High fences blocked Parisians and tourists from several streets and a bridge around the monument on Tuesday.
The culture ministry said workers plan to use two decontamination techniques.
One involves spreading a gel on public benches, street lights and other fixtures to absorb the lead, letting it dry for several days before removing it.
Another method will feature high pressure water jets with chemical agents.
The clean-up work inside Notre Dame, suspended last month for safety reasons, will resume next week.
Hundreds of tons of lead in Notre Dame's spire and roof melted during the April fire.
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