Atmospheric pollutants cause health and environmental harm
Chemistry of the atmosphere • Atmospheric pollutants
Flashcards
Test your knowledge with interactive flashcards
Key concepts
What you'll likely be quizzed about
Definition of pollutant
A pollutant is a substance present in the atmosphere at higher concentrations than normal that causes harm to organisms, ecosystems or materials. Pollutants include gases, aerosols and particulate matter that alter normal chemical or physical processes in the air and on surfaces. Limiting factors for pollutant impact include concentration, persistence, reactivity, exposure time and local conditions such as temperature and wind. Low concentrations may cause no noticeable effect, while higher concentrations increase risk and severity of harm.
Carbon monoxide (CO) - cause and effect
Carbon monoxide forms by incomplete combustion of carbon-containing fuels. CO binds strongly to haemoglobin in blood and displaces oxygen, reducing oxygen transport to tissues. Effects include dizziness, impaired cognitive function and, at high exposure, death from asphyxiation. Limiting factors include CO concentration, duration of exposure, ventilation and individual health. Chronic low-level exposure worsens cardiovascular conditions and increases vulnerability in children and older adults.
Particulates - cause and effect
Particulate matter consists of fine solid or liquid particles suspended in the air, produced by combustion, industrial processes and erosion. Fine particulates (PM2.5 and smaller) penetrate deep into the lungs and enter the bloodstream, causing respiratory and cardiovascular disease. Particulates also reduce visibility and contribute to global dimming by scattering sunlight. Particle size, chemical composition and exposure time determine severity. Smaller particles cause greater health effects and longer atmospheric lifetimes increase transport and regional impact.
Sulfur dioxide (SO2) and nitrogen oxides (NOx) - acid rain and respiratory effects
Sulfur dioxide and nitrogen oxides form from burning fossil fuels and high-temperature combustion in engines. Both gases react with water in the atmosphere to form dilute acids (sulfuric and nitric acids). Acid rain causes soil acidification, damage to plant tissues, leaching of nutrients and corrosion of buildings and monuments. SO2 and NOx also irritate the respiratory system and increase vulnerability to infections and asthma. Local emission rates, atmospheric chemistry, rainfall patterns and buffering capacity of soils and water bodies limit the extent and distribution of acidification.
Ground-level ozone and photochemical smog
Nitrogen oxides and volatile organic compounds (VOCs) react under sunlight to form ground-level ozone, a major component of photochemical smog. Ground-level ozone irritates eyes and airways, reduces lung function and damages plant tissues, lowering crop yields. Ozone formation depends on sunlight intensity, temperature and precursor concentrations. Urban areas with high traffic and stagnant air show the greatest ozone pollution and associated health problems.
Greenhouse gases and climate change
Greenhouse gases such as carbon dioxide and methane absorb outgoing infrared radiation and trap heat in the atmosphere. Increased concentrations of these gases enhance the greenhouse effect and cause global temperature rise. Climate change produces sea-level rise, altered weather patterns, and stresses ecosystems and agriculture. The magnitude of climate impact depends on greenhouse gas concentration, atmospheric lifetime of the gas and feedback mechanisms such as ice melt and changes in vegetation.
Materials damage and economic impacts
Acid deposition and pollutants such as ozone and particulates cause physical and chemical deterioration of buildings, statues and infrastructure through corrosion and chemical attack. Corrosion increases maintenance costs and shortens service life of materials. Economic impacts follow from reduced crop yields, increased health care costs, loss of tourism and higher repair expenses. The distribution of economic harm depends on pollutant sources, affected infrastructure and local economic resilience.
Limiting factors and local variability
Pollutant effects depend on concentration, exposure duration, chemical form, particle size and meteorological conditions. Geography, temperature inversions, wind patterns and urban layout influence local pollutant buildup and dispersion. Natural sinks and chemical reactions may reduce pollutant concentration over time. Risk assessment requires consideration of population density, vulnerable groups, and ecological sensitivity. Emission control and dispersion management alter exposure and therefore change the scale of harmful effects.
Key notes
Important points to keep in mind