The majority of nitrogen oxide originates from:

The majority of nitrogen oxide emissions originate from motor vehicles primarily because these sources burn fossil fuels, which release nitrogen oxides (NOx) as a byproduct of combustion. Internal combustion engines in cars, trucks, and buses produce these emissions when fuel is burned at high temperatures, leading to a reaction between nitrogen in the air and oxygen in the combustion process.

The relevance of this understanding helps emphasize the significant impact of transportation on air quality and the importance of implementing regulatory measures to mitigate vehicle emissions. Additionally, this knowledge informs public policy and environmental health initiatives aimed at reducing air pollution and protecting public health.

While volcanic eruptions can contribute to nitrogen oxide levels, they are not a primary or consistent source compared to motor vehicles. The same holds true for home waste incineration and burning of industrial wastes, which contribute much less to the overall nitrogen oxide emissions in comparison to emissions from vehicles.