However, in freshwater, beryllium is somewhat more common, with a concentration of 0.1 parts per billion.

Jet fuel contains water, as a contaminant, in concentrations of up to 100 parts per million.

Breathing in chlorine at a concentration of 50 parts per million is highly dangerous.

Breathing in chlorine at a concentration of 500 parts per million for a few minutes is lethal.

Germanium occurs in the human body at concentrations of 71.4 parts per billion.

Lead exists in seawater at concentrations of 2 parts per trillion.

They are lachrymators, causing eye irritation at concentrations of only a few parts per billion.

These compounds are detectable by the human nose at concentrations of only 10 parts per billion.

At Wooster, which had the higher levels, tests found concentrations of 11 parts per trillion.

The chemicals are considered extremely hazardous in a concentration of 1,000 parts per million, he said.