The test widely used for the last 15 years is not sensitive enough to detect levels that low.

In several instances, these results detected high levels of contamination.

The level detected is far below a level of public health concern.

Lead-content tests can detect levels down to 2 parts per billion.

Generally the latter detect levels that are excessively high or low.

These stress proteins can be used as an early warning system to detect high levels of pollution.

The highest level detected in a Vietnam ground soldier was 45 parts per trillion.

Mab can be used to detect levels of gluten in food products.

Note that the body can actually detect low levels of oxygen but that this is not normal.

They also have three small ocelli (simple eyes) on the top of the head that detect light levels and polarization.