What is smog and why is it a problem?
The term “SMOG” was first used in the early 1900s to describe a mixture of smoke and fog, although the phenomenon is distinct from actual meteorological fog. It originally referred to what we now often categorize as winter smog, which results from the industrial and domestic combustion of coal and other low-grade biomass in cold conditions. Summer smog—or, more accurately, photochemical smog—refers to a visible haze that occurs when sunlight reacts with pollutants in the atmosphere, particularly those associated with dense urban centers and major roadways.
Both winter smog and photochemical smog are intensified by weather phenomena known as atmospheric inversions. Air temperature normally decreases as altitude increases, but during an inversion cool air at ground level is overlain by a layer of warm air. This effectively traps pollutants in and around the cities in which they are produced by preventing dissipation to the surrounding atmosphere. This accumulation of pollutants is worsened in cities that are situated within or against mountains—e.g., Mexico City, Los Angeles, Tehran, and Beijing—as the topography forms a basin from which smog cannot disperse.
Regardless of the type or location, smog is a particularly hazardous form of air pollution that is strongly associated with negative human health impacts. In addition to interfering with normal breathing, the pollutants that comprise smog are known risk factors for respiratory conditions like asthma and lung cancer as well as cardiovascular problems like heart attacks and strokes. It is therefore advisable to limit exposure to smog whenever possible; this requires accurate measurement of the air pollutants from which it is comprised and a thorough understanding of their origin and behavior.
Main causes of smog
1. Combustion of Coal
Coal was commonly used in England during the Industrial Revolution for domestic heating during cold winter months. The coal used was generally of a lower grade—referred to as “soft” coal—which produces noxious smoke due to a relatively high percentage of impurities. Atmospheric inversions are common during winter, which prevented the dissipation of this coal smoke and resulted in the infamous “pea soup fog” of London. The enaction of clean air legislation in the 1950s effectively put a stop to this recurring problem, but winter smog continues to occur in many parts of the world. In 2013, Northeast China suffered a severe bout of smog when the startup of the region’s coal-fired municipal heating system coincided with unusually windless conditions. Visibility was dramatically reduced, leading to the closure of roads, schools, and airports.
The major pollutant of concern from coal combustion is particulate matter (PM). Coal smoke is comprised of fine particles that are easily inhaled, with the smallest of these capable of reaching the alveoli and entering the bloodstream. Some of this PM is in the form unburned or partially burned coal particles, commonly called soot, which contains many polycyclic aromatic hydrocarbons that are known to be carcinogenic; the remainder is comprised of ash particles that contain significant amounts of toxic heavy metals such as lead and mercury. The other major pollutant that is characteristic of coal combustion is sulfur dioxide, a pungent gas that irritates the lungs and exacerbates existing respiratory conditions. Other gaseous components from coal combustion include nitrogen oxides (NOX), carbon monoxide (CO), and volatile organic compounds (VOC).
2. Vehicular and Industrial Emissions
Most of the smog seen around the world nowadays is photochemical smog. This arises due to the complex interaction of NOX with VOCs and/or CO and sunlight—specifically UV radiation—which generates ground level ozone (O3). NOX is produced by stationary combustion (i.e., thermal power plants) and various industries, but originates primarily from diesel engines. Gasoline engines are the major anthropogenic source of CO, while VOCs may come from many sources such as fuel and chemical storage, incomplete fuel combustion, and industrial processes. All of these sources tend to be concentrated in large cities; it is therefore no coincidence that photochemical smog is mostly an urban problem.
Formation of ground level O3 is at its greatest in hot summer months because of the increased solar energy. In low-wind conditions, or during an atmospheric inversion, O3concentrations can reach levels that are potentially deadly to asthmatics and other sensitive individuals. The visible haze above cities during these summer smog events is not due to O3, however, but rather a combination of accumulated nitrogen dioxide (which imparts a brownish color) and PM formed from a mixture of mineral dust, organic matter, and oxidation of gaseous precursors, e.g., sulfuric acid droplets and particles of ammonium salts. All these pollutants taken together make a potentially lethal mixture that has become an increasingly common problem worldwide.
3. Overpopulation & Excessive Consumption
The steady growth of the global population necessitates a proportional increase in energy and resource consumption, and this has had the unfortunate side effect of increased air emissions. Industries alone are not to blame for urban smog; behavioral problems such as over-consumption and over-reliance on personal vehicles for transportation are largely responsible. The products which have become easier than ever to purchase cheaply online must be produced in industrial processes and transported to our doors by fuel burning delivery vehicles; every step in the process emits pollutants to the atmosphere which contribute to the formation of smog. This behavioral shift was exacerbated by the global COVID-19 pandemic and shows no signs of slowing down unless ordinary individual citizens are made aware of the consequences of these modern conveniences.
How AirSENCE can help
Reckless industrialization and the demands of modernization have been the key causes of urban smog, and this has taken an enormous toll on humanity over the past century. Nevertheless, the Information Age has fostered a growing public awareness with regards to air quality and its impacts on human quality of life. Numerous laws and guidelines aimed at controlling harmful emissions and protecting public safety have been enacted, but these require constant vigilance and prohibitively expensive equipment. These economical and operational challenges are compounded by the need to monitor smog-related pollutant snot only nearby to their sources (e.g., heavy industries, thermal power plants, etc.), but at several points within the potential radii of influence. AirSENCE was designed for this task: it is an Advanced, Accurate & Affordable continuous ambient air quality Micro-Monitoring Station (caaqMMS) which provides real-time, accurate, and reliable measurements of smog-related pollutants along with local weather data. Its low cost, ease of installation, and trouble-free maintenance make it perfectly suited for the ambient air quality monitoring needs of today, and an ideal complement to any Smart City solution.
There is a very appropriate saying: “Breath healthy, be healthy”. AirSENCE has been designed with the understanding that comprehensive and accurate air quality monitoring is the first and most crucial step to both controlling air pollution and staying informed of air quality conditions. AirSENCE allows users to determine whether it is safe to go outdoors or better to stay at home under given conditions.AUG Signals’ caaqMMS provides concentrations for gaseous pollutants including NO, NO2, CO, O3, SO2, VOC, H2S, and CO2, in addition to all particulate matter fractions such as PM10, PM2.5, and PM1. Local weather and environmental data, including gas wind speed and direction, noise, rainfall, and light can also be measured. Talk to an AirSENCE monitoring expert to determine the optimal sensor package for up-to-the-minute surveillance of smog-related pollutants in your community—the health of you and those around you is intimately tied to the quality of the air you breath. Breath health, be healthy.
