Prior to the introduction of Opal, Comgas (a brand of the aviation fuel avgas) was used in many communities to discourage use of fuel as an inhalant. Unlike Opal, however, Comgas contains tetraethyllead (TEL), a substance that is poisonous and is banned for automobile use in most parts of the world  after the discovery that it increased concentrations of lead particles over the entire earth, including the poles.Opal fuel BP p.l.c. Retrieved 2007-06-08.
Prior to the introduction of Opal, Comgas (a brand of the aviation fuel avgas) was used in many communities to discourage use of fuel as an inhalant. Unlike Opal, however, Comgas contains tetraethyllead (TEL), a poisonous substance that inhibits catalytic converters and is therefore banned for automobile use in most parts of the world especially after the discovery that it increased concentrations of lead particles over the entire earth, including the poles.Opal fuel BP p.l.c. Retrieved 2007-06-08.
R
substance that is poisonous and is
poisonous substance that inhibits catalytic converters and is therefore
A
especially