Final answer:
Cars contribute significantly to the formation of smog in the US due to their emissions, impacting air quality and human health.
Explanation:
Cars are responsible for 60 percent of the makeup of smog in the US. Smog is a mixture of air pollutants like sulfur dioxide and nitrogen oxides that form over urban areas due to fossil fuel combustion. Vehicle emissions contribute significantly to air pollution, leading to smog formation.
Learn more about Smog formation and vehicle emissions here:
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