What is Smog?

Smog is a serious problem in most big urban areas. The emissions from vehicles and industries as well as the combustion of wood and coal together with the buildup of certain weather conditions are the main causal agents of smog. The terminology refers to a mixture of liquid and solid fog and smoke particles. It is usually seen as yellowish or blackish fog which suspends in the atmosphere or forms a ceiling in the air. It happens when fume, emissions, and particulates (nitrogen and sulfur oxides and volatile organic compounds) react in the presence of sunlight to form ground-level ozone.

The gaseous emissions are the main elements that form smog when acted upon by the sun’s ultraviolet light together with particulate matter and volatile organic compounds. Dense urban areas suffer more from smog because of huge numbers of traffic, industries and combustion of different types of fuel. Smog has serious negative effects on people, plants, and animals. Below are few causes, effects and solutions to smog pollution.


Wikipedia defines smog as,

Smog is a type of air pollutant. The word “smog” was coined in the early 20th century as a portmanteau of the words smoke and fog to refer to smoky fog, its opacity, and odour. This kind of visible air pollution is composed of nitrogen oxides, sulfur oxides, ozone, smoke or particulates among others (less visible pollutants include carbon monoxide, CFCs and radioactive sources). Human-made smog is derived from coal emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.

Main Causes of Smog

Smog-forming pollutants from numerous sources such as factories, consumer products or vehicles are the typical causative factors of smog. In most urban areas, more than 50% of smog is formed in consequence of vehicular emissions. Mostly, the occurrences of smog are associated with the relationship between weather patterns and heavy motor vehicle traffic, industrial and other consumer product emissions. Consumer products include solvents, paints, plastic packaging and sprays.

Smog is of two types: photochemical smog – commonly formed in urban areas and originates from elevated levels of hydrocarbon vapors and nitrogen oxides in the presence of sunlight, and sulfur smog – formed when there is an increased level of sulfur oxides in the atmosphere. Below are the main causes of smog.

  1. Using coal as a fuel

Use of coal as fuel in heating or in power-producing plants discharges high concentrations of sulfur oxides in the atmosphere. The effects are worsened by high levels of suspended particulate matter in the air and dampness. Burning coal also generates significant amounts of smoke which lead to smoggy environments. For instance, coal induced smog has been widely experienced in London up to the middle ages of the 20th century. In China, Harbin, coal-induced smog contributed to the closure of roads, schools, and airport in the autumn of 2013.

  1. Vehicular and industrial emissions

Emissions from the transportation sector resulting from fossil fuel combustion in cars, trucks, buses, motorbikes, and boats are the chief contributors of smog formation. Industries equally emit scores of gaseous emissions and fumes which leads to smog formation. Most of the smog formed in large cities are as a result of traffic emissions.

The primary precursors are oxides of nitrogen, volatile organic compounds, carbon monoxide, fumes, sulfur oxides and hydrocarbons. These substances react with moisture, heat, sunlight, and ammonia among other compounds to form the toxic vapors, particulates, and ground level ozone that make up smog.

  1. Natural causes

Smog can as well occur due to natural causes like volcanic eruption and some specific plant life effects. Volcanic eruption discharges high concentrations of sulfur dioxide and particulate matter in the air, the two primary constituents for smog formation. Radiocarbon amounts of some specific plant life are believed to cause smog in some locations. For instance, the Los Angeles creosote bush is linked to smog occurrences in the area.

Terrible Effects of Smog

  1. Effects on human health

Smog is composed of a mixture of air pollutants which can endanger human health. Various human health problems such as emphysema, asthma, chronic bronchitis, lung infections, and cancers are caused or exacerbated by the effects of smog. The effects include:

  • Coughing and irritation of the eyes, chest, nose and throat: High ozone levels can irritate the respiratory system leading to coughing and wheezing. These effects generally last for only a few days after exposure, but the particles in the smog can continue to damage the lungs even after the irritations disappear.
  • Aggravation of asthma: Asthma conditions are severely worsened by smog and can trigger asthma attacks.
  • Breathing difficulties and lung damage: Bronchitis, pneumonia and emphysema are some of the lung conditions linked to the effects of smog as it damages the lining of the lungs. Smog also makes it difficult for people to breathe properly.
  • Premature deaths because of respiratory and cancer diseases: A 2013 WHO report indicated that cumulative exposure to smog heightens the chances of premature death from cancers and respiratory diseases. Thousands of premature deaths in the United States, Europe, and Asian countries are linked to inhalation of smog particles. Such chemical particles include benzene, formaldehyde, and butadiene which are all comprised of cancer-causing carcinogens.
  • Birth defects and low birth weights: Smog is highly linked to birth defects and low birth weight. Pregnant women who have been exposed to smog have had babies with birth defects. Spina bifida – a condition depicting malformations of the spinal column, and anencephaly – underdevelopment or absence or only part of the brain are birth defects associated with smog exposure. Furthermore, studies suggest that even as low as 5 μg exposure to smog particulate matter can result in risks of very low birth weights at delivery.
  • The risk of developing rickets: Heavy smog that lasts for prolonged periods blocks UV rays from reaching the earth surface. This results in low production of Vitamin D leading to rickets due to impaired metabolism of calcium and phosphorus in the bone marrow.
  • Risks of road accidents or even plane crash: Smog interferes with natural visibility and irritates the eyes. On this basis, it may prevent the driver or flight controller from reading important signs or signals thereby increasing the probability of road accidents or even plane crash.
  1. Implications for plants and animals

Smog inhibits the growth of plants and can lead to extensive damage to crops, trees, and vegetation. When crops and vegetables such as wheat, soybeans, tomatoes, peanuts, cotton and kales are exposed to smog, it interferes with their ability to fight infections thus increasing susceptibility to diseases.

The smog’s impact of altering the natural environment makes it difficult for animals to adapt or survive in such toxic conditions, which can kill countless animal species or make them susceptible to illness. Photochemical smog caused when nitrogen oxides react in the presence of sunlight, is established to destroy plant life and irritate sensitive tissues of both plants and animals.


Remarkable Solutions to Smog Pollution

  1. Purchase renewable energy

By purchasing renewable energy, it helps in the reduction of emissions from power generating plants that heavily depend on fossil fuel. In other words, the use of renewable energy not only reduces environmental impacts but also trims down the presence of smog causing pollutants in the air.

  1. Reducing and managing vehicular and industrial emissions

Vehicles and industries constitute the largest contributors of smog forming pollutants. The best way to reduce smog is to therefore to take the lead in managing gaseous emissions from cars and industries. For industries, the use of renewable energy sources and the manufacturing of environmentally friendly consumer products are fundamental. For cars; aspects such as combining errands in one trip, use of public transport, proper maintenance of the car and walking or biking instead of driving can significantly reduce smog pollution.

  1. Increasing energy efficiency and conserving energy

Increasing energy efficiency and at the same time conserving energy leads to reduced gaseous emissions into the atmosphere that often result in the formation of smog. A capable and productive energy management system can go a long way in reducing smog causing pollutants in the air such as nitrogen and sulfur oxides.

  1. Use of environmentally friendly consumer products

The use of household products that have high levels of volatile organic compounds should be completely avoided. These products not only release hazardous materials into the atmosphere but also emit particulate matter that reacts in the presence of sunlight to form ground-level ozone. The use of environmentally friendly consumer products such as eco-friendly paints, paper, sprays, solvents and plastics therefore provides a basis for addressing smog pollution.

  1. Smog detection and monitoring systems

As much as smog is easily visible when it’s present in the atmosphere, the use of appropriate smog detectors and monitoring systems can act as early warning systems. Respective metrological departments can help with this by installing monitoring equipment that consistently records the amount of emission and particulate matter in the air.

Such a strategy is the Air Quality Index (AQI) or the Clean Air Act which is used for reporting and monitoring the relative concentrations of common air pollutants and ground-level ozone. Nonetheless, this measure only monitors the levels of the smog causing pollutants in the air and subsequently helps in putting in place strategies that can cut back emissions and air pollution. Preventive measures are the best in the very first place.

Image credit: Inkelv , Espino


Rinkesh is passionate about clean and green energy. He is running this site since 2009 and writes on various environmental and renewable energy related topics. He lives a green lifestyle and is often looking for ways to improve the environment around him.