foreign substances
Unwanted alien materials
Foreign substances are materials that don't belong in a particular place or system—contaminants, impurities, or intrusions.
The term appears most often in medical and legal contexts: The autopsy revealed foreign substances in her bloodstream.
A foreign substance in the eye might be dust or grit.
In sports, foreign substances on equipment (pine tar on a baseball, adhesive on a quarterback's gloves) may violate rules.
The foreignness is relative to context—what belongs in one place is foreign to another.
- contaminantsUnwelcome substances in something pure
- impuritiesUnwanted substances within something
- pollutantsHarmful environmental substances
- toxinsHarmful biological substances
- debrisScattered broken fragments
particles · particulate matter · airborne particles · allergens · intruders · invaders · pathogens · germs · bacteria · microbes · residue · sediment · additives · chemicals · irritants · splinters · dust · pollen
foreign, foreigner, foreigners, foreignness, substance, substances, substantial, substantially, substantive