are you wondering what the different colors and numbers below mean?
may 5th 2020
april 28th 2020
back in 2008, when the world air quality project started, all of the existing air quality monitoring stations where based on highly professional and expensive bam and toem technology. this kind of stations are always maintained by professional and highly qualified operators - and this ensures that the output of this station can be trusted.
12 years later, the bam and toem stations still do exist. but with the development of laser scattering technology and low-cost dust sensor, the bam and toem stations are now outnumbered by immense and dense low-cost sensor networks. nowdays, there are just so many of those networks - to name a few: urad, luft-daten, airqo, airbg, opensense, yakkaw, econet, airkaz, ccdc, ambente, green air, etc..
january 10th 2017
univ. of arizona ()
a common question asked is why are nitrogen dioxide (no2), sulphur dioxide (so2) and carbon monoxide (co) concentrations always so low and is measuring them useful?
to highlight the importance of monitoring these substances this article is going to explain where these pollutants come from and how to they affect our health and the environment.
to keep things short this article will just focus on no2.
august 10th 2016
univ. of arizona ()
it is already several months since the us epa updated its aqi standard for ozone 8 hours breakpoints. this is definitely a positive step towards strengthening air quality in the usa, since the us epa standard was actually among of the least conservative standard for ozone, compared, for instance, to similar standards in india, china or europe!
but more interestingly, recently took a step further by introducing the ozone formula, which allows to use the weighted 8 hours breakpoint standard in place of the 1 hour breakpoint. this change, which the airnow team did not widely communicate to the public, makes quite a change to the way ozone aqi is reported, and this is what we will be looking at in this article.
february 28th 2016
during the past months, the world air quality team has been working on analyzing several new air quality forecast models, as well as improving the air quality forecast model demonstrator.this article will present the latest forecast model demonstrator, which is based on the gridded population of the world (), and which will be applied to analyze the air quality forecast for the northern india region (including bangladesh, pakistan and nepal).
november 5th 2015
a perfect dust storm ()
october 28th 2015
it is almost two months since our colleagues from the have been making an interesting move towards promoting the idea that air quality is as important as any other business within the united nations. they started to invest in this domain, and came up with the excellent initiative to create an open footprint for affordable air quality monitoring stations.
september 20th 2015
this is a small contribution form the world air quality index project to the asmc - asean specialised meteorological centre () during this heavy period of haze in south asia.
september 18th 2015
map overlay process
we have been recently cooperating with quite a few more epas worlwide. among all the requests which we have had, it is actually to provide a web map service so that the epa themselves can include the real-time air quality data onto the map from their website.one of the obvious advantages of using such a map web service from us is to benefit from the transboundary data which we are curating, i.e. a world wide air quality information is provided without country boundary limits.
the second advantage is not only that this is a free service, but it is also completely compatible with standard map technologies from google, bing or leaflet, which allows a quick and easy integration with any existing website.
september 6th 2015
the ambient , refered as o3 and also called called ground-level or ozone impacts everyone on earth regardless of the country, as shown on the image on the right .
unlike particulate matter (pm2.5), the ground-level ozone is not emitted directly. it is instead produced through a series of chemical reactions that occur in presence of nitrogen oxides, volatile organic compounds, sunlight and high temperatures, as shown on the following visual:
quantifying the impact of this ground level ozone on health is done via the air quality index standard which each countries defines. what is interesting is that half of the world is using a standard based on milligrams measurement, while the rest is using ppb based measurement. but is this really a problem? this is what we will be looking at in this article.
september 3rd 2015
inspekcja ochrony środowiska.
(inspection of environmental protection)
the air quality data for has been available for a while, but we recently got few questions about the aqi scale used by the inspekcja ochrony środowiska, i.e. the regional inspections of environmental protection, and how it differs with the scale used on the world air quality index project. one of them is from sylwia, who asked:
i am confused with all those numbers, and why there is a difference with the numbers shown on the warsaw epa website.this is actually a very good question, since, when it comes to data, no one should take data as "granted" (refering to the excellent from on 'own your body's data'). this is also the reason why the world air quality index project exists, i.e. to explain every one how to understand the number behind air pollution.
could you please kindly inform me about the source of the data in warsaw and the reliability of the data you provide with?
july 28th 2015
in order to improve the integration of our aqi widgets within external websites, we have developped a new widget api feed. compared to the existing widget feed, this new api feed provides much more flexibility for the integration, but also many more options for customzing the widget appearance.
july 18th 2015
real-time air quality data for is now available for indonesia. 10 stations located in major cities across indonesia are measuring in real-time pm10 pollution.
the monitoring stations are operated by (badan meteorologi klimatologi dan geofisika), the indonesian department of meteorology, climatology and geophysics.
july 16th 2015
the fleurdelisé, flag of quebec.
the air quality data for and has been available for a while, but we recently got few questions about the aqi scale used in this part of canada. one of them is from marie a., who asked:
i would like to know why the air quality index on your web site is different from the aqi on the montreal's website? do you recalculate anything to meet the us epa aqi standards? if so, how? with what data?this is indeed a very good question. and we will explain in this article the different scales in use, how the scales compare to each other, and how the convertion can be done.
july 1st 2015
thanks to the world air quality index project community, translations for the are now available for the website and web-application. many thanks especillay to the user "airs" for the excellent contribution.
june 8th 2015
beijing citizens do know for long that the best natural way to clean the pollution in the air is strong winds from the north, while winds from the south might, on the contrary, bring more pollution from hebei.
in , ecuador, there is a similar problematic, except that the pollution comes from the active . fortunately, they do not erupt that often, but when they erupt, better avoid being under the the heavy formed by the explosive eruptions (see picture).
june 3rd 2015
it is already a long time since the hong kong epa has updated its air quality index standard from the traditional air pollution index to the so called air quality health index (aqhi), but we never got a change until now to have a deeper look at it, which we will do in this article.
the hong kong epa has actually done an excellent work at explaining how the aqhi is defined, and the information one needs to understand the aqhi is available from their . the most obvious simplification is the change of the traditional 0-500 index into a new simplifed 0-10 range, sub-divded in five health risk categories, as shown below:
but there is actually much more than a range simplification: the new aqhi is also introducing the very clever concept of added health risk (%ar), which was originally , in 2007, by a team of four partners from south africa, and first used in .
may 30th 2015
the air quality forecast for south america is now available on the , in parnership with the brazilian centro de previsão do tempo e estudos climáticos (). the forecast can be accessed freely accessed from as well as . the cptec team has done an excellent work at providing a simple and detailled on the underlying concepts used by their forecast model, called (for brazilian developments on the regional atmospheric modelling system). the picture below (from the cptec) is giving an insight on the workflow for their model (source -> transport -> deposition).
may 18th 2015
the ground ozone air quality index calculation has just been updated to follow the instant cast concept, i.e. to report the pollution right now instead of the pollution from the previous hours. for more information about the instant cast, please refer to this article.the calculation for the ozone index is now using the hourly reading, instead of the previous 8 hours average, but still applying the same 8 hours aqi breakpoints formula for aqi below 100. the previous for calculating the 8-hour average concentrations is not used any more for instant reporting. above aqi 100, the normal 1 hour ozone breakpoints are used (while before, the aqi above 100 was defined as the maximum of the 1 hour and 8 hours readings).
may 16th 2015
it is already more than one year since the world health organization has released their ' database 2014'. the who team who worked on this project have done an excellent work at gathering the data for so many countries, and putting it all together in a single place accessible for all.we wrote about it in several of our past articles (like for the air quality or in ), but we never had the chance to look at the different options to visualize their data set. so, this is what we will be writing about in this article.
may 15th 2015
the indian central pollution control board has recently announced, in april 2015, the publication of india's national air quality index standard (naqi ). all the details on this standard are available from , or from this from indian institute of technology, kanpur ().this is actually a very important step forward in the air quality world awarness, since the air pollution in each country is very much specific to the country pollution type: for instance because of dust (in arabic peninsula), because of transport (new delhi) or topography (chile).
may 10th 2015
latin america, just like any other continent in our world is facing air pollution. the recent 2014 report by the on ambient (outdoor) air pollution gives some annual mean figures for several cities in latin america. without surprise, the worst scenarios are in asia, but yet, some cities in latin america have high indexes too (see table on the left).
the ranking from the who should however by considered carefully, especially considering the measurement methods used the report can be argued - for instance, for lima, the peruvian epa is arguing that the data from the who is not correct because the samples were not taken in the right places (read this article from for full feedback from several countries). this is actually for this reason that we only publish real-time information on the world air quality project since we do believe than more than ranking, it is the current conditions that are important for the world citizen.
may 2nd 2015
air quality for malaysia has been available for a long time, but unlike other countries, only the composite aqi is provided. the aqi for the individual pollutants such as pm10, ozone ... is not available, which makes the convertion to the us epa scale more difficult.
fortunately, the information about the aqi scale used in malaysia, also known as api (for air pollutant index) is clearly explained in the document ''.
april 28th 2015
many of the countries in the balkans are providing real-time air quality readings. the data for (thrace), and have already been available on the world air quality index project for a long time. today, we are able to roll-out the data for 3 new countries: , and .
april 26th 2015
we had the honor to be invited by from the nasa applied remote sensing training () team to give a presentation about our world air quality index project at the earth observations and tools for air quality applications
april 8th 2015
when talking about air quality, the first countries that comes to people's mind are china and india, and more generally asia. even on the world air quality index project, asia has always been, since the begining, our strong focus (most likely because this is where our hq is located!).
few years ago, in 2012, we decided to extend our scope to cover the other , starting with , and then following with and , . but one of seven continents, namely africa, has been surprisingly lacking behind. we received many inquiries about this lack of data, and one of the last was from said e. who wrote:
thanks for making the world air quality index project site. it gives very useful information.
my only concern is why africa is not considered.
for information i am a moroccan citizen.
march 23rd 2015
in weather prediction, forecast models are used to predict future states of the atmosphere, based on how the climate system evolves with time from an initial state. while the forecast models are quite (and do require strong scientific and engineering capabilities), the science of analyzing those forecast models, and verifying their , by comparing actual empirical observations to predicted values, is quite straightforward.
for the domain of air quality, just like for weather prediction, it is possible to define models used to predict the future set of atmospheric pollution. there are actually , often referred as . and just like weather prediction, the same concept of accuracy analysis can be applied to atmospheric pollution predictions.
march 20th 2015
very often we receive inquiries from users asking about the numbers published on the world air quality index project, and wondering about the difference with the values expressed in other websites. and that's actually normal, since the numbers, also called air quality indexes (aqi), can be very confusing for beginners. the last message we received is the following one:
we have been checking air quality index for the tianjin, china since last year, however we found the data has such a big difference between your website and another official (air.tjemc.org.cn) one which is stated on yours as well. i am wondering which one can provide more accurate data, as it will affect the decision for outdoor or indoor. please help me with this issue. thank you!we have been writing quite a lot about this issue before, for instance from , and more recently about the nowcast. but, because we are still getting many questions, we are now writing this article to explain the difference of the aqi scales used all over the world.
march 15th 2015
among all the topics that were addressed, there is one worth writing about, namely the "nowcast" system. this system used by the us epa to convert the raw pollutants readings, expressed in µg/m3 or ppb, into the aqi (scale from 0 to 500). it is used for all the aqi values reported on the website.
the concept behind the nowcast is to compensate the "24 hours averaging", which should be used when converting concentrations to aqi. the reason for this averaging is that the specifies that each of the levels of health concern (i.e. good, moderate,... unhealthy...) is valid under a 24 hours exposure. for example, when seeing a 188 aqi (unhealthy), one need to read it as "if i stay out for 24 hours, and the aqi is 188 during those 24 hours, then the health effect is unhealthy". this is quite different from saying that "if the aqi reported now is 188, then the health effect is unhealthy".
february 23rd 2015
as there is also a huge demand for pm2.5 monitoring for (especially chiang mai and bangkok), or for more station in (ho chi minh city), the extension will also cover selected countries with existing network.
but, this time, unlike for the previous countries, we do need the help of everyone, and especially your help if you are living in one of those countries. the reason is that, this time, since the real-time air quality information is not publically available from the environmental protection agencies (epa) of those countries, the world air quality index project will start to crowdsource air quality monitoring stations in the main cities of the above countries1.
visible air pollution on the manilla and jakarta skylines
february 15th 2015
we recentely had the priviledge to start a cooperation with the .; the objective is to use the remote air quality sensing based on the nasa satelites to determine the air quality in areas where sensors are not available (e.g. over the sea, but also for countries where sensors are not yet available).
february 8th 2015
earlier this week (of february 2015), we got several inquries from hanoi citizen wondering about the air quality index which was displayed on the hanoi page ().
the main reason for the inquiry was that the air quality index displayed on the world air quality index project was around 50 (green aqi) level, while the outdoor visibilty in hanoi looked like this:
october 28th 2014
october 6th 2014
like every other year since 2002, our collegues from (aka clean air initiative) are organiznig the biennial (). this time, it will take place in sri lanka, from november 19th to 21st 2014, and will be co-hosted together with the environmentally sustainable transport (est) forum.
the "integrated conference of baq 2014 and intergovernmental 8th regional est forum in asia" co-organized by the , , , , and , in partnership with the , , and .this year theme is "next generation solutions for clean air and sustainable transport − towards a livable society in asia":
recognizing that clean air and sustainable transport are essential to a livable society in asia, we call for innovative and smart solutions (policy, institution, technology and financing) that significantly reduce air pollution and greenhouse gases from energy, industry, transport, and area sources, and ensure a safe, equitable, environment and people-friendly transport system by accelerating the shift towards more environmentally sustainable transport (est) in asian cities and countries.check out the . more than 800 participants are expected to join the baq 2014, and we will be part of them, presenting our recent research on we have been conducting within our .
september 6th 2014
august 1st 2014
它声称能够同时测量挥发性有机化合物（，即臭氧），和pm2.5颗粒物。 但是他的真实效果如何呢？ 要知道答案，请查看我们的最新正在进行的实验有关海尔的airbox连接: 。
july 21st 2014
october 21st 2013
注意到在空气严重污染的情况下，dylos 与bam 之间的相关图表读数在浓度超过38000以上的差距越来越大后，所以我们决定检查dylos计数器内部的工作情况. 这种饱和现象是由于内部空气不能正常流通引起的严重结果,而空气不能正常流通是由于空气管道饱和后引起的。在空气严重污染的期间， 由于大量颗粒物通过空气管道形成的这种现象是完全正常的。
- 北京的灰尘 可以影响 dylos空气颗粒物 计数器 内部工作 -
- 真实的北京灰尘，北京的人们在空气严重污染时所呼吸的。 -
清洁维护已经过去10天了。从箭头2指示的部分，可以看出清洁前与清洁后dylos 的读数数据与bam的数据已经十分接近了。 尽管清洁维护确实起到了效果，但是在空气污染极其严重的情况下，这种差距还是会存在的（可以比较1与3 部分）。 我们会与dylos公司联系，咨询他们对此种情况的解释与看法。
september 9th 2013
因为一些历史原因，世界空气质量指数项目的网站上一些城市的空气质量指数换算公式没有使用2012 epa 更新的pm2.5 标准 。 仅涉及到亚洲，例如日本，台湾。其他大洲（包括美洲，欧州及大洋洲）则一直使用2012 标准。
与（1999年发布的）前一版相比，2012年12月14日发布的新版epa标准的主要变化是吧pm2.5空气质量指数的每个等级的15µg/m 3 降到了12µg/m3。
2013年9月9日以后，所有的 国家都使用更新后的pm2.5 空气质量换算数值范围，如表格所示：
september 8th 2013
bam仪器的唯一的主要问题就是它的价格。它的价格预计在12万人民币左右（1万5千欧元）。在中国，目前官方监测站大约有500个bam仪器（平均每个城市 大约有10个监测站）。但是这些还不够，由于还有许多城市不能提供pm2.5读数。在泰国，有21个自动（提供每小时读数的）监测站， 但是却没有一个可以提供pm2.5数据的监测站。在越南，全国只有3个监测站。
因此，在等待全世界各国政府过买更多最新的beta 衰减检测器的时候，有没有别的事情可以做呢？答案是有的！事实上，有一种相对可负担得起的仪器可以用来检测空气质量中的pm10 和 pm2.5的数值。其中最有名的是dylos空气微粒计数器(dylos air particule counter)：
如果你想了解更多有关dylos空气微粒计数器的工作原理，请参考 在逆向工程方面杰出的研究，或者直接访问dylos的网站(). 您也可以参考resarch纸 “”来了解测量理论。
为了证明dylos仪器同样可以用来作为检测空气质量的仪器，我们在我们的实验室里用dylos dc 1100 pro, 带pc接口设置了一个实验。这个专业版的仪器可以在亚马逊上买到，价格是319美元 （1888人民币）。虽然相比之下dylos dc 1100 较便宜些，但是需要注意的是必须要购买专业版的仪器 （pro, 带pc接口），因为它提供一个电脑接口，可以强制自动提取数据。
如果你想在中国购买dylos dc 1100 pro, 带pc接口仪器，请确定你购买的正确的专业版仪器。目前，在京东上海没有找到出售专 业版仪器的卖家，在淘宝上只有几个卖家。如果你真的想尽快买到我们推荐的dylos dc 1100 pro, 带pc接口 专业版仪器，但是又不想等待到货时间，可以购买价格更贵的，但是dylos dc1700仅是做了一些简单的升级，并不会改变我们检测出的空气质量检测结果。
为了把自动提取的数据传输到服务器，还需要： （278人民币） 和一个（20人民币）， 清单总计：2188人民币左右。
| dylos dc1100 pro|
with pc interface
|serial to usb cable||raspberry pi|
the documentation and scripts for connecting the dylos particules counter to the raspberry pi, and automatically uploading the dylos data to the world air quality project server are available freely from github: . if you have any questions, you can contact us with the subject "dylos experiment".
also, please note that when you setup your dylos particule counter outside, you need to be carefull where you locate it. ideally, it should be in a place which is not too windy, as the wind can have a significant impact on the readings (the reason is that the dylos counter is using a simple fan to get the air inflow, and the volume of air inflow per minute needs to be constant in order to have accurate readings ~ this simple fan is one of the reason why this kind of material is so affordable compared to the professional metone bam sensors).
june 25th 2013
with the recent affecting singapore and now , we got many questions about why there is a difference between the data which can be read from singapore nea website () and the world air quality index project .
for instance, here is what can be read today in nea website:
may 20th 2013
shenyang city aqi data is now based on the maximum of the , and . for more infomation, please refer to the article about
february 7th 2013
|51-100||good||moderate||好||良||良||초록||неподходящее для особо восприимчивых|
|101-150||lightly polluted||unhealthy for sensitive groups||微污染||轻度污染||軽微汚染||노랑||плохое|
|201-300||heavily polluted||very unhealthy||中度污染， 重污染||中度污染||中度汚染||빨강||очень нездоровое|
february 3rd 2013
实际上，这是一个非常好的问题！在北京，如果你不得不戴口罩，那么最好确保口罩真的可以过滤那些有害物质。 由于我没有答案来回答他的问题，我给新加坡totobobo口罩制造公司的francis chu 发了一封邮件，他马上给出了回答：
是的，我们的口罩能够降低99.85%的0.1微米的微粒。对于不熟悉微粒大小的读者来说，pm10 指的是小于10微米的颗粒物质，对于pm2.5来说，它指的是小于2.5微米的颗粒物质。 因此，过滤掉所有小于0.1微米的物质，意味着它可以过滤掉小于pm2.5 25倍的有害物质！所以，klaus，不用担心，最新的技术肯定是有效的！
有关颗粒大小的详细信息，可以参考维基百科网页。 如想获知更多空气过滤器如何实际测验的，或者如何比较各种口罩品牌，可以查看totobobo信息丰富的 。
february 2nd 2013
本周我们从severine p收到了一个很好的相关问题。 他问了有关pm2.5与pm10相抵触的问题。 sp在邮件里问道：
我不明白为什么pm2.5 的浓度 经常比pm10 的高。sp的问题是完全正确的：pm2.5 用定义来解释，就是比2.5微米小的颗粒，所以它们确实应该被包括在比10微米小的颗粒里面。
为了双重确定我们的理解是对的，我们联系了在世界上享有声誉的空气质量专家，来自 的 博士，她回复到：
你说的这些是对的。差别是由于对于pm2.5和pm10的不同拐点 (break points)， 流行病学的数据与pm2.5及pm10浓度的不同幅度 是如何关联的。 (how the data is correlated to each of the fractions)
所以，下一个问题是关于pm10的关联（中肯），尤其是在中国，大多数时候（尤其是被确认过的）都是完全正确的，这空气质量指数中pm2.5是具有显著优势的价值，因此，我们依然需要pm10的检测吗？它还是中肯的吗？ 此外，当遇到从他出得到了pm10的空气质量指数比pm2.5的高的情况时呢？有关这个问题，我们再次咨询了 博士，他回复到：
现在有新的研究可以提供证据，即pm2.5比pm10更为有害。 从身体角度来说，这可以说明，更小的颗粒更有可能进入肺的深处来伤害我们。这也是世界卫生组织（who）推动所有的国家拥有pm2.5标准的一个重要原因之一。非常感谢sarath guttikunda博士既迅速又专业的解答。
january 19th 2013
上海空气质量指数目前以 、 和 三个监测站的最大值为基础。
第一个监测站主要由 维护， 后两个监测站的数据由 提供，都是政府管理的监测中心。
january 11th 2013
for more information, please refer to the shanghai aqi update explanations. the following graphics show the relative pm2.5 aqi data for beijing stations on which the overall beijing aqi is based.
january 11th 2013
for more information, please refer to the shanghai aqi update explanations. the following graphics show the relative pm2.5 aqi data for chengdu stations on which the overall chengu aqi is based.