There are some concerns about the safety of tryptophan supplements, which have been found to contain impurities and contaminants.

He said the slide might contain contaminants, a violation of state and federal law if or when it reaches the river.

The reason is said to be that the oil contains sulfurous contaminants that make it smell.

Studies have shown that some, at least, even contain contaminants that could endanger users' health.

E85 ethanol contains far fewer potential contaminants than found in gasoline.

Surface water run-off can contain contaminants such as oil, organic matter and toxic metals.

Environmental clean up began in 1996, with the objective being to contain contaminants at the site and limit exposure to persons who visit the area.

Runoff containing industrial or urban contaminants can directly cause fish mortality and decreased reproduction.

"Clearly the material from that part of the harbor contains contaminants," she said.

The supernatant containing contaminants can be carefully removed so as not to disturb the beads.