Contaminant 05 : A harmful or undesirable constituent; any substance that might constitute a health hazard or adversely affect desirable properties of drilling fluids. (Bul D11)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}