Phytotechnologies to manage soils polluted by metals

Around the world, thousands of contaminated sites have been identified as a legacy of decades of industrial activity. This phenomenon raises societal concerns regarding potential health impacts. Among the various pollutants present in soil, trace metals (referred to as “TM”), such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), cobalt (Co), nickel (Ni), etc., are widely found globally due to their numerous uses and high persistence. These pollutants are (eco)toxic at varying concentrations depending on the nature of the element and are more or less bioavailable depending on their chemical speciation; they cause degradation of ecosystems and their ability to provide ecosystem services, as well as potential health risks.

In addition to the genome, the exposome ( https://www.inserm.fr/c-est-quoi/ambiance-ta-life-cest-quoi-lexposome/ ) influences health. Environmental factors are believed to be responsible for more than 70% of noncommunicable diseases: cardiovascular or metabolic diseases, cancers, and chronic respiratory problems. And as our understanding of the subject has grown, it has become clear that it is crucial to consider the various implicated factors as a whole. Indeed, some act synergistically (the “cocktail effect”), while others counteract one another. Furthermore, these factors do not have the same impact depending on the stage of life at which one is exposed to them, nor on the duration of exposure.

From a reflexive perspective, as conceptualized in the European REACH Regulation ( https://www.ecologie.gouv.fr/politiques-publiques/reglement-reach ) – Regulation No. 1907/2006 of the European Parliament and of the Council –, which entered into force in 2007 to protect human health and the environment from the risks posed by chemical substances and to adopt common rules to promote the sustainable development of the European chemical industry, it is now essential to limit as much as possible the use of (eco)toxic and persistent chemical substances in the environment; however, today it is necessary to inventory, characterize, and manage historical contamination. As discussed later in this paper, phytotechnologies are particularly well-suited for moderate to low levels of soil contamination.

In Europe, structural changes in the industrial sector are leading to the closure of many facilities and, consequently, to an increase in the number of brownfield sites. In fact, there are 2.8 million sites with potentially polluting activities—whether currently operational...