A purification step is necessary to remove contaminating substances.

A contaminating substance in this is nitronium pentanitratozirconate.

Purification in a chemical context is the physical separation of a chemical substance of interest from foreign or contaminating substances.

The lotion is safe for use on all intact skin and for limited use in the eyes and remains non-toxic after reacting with the contaminating substance.

In the past, the maximum concentration of a contaminating substance that was permitted in the environment was usually set at the natural (background) level of that substance.

Food poisoning is illness caused by any harmful amount of a natural or contaminating substance in a food, but especially illness caused by some highly infective kinds of bacteria.

Ms. Henderson contended that people who eat fish would be safe if they studied and carried out the recommendations by the New Jersey Department of Health on such subjects as preparing fish so as to remove contaminating substances, if necessary.

• A person is not responsible for a contaminated site that became contaminated owing to an act of God, an act of war, or an act or omission of a third party (other than an employee, agent or contractor), where the potentially responsible person exercised due diligence with respect to the contaminating substance.