How does nitrogen dioxide primarily affect the respiratory system?

Nitrogen dioxide (NO2) primarily affects the respiratory system by forming nitric acid upon interaction with moisture in the lungs. When inhaled, nitrogen dioxide can react with the water present in the respiratory tract to form nitric acid (HNO3), which is a strong acid. This process can lead to irritation and damage to the lung tissues and airways, making it a significant concern for respiratory health, particularly for individuals with preexisting conditions or compromised immune systems.

The formation of nitric acid can contribute not only to acute respiratory distress but also to longer-term consequences if exposure is repetitive or prolonged. This is central to understanding how nitrogen dioxide impacts respiratory function and why it can exacerbate conditions such as asthma and other respiratory diseases.

While other options discuss serious health outcomes, such as lung cancer, chronic obstructive pulmonary disease (COPD), and acute lung fibrosis, they are not primarily attributed to nitrogen dioxide exposure as directly as the formation of nitric acid in the lungs. Understanding the mechanisms through which NO2 operates helps industrial hygienists develop appropriate interventions and regulations to minimize exposure in occupational and environmental settings.