Nitrogen dioxide (NO2) primarily pollutes the air by contributing to the formation of other harmful pollutants like particle pollution and ground-level ozone. It is recognized as one of six major air pollutants regulated by national air quality standards.
How NO2 Causes Air Pollution
NO2 is a key player in complex atmospheric chemistry. According to the reference, NO2 and other nitrogen oxides contribute to particle pollution and to the chemical reactions that make ozone. This makes it a significant environmental concern.
Let's break down these two main ways NO2 contributes to air pollution:
1. Contribution to Particle Pollution
Nitrogen dioxide reacts in the atmosphere to form nitrates. These nitrates can combine with other substances to create fine particulate matter (PM2.5).
- Process: NO2 undergoes chemical transformations, leading to the formation of secondary particles composed partly of nitrogen compounds.
- Impact: Fine particles can penetrate deep into the lungs and bloodstream, causing respiratory and cardiovascular health problems. They also contribute to haze, reducing visibility.
2. Formation of Ground-Level Ozone
NO2 is a crucial precursor to the formation of ground-level ozone (O3), especially during warm, sunny conditions.
- Process: NO2 absorbs sunlight and breaks apart, releasing an oxygen atom. This free oxygen atom can then combine with an oxygen molecule (O2) to form ozone (O3). This process happens in the presence of other volatile organic compounds (VOCs).
- Impact: Ground-level ozone is a powerful respiratory irritant that can worsen asthma, cause coughing, and make breathing difficult. It also harms vegetation and ecosystems.
A Regulated Pollutant
Due to its significant impact on air quality and public health, nitrogen dioxide is classified as a widespread air pollutant. As noted in the reference, it is "one of six widespread air pollutants for which there are national air quality standards to limit their levels in the outdoor air." This highlights its importance in air quality management and regulation efforts.
Understanding how NO2 pollutes is crucial for developing strategies to control emissions from major sources like vehicle exhaust, power plants, and industrial processes, thereby improving air quality and protecting public health.
