Assertion: comfrey's use | /r/HasProperty | recognized as substantial health hazard
Facets:
value: in the 1980s
type: TEMPORAL
Source sentences:
text: However, in the 1980s, the use of comfrey leaves was recognized as a substantial health hazard causing hepatic toxicity in humans and with carcinogenic potential in rodents due to the presence of toxic pyrrolizidine alkaloids (see Potential constraints on the "Nutritional aspects" tab).