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Air pollution is one of the most significant threats to human health in the modern world. It is estimated that smog kills 5.5 million people every year, making it a leading cause of death. In places like Beijing China, it is estimated that simply living there is equivalent to smoking two packs of cigarettes per day. And, it is not just a problem for countries like China and India. In fact, London reached its entire year’s quota for air pollution within the first 5 days of 2017, and Seoul is now routinely choked in smog.
One of the most interesting ways to combat smog is to monitor air quality yourself. In this article, I will show you that for less than $35, you can build a NodeMCU-based air quality monitor device (see The assembled prototype device with power source.). Since the device has its own power source (the portable battery), it can be placed anywhere there is Wi-Fi signal. I typically place it in a room to monitor indoor air, or next to an open window to monitor outdoor air. It is not only a science project, but also a potential game changer for health-care (including public health research), as we can now track an individual’s accurate exposure to smog and study how it correlates with health problems.
High concentrations of dust or PM is a serious health concern. pm 2.5 is less than 2.5 microns in diameter, and pm 10.0 is less than 10 microns in diameter. This means, a pm 10.0 report includes pm 2.5 as well. Both these particles are much smaller than a human hair, which is about 70 microns in width.
Particulate matter can come from both human and natural sources. Natural sources include sea salt, forest fires, pollen and mold. As they are natural occurrences they are harder to control and are usually left unregulated. Human sources, however, can be regulated and understanding where PM comes from is very important. PM 10.0 is most commonly associated with road dust and construction activities. Wear and tear of brakes and tires on vehicles and crushing activities at construction sites can all contribute to a rise in PM 10.0. Alternatively, PM 2.5 is more associated with fuel burning, industrial combustion processes and vehicle emissions.
The growing awareness of both PM 10.0 and PM 2.5 is largely associated with the potential damaging effects they can have on the human body. The World Health Organisation (WHO) believes particles are affecting more people worldwide than any other pollutant. Primary health effects include damage to the respiratory and cardiovascular systems. Due to the small size of PM 10.0 and PM 2.5 particles, they can penetrate the deepest parts of the lungs as well as access the gas exchange regions of the lung via diffusion.
As a result of the damaging health effects from PM 10.0 and PM 2.5 the WHO recommend the following exposure limits:
| PM | Exposure limits |
|---|---|
| PM 2.5 | 10 ㎍ / ㎥ Annual Mean |
| 25 ㎍ / ㎥ 24 hour Mean | |
| PM 10.0 | 20 ㎍ / ㎥ Annual Mean |
| 50 ㎍ / ㎥ 24 hour Mean |
These guidelines can be hard to follow and many authorities do not meet the limits above, for example, the United States and Europe have much higher PM 10.0 exposure thresholds. Governments must weigh up the potential damage to population health with the cost of reducing particulate concentrations. A great first step to understanding the seriousness of the issue is to monitor PM.
It is worth also mentioning larger particles (above 10µm). These sized particles are not usually acknowledged in government health legislation as they can be filtered out in the nose and throat. Instead, they are known as a nuisance rather than a health risk. Total Suspended Particles (TSP) is the term used when referring to larger particles. TSP does not have a specified size limit and therefore covers the full range of particle sizes. It is common for TSP to be measured alongside PM 10.0 and PM 2.5, particularly at industrial sites where nuisance dust assessment and monitoring is becoming more frequent.
Operations such as stone crushing, coal grinding, rotary kilning in cement industry and dust on road stirred by moving vehicles can increase pm 10.0 levels. pm 10.0 limit for 24-hour average is 150 ㎍ / ㎥.
This is a result of fine particles produced from all types of combustion, including motor vehicles, thermal power plants, residential wood burning, forest fires, agricultural burning and other industrial processes. pm 2.5 limit for 24-hour average is 35 ㎍ / ㎥.