What type of pollutants are released directly from the source into the air in a harmful form?

Primary pollutants are substances that are emitted directly into the atmosphere from a specific source in their harmful form. These pollutants include substances like carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matter. They are typically released from sources such as vehicle exhaust, industrial processes, and combustion of fossil fuels. These pollutants can have immediate adverse effects on air quality and human health.

In contrast, secondary pollutants are not emitted directly from a source. Instead, they form in the atmosphere through chemical reactions involving primary pollutants and other atmospheric constituents. Examples include ozone and smog, which are products of reactions between nitrogen oxides and volatile organic compounds in the presence of sunlight.

Combustion pollutants refer specifically to emissions that result from the burning of fuel. While these can often be primary pollutants, the term is more focused on the process rather than the classification of how they are released.

Fugitive pollutants are those that escape into the air from a source without being emitted through a smokestack or exhaust pipe; these are usually not intentional emissions and can include things like dust from construction sites or leaks from pipelines.

Understanding the distinction between primary pollutants and others is crucial for identifying sources of air pollution and addressing air quality issues.