Explain why the formation of oxides of nitrogen in engines is a concern for environmental pollution.

The formation of oxides of nitrogen is a concern because they can contribute to air pollution and lead to the formation of acid rain and photochemical smog. These pollutants can have harmful effects on human health and the environment.

A strong answer should directly address the approved learning objective to explain that oxides of nitrogen form when nitrogen and oxygen react at high temperatures in engines. This question belongs to Atmospheric pollutants from fuels within Common atmospheric pollutants and their sources, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to oxides of nitrogen, and keeps the wording specific to AQA GCSE revision.