Wetlands act as natural filters to protect water quality.

The limestone shelf acts as a natural filter for water that passes over it.

Architect Christian de Portzamparc's initial idea was to mark the entrance into the world of music through a natural filter.

And if it failed, at least he would still be conscious, his natural respiratory filters protecting him.

They serve the body as a natural filter of the blood, and remove wastes which are diverted to the urinary bladder.

The mangroves were a natural filter for the ocean and a nursery for marine life.

They act as a natural filter for the solids that come out of the water treatment plant.

It seemed to serve as a natural filter that screened out superfluous influences.

There aren't any natural media-style filters, and it doesn't support Photoshop plug-ins.

Development would not only rob the region of a huge natural filter.