What type of environmental issue is created when nitrogen oxides are combined with hydrocarbons?

When nitrogen oxides are combined with hydrocarbons, they react in the presence of sunlight to form ground-level ozone, which is a key component of smog. Smog is characterized by a mixture of air pollutants that typically create a haze in the atmosphere and can have serious health effects on humans, particularly respiratory issues.

The formation of smog typically occurs in urban areas where vehicle emissions and industrial activities release nitrogen oxides and hydrocarbons into the air. The heat and sunlight initiate chemical reactions, leading to the generation of ozone, which, while beneficial in the stratosphere (where it protects against ultraviolet radiation), becomes a harmful pollutant at ground level.

Understanding this process helps highlight the importance of regulating emissions from vehicles and industries to reduce the occurrence of smog, thereby improving air quality and public health. Other options like acid rain, ozone layer depletion, and global warming involve different chemical reactions and pollutants, making them distinct environmental issues.