Housing and business premises are often built on former industrial sites. As a result of industrial activities, the soil may have been contaminated by substances dangerous to humans and accumulated pollution for several decades.
Soil pollution is therefore a priority public health issue because of the health impact of exposure to toxic substances on the populations living near contaminated areas. This risk is particularly important for pregnant women and children.
Soil pollution can have a natural or accidental origin. The main pollutants sought in soils are heavy metals, hydrocarbons, solvents, pesticides and industrial chemicals.
Why can soil pollution affect indoor air quality?
When the pollutant is not volatile, as is the case with heavy hydrocarbons, heavy metals and pesticides, it is present in dust particles in the soil. These are brought inside buildings mainly through the soles of shoes and by the wind, which disperses the fine (PM10 and PM2.5) and ultra-fine (PM1 and PM0.1) dust contaminated by these pollutants.
The mechanism of indoor air pollution is different for volatile substances such as solvents and hydrocarbons. These volatile organic compounds (VOCs) will be emitted continuously from the ground under the building or in its immediate vicinity. These toxic gases will diffuse into the building from the ground and spread throughout the floors.
What indoor air quality parameters are indicative of soil pollution?
The presence of heavy metals, heavy hydrocarbons and pesticides in significant quantities in the indoor environment can be the result of soil pollution, even if this is difficult to characterise from a house dust analysis. Consequently, if significant levels of heavy metals or hydrocarbons are present in the dust, it is recommended to carry out a soil analysis in addition to the dust analysis.
In the case of lead pollution, it is recommended to look for the presence of old paints that may contain this toxic metal.
In the case of more volatile pollutants, high concentrations of BTEX (Benzene, Toluene, Ethylbenzene and Xylene) or hydrocarbons, with no known source in the building, may indicate soil pollution by petrol or fuel oil. Light hydrocarbons (petrol, fuel oil, etc.) are responsible for a very large number of soil pollution incidents.
Soil pollution by industrial solvents such as trichloroethylene or perchloroethylene (tetrachloroethylene) is not uncommon and potentially more dangerous for humans. Thus, high concentrations in the air can indicate soil pollution by these toxic solvents.
Trichloroethylene has been banned in cleaning and maintenance products for many years. Its presence is a strong indication of soil pollution.
It is prohibited in products available on the market for private individuals, and the use of perchloroethylene is still authorised for certain craft and industrial activities. These include dry-cleaning dry cleaners. The presence of a dry cleaner near the building or clothes cleaned at the dry cleaner's can also be the cause of the presence of this chemical in the indoor air.
For VOCs, only a laboratory analysis can identify with certainty the chemicals in the indoor air that may be the cause of soil pollution. The connected sensors give an estimate of the total VOC concentration but do not allow to know which ones.