Setting up two monitoring networks for pesticides in ambient air and soil in Wallonia


In Europe, Directive 2009/128/EC requires Member States to develop action plans to reduce the risks and effects of pesticide use on human health and the environment.

Despite these directives and the good practices adopted by users of plant protection products (PPP), the dispersion of pesticides in the environment remains poorly controlled. PPPs can therefore be omnipresent in our living environments, causing risks to human health and biodiversity.

At present, environmental pesticide monitoring networks exist for surface water, groundwater and distribution water, as well as for food, but there is no monitoring for air and soil. These existing networks focus mainly on the analysis of so-called “old” pesticides (many of which are now banned), while regular updates of the lists of substances to be monitored enable us to take into account many more recent and still-approved active substances (AS).

Although some active substances have been banned because of their potential impact on health and ecosystems, some SAs approved in Belgium and not monitored by existing networks are on the list of substances suspected of being carcinogenic, reprotoxic or toxic to specific organs after repeated exposure in humans. What’s more, these SAs can also have acute and chronic toxic effects on aquatic and/or terrestrial organisms.

It is therefore essential to monitor these SAs in the environment, in order to better characterize and prevent risks to people and biodiversity.

As part of the 3rd Walloon Pesticide Reduction Program (PWRP3), ISSeP is in charge of action sheet, which aims to “Set up monitoring of pesticide-related risks in the environment (water, air, soil, agricultural production)”, or “SuRiPest” for short.

Study objectives

The aim of this monitoring proposal is to set up two monitoring networks for PPPs in air and soil, and to collect the data needed to better assess the risks associated with pesticides in the environment. This will not only improve the prevention of PPP contamination, but also complement the risk assessments carried out using data obtained from existing networks. These two new networks will also make it possible to assess the effectiveness of measures to reduce the use of PPPs taken under the PWRP.

Job description

Overview of monitoring data in Belgium and benchmarking of PPP monitoring abroad :

  • Use all available data (e.g. CORDER reports, phytoweb, EU pesticides, etc.) to draw up a balance sheet of active substances authorized and used in agriculture in Wallonia,
  • Prioritize the PPPs to be monitored on the basis of physico-chemical, (eco)toxicological, sales, use, etc. criteria, in order to define a list of PPPs of interest to be monitored,
  • Review existing monitoring networks in the Walloon Region, Belgium and abroad (PPPs analyzed, analytical techniques used, sampling protocols, etc.).

Preliminary and prospective screening of PPPs :

Pesticide contamination of the environment will be assessed on a preliminary basis using a screening exercise, carried out with CRA-W, in the 4 agricultural super-regions of Wallonia (Habran et al., 2022), in order to obtain an overall view of PPP contamination of ambient air and soil, over a one-year period.

This will involve non-targeted analysis of ambient air and soil samples to determine the PPPs found and possibly their concentrations.

The results of the non-targeted analyses will be compared with the list of PPPs of interest (step 1-hierarchization), and a re-evaluation of the PPPs to be monitored will be considered and discussed if necessary, as will the analytical methods to be optimized (or developed if necessary).

Optimization of analytical methodologies :

This step will be carried out with the aim of reducing the analytical cost over the long term (network sustainability).

The aim is to identify PPPs of interest for which no analytical methodologies have been developed, based on the assessment carried out (step 1) and the preliminary screening (step 2).

Analytical optimization options to achieve quantification limits relevant to the study will be discussed and tested.

This analysis and optimization of analytical methods can be carried out throughout the duration of the project, as required. These analytical adaptations will be based on the experience and skills of the project team (ISSeP and CRA-W) and data from the scientific literature.

Operational organization of the PPP air and soil monitoring program :

All the information obtained in the previous stages will be used to organize an operational pesticide monitoring program that is as relevant as possible for the air and soil matrices (number of samples to be analyzed per matrix, number of sampling sites, sampling frequency, etc.).

Ongoing monitoring of PPP air and soil monitoring networks, analysis of results and drafting of annual reports:

The task will be to set up the devices and protocols defined in step 4 for the air and soil networks, and to monitor the smooth running of the various stages of the network (sampling schedule, sample analysis, analysis of results and report writing).

Regular updating of the air and soil databases with new results.

Adjustments to the networks will be made if necessary, and will mainly concern the sites studied, the sampling frequency, the number of samples analyzed, and the list of PPPs to be monitored.

An annual report will be drawn up to present the results obtained in each of the two matrices during the previous year’s monitoring.

Expected results

  • Setting up an observatory to monitor soil contamination by PPPs
  • Setting up an observatory for PPP contamination of ambient air


For further information before, during or after the study, please contact us:

Caroline Thiry and Eric Gismondi

ISSeP – Cellule Environnement-Santé, 200 Rue du Chéra – 4000 Liège

Email :


Center wallon de recherches agronomiques (CRA-W, Gembloux)

A player at the service of citizens, consumers, the economy and the transition to more sustainable agriculture in Wallonia. CRA-W combines scientific research, service and support functions for the benefit of Walloon farmers, livestock breeders, horticulturalists, foresters and operators in the agri-food sector.

Unit 10 of the CRA-W is contributing to this project with its expertise in the analysis of plant protection products in various environmental matrices. After screening soil and air samples to determine the molecules to be monitored in the air and soil matrices, appropriate analytical methods will be developed.


PWRP3 – Ministry of the Environment, Nature, Forestry, Rural Affairs and Animal Welfare

FAQ – General

1 Why develop a monitoring network for pesticides in ambient air and soil in Wallonia?

At present, environmental pesticide monitoring networks exist for surface water, groundwater and distribution water, as well as for food, but there is no monitoring for ambient air and soil.
The development of these two networks would not only complete the environmental monitoring of pesticides, but also improve the monitoring of the risks associated with their presence in the environment.

2 - What active substances are we looking for?

In this 1st phase of the project (screening), there is no defined list of molecules to be analyzed. Analyses will be carried out using multi-residue methods (partner CRA-W), with the aim of identifying molecules present in ambient air and soil.
As the project continues, a list of substances of interest will be defined according to several criteria (presence/absence, persistence, use, toxicity, etc.) in order to be monitored in each of the networks set up.

3) Can all pesticides present in ambient air and soil be analyzed?

Current analytical laboratory capacities do not allow us to analyze all the active substances in plant protection products.
A specific part of the project has been set aside to develop new analytical methods to increase the number of molecules analyzed.

4 - Will there be a risk assessment?

No risk assessment will be carried out in the 1st phase of the project (screening) as no concentrations will be measured.
Once the monitoring network is up and running, a risk assessment will be carried out on all the results obtained.

FAQ – Floor shutter

1 - Does the project target only agricultural land?

For the 1st phase of the project (screening), the aim is to identify the molecules present in Walloon soils in order to define the list of active substances of interest.
As farming is the activity that uses the most phytopharmaceutical products (in terms of quantity and diversity), samples will be taken from the 16 main crops (representing around 82% of the usable agricultural area) in order to identify the molecules present in the soil, and therefore possibly of interest to the monitoring network.
For the remainder of the project, samples will be taken from all types of land (industry, private individuals, parks, forests, cemeteries, railroads, organic crops, etc.).

2 - What are the 16 main crops grown in Wallonia?

The 16 main crops in Wallonia were originally 17, but for the SuRiPest project it was decided to group temporary and permanent grassland together.
The 16 main crops are

  • Winter oats
  • Spring oats
  • Fodder beet
  • Sugar beet
  • Chicory
  • Rapeseed
  • Spelt
  • Winter wheat
  • Bean
  • Silage corn
  • Grain corn
  • Winter barley
  • Spring barley
  • Peas and green peas
  • Potatoes
  • Meadows (temporary + permanent)

3.Qui va réaliser les prélèvements ?

The samples will be taken by ISSeP-approved sampling agents. Participating farmers will not be asked to carry them out.

4.Pourquoi demander l’historique des cultures et des pulvérisations de la parcelle prélevée ?

This will enable a more accurate and nuanced interpretation of the results (presence/absence of substances).
Example: if a molecule is not detected even though it has been sprayed on the crop, this means that it has either been rapidly degraded, or that it has been rapidly transferred to groundwater or surface water. As a result, the risk associated with this substance in soil would be lower, and so its monitoring in the soil monitoring network would be less relevant.

5.Est-ce qu’il y aura des mesures des concentrations pour la 1ère phase du projet (screening) ?

No, the screening only seeks to identify the molecules present, not to quantify them. There will therefore be no concentration measurements.

6.Comment seront interprétés les résultats du screening ?

The analyses will reveal the identity and number of active substances present for each of the 16 main crops, and their persistence in the soil (samples taken before, during and after use).
These results will be used to target the molecules of interest to be monitored in the soil monitoring network.

7.Est-ce que la localisation des prélèvements sera indiquée lors de la diffusion des résultats ?

As with any project involving personal data, the anonymity of participants is guaranteed. In addition, ISSeP’s Data Protection Officer (DPO) ensures compliance with the General Data Protection Regulation (GDPR).
In fact, only ISSeP staff working on the project will know the identity of the participants and be able to establish a link between the results and the participants. The laboratories carrying out the analyses will receive samples identified by a code, so they will have no information on the origin of the samples.
When the screening results are published, the precise location of the samples will not be indicated, so as not to be able to identify the participating farmers.
In addition, several samples from different plots of the same crop will be mixed before analysis. It will therefore not be possible to know the results for each individual plot.

8.Est-ce que les agriculteurs participants recevront les résultats de leur parcelle ?

Several samples will be taken from plots of the same type of crop. As far as possible, a minimum of 2 to 3 plots per crop type should be mixed before analysis.
As a result, the results obtained cannot be attributed to a particular farmer.

9.Est-ce que les échantillons de sols seront conservés ?

Yes, samples will be stored at -20°C, in order to study the maximum shelf life of samples. Their preservation will also enable the project team to carry out additional analyses (confirmation of initial results, research into new substances following analytical development, ….).