experts.</p>
<p>Given their cost and level of sophistication, there are a limited number of sites in France that are equipped with these tools. <a href="http://www2.prevair.org/">Thanks to these simulations</a>, the analysis of daily averages makes it possible to create maps with a 50km by 50km grid.</p>
<p>Since these means of measurement do not make it possible to establish a real-time map with finer spatio-temporal scales – in terms of the km<sup>2</sup> and minutes – the scientists have recently begun looking to new tools: particle microsensors.</p>
<h2>How do microsensors work?</h2>
<p>Small, light, portable, inexpensive, easy to use, connected… <a href="http://www.ladepeche.fr/article/2016/05/11/2342312-microcapteurs-rendre-pollution-air-visible-concrete.html">microsensors</a> appear to offer many advantages that complement the range of heavy analytical techniques mentioned above.</p>
<p>But how credible are these new devices? To answer this question, we need to look at their physical and metrological characteristics.</p>
<p>At present, several manufactures are competing for the microsensor market: the British <a href="http://www.alphasense.com/index.php/products/optical-particle-counter/">Alphasense</a>, the Chinese Shinyei and the American manufacturer, <a href="http://www.mouser.fr/new/honeywell/honeywell-hpma115so-sensor/">Honeywell</a>. They all use the same measurement method: optical detection using a laser diode.</p>
<p>The principle is simple: the air, sucked in by the fan, flows through the detection chamber, which is configured to remove the larger particles, and retain only the fine particles. The air, loaded with particles, flows through the optical signal emitted by the laser diode, the beam of which is diffracted by a lens.</p>
<p>A photodetector placed opposite the emitted beam records decreases in luminosity caused by the passing particles, and counts the number by size ranges. The electrical signal from the photodiode is then transmitted to a microcontroller that processes the data in real time: if the air flow rate is known, the concentration number can then be determined, and then the mass, based on the size ranges, as seen in the figure below.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176960/original/file-20170705-28939-waetlw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An example of a particle sensor, in this case the Honeywell HPM series.</span>
</figcaption>
</figure>
<p>From the most basic to the fully integrated version (including acquisition and data processing software, and measurement transmission via cloud computing), the price can range from 20 to 1,000 euros for the most elaborate systems. This is very affordable, compared to the techniques mentioned above.</p>
<h2>Can we trust microsensors?</h2>
<p>First, it should be noted that these microsensors do not provide any information on the fine particles’ chemical composition. Only the techniques described above can do that. However, knowledge of the particles’ nature provides information about their source.</p>
<p>Furthermore, the microsensor system used to separate particles by size is often rudimentary; <a href="http://www.climato.be/aic/colloques/actes/ACTES_AIC2015/2%20Climatologie%20appliquee/022-DUCHE-140-145.pdf">field tests</a> have shown that while the finest particles (PM2.5) are monitored fairly well, it is often difficult to extract the PM10 fraction alone. However, the finest particles are precisely what affect our health the most, so this shortcoming is not problematic.</p>
<p>In terms of the detection/quantification limits, when the sensors are new, it is possible to reach reasonable thresholds of approximately 10µg/m<sup>3</sup>. They also have sensitivity levels between 2 and 3µg/m<sup>3</sup> (with an uncertainty of approximately 25%), which is more than sufficient for monitoring the dynamics of how the particle concentrations change in the concentration range of up to 200µg/m<sup>3</sup>.</p>
<p>However, over time, the fluidics and optical detectors of these systems tend to become clogged, leading to errors in the results. Microsensors must therefore be regularly calibrated by connecting them to reference data, such as the data released by air pollution control agencies.</p>
<p>This type of tool is therefore ideally suited for an instantaneous and semi-quantitative diagnosis. The idea is not to provide an extremely precise measurement, but rather to report on the dynamic changes in particulate air pollution on a scale with low/medium/high levels. Due to the low cost of these tools, they can be distributed in large numbers in the field, and therefore help provide a better understanding of particulate matter emissions.</p>
<hr>
<p><em>This article was translated by the Institut Mines-Télécom. The original version can be found <a href="https://blogrecherche.wp.imt.fr/en/2017/09/20/pollution-trust-microsensors-readings/">here</a>.</em></p><img src="https://counter.theconversation.com/content/84406/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathalie Redon has received financing from the LCSQA.</span></em></p>The use of small devices to measure the presence of fine particles in the air is becoming widespread. They’re one more weapon to fight against air pollution, but questions remain on their reliability.Nathalie Redon, Maître-assistante, co-responsable du Laboratoire « Capteurs », IMT Nord Europe – Institut Mines-TélécomLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/825492017-09-24T19:51:34Z2017-09-24T19:51:34ZCan facemasks help reduce the negative health impacts of air pollution?<figure><img src="https://images.theconversation.com/files/185310/original/file-20170908-32330-n7968z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beijing residents with a variety of approaches to urban air pollution.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/ledgard/116065372/in/photolist-haWeNh-RK4Tjm-9FE8cp-79WsTj-jsNZo8-ffafHW-quQE5U-4Eg9TB-5SkWKV-5Hmfcj-7627Bw-7z5pib-bfSc7-nixXzg-6228Bh-2KEGv-pdDho3-H7e6J">Bryan Ledgard/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Research has shown that exposure to air pollution, be it brief or over the long term, can have negative impacts on the lungs and hearts, and potentially the brain as well (<a href="http://dnr.wi.gov/topic/AirQuality/documents/AHA_Circulation_2010.pdf">Brook 2009</a>). It is estimated that outdoor air pollution causes 3 million excess deaths worldwide each year (<a href="http://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(15)00128-2.pdf"><em>The Lancet</em> 2015</a>). In response, a number of cities have introduced policies aimed at reducing urban air pollution, including <a href="https://en.wikipedia.org/wiki/London_congestion_charge#Proposed_CO2_emissions_based_charging">congestion charging</a> in London, <a href="https://www.theguardian.com/environment/bike-blog/2015/dec/01/how-cycling-could-help-the-paris-climate-talks-change-the-world">bike sharing</a> in Paris, and an <a href="https://www.theguardian.com/world/2017/jan/09/beijing-creates-anti-smog-police-to-tackle-air-polluters">“environmental police force”</a> in Beijing.</p>
<p>However, because time is required to implement policies intended to improve air quality and for them to actually have an effect, a growing number of <a href="https://www.standard.co.uk/lifestyle/london-life/do-pollution-masks-really-work-how-cyclists-are-trying-to-filter-out-the-filth-10442477.html">pedestrians and bicyclists</a> are choosing to wear masks or other devices that claim to reduce the risks. Options range from simple paper dust masks to those that supply clean air and prevent exposure to even the worst air pollution, like that found in dangerous work settings. Masks that are appropriate for outdoor use lie somewhere between these two extremes.</p>
<h2>Risks and risk reduction</h2>
<p>Air pollution is made up of particles and gases. Gases include ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide and a large group of chemicals known as <a href="https://en.wikipedia.org/wiki/Volatile_organic_compound">volatile organic compounds</a> (VOCs). While gases can have <a href="https://www.ncbi.nlm.nih.gov/pubmed/17435419">harmful effects</a>, research indicates that we should be most concerned about negative health impacts of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4335916/">fine particles</a> – those under 2.5 microns in size.</p>
<p>So are facemasks effective in reducing or preventing air pollution exposure? Their ability to limit exposure depends on the type of pollutant, the mask itself and how it’s used. Masks are assigned a <a href="https://en.wikipedia.org/wiki/Respirator_assigned_protection_factors">protection factor</a>, which is the percentage of a pollutant that the mask does not remove. A protection factor of 10 means that all but 10% of the pollutant is filtered out by the mask, assuming that the mask fits tightly on the face. </p>
<p>Simple paper dust masks are largely useless when it comes to lessening air pollution exposure. However, some inexpensive HEPA filter masks can be effective in limiting exposure to fine particles, particularly those known as <a href="https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/n95list1.html">“N95 respirators”</a> because they have a protection factor of 5 and thus can filter out all but 5% of particles. Effectiveness is reduced for particles smaller than 0.3 microns – bacteria are larger, but viruses and many fine particles in motor-vehicle emissions are smaller. While N95 masks do not remove harmful gases from the air, they can be combined with features such as activated charcoal that also reduce exposure to gases. These masks are more expensive and care should be taken to identify which gases they filter and how effectively.</p>
<h2>What does the research say?</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=747&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=747&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=747&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=939&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=939&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185309/original/file-20170908-32330-1qocbs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=939&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New York City police officer wearing respirator.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Respirator#/media/File:Police_officer_wearing_half-mask_respirator.jpg">Ryssby/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>There have only been a limited number of studies on the ability of facemasks to prevent or lessen negative health effects caused by exposure to air pollution, and their conclusions should be interpreted cautiously. In two of the three experimental studies, all from China, when wearing an N95 facemask while walking in the center of Beijing, blood pressure was lower than when not wearing a facemask in both healthy study participants (<a href="https://particleandfibretoxicology.biomedcentral.com/articles/10.1186/1743-8977-6-8">Langrish 2009</a>) and in participants with heart disease (<a href="https://ehp.niehs.nih.gov/1103898/">Langrish 2012</a>). In the participants with heart disease, blood flow and oxygen delivery to the heart was seen to be better when wearing the N95 facemask. In the third study, from Shanghai, healthy participants also had lower blood pressure when wearing an N95 facemask (<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5289918/">Shi 2017</a>). These studies suggest that wearing a particle-filtering mask can reduce the short-term exposure effects on the heart and blood vessels of exposure to urban air pollution.</p>
<p>The main reason that these findings should be interpreted cautiously is that participants were aware that they were breathing filtered air. While this sounds obvious, this awareness – rather any pollution reduction – could have produced the results observed. Studies to address questions as to whether the facemasks also lessened effects on the lungs and whether effects of long-term exposure could also be prevented have not been done.</p>
<p>To be more confident in such results, studies that look at health effects on the lungs as well as the heart, and that can avoid study participants knowing whether or not they are breathing filtered air, are needed. Furthermore, we need to know whether wearing masks that filter the gas pollutants in addition to fine particles provide added benefits. These shortcomings were addressed in a study that we recently completed in China, findings of which will be published shortly.</p>
<h2>Considerations and limitations</h2>
<p>Wearing a facemask to lessen air-pollution exposure can be difficult for some people – they could find them to be uncomfortable, that breathing seems more difficult or that they feel claustrophobic. In addition, a facemask is only effective if it provides a good seal around the face. Men with beards or who are unshaven cannot achieve an adequately tight fit around the nose and mouth. </p>
<p>Moreover, while our exposure to air pollution is typically greater outdoors, we spend the vast majority of our time indoors, where we’re also exposed to air pollutants, including gases and fine particles. Since facemasks are seldom worn indoors, use of indoor air cleaners that have particle- and gas-filtering capabilities would still be needed to more fully provide protection from pollutants in our air.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=121&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=121&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=121&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=152&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=152&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=152&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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<p><em>Created in 2007, the <a href="https://www.axa-research.org">Axa Research Fund</a> supports more than 500 projets around the world conducted by researchers from 51 countries.</em></p><img src="https://counter.theconversation.com/content/82549/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sverre Vedal ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>In recent years the number of motor vehicles – and the pollution they generate – has grown astronomically, leading some citydwellers to wear facemasks in the hopes of protecting themselves. So do they work?Sverre Vedal, Professor, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/828592017-09-15T08:48:53Z2017-09-15T08:48:53ZCommuting by subway? What you need to know about air quality<figure><img src="https://images.theconversation.com/files/184227/original/file-20170831-22427-faa9vm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sao Paulo, Brazil, 2013. Subways abound in fine particles often carried by brakes or trains.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/3336/10915927833/">Diego Torres Silvestre/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><a href="http://economictimes.indiatimes.com/news/politics-and-nation/in-pace-change-govt-to-double-network-in-18-months-add-4-cities-on-metro-map/articleshow/60149847.cms">Four more major Indian cities</a> will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building <a href="http://www.scmp.com/magazines/post-magazine/long-reads/article/2106229/shanghai-metro-keeping-worlds-longest-mass">its 15th subway line</a>, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line <a href="http://www.newyorker.com/magazine/2017/02/13/the-second-avenue-subway-is-here">after waiting for almost 100 years</a> for it to arrive.</p>
<p>In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than <a href="http://mic-ro.com/metro/metrostats.html">120 million people</a> commute by them every day. We count around <a href="https://tfl.gov.uk/corporate/about-tfl/what-we-do/london-underground">4.8 million</a> riders per day in London, <a href="https://fr.wikipedia.org/wiki/M%C3%A9tro_de_Paris">5.3 million</a> in Paris, <a href="https://en.wikipedia.org/wiki/Tokyo_subway">6.8 million</a> in Tokyo, <a href="https://en.wikipedia.org/wiki/Moscow_Metro">9.7 million</a> in Moscow and <a href="https://en.wikipedia.org/wiki/Beijing_Subway">10 million</a> in Beijing.</p>
<p>Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, <a href="http://www.un.org/en/development/desa/news/population/world-urbanization-prospects-2014.html">half of the world’s population is now urban</a>. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.</p>
<p>Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO<sub>2</sub>), produced in part by industrial emissions and road traffic, <a href="http://www.euro.who.int/en/health-topics/environment-and-health/Housing-andhealth/publications/pre-2009/air-quality-guidelines.-global-update-2005.-particulate-matter,-ozone,-nitrogen-dioxide-and-sulfur-dioxide">are responsible</a> for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.</p>
<p>But what is the air like that we breathe underground, on the rail platforms and inside trains?</p>
<h2>Mixed air quality</h2>
<p>Over the last decade, several <a href="http://improve-life.eu/en/scientific-publications-on-subway-air-quality/">pioneering studies</a> have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/184215/original/file-20170831-22617-1ffjqel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Subway, Tokyo, 2016.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/132514254@N04/31341365561/">Mildiou/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in <a href="http://www.sciencedirect.com/science/article/pii/S0013935115300426">Barcelona</a>, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in <a href="http://www.sciencedirect.com/science/article/pii/S1352231002006878">Hong Kong</a>, <a href="http://www.sciencedirect.com/science/article/pii/S1352231006008727">Mexico City</a>, <a href="http://www.sciencedirect.com/science/article/pii/S1309104215303792">Istanbul</a> and <a href="http://pubs.rsc.org/-/content/articlehtml/2014/em/c3em00648d">Santiago de Chile</a>.</p>
<h2>Of wheels and brakes</h2>
<p>Such <a href="http://www.sciencedirect.com/science/article/pii/S135223100700698X">differences</a> have been attributed to different wheel materials and braking mechanisms, as well as to variations in <a href="http://www.sciencedirect.com/science/article/pii/S0048969717302449">ventilation</a> and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/184220/original/file-20170831-22617-1mtzmna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Second Avenue Subway in the making, New York, 2013.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Second_Avenue_Subway_-_72nd_Street_Station_(8744771284).jpg">MTA Capital Construction/Rehema Trimiew/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.</p>
<p>In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.</p>
<p>To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. <a href="https://www.ncbi.nlm.nih.gov/labs/articles/19926083/">New York subway workers</a> have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the <a href="http://onlinelibrary.wiley.com/doi/10.1002/ajim.20584/abstract">Stockholm subway system</a>.</p>
<p>But a note of caution is struck by the observations of <a href="https://www.ncbi.nlm.nih.gov/pubmed/18178587">scholars</a> who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.</p>
<p>The dominantly ferrous particles are mixed with <a href="http://improve-life.eu/en/scientific-publications-on-subway-air-quality/">particles from a range of other sources</a>, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.</p>
<h2>Comparing platforms</h2>
<p>The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of <a href="http://improve-life.eu/">IMPROVE LIFE project</a> with additional support from the AXA Research Fund.</p>
<p>It reveals substantial variations in <a href="http://www.sciencedirect.com/science/article/pii/S004896971401715X">particle-matter concentrations</a>. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of <a href="http://www.sciencedirect.com/science/article/pii/S004896971401715X">air-conditioning</a> has been shown to produce lower particle-matter concentrations inside carriages.</p>
<p>In trains where it is possible to open the windows, such as <a href="http://www.sciencedirect.com/science/article/pii/S0013935115301705">in Athens</a>, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at <a href="https://www.ncbi.nlm.nih.gov/pubmed/27325017">high speed</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/184222/original/file-20170831-22559-qedm6u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">According to their construction material, you may breath different kind of particles on various platforms worldwide.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:London_Tube_(6549832833).jpg">London Tube/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Monitoring stations</h2>
<p>Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the <a href="http://improve-life.eu/en/welcome/">Barcelona subway system</a>, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.</p>
<p>To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.</p>
<p>Such research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=121&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=121&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=121&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=152&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=152&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202296/original/file-20180117-53314-hzk3rx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=152&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em>Created in 2007, the Axa Research Fund supports more than 500 projets around the world conducted by researchers from 51 countries. To learn more about the work of Fulvio Amato, visit the <a href="https://www.axa-research.org/en/projects/fulvio-amato">dedicated site</a>.</em></p><img src="https://counter.theconversation.com/content/82859/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fulvio Amato receives funding from Spanish Ministry of Economy, Industry and Competitiveness and from AXA Research Fund. More information on Fulvio Amato's work is available on the website of the Axa Research Fund <a href="https://www.axa-research.org/en/projects/fulvio-amato">https://www.axa-research.org/en/projects/fulvio-amato</a>.
</span></em></p><p class="fine-print"><em><span>Teresa Moreno receives funding from the European LIFE Programme (IMPROVE LIFE13 ENV/ES/000263) and the Spanish Ministry of Economy and Competitiveness with FEDER funds (METRO CGL2012-33066). </span></em></p>Subways seem like the perfect solution to improve air quality in cities. But what about air quality underground?Fulvio Amato, Tenured Scientist, Consejo Superior de Investigaciones Científicas (CSIC)Teresa Moreno, Director of the Institute of Environmental Assessment and Water Research (IDAEA), Instituto de Diagnóstico Ambiental y Estudios del Agua (IDAEA - CSIC)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/818302017-08-01T01:57:52Z2017-08-01T01:57:52ZClimate change set to increase air pollution deaths by hundreds of thousands by 2100<p>Climate change is set to increase the amount of ground-level ozone and fine particle pollution we breathe, which leads to lung disease, heart conditions, and stroke. Less rain and more heat means this pollution will stay in the air for longer, creating more health problems.</p>
<p>Our research, published in <a href="https://www.nature.com/articles/doi:10.1038/nclimate3354">Nature Climate Change</a>, found that if climate change continues unabated, it will cause about 60,000 extra deaths globally each year by 2030, and 260,000 deaths annually by 2100, as a result of the impact of these changes on pollution.</p>
<p>This is the most comprehensive study to date on the effects of climate change on global air quality and health. Researchers from the United States, the United Kingdom, France, Japan and New Zealand between them used nine different global chemistry-climate models.</p>
<p>Most models showed an increase in likely deaths – the clearest signal yet of the harm climate change will do to air quality and human health, adding to the millions of people who die from air pollution every year. </p>
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Read more:
<a href="https://theconversation.com/can-we-blame-climate-change-for-thunderstorm-asthma-69564">Can we blame climate change for thunderstorm asthma?</a>
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<h2>Stagnant air</h2>
<p>Climate change fundamentally alters the air currents that move pollution across continents and between the lower and higher layers of the atmosphere. This means that where air becomes more stagnant in a future climate, <a href="https://www.nature.com/news/air-quality-to-suffer-with-global-warming-1.15442">pollution stays near the ground in higher concentrations</a>. </p>
<p>Ground-level ozone is created when chemical pollution (such as emissions from cars or manufacturing plants) reacts in the presence of sunlight. As climate change makes an area warmer and drier, it will produce more ozone.</p>
<p>Fine particles are a mixture of small solids and liquid droplets suspended in air. Examples include black carbon, organic carbon, soot, smoke and dust. These fine particles, which are known to cause lung diseases, are emitted from industry, transport and residential sources. Less rain means that fine particles stay in the air for longer.</p>
<p>While fine particles and ozone both occur naturally, human activity has <a href="https://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm">increased them substantially</a>.</p>
<p>The <a href="https://www.ipcc.ch/organization/organization.shtml">Intergovernmental Panel on Climate Change</a> has used four different future climate scenarios, representing optimistic to pessimistic levels of emissions reduction. </p>
<p>In a <a href="https://www.atmos-chem-phys.net/16/9847/2016/">previous study</a>, we modelled air pollution-related deaths between 2000 and 2100 based on the <a href="https://link.springer.com/article/10.1007/s10584-011-0149-y">most pessimistic of these scenarios</a>. This assumes large population growth, modest improvements in emissions-reducing technology, and ineffectual climate change policy. </p>
<p>That earlier study found that while global deaths related to ozone increase in the future, those related to fine particles decrease markedly under this scenario. </p>
<h2>Emissions will likely lead to deaths</h2>
<p>In our <a href="https://www.nature.com/articles/doi:10.1038/nclimate3354">new study</a>, we isolated the effects of climate change on global air pollution, by using emissions from the year 2000 together with simulations of climate for 2030 and 2100.</p>
<p>The projected air pollutant changes due to climate change were then used in a health risk assessment model. That model takes into account population growth, how susceptible a population is to health issues and how that might change over time, and the mortality risk from respiratory and heart diseases and lung cancer. </p>
<p>In simulations with our nine chemistry-climate models, we found that climate change caused 14% of the projected increase in ozone-related mortality by 2100, and offset the projected decrease in deaths related to fine particles by 16%. </p>
<p>Our models show that premature deaths increase in all regions due to climate change, except in Africa, and are greatest in India and East Asia.</p>
<p>Using multiple models makes the results more robust than using a single model. There is some spread of results amongst the nine models used here, with a few models estimating that climate change may decrease air pollution-related deaths. This highlights that results from any study using a single model should be interpreted with caution.</p>
<p>Australia and New Zealand are <a href="https://www.stateofglobalair.org/sites/default/files/SOGA2017_report.pdf">both relatively unpolluted</a> compared with countries in the Northern Hemisphere. Therefore, both ozone and fine particle pollution currently cause relatively few deaths in both countries. However, we found that under climate change the risk will likely increase. </p>
<p>This paper highlights that climate change will increase human mortality through changes in air pollution. These health impacts add to others that climate change will also cause, including from heat stress, severe storms and the spread of infectious diseases. By impacting air quality, climate change will likely offset the benefits of other measures to improve air quality.</p><img src="https://counter.theconversation.com/content/81830/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Guang Zeng receives funding from the New Zealand Government's Ministry of Business, Innovation and Employment (MBIE) through their Strategic Science Investment Fund.</span></em></p><p class="fine-print"><em><span>Jason West receives funding from the US Environmental Protection Agency, NASA, National Science Foundation, and the National Institute of Environmental Health Sciences. </span></em></p>A new study suggests climate change will cause changes to patterns of ground-level ozone and smog – two deadly pollutants set to increase deaths by about 260,000 worldwide by the end of the century.Guang Zeng, Atmospheric Scientist, National Institute of Water and Atmospheric ResearchJason West, Associate Professor, Department of Environmental Sciences and Engineering , University of North Carolina at Chapel HillLicensed as Creative Commons – attribution, no derivatives.