Mobile monitoring can offer better data to help manage air pollution challenges: pictured, ultra-low radiation readings due to cosmic rays shielding inside the Salina Turda underground mine. Photo credit: Radu Motisan
Pollution kills, just as surely as wars, accidents, or terrorism. There are places where the air is so polluted that the sun never shines and people are wearing masks. There are also places where the sun still shines and people are not wearing masks, but that does not mean these places have clean air, since air pollution is not always visible. It usually is invisible, in fact, nor does it usually smell. The air of our urban landscapes has been compromised since the industrial revolution and although we have taken many technical and regulatory steps to reduce it, the problem remains unsolved.
These are some of the most pertinent air pollutants of our time and their effects:
- Volatile organic compounds (or VOCs) — a class of substances that evaporate at room temperature. Being a collection of different substances, they may be responsible for a broad category of disorders, including respiratory problems, allergies or weakening immunity in children. Some VOCs are responsible for the formation of smog, irritation of eyes, nose and throat, headaches and concentration problems. In extreme circumstances, more severe complications can occur, such as damage to liver, kidney and central nervous system or cancer. 
- Ionizing radiation — it can cause damage to cells that can result in multiple disorders, the most common of which is cancer. Ionizing radiation is naturally occurring from cosmic and terrestrial sources, but there are also artificial generators related to nuclear activities or X-ray devices. The worldwide global average dose is 3.01 mSv/y. 
- Particulate matter PM2.5 — small particles with a diameter of up to 2.5 microns. These particles can penetrate deep into the lungs, causing allergies, respiratory and cardiovascular diseases. 
- Formaldehyde — a toxic colorless gas with a pungent smell, which results from the burning of carbon-based materials. It can be found in forest fires, in automobile exhaust and cigarette smoke. It is an allergenic and a known carcinogenic compound that can cause serious health effects, depending on concentration and exposure. Even in tiny quantities just above 0.1 ppm it can irritate the eyes and nose, and can worsen asthma symptoms. 
- Carbon dioxide —heavier than air, in concentrations of up to 5,000 ppm it can cause headaches, lethargy, slowing of intellectual ability, irritability, and sleep disturbance. In larger quantities it can cause dizziness, loss of sight, hearing or memory. CO2 concentration in urban areas averages between 400 ppm and 700 ppm. [5, 6]
The biggest challenge to dealing with these agents is that one cannot manage what one cannot measure. The public, the legislators, and all social actors need more air pollution data, over space but also over time. This can be achieved by mobile air pollution monitoring. Mobile air pollution monitoring consists of devices that measure air pollutants on-line and in real-time, continuously measuring pollutant concentrations with time resolution on the order of minutes or even seconds.
With the cost of sensors decreasing and devices becoming ever smaller, it is now becoming feasible for anyone who wishes to study air pollution to acquire a device and use it to detect all those things that do you harm when you go to work, or when you take your kids to school. This kind of mobile monitoring becomes even more informative and robust when the data from multiple devices is centrally collected and shared, such as in the global uRADMonitor Network .
Governments also have a role in protecting the public, and many governments already institute some form of air pollution monitoring, going as far as publishing Air Quality Index (AQI) values. But there is no guarantee that government will monitor air pollution in enough locations or at least in the most important locations. There is also no guarantee that AQI values will be published quickly enough for the public to take precautions on the days with worst air quality.
Take the example described by Sotirios Papathanasiou in his blog See The Air, about a situation in Almeria, Spain . He analyzed the location of two air pollution monitoring stations in the city. One station is located too far from the city center and too close to agricultural fields to be representative of the city’s background pollution levels, while the other is located in a city centre park, surrounded by trees. While these stations take measurements every 10 minutes, they only report the previous day’s data .
Local authorities have had good intentions in monitoring air pollution and reporting the data openly. But their job, and that of governments all over the world, could be much improved with mobile air pollution monitoring. Buses, for example, are synonymous with particulate pollution, with black smoke billowing out of their tailpipes as they pull away from a stop. Now imagine buses carrying mobile air pollution monitors on their rooftops . They travel long distances within cities each day and could collect air pollution data from multiple locations at different times of the day. This information would be of interest to the bus passengers, who are exposed to those pollutants along their journey, pedestrians who walk along the bus route, and even scholars and professionals who need air pollution data to calibrate and verify their dispersion models.
Rafael M. Santos is an assistant professor in the University of Guelph’s School of Engineering. Radu Motisan is founder of the uRADMonitor.
 Volatile Organic Compounds’ Impact on Indoor Air Quality, US Environmental Protection Agency.
 Radiation Health Effects, US Environmental Protection Agency.
 Health and Environmental Effects of Particulate Matter (PM), US Environmental Protection Agency.
 ToxFAQs™ for Formaldehyde, Agency for Toxic Substances and Disease Registry.
 Health Risk Evaluation for Carbon Dioxide, US Bureau of Land Management.
 H. Kim, I. Lee, E. Jeon, Assessment of urban area CO2 concentrations using the atmospheric dispersion model for micro areas, J. Env. Sci. Pollut. Res. 2016, 2 (1), 64–68.