Cadmium, lead, and mercury are the heavy-metal components most likely to be the target of environmental concerns.
(Cadmium, lead, and mercury; are; the heavy-metal components most likely to be the target of environmental concerns) (the heavy-metal components most likely; to be; the target of environmental concerns)
Cadmium, lead, and mercury the heavy-metal components most likely
are to be
the heavy-metal components most likely to be the target of environmental concerns
the target of environmental concerns