Assertion: gas | /r/MadeOf | several percent benzene
Facets:
value: often
type: TEMPORAL
value: as a consequence
type: OTHER
value: before the 1950s
type: TEMPORAL
Source sentences:
text: As a consequence, gasoline often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely used antiknock additive.