Vehicular emissions are the primary source of air pollution in urban areas, contributing to high levels of particulate matter, nitrogen oxides, and carbon monoxide.

Sulfur dioxide is primarily responsible for acid rain, as it reacts with water in the atmosphere to form sulfuric acid.

Photochemical smog is the term used to describe the formation of ground-level ozone, which occurs when sunlight reacts with nitrogen oxides and volatile organic compounds in the atmosphere.

Particulate matter, especially fine particles (PM2.5), is primarily responsible for respiratory problems such as asthma and bronchitis, as it can penetrate deep into the lungs.

The high cost of pollution control technologies is a primary challenge in controlling air pollution from industrial sources, as it can make it difficult for industries to implement effective pollution control measures.

Electric vehicles are a future direction in air pollution control that focuses on reducing emissions from transportation sources by replacing gasoline-powered vehicles with zero-emission electric vehicles.

Air pollution control is the term used to describe the process of removing pollutants from the air, typically through the use of pollution control technologies or strategies.

Carbon capture and storage is a future direction in air pollution control that focuses on capturing and storing carbon dioxide from industrial sources, preventing its release into the atmosphere.

Difficulty in monitoring emissions is a primary challenge in controlling air pollution from agricultural sources, as agricultural activities can be dispersed and emissions can vary depending on factors such as weather and crop type.

Energy efficiency measures are a future direction in air pollution control that focuses on improving energy efficiency in buildings and industries, reducing the demand for fossil fuels and consequently reducing air pollution.

Emission reduction is the term used to describe the process of reducing the amount of pollutants emitted into the air, typically through the use of pollution control technologies or strategies.

Renewable energy sources are a future direction in air pollution control that focuses on using renewable energy sources such as solar and wind power, reducing the reliance on fossil fuels and consequently reducing air pollution.

Difficulty in monitoring emissions is a primary challenge in controlling air pollution from residential sources, as residential activities can be dispersed and emissions can vary depending on factors such as heating and cooking practices.

Research and development is a future direction in air pollution control that focuses on developing new technologies for pollution control and monitoring, improving the effectiveness and efficiency of air pollution control strategies.