An African approach for Risk Reduction of Obsolete Pesticides. Large amounts of pesticides have been shipped to Africa for locust control from the fifties of last century, but did not arrive on the proper place or proper moment thereby be coming obsolete. Stockpiles of these pesticides have created a serious problem and The Africa Stockpiles Programme (ASP), launched by FAO, is designed to rid Africa of stockpiles and to dispose them in an environmentally sound manner.
High concentrations of pesticides can be found in soils on the stockpiles and are a risk. Because removal of the high concentrations using northern technologies (e.g. incineration, bioreactor) or removal and transport of high amounts of contaminated soils were not found to be feasible, an approach making use African conditions has been investigated. Following a risk-based approach site specific remediation technology using biodegradation and isolation were developed and implemented.
The Africa Stockpiles Programme (ASP), launched by FAO, the Food and Agriculture Organization of the United Nations, is designed to rid Africa of stockpiles of obsolete pesticides and to ensure that new stockpiles do not accumulate. A key objective of this programme is to ensure that stockpiles are disposed of in an environmentally sound manner. Most of the pesticides have been shipped to Africa for locust control from the fifties of last century, but did not arrive on the proper place or proper moment thereby be coming obsolete.
High concentrations of pesticides (e.g. dieldrin, parathion, malathion, chlorpyrofos) can be found in soils on the stockpiles and are a risk for human health, health of cattle, and quality of ground- and surface water. Removal of the high concentrations using northern technologies (e.g. incineration, bioreactor) or removal and transport of high amounts of contaminated soils was not found to be feasible for most of the sites involved. It is necessary to know the behavior of pesticides under different African conditions and explore local remediation technology for each site following a risk-based approach, not only based on removal of high concentrations of pesticides.
Sites are distributed over the whole African continent, and can also be found in delta areas. In cooperation with the different partners Alterra investigated sites in Mali, Mauretania and Botswana.
In risk assessments, the risks of pesticides are evaluated on the basis of concentrations present and maximum allowable values in soil and water. If finance or technology to remove the pesticides are lacking, this kind of assessment will not lead to solve the local problems. From a risk-based point of view, contaminations are only a risk if they are or may become available. This widens the range of options and therefore can facilitate more tailor-made solutions for individual sites.
To solve the problem of sites polluted by pesticides, the following steps are necessary:
- Investigation of the site (e.g. historical use, hydrology, climate, transport)
- Defining of the site specific risks
- Gathering of missing information, including local conditions and sampling
- Possibilities for site specific and sustainable remediation by risk reduction
- Implementation of the risk reduction measures.
Three sites in Mali and three sites in Mauretania have been investigated in 2007 according steps 1-3. Most important risks identified were: a) inhalation of volatilized pesticides, b) transport to groundwater, c) physical contact by human and cattle, d) run-off by rain (Mali) and e) wind erosion (Mauretania). Based on the results obtained and results of analysis of the samples taken, risk reduction proposals have been made and discussed locally (step 4). All proposals are based on the use of local conditions to stimulate biodegradation and/or to prevent rain water to transport the pesticides both vertical and horizontal.
In populated areas, a plan for future use was part of the solution to prevent houses from being built on the isolated site. All plans have in common that they reduce the risks for the local population. Furthermore, they are simple and cheap and can be implemented on a sustainable way, even under the difficult African conditions.
Implementations (step 5) in both countries have been started in summer 2008.
The results have been presented and discussed in a workshop in Bamako (Mali) in 2010. Participants originated from the whole African continent discussed the possible application of the approach in their countries. The research has been continued in Botswana and also outside Africa in Paraguay.