Paris (AFP)
What are the health risks of lead? From what quantity in the environment is there a danger? Update on the health issues posed by pollution of this heavy metal, six months after the fire at Notre-Dame Cathedral.
- What are the risks?
During the disaster, which severely damaged Notre-Dame on April 15, 300 tons of lead contained in the boom frame and the roof melted and some of it spilled into the air in the form of particles.
Lead is a toxic substance. "There is no concentration in the blood that is safe," warns the World Health Organization (WHO).
This metal enters the body by inhalation or ingestion and then spreads to reach the brain, liver, kidneys and bones. Acute or chronic exposure to high levels results in digestive disorders, kidney disruption, nervous system damage or reproductive abnormalities.
Children with a developing nervous system are very vulnerable to this intoxication, also known as "lead poisoning". And their tendency to carry objects to the mouth exposes them more.
Even low blood levels "can affect the child's intelligence and lead to behavioral problems and learning difficulties," according to the WHO.
In France, since 2015, we have been talking about cases of lead poisoning above a blood level (blood lead level) of 50 micrograms per liter of blood (μg / l). 837 new cases were notified in 2016, according to Public Health France. A "vigilance threshold" is set at 25 μg / l.
- What concentration in the environment?
After reassuring measurements on air quality, the debate focused on the concentration of lead on soils around Notre-Dame.
Walking on lead dust is not dangerous, but it can be brought home under his soles, with the risk of children ingesting them.
The High Council of Public Health (HCSP) recommends screening for child lead poisoning if the threshold of 70 μg / m2 is exceeded in "dusts deposited in dwellings". In this configuration, he can expect to find a blood lead level greater than 50 g / l in about 5% of children.
The HCSP advocates special attention to the floors of schools and other collective spaces for children.
It is on these recommendations that the mayor of Paris relied to reassure the parents after the samples taken in a dozen establishments of the district mid-May: none exceeded "on average" 70 μg / m2, even if some punctually higher values were found.
A "thorough cleaning" of the schools surrounding the cathedral was nevertheless done "as a precaution" during the summer, followed by new measures. The results of these led to a delay of a few days in the return to five private schools.
At the end of July, the Robin des Bois association lodged a complaint against X after the lead pollution caused by the fire, accusing the authorities of being slow to react and lacking transparency.
- What did the tests on children do?
According to the latest available figures, nearly 750 children were screened on September 12 to control the lead in their blood. Conclusion at this point: there is "no health alert", according to the ARS.
Of this total, we know the detailed results of 398 screenings. Among them, there were 34 cases above the "threshold of vigilance" (25 to 50 μg / l), and three cases slightly above the threshold for mandatory reporting of lead poisoning (50 μg / l).
For two of them, a source of contamination in the home was identified, unrelated to the fire.
The detailed results of blood lead levels carried out in September are not yet known. We just know that three new cases exceed the threshold of 50 μg / l, which makes it 6 in all. Again, we can not say whether or not these cases are related to Our Lady.
However, according to the ARS, these three cases "do not change the overall conclusions", reassuring at this stage.
- Older pollution? -
This is the question that the health authorities are now asking: is the presence of lead in Paris due to the Notre-Dame fire or to older sources (roofing, ironwork of balconies, soils polluted by fire? lead contained in gasoline until 2000)?
To see more clearly, the Anses sanitary safety agency was asked to assess the reality and the impact of this pre-fire pollution.
The task is complicated by the fact that there is no regulatory threshold on the presence of lead in the streets. This is why the fire of Notre-Dame has put the authorities in front of a new problem.
After the disaster, the levels measured on the square (500.000 to 900.000 μg / m2) and in the cathedral justified the closure to the public and the suspension of the building site at the end of July. It resumed on August 19, with new protections for workers.
But measures taken in the surrounding area revealed disparate values, difficult to interpret: 50,000 μg / m2 rue de la Cité or 20,000 μg / m2 place Saint-Michel, on the other side of the Seine.
To try to understand better, the authorities sought to determine what rate of the famous metal was already present on Parisian soil before the fire.
From samples taken in recent years, the ARS has estimated that the level of lead pollution that can be expected to be found in the streets of the capital city is 5,000 μg / m2. Based on this benchmark, targeted testing and decontamination operations were implemented in some schools.
© 2019 AFP