Which of the following is considered a secondary pollutant?

Sulfuric acid is considered a secondary pollutant because it is not directly emitted into the atmosphere but is formed through chemical reactions involving primary pollutants. These primary pollutants, such as sulfur dioxide and nitrogen oxides, undergo transformations in the atmosphere under certain conditions, often in the presence of sunlight and water vapor.

In the case of sulfuric acid, it is primarily formed when sulfur dioxide reacts with water vapor and oxygen in the air to produce sulfuric acid aerosol, which can contribute to acid rain and other environmental issues. Understanding the difference between primary and secondary pollutants is crucial in environmental health, as it helps in evaluating pollution sources and their impacts on air quality and human health.