Overview of exposure of employees working to decontaminate contaminated soils

Outline of reasons and objectives
Rehabilitating polluted sites and soil is a sector of activity that is booming in France, due to an industrial context that is leading to an increase in industrial wasteland, and to the action of the French Ministry of Ecology who made it a priority at the “Grenelle de l’Environnement” talks. Beyond the risks that such sites can have for health and the environment, depollution of soil, which is still a recent activity, raises chemical risk issues. The objective of this study was to produce an overview of the sector so as to identify the decontamination techniques used and the risky jobs involved in decontaminating soil, and so as to assess and measure worker exposure to chemicals and, in certain cases, biological agents during the various treatment operations. If high levels are brought to light, the reasons for them will need to be analysed, and collective prevention measures will need to be studied.

Approach
The methodology for identifying depollution sites used the database Basol developed by the French Ministry for Ecology, Sustainable Development, and Energy (MEDDE), but, above all, it was based on cooperation with the Union des Professionnels de la Depollution des Sites (UPDS, the French Association of Site Decontamination Professionals) for collecting the necessary information from the decontamination sites before conducting measurement campaigns on them. Seven campaigns of measurements were conducted on building sites or other sites polluted with
hydrocarbons, the main pollutant, and they made it possible to assess the chemical exposure of the workers during the decontamination work.

Main results
On the outdoor worksites, the study highlighted total particulate matter (TPM) concentration levels that were low, and showed that the various operatives, be they ground workers or excavator drivers, were exposed only to very low levels. As regards the total hydrocarbons potentially present in the soil, the analyses of the samples generally indicated low content for aromatic hydrocarbons of the BTEX (benzene, toluene, ethylbenzene and xylenes) type present in the working atmosphere, except on one worksite, where the content was higher (50% of the occupational exposure limit (OEL) value for benzene).
Conversely, on a worksite enclosed under a tent, the study showed TPM and BTEX concentrations that were high, but that did not exceed the OEL values. The use of direct-read photoionisation detectors (PIDs) also showed that the operatives could be subjected to large exposure peaks in spite of the suction/extractor devices. It should be noted that other pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and chlorinated solvents that were potentially present in soil (diagnostic survey stage), were measured on certain worksites as traces in the ambient air.

Discussion
Due to the considerable diversity of the parameters governing the activity, the study enabled only a partial approach to be taken, by targeting the work sites proposed by the French Association of Site Decontamination Professionals (UPDS). However, most of those building sites or other sites having soil polluted with hydrocarbons and using biological decontamination techniques account for 60% of the quantities, excluding confinement. On those sites, the TPM concentrations and the volatile organic compound (VOC) concentrations are generally low when the worksites are outdoors and not enclosed or covered. The study also shows that, despite the suction and extractor devices and systems put in place, a covered excavation worksite can be (very) polluting.
The results will be the subject of a publication in the journal Hygiene et Securite du Travail (HST), that will be intended for the professionals of the sector, and for OSH specialists.