Health impacts of nitrogen dioxide (NO2): Higher concentrations of NO2 in ambient air primarily lead to which adverse effect in exposed populations?

Introduction / Context:
Nitrogen dioxide is a reactive gaseous pollutant produced by high-temperature combustion (vehicles, boilers). Understanding its principal health effects aids risk assessment, ambient standard setting, and control technology choices.

Given Data / Assumptions:

• Exposure refers to elevated urban or near-source concentrations.
• Short- and long-term respiratory outcomes are considered.
• We distinguish primary health effects from material damage like corrosion.

Concept / Approach:
NO2 acts as a potent respiratory irritant: it inflames the lining of the airways, exacerbates asthma, reduces lung function, and increases susceptibility to respiratory infections. It contributes to bronchitis-like symptoms. While NO2 participates in acid deposition and can cause material corrosion indirectly, its most immediate human health effect is respiratory tract inflammation.

Step-by-Step Solution:
Link pollutant to organ system: NO2 → lungs/airways.Identify clinical picture: cough, wheeze, bronchitic symptoms, decreased FEV1.Select “Bronchitis and respiratory inflammation” as the dominant effect.

Verification / Alternative check:
Epidemiological studies correlate ambient NO2 with increased hospital admissions for respiratory distress and worsened asthma control.

Why Other Options Are Wrong:
Cancer: NO2 is not classified as a strong direct carcinogen in ambient contexts.Asphyxiation: unlike CO, NO2 does not displace oxygen at typical urban levels.Only corrosion: material damage occurs, but human health impact is key.Neurological paralysis: not a typical NO2 outcome.

Common Pitfalls:
Confusing NO2 with CO (asphyxiant) or with particulate matter; each has distinct mechanisms and outcomes.

Final Answer:
Bronchitis and respiratory inflammation