Ozone (O3) is a molecule that consists of three oxygen atoms. It is formed when ultraviolet (UV) light radiation strikes oxygen (O2). The sun’s energy splits the O2 into single molecules, which then join together to form ozone. This creates smog and can damage human health by irritating eyes, noses, and throats.
Ozone does not have to travel far from its source before it starts to break up. By 24 hours after its formation, half of the ozone in the lower atmosphere will have decomposed due to chemical reactions with other compounds. Sunlight plays a key role in these chemical reactions to form ozone harming compounds.
Nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with sunlight to form ozone on hot summer days. Cars, power plants, and industrial facilities are all main sources of NOx and VOCs. However, human activity is not the only source as lightning can also initiate these reactions and some natural processes such as forest fires and grassland fires.
Nitrogen dioxide (NO2) is one of the main gases that contributes to ozone production in the lower atmosphere, damaging human health. Nitrous oxide (N2O) and Non-methane volatile organic compounds (NMVOCs) are significant contributors to ozone formation.
Table of Contents
What are Ozone Harming Compounds?
These harmful substances may appear as solids, liquids, or gases and include a wide range of compounds in various categories. They include:
- Volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylene are found in paints, cleaning supplies, and gasoline
- Nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2) emitted when fossil fuels are burned
- Perfluorocarbons (PFCs), synthetic compounds containing only carbon and fluorine that do not interact with sunlight or ozone but which still affect the atmosphere because they are very stable
- Sulfur dioxide (SO2) is released by power plants in the burning of fossil fuels containing sulfur.
- Chlorofluorocarbons (CFCs), manufactured organic compounds once used in various products, such as aerosol sprays and refrigeration equipment.
- Methyl chloride (CH3Cl) is released from the processing of fossil fuels and biological sources such as bacterial decomposition.
- Hydrogen chloride (HCl), which is found naturally in some volcanic gases but is mainly released as a byproduct of fossil fuel combustion and as a result of some industrial processes such as smelting aluminum
- Bromine organic compounds such as methyl bromide, which has been used extensively as a soil fumigant
The fact that ozone may be beneficial to life on Earth in one area but detrimental to life – even deadly – in other areas is the reason why it’s important to monitor and regulate ozone concentrations. The reduction of VOCs and NOX emissions and PFC emissions can help reduce tropospheric concentrations of ozone. Moreover, using alternative energy sources that do not emit these harmful substances into the atmosphere can also help reduce ozone concentrations. Although CFCs are no longer used on Earth, their long atmospheric lifetime means they still contribute to high ozone concentrations in the stratosphere.
Sources of nitrogen oxides and volatile organic compounds include:
Vehicle exhaust: One of the main sources of nitrogen oxides and volatile organic compounds is emission from vehicles like cars, trucks, and buses (NOx). However, even electric and hybrid vehicles produce some nitrous oxide through the vehicle’s catalytic converter. Catalytic converters increase gas mileage but break down NOx into nitric oxide (NO) and nitrogen dioxide (NO2).
Smoking: When people smoke cigarettes, the burning process emits chemicals like nitrogen oxides and NMVOCs. People who are around secondhand smoke also inhale additional toxic compounds like carbon monoxide (CO), formaldehyde (HCHO), acrolein, and polycyclic aromatic hydrocarbons (PAHs).
Industry: The burning of fossil fuels by power plants, steel mills, and incinerators can produce nitrogen oxides through combustion. Incomplete combustion in diesel engines produces the same harmful compounds, contributing to ozone production in the lower atmosphere.
Manufacturing: Some chemical processes such as those used to produce paper and foam and metalworking and petroleum refining also involve the burning of fossil fuels like coal and gasoline.
VOCs are a broad category that includes many different chemicals such as benzene, acetone, and ethanol and are widely used in many products like cleaning products. While most VOCs do not lead to ozone production, some VOCs like isoprene, which is emitted by trees and shrubs, are important precursors to ozone formation.
Farms: Fertilizers used on farms contain large amounts of nitrogen compounds (ammonia N) that can convert into nitric acid (HNO3). This can promote the production of NOx, the main source of ozone formation. Fertilizers also contain phosphate compounds that help plants absorb nitrogen from the soil and release this into the atmosphere as volatile organic compounds (VOCs) through decomposition.
Cigarette smoke: In addition to carbon monoxide (CO), smoking releases NOx and NMVOCs, which is a subset of VOCs?
Paints and household cleaners: Many household cleaning products contain volatile ingredients like solvents and detergents that contribute to ozone production when they evaporate into the atmosphere.
Toxicity: Some compounds like toluene and benzene (both VOCs) can be toxic to humans at high concentrations.
Natural processes: Forest fires and grassland fires can emit as much as 40 percent of their heat as infrared radiation breaks down into NOx, another ozone precursor. Lightning strikes result in the same chemical reactions and also contribute to ozone formation.
Cement manufacture: Cement kilns release VOCs and NOx due to the calcining process (heating calcium carbonate to drive off carbon dioxide). Other materials like Portland cement release small amounts of toxic compounds such as mercury.
Pesticides: Many pesticides contain methyl or ethyl parathion, which emit VOCs when their molecules break down in sunlight.
Ozone is a major chemical component of smog and causes significant harm to human health. It causes respiratory distress, triggers asthma attacks, and contributes to cardiac disease.
Vehicle exhaust: Nitrogen dioxide (NO2) and volatile organic compounds (VOCs), both ozone precursors, are released from vehicle engines through incomplete combustion. Cars, trucks, and busses account for nearly half of the VOC emissions in the U.S. but contribute less than 10 percent of NO2 emissions.
Industry: Power plants, steel mills, incinerators, and petroleum refineries all release nitrogen oxides (NOx) into the atmosphere in large quantities.
Chemical compounds used in manufacturing: Paper, foam, and rubber production often involve volatile organic compounds (VOCs). Chlorine gas is also a source of ozone formation.
Cement kilns: Cement kilns release VOCs and NOx, both ozone precursors, through calcination (heating calcium carbonate to drive off carbon dioxide).
Residential heating sources: Residential heaters burning coal, natural gas, or kerosene emit about one ton of NOx for every 100 tons of fuel burned.
Electric power plants: According to the Clean Air Task Force, electricity generation accounts for 48 percent of U.S. NOx emissions and 33 percent of its VOC emissions. Power plants are the largest source of NOx emissions in the U.S. but contribute less than 10 percent of VOC emissions. Coal-fired power plants emit the most NOx, followed by gas-fired plants, petroleum coke, and oil-burning plants, which all emit sizable amounts of NOx. Oil-fired plants contribute the most VOCs to the atmosphere.
Natural processes: Forest fires, grassland fires, and lightning strikes are all-natural sources of NOx.
Fertilizer use: Fertilizers used on farms contain large amounts of nitrogen compounds (ammonia N) that can convert into nitric acid (HNO3). This can promote the production of NOx, the main source of ozone formation. Fertilizers also contain phosphate compounds that help plants absorb nitrogen from the soil and release this into the atmosphere as VOCs through decomposition.
Bacteria during sewage treatment: Bacteria that break down organic matter in wastewater generate VOCs that react with other compounds to produce ozone.
Development: Houses, roads, and parking lots replace vegetation that absorbs the sun’s ultraviolet radiation and helps convert VOCs into less harmful forms.
Petroleum refineries: Petroleum refineries account for 24 percent of U.S. NOx emissions and 63 percent of U.S. VOC emissions from stationary sources, according to the Clean Air Task Force report “Smokestacks and Tailpipes: An Analysis of Air Pollution from Motor Vehicles.”
Gasoline combustion: Ethylbenzene and other VOCs are released during the petroleum refining process. Benzene evaporates directly into the atmosphere while VOCs combine with NOx in sunlight, forming ozone.
Wood burning: A major source of indoor air pollution, wood burning is a major source of human exposure to fine particles and is an ozone precursor.
House fires: House fires contribute to ozone formation by emitting VOCs, NOx, and other chemicals into the atmosphere.
FAQ’s
Q: What is ozone harming compounds?
A: Ozone is a chemical component of smog that causes significant harm to human health. Compounds such as nitrogen dioxide and volatile organic compounds, both ozone precursors, pollute the atmosphere and trigger asthma attacks and cardiac disease. Vehicle exhaust, industry, chemical compounds used in manufacturing, cement kilns, and residential heating sources emit nitrogen dioxide and volatile organic compounds, both ozone precursors.
Q: Why is ozone harmful to human health?
A: Ground-level ozone can irritate the eyes, nose, and throat and damage the lungs. Prolonged exposure causes wheezing, coughing, chest pain, and congestion. It can exacerbate asthma or cause wheezing in people with lung disease. Chronic exposure to ozone may permanently scar lungs and even kill lung tissue, leading to premature death.
Q: What are the sources of NOx?
A: Natural processes, fertilizer use, bacteria during sewage treatment, development, petroleum refineries, gasoline combustion, coal-fired power plants, natural gas-fired power plants, oil-fired power plants, and wood-burning are all sources of NOx.
Q: What are the sources of VOCs?
A: Natural processes, fertilizer use, bacteria during sewage treatment, development, petroleum refineries, gasoline combustion, coal-fired power plants, natural gas-fired power plants, oil-fired power plants, and wood-burning are all sources of VOCs.
Conclusion
The truth is that ozone harms everyone, but the effects are often more pronounced for those with respiratory or cardiovascular issues. It can cause coughing, wheezing, and other symptoms in people who already have asthma or heart disease. However, there are many ways to protect yourself from this harmful gas, including staying indoors on hot days when possible because you’ll be breathing less of it outdoors where it forms most readily. Live near a major city like New York City, Austin, TX, or Los Angeles, CA. Your risk may be even greater due to air pollution caused by cars and industrial emissions, which contribute significantly to ground-level ozone production. To avoid these risks altogether, follow our guide below! Follow this guide to know about Ozone harming compounds.
