The level of contamination was not high enough to be considered a health risk.

The new state guidelines would set contamination levels as 70 parts per billion.

Therefore a negative result does not rule out a lower level of contamination.

Studies show that fish from the lake contains significant levels of contamination.

Nor would a tape sample provide the level of contamination in the air.

The level of contamination is less than it was a century ago, but it's still dangerously high.

There are many ways for producers to reduce the levels of contamination to meet the system's standards.

High levels of contamination may pose major risks to people and the environment.

In some areas the level of contamination is high.

The level of contamination in the 1988 crop thus appears to be at least 10 times greater than usual.