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Why did gasoline-powered vehicles create major air-quality problems in cities?

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New York City skyline tinted orange from wildfire smoke. — air pollution control Even something as simple as breathing can get complicated.

Gasoline-powered vehicles created major air-quality problems in cities primarily because their internal-combustion engines release a variety of noxious gases and pollutants into the atmosphere. These emissions originate from the exhaust pipe, the crankcase, and the evaporation of fuel from the tank and carburetor.1

Key pollutants released by these vehicles include:
* Carbon monoxide and nitrogen oxides, which are toxic and contribute to respiratory issues.234
* Hydrocarbons, which are released as unburned fuel or through evaporation.15
* Particulate matter (such as PM2.5), which significantly degrades urban air quality.3

In many cities, these pollutants react in the presence of sunlight and stagnant air to form photochemical smog, a reddish-brown haze that irritates the eyes and respiratory system and exacerbates conditions like asthma. Furthermore, because motor vehicles are a primary source of volatile organic compounds (VOCs) and greenhouse gases, they contribute significantly to both urban air toxicity and global warming. High traffic congestion in urban areas intensifies these effects, leading to excessive pollution levels.4253