Tougher work safety measures, including footbaths, showers and strict entry and exit rules, are in place at the fabled medieval-era cathedral that suffered extensive damage in a blaze on 15 April.
The new safety measures were introduced to guarantee the safety of personnel working on the church and to prevent the dispersion of lead dust out of the site, which was sealed earlier this month.
Hundreds of tonnes of lead in the roof and steeple melted during the fire that nearly destroyed the gothic masterpiece, with winds spreading the particles well beyond the church's grounds.
After weeks of denying any poisoning risks, authorities admitted in late July that anti-contamination measures were insufficient, and two schools near the church were closed after hazardous lead levels were detected.
Safety gel on school playgrounds
In early August, workers dressed head-to-toe in white hazmat suits sprayed a blue-green gel onto the playground at two schools on the Rue Saint-Benoit, where dozens of children had been attending summer day-care programmes.
According to city officials, the gel attracted and trapped the lead particles on the ground as it dried, and was later removed with high-pressure hoses.
Readings of more than 70 microgrammes per square metre indicate potential health hazards, but testing has found much higher levels at buildings as far as one kilometre from Notre-Dame.
In late July, the city revealed that some schools and day-cares beyond a 500-metre perimeter of the church still showed isolated readings of more than 1,000 microgrammes on playgrounds or windowsills.
Critics have accused the city of failing to notify the public about the worrying results, while an environmental group has filed a lawsuit alleging that officials failed to sufficiently contain the contamination.
Others have urged authorities to cover the entire church with protective cladding to contain the particles, a system often used when removing asbestos.
City officials have rejected the proposal as too costly and complex.
But they have vowed that no schools will reopen in September unless the lead risk has been completely eradicated.