| Emission | Description | Sources | Harmful Effects |
| Carbon monoxide (CO) | Incomplete conversion of fuels containing carbon releases carbon dioxide (CO), a colorless, odorless toxic gas that can also be produced industrially and used to create both organic and inorganic chemical products. | Human-caused sources Burning of wood for cooking fuel and heat, burning of fossil fuels for transportation or power generation, and agricultural burning. Organic resources Methane and non-methane hydrocarbon oxidation, emissions from plants and the ocean, and forest fires. | Impacts on health Carbon monoxide poisoning symptoms include headache, weakness, nausea, dizziness, and fainting. Severe cases may also include coma and respiratory failure that results in death. |
| Nitrogen oxides (NOX) | Nitric oxide (NO) and nitrogen dioxide (NO2) are combined to form the term NOX. While NO is a colorless, tasteless gas, NO2 is a potent oxidant that is yellowish-orange to reddish-brown in color and has an overpowering rotten egg smell. | Human-caused sources Fossil fuel combustion in power generating units and automobiles, mostly on roads. Organic resources Lighting, wildfires, and soil microbial activity. | Impacts on health • Reasons for Irritation of the eyes and lungs. • May increase the likelihood of developing or exacerbating respiratory conditions. Effects on the environment • Hastens the eutrophication process. • Increases the acidity of freshwater ecosystems and soils. • Causes haze to form in the air, which reduces visibility. |
| Ozone (O3) | It is a colorless, unstable, toxic gas with strong oxidizing abilities that is produced when NOx and VOCs combine in the presence of sunlight. | VOC and NOx are secondary pollutants. | Impacts on health cause cardiovascular and respiratory issues. Environmental effects Particularly vulnerable vegetation and ecosystems that are affected include forests, parks, wildlife refuges, and wilderness areas. |
| Sulphur dioxide (SO2) | SO2 is a colorless, non-flammable gas with a strong, disagreeable smell. | Human-caused sources Fossil fuels are burned to generate electricity and power industries, ships, and rail cars. Organic resources Fires, phytoplankton, and volcanoes. | Impact on health Irritates the throat, nose, and eyes while having an impact on the respiratory system. Effects on the environment • Reduces the rate of plant growth. • Hastens the withering and early demise of plants. • Damages and stains stone and other materials, including statues. • May cause haze to form in the air, which may reduce visibility. |
| Particulate matter (PM10, PM2.5) | A mixture of solid and liquid droplets that are visible to the unaided eye in the atmosphere is referred to as particulate matter (PM). PM can take many forms, such as smoke, soot, dust, and dirt. Pollutants classified as primary or secondary can be PM. PM10 is the term for particles that are too small to breathe in. PM2.5 is the term for fine inhalable particles with a diameter of less than 2.5 µm. | Human-caused sources Emissions from fugitive dust during construction, power plants, automobile engines, domestic heating and cooking, and mining and quarrying. Natural resources. Natural material erosion, soil suspension by wind, and sea spray composition. | Impacts on health Cardiovascular and respiratory issues (primarily linked to PM2.5). Effects on the environment. • Particles containing sulfur and nitrogen have the potential to cause soil and water to become acidic. • Excessive dust deposition on vegetation can hinder growth and have an adverse effect on plant health. |