Introduction It has been close to 20 years that engineered nanomaterials have entered commerce. There are tens of thousands of types of nanomaterials that have been produced and the hazard potential varies across them. Some may be hazardous and some not. The last decade of research has begun to identify important determinants of ENM toxicity but there is still much uncertainty about hazard potential. It is useful to attempt to sort out what currently is known and not about hazards of ENMs.

Methods The scientific literature from 2000–2017 was assessed using keywords and environmental scanning techniques to capture information about the health effects of ENMs. The focus will be on high volume ENM.

Result The extent of research health effects that have been identified for various high volume ENMs will be described. While many nanomaterials have been developed there are a limited number that are widely used in commerce. Common determinants of toxicity will be identified.

Discussion Assessing the hazard potential of ENM is a complex task since there are so many combinations of physio-chemical parameters that may lead to ENMs having differential toxicity. The implications of this will be discussed as well the research needed to address the hazard potential of engineered of nanomaterials that are or could be in commerce.