[canadaduane]

By "lowest elements" do you mean elements with lowest atomic number (Hydrogen, Helium, Lithium, etc.), or closest to the bottom of a chart hanging on a wall (Rubinium, Strontium, Yttrium, etc.)?

[selimthegrim]

It would seem to be the latter, given the reference to heavy metals (they probably mean noble metals more likely)

[ncmncm]

No. They are contrasting the elements operated on, mostly light elements, with heavier ones used in catalysts that are also toxic, for reasons.