Carbon dioxide is a natural constituent of the atmosphere.

Besides being a natural constituent of plants, it and its analogs are insect pheromones.

Where the smell of decay was strong, violence somehow seemed a natural constituent also.

Civil servants, the elderly, students, joggers and vegetarians are more natural constituents, he said.

Samples had been taken of air, water, and other natural constituents.

Ozone, a pollutant at ground level, is a natural constituent of the stratosphere.

And there's even this inside joke: The novel's natural constituents, media types, all got free copies.

They should be talking about carbon dioxide which is, by the way, not a pollutant but a natural constituent of the atmosphere.

The global warming theory has cast CO2, a natural constituent of the atmosphere, as a demon gas.

Lead is also a natural constituent of surface and ground waters that supply drinking water to many millions of Americans.