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Toxic Waste from Obsolete Pesticides—A Growing Threat in Developing Countries

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November 4, 2009  Susmita DasguptaBrian Blankespoor, Walid Dhouibi, Abdelaziz Lagnaoui, Craig Meisner, and Hassine Ben Salah

Abandoned pesticide stockpiles pose a growing threat to people and ecosystems in developing countries. A geo-referenced method developed for policy makers in Tunisia is also being presented to Mali and other African countries to prioritize stockpile clean-up as inventories become available. 

pesticide drums
Photo: Africa Stockpiles
Obsolete pesticides have accumulated in many low and middle-income countries. In Tunisia the accumulation can be traced to product bans, outdated products, donations or purchases in excess of requirement, and poor stock management.1

As part of the ongoing Africa Stockpiles Programme, Tunisia’s Ministry of Environment and Sustainable Development conducted a detailed inventory of publicly held pesticide stockpiles, including a location for each storage site, the identity and quantity of contaminants, and the general condition of containers.2 

Considering the number of storage facilities and contaminated sites in Tunisia and elsewhere, geographic information systems are being used integrate site information with a rich database of toxicities and risk to people, fish, plants, and animals. This method provides a spatial grid for policy makers to visualize threats to humans and wildlife, and locations with unacceptable exposure risks to both.

Identifying the most potentially harmful sites

The inventories from Tunisia were used to locate and assess potential risks from approximately 1,984 metric tons of obsolete pesticide formulations (with 759 tons of active ingredients of concern) in 197 storage sites.

A preliminary investigation revealed 47% of storage containers were either broken or showed surface damage, 8% indicated leakage, 34% were contaminating soil and equipment, and only 11% were undamaged.

Population Density vs. Stockpile Hazard

human health hazards map
Larger View (159 kb)

Note: Population density: yellow (low), brown (high)
Hazard ranking: high (red), medium (pink), and low (grey).
Assessing risks to human health 

The approach developed for Tunisia integrates information on populations at risk and their proximity to stockpiles with the relative toxic hazards3 of nearby stockpiles. A composite measure of potential exposure risk for each site was calculated as a function of the volume of pesticides, their relative hazards, and the condition of the storage containers.

This information was converted to per-capita exposure risk using a risk-decay factor as a function of inhabitants’ average distance from the site.

The per-capita risks were then aggregated to compute total exposure risks for nearby populations, taking into account the relative vulnerability of children and women of childbearing age (see figure right).

The ranking of the 197 stockpile sites from most to least risk allowed authorities to plan a sequence of clean-up and safeguard priorities.4 

Assessing risks to ecosystems and biodiversity

Stockpiles with Lethal Concentrations for Fish 
(near Ichkeul National Park)
fish toxicity map
Note: LC50 fish hazard ranking: high (red), medium (pink), and grey (low).
A similar approach was taken to integrate information about risks to eco-regions and biodiversity, using information on their proximity to stockpiles, the relative toxic hazards of the chemicals in stockpiles, and the condition of storage containers.5

Using information from the Third National Report on Biodiversity in Tunisia, and a list of global biodiversity hotspots from Conservation International, the location of storage sites and their relative toxicity were mapped against the geographic range of critical/endangered or “vulnerable” eco-regions and species.6 

The figure (right) shows that three chemicals stockpiled near the lake in Ichkeul National Park7 are particularly deadly for fish (see figure right).8 Other work focuses on land-based wildlife at risk in these areas. Overall, sufficient information was available in Tunisia to identify priority sites for clean-up.

SUSMITA DASGUPTA is a Lead Environmental Economist in Development Research Group. Her research interests include health hazards of pollution, the poverty- environment nexus, setting priorities in pollution control, estimation of pollution abatement cost, cost effective regulations, monitoring and enforcement of regulations, informational approaches to pollution control, and cleaner production alternatives. Email:

BRIAN BLANKESPOOR is an Environment Specialist in the Development Research Group. His research interests are in the geographic aspects of development related to topics such as water, climate change, conservation biology, economic geography, and public health.


1. This note is based on World Bank research on toxic pollution. The research uses spatial analysis----Geographic Information Systems (GIS)---to collect, integrate and analyze information about pesticide stockpile locations and contamination site hazards. The approach described here was developed for Tunisia to prioritize clean-up sites, but it could be used any country with basic information on the location and composition of public stockpiles.

2. Africa Stockpiles Programme ( Countries in the programme include Ethiopia, Mali, Morocco, Nigeria, South Africa, Tanzania, and Tunisia.

FAO. 1995a. “Prevention of Accumulation of Obsolete Pesticide Stocks. Provisional Guidelines, No. 2. Rome: Food and Agriculture Organization of the United Nations.
Available at

Six key factors lead to the accumulation of obsolete pesticides in developing countries: (i) product bans, (ii) inadequate storage and poor stock management, (iii) unsuitable products or packaging, (iv) donation or purchase in excess of requirements, (v) lack of coordination between donor agencies, and (vi) commercial interests of private sector and hidden factors.

3. Alternative hazard indicators were assigned using World Health Organization toxicity class and Median lethal dose or concentration (LD50) of the active ingredients.

4. “Stockpiles of obsolete pesticides and cleanup priorities: a methodology and application for Tunisia,” S. Dasgupta, C. Meisner, and D. Wheeler, World Bank Policy Research Working Paper 4893, 2009.

5. For more details on the methodology and explanation of lethal doses for fish and other wildlife see project note: Stockpiles of Obsolete Pesticides: Threats to Ecosystems and Biodiversity.

6. Rapport National sur la Diversité Biologique – TUNISIE (2006), available at

Conservation International – Biodiversity Hotspots for the Mediterranean Basin, available at

7. Ichkeul National Park is a UNESCO World Heritage Site and a RAMSAR site (The Convention on Wetlands of International Importance, especially as Waterfowl Habitat).

8. The median lethal dose, LD50 (abbreviation for “Lethal Dose, 50%”), or LC50 (Lethal Concentration) of a toxic substance is the dose required to kill half the members of a tested population. LD50 figures are frequently used as a general indicator of a substance's acute toxicity.

Last updated: 2009-11-04

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