Soil pollution: understanding the causes, risks and solutions for healthy soil

Why can the soil be polluted?

Soil can be polluted for several reasons:

• Some soils are naturally polluted, such as certain lands that may be radioactive or have a high content of metals like cadmium and lead and metalloids, such as arsenic or boron.
• Other soils contain anthropogenic pollution, that is, pollution caused by human activity. This is the case with pesticides, PFAS generated by certain chemical or metallurgical industries, or PAHs, polycyclic aromatic hydrocarbons, notably generated by the combustion of fossil fuels or forest fires.

Who is affected by soil pollution?

Everyone is affected by soil pollution. According to the General Commission for Sustainable Development, France has nearly 7,000 polluted sites and soils. These are listed in the Basol database. No region is spared, not even mountainous areas. Among the most frequently found pollutants are hydrocarbons and chlorinated hydrocarbons, volatile organic compounds (VOCs), cyanide, metals and metalloids, and PAHs.

Farmers and industrial entrepreneurs are on the front line in the fight against soil pollution. They are often both sources of pollution and victims of these emissions, since they are the ones who come into contact with them on a daily basis.

Local authorities are also affected, depending on the history of their soil and the presence, or absence, of industrial sites, industrial wastelands or intensive agricultural operations.

Finally, individuals, especially if they consume fruits and vegetables from their own garden or drink water from polluted groundwater, are particularly exposed in the medium or long term.

Chemical pollution: hydrocarbons, solvents, heavy metals…

Chemical pollution is the most frequently observed form of pollution in soils. The table below indicates the main sources of pollution for each class of pollutant:

Within chemical pollution, we can also mention PFAS, which are known as perennial pollutants. They can remain in soils and groundwater for hundreds of years. These substances are widely used in the aerospace, automotive, construction, and electronics industries.

Organic pollution: pesticides, PAHs, etc.

Pesticides constitute a form of organic pollution. They are primarily used in agriculture and viticulture. Their purpose? To destroy crop pests or render them harmless, promote plant growth, and treat livestock with antiparasitics or as disinfectants. The most common are herbicides, fungicides, and insecticides.

PAHs, or polycyclic aromatic hydrocarbons, are persistent organic pollutants. The most prevalent in French soil are fluoranthene and pyrene. Fluoranthene, for example, is found in soils that have been used for mining, particularly in the north and east of France.

Bacteriological/biological pollution

This bacterial pollution is also organic in nature. It can be exacerbated by domestic waste such as household garbage and wastewater, as well as agricultural manure or industrial discharges, particularly when no prior treatment is carried out.

Physical pollution (waste, plastics, etc.)

Physical pollution is undoubtedly the most visible. It manifests itself through the presence of waste such as plastics, remnants of industrial buildings, or evidence of chemical activity through the storage of drums, for example. It also takes the form of visible traces such as blackish spills or areas where the soil is completely barren and on which no grass or plants grow.

For the environment (water, biodiversity)

First, soil pollution has consequences for biodiversity and water quality. For example, pesticides are biocides that destroy living organisms, particularly aquatic organisms. These pollutants can also contaminate groundwater, which in turn affects the soil and the water used to irrigate plants. Finally, chemicals can also contribute to soil sterility, depriving the soil of the nutrients necessary for plant growth and survival.

For human health (contact, indirect ingestion, culture)

Many soil pollutants are considered carcinogenic or probably carcinogenic by health authorities. The International Agency for Research on Cancer (IARC) has published a table classifying chemical agents as carcinogenic to humans. This is the case, for example, for certain PAHs such as pyrene, solvents such as benzene, and metals such as arsenic, cadmium, and nickel compounds. Some PFAS, such as PFOA, also fall into this category.

Ingesting these products through the consumption of contaminated vegetables or eggs, as well as consuming polluted water, can be dangerous to human health.

For agricultural and forest ecosystems

Agricultural and forest ecosystems can also be impacted by human-caused pollution, particularly through heavy metals and PAHs that contaminate the soil. Frequent forest fires, proximity to industrial or chemical sites, or former mining sites can prevent certain tree species from developing properly.

There are several ways to diagnose soil pollution.

Visible signs / local alerts

Some sites show visible signs of soil pollution: traces of hydrocarbons or chemical storage, yellowed grass or sterile areas where nothing grows, plastic waste or even open-air landfills with the presence of metals and strong odors.

The history of the soil also helps to determine the potentially polluted nature of a plot of land. For example, if it is located on a former industrial wasteland, a former mining basin or an area belonging to a chemical company or heavy industry.

Laboratory analysis (heavy metals, solvents, HCT…)

In the laboratory, it is possible to have most heavy metals, PAHs, PFAS, hydrocarbons, and pesticides analyzed. If you have an idea of ​​the nature of the pollutants (former industrial site, proximity to intensive agricultural activities), tailor your request to reduce costs.

There are also companies, like Pouryère, that offer laboratory-prepared test kits starting at under €100. You collect the soil sample yourself, but the analysis and interpretation are carried out by scientists. There are kits specifically designed for detecting heavy metals (arsenic, cadmium, chromium, lead, etc.), major pollutants such as HCT and PAHs, PFAS, or pesticides (trinitrogens, triazines, or organophosphate compounds).