The lead pollution episode of the Notre-Dame de Paris Cathedral fire reminded us how dangerous lead is to health. This toxic metal is classified as an international public health priority and integrated into health policies in many countries such as the United States, Canada and the European Union.
Lead is naturally present in our environment and lead pollution can affect anyone. Due to its physical and chemical properties, it has been extracted and used since antiquity in many applications including the covering of historical monuments, painting, crockery, gasoline...
This wide use has led to lead pollution of our daily environment. As lead is very stable, pollution by this toxic metal is long-lasting.
As we spend most of our time in buildings, the pollution of the indoor air we breathe there is very impacting on the health of the occupants. As lead is particularly harmful to children, it is essential to protect them from contact with this pollutant. As lead easily passes through the placental barrier, exposure of pregnant women is particularly harmful to the embryo and fetus.
What are the health reference values for the assessment of lead pollution in housing?
Lead residues are contained in the dust we inhale and ingest daily. The analysis of dust in a building is therefore a very good indicator of the level of indoor air pollution.
The lead content of ambient air is between 0.01 and 0.5 µg/m3, and on average 0.15 µg/m3.
The World Health Organization (WHO) recommends not to exceed a threshold of 0.5 µg/m3 as an annual average.
The lead content must also be below the threshold for soil pollution. This varies according to the country and the destination of the occupation (kindergarten, housing, commerce or industry) and varies between 70 and 1200 mg/kg (equivalent to ppm and µg/g).
In the European Union, soil is considered polluted when its lead content exceeds 300 mg/kg
As part of the investigations relating to lead pollution following the Notre-Dame de Paris fire, numerous surface samples were taken using wipes. As it is not possible to know the mass of dust collected with a wipe, the results of a lead analysis attached to a wipe do not allow a comparison with the health reference values. However, it can be used to assess lead contamination of a surface and the effectiveness of decontamination following lead pollution.
Lead analysis on a surface with a wipe does not assess health risks.
What are the recommended values for the lead concentration on a surface?
The recommended values for lead concentration on a surface vary from country to country:
- United States and Canada: 430 µg/m2 (40 µg/ft2) for floors, 2690 µg/m2 (250 µg/ft2) for window sills, 4305 µg/m2 (400 µg/ft2) for window frames.
- France: Following the Notre-Dame fire, the Agence Régionale de Santé d'Île de France defined reference values of 1000 µg/m² as a precautionary threshold after decontamination and 5000 µg/m² as an alert threshold.
The ARS points out that these thresholds do not constitute a health reference.
As a precaution, a threshold limit of 70 µg/m² indoor was considered as the maximum acceptable level of contamination for facilities for young children such as nurseries or schools.
Dust analysis, such as that proposed by YOOTEST, makes it possible to accurately assess the level of lead pollution and, above all, to monitor the effectiveness of the actions put in place to decontaminate a lead-polluted dwelling.
