stikstofdioxide

Stikstofdioxide, chemically known as nitrogen dioxide (NO₂), is a reddish‑brown gas that is a key component of air pollution. It is produced naturally by lightning, volcanic eruptions, and microbial activity in soils, but the dominant source in the modern world is combustion of fossil fuels in transportation, power generation, and industrial processes. NO₂ is also formed in the atmosphere through the reaction of nitrogen oxides (NO and NO₂) with hydroxyl radicals.

The gas is highly reactive; it dissolves in water to form nitrous and nitric acids, contributing to acid rain. In the atmosphere, nitrogen dioxide participates in a series of photochemical reactions that produce ozone in the lower troposphere, forming the non‑ozone layer of the atmosphere. It is a precursor to the formation of particulate matter and contributes to the smog that impairs human health.

Human exposure to high concentrations of NO₂ can irritate the respiratory tract, causing coughing, throat pain, and shortness of breath. Long‑term exposure is associated with reduced lung function and exacerbation of asthma. The United States Environmental Protection Agency classifies NO₂ as an air toxics substance; it is regulated under the Clean Air Act with National Ambient Air Quality Standards that limit its concentration in ambient air.

Measurement of nitrogen dioxide is typically conducted by remote sensing, chemiluminescence sensors, or electrochemical detectors. Monitoring of NO₂ levels is integrated into air quality assessment networks worldwide. Efforts to reduce NO₂ emissions focus on emissions controls for vehicles, such as catalytic converters, transitioning to cleaner fuels, and adopting renewable energy sources.