New technology to monitor pesticide residues in West African waters

FAO is partnering with Oregon State University (OSU) to deploy new technology in West Africa for monitoring pesticides in surface and ground waters. The “passive sampling device” (PSD) uses an artificial membrane suspended within a stainless steel frame and submerged in surface waters for a chosen duration (a day to a month).

During this time the pesticides in the water passing over the membrane accumulate by chemically bonding to the polymer. Once removed from the water the membrane is easily dried and shipped to the laboratory where the accumulated chemicals are dissolved from the membrane and analysed for composition and concentration. This method avoids the high degree of uncertainty in the usual “bulk water method” as well as the expense and inconvenience of shipping large amounts of water within the subregion.

This new technology (patent pending) promises to revolutionize the science of water quality assessment through greatly increasing the ease and reliability of water quality analysis while substantially lowering the costs associated with sampling. The sampling devices will be used to monitor pesticide movement in irrigation and drainage waters as well as in the two River systems. The devices can also be submerged in wells to detect the movement of pesticides in the water table.

The work is part of an FAO/UNEP/GEF project entitled Reducing Dependence on POPs and other Agro-Chemicals in the Senegal and Niger River Basins through Integrated Production, Pest and Pollution Management, which became operational in May 2009. The project has been Development Objective, “To protect transboundary waters in the Niger and Senegal River Basins through elimination of POPs pesticide-use and substantial reduction and elimination of other toxic pesticides used in agriculture; while augmenting agricultural productivity and net economic benefits to farmers”.

Participating countries include Guinea, Senegal, Mauritania, Mali, Niger and Benin.

Key technical partners on the project include the regional NGO, ENDA Pronat, responsible for the baseline agronomic, economic and social surveys, together with the technical team at Oregon State University’s Integrated Plant Protection Centre (OSU/IPPC), which is one of the most experienced groups in the world for monitoring pesticides in the environment. Other partners include eco-toxicology laboratories in Senegal, Mali and Burkina Faso, which will be linked with the OSU team to form a network of laboratories in support of project activities.

Data from the six-country intensive water sampling will be used in models being developed to estimate the transport and chemical fate of pesticides in transboundary waters and also in models used to estimate human health risk. These outputs will feed directly back to the communities at risk, through FAO's IPPM farmer training program, as well as to national decision-makers and regional and international pesticide legislation bodies.

During a pilot phase in three communities along the Senegal River, a total of 19 chemical pesticides were found of which 16 surpassed European standards for safety on the order of tens-to-hundreds of times above established thresholds for safety. The samples came from water sources that are often consumed directly by local communities. Most of these chemical pesticides were in the moderate to highly toxic categories. Some of them, such as Endosulfan, were extremely toxic to aquatic organisms. One of the chemicals detected, Dieldrin, was in the category of persistent organic pollutant (POP) and had been banned for use in the region since the 1980s.

The project is co-financed by two of GEF's Operational Programmes: International Waters (OP 10) and Persistent Organic Pollutants (OP 14), together with contributions by the participating countries and co-financing from the government of The Netherlands through FAO’s Integrated Production and Protection Management programme (IPPM).
For more information, contact Dr. William Settle ( or Dr. Hama Garba (


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