Persistent Organic Pollutants (POPs) and Pesticides

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POPs are a set of toxic chemicals that are persistent in the environment and able to last for several years before breaking down (UNEP/GPA 2006a). POPs circulate globally and chemicals released in one part of the world can be deposited at far distances from their original source through a repeated process of evaporation and deposition. This makes it very hard to trace the original source of the chemical (http://web.worldbank.org/). POPs are lipophilic, which means that they accumulate in the fatty tissue of living animals and human beings (http://www.unece.org/spot/s01.htm). In fatty tissue, the concentrations can become magnified by up to 70 000 times higher than the background levels (http://web.worldbank.org/). As you move up the food chain, concentrations of POPs tend to increase so that animals at the top of the food chain such as fish, predatory birds, mammals, and humans tend to have the greatest concentrations of these chemicals, and therefore are also at the highest risk from acute and chronic toxic effects.

In 1995. the United Nations Environment Programme expanded its research and investigation on POPs with an initial focus on what became known as the “Dirty Dozen”.  These were a group of 12 highly persistent and toxic chemicals: aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzen, mirex, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and toxaphen.   Many of the pesticides in this group are no longer used for agricultural purposes but a few continue to be used in developing countries.

Since then, additional substances such as carcinogenic polycyclic aromatic hydrocarbons (PAHs) and certain brominated flame-retardents, as well as organometallic compounds such as tributyltin (TBT) have been added to the list of Persistent Organic Pollutants (http://en.wikipedia.org/wiki/Persistent_Organic_Pollutant).

Sources of pollution from POPs include the improper use and/or disposal of agrochemicals and industrial chemicals, elevated temperatures and combustion processes, and unwanted by-products of industrial processes or combustion (http://web.worldbank.org).

 

Effects

POPs are highly toxic and exposure can take place through diet, environmental exposure, or accidents.  They negatively affect humans, plant and animal species and natural ecosystems both in close proximity and at significant distances away from the original source of discharge. 

Exposure to POPs in humans can cause several negative health effects including (http://en.wikipedia.org/wiki/Persistent_Organic_Pollutant, http://web.worldbank.org/):

  • Death
  • Cancers
  • Allergies
  • Hypersensitivity
  • Developmental changes
  • Damage to the central and peripheral nervous systems
  • Disruption of the endocrine, reproductive, and immune systems
  • A study published in 2006 suggests that an increased level of POP.s in human blood serum can be linked to Diabetes (Lee et al 2006).

 

According to the U.S Environmental Protection Agency (EPA) there are links between POPs exposure and the increased frequency of diseases and/or abnormalities in wildlife species, including certain kinds of fish, birds, and mammals (http://www.epa.gov/international/toxics/pop.htm#affect).  The negative effects of pesticides in the marine and coastal environments include changes in reef community structure, such as decreases in live coral cover and increases in algae and sponges and damage to seagrass beds and other aquatic vegetation from herbicides.

 

Global versus Caribbean Studies on POPs

The capacity to monitor Persistent Toxic Substances (PTS), including POPs varies significantly from one country to another. For many regions, including Central America and the Caribbean, monitoring of POPs is mainly ad hoc and relies on analysis from research, accidents or evaluation of specific hot spots. This limits efforts to undertake an accurate global appraisal of PTS (UNEP 2003).

According to a UNEP global report of 2003 levels of many of the persistent pesticides in the environment of industrialized countries are declining when compared to the 1980’s or 1990’s. This is particularly so for pesticides such as DDT, heptachlor and chlordane. However, the report further suggests that the lack of effective alternatives to the use of persistent chemicals such as DDT in several developing countries  continues to limit efforts to completely phase out the use of this chemical.  DDT continues to potentially affect the health of millions of people around the world.

Persistent pesticides are still a problem in areas highly dependent on agricultural goods, such as in the Central and South American Regions. The same is true for the countries that produce these chemicals such as in the East Asian region. In the Arctic, there has been an increase in some levels of persistent pesticides. The environmental condition in this region favors a higher persistence and therefore a higher chance of entering into aquatic food webs.

PCB’s are of concern in several regions of the world. In the developing world where little data exist, PCB’s are of particular concern and levels have even increased in some countries (UNEP 2003).

Data available from Europe, North America, East Asia and Mediterranean Regions show that dioxins and furans levels, two of the non-pesticide POPs, are higher in urban and industrialized areas. A major source of these two chemicals is from poor waste management practices and improper burning (UNEP 2003).

The potential impacts of some new chemicals are also a global concern.  There is evidence of ecotoxicological effects for brominated flame retardants and alkylphenols, two groups of these newer chemicals (UNEP 2003).

POPs ranked second in the Wider Caribbean Region priority rankings of the GPA contaminant categories (GESAMP 2001). However, POPs may not be a priority for the smaller SIDS with limited industrial development (UNEP/GPA 2006b). According to a regional report covering over 23 countries in Central America and the Caribbean, it is reported that there is a lack of data and monitoring capacity for Persistent Toxic Substances (PTSs) (UNEP 2002). This is further confirmed by Fernandez et al (2007), who confirmed the limited availability of data in the Wider Caribbean Region.

None of the countries examined in the UNEP Regional Report of 2002 reported the existence of facilities to monitor all the PTSs of concern. Additionally, there are no facilities in the Wider Caribbean region for the routine monitoring of dioxins and furans and a number of emerging PTSs of concern, such as flame retardants. Only some countries reported the presence of laboratories capable of monitoring selected PTSs including Cuba, Trinidad & Tobago, Barbados, Jamaica, Bahamas, Guyana, and Saint Lucia (UNEP 2002).

According to Singh (2005), poor land management practices and the lost of agricultural lands to other economic activities have led to increased pesticide usage. It is predicted that 90% of the pesticides used in the Wider Caribbean Region do not meet their intended target and a high proportion enters the marine environment via surface and drainage, runoff, erosion, misapplication and atmospheric transport (UNEP 1994). The steep topography of most of the islands and cultivation on steep slopes encourages soil erosion and the movement of pesticides to coastal areas. According to (UNEP 2002) massive coral mortalities and egg shell thinning cases have been reported. Fish mass mortality has occurred in areas of agricultural runoff where pesticides have been illegally used. For example, in Jamaica an increase in fish mortality in coastal areas coincides with the period of the year when pesticides are applied on coffee plantations (Chin Sue 2002).

Polychlorinated biphenyls (PCBs) have been used extensively in the Wider Caribbean Region since the 1930s (Fernandez et al 2007). The PCBs have been detected in atmospheric, marine, freshwater, groundwater, sediment, soil, food and biota samples, including human blood and milk. Electrical transformers, containing PCB oil, were still in use in 2002 in the Wider Caribbean Region and were reported in use in countries such as Panama and Guyana (UNEP 2002).

DDT residues have been reported in agricultural areas of all the 23 countries of the Wider Caribbean Region. According to Fernandez et al (2007) DDT and its metabolites is one of the organic pollutants most frequently reported in the Wider Caribbean Region. The presence of these compounds suggests the existence of long-range transport within the Wider Caribbean Region (Fernandez et al 2007).

Other POP pesticides still in use in 2002 were Toxaphene, which was used as an insecticide on bananas and pineapples in Puerto Rico and the Virgin Islands (UNEP 2002) and the Organochlorine (OC) insecticide Endosulfan. Endosulfan is used to control pests on various crops in a number of countries in the region. According to UNEP (2002), cases of acute human poisoning by pesticides have been reported in Colombia, Guatemala, Nicaragua and El Salvador.

The major source of polycyclic aromatic hydrocarbons (PAHs), dioxins and furans in the region is from the burning of domestic, industrial and agricultural waste and burning of vegetation for clearing land. Another source of PAHs in the region is from the importation and national production of crude oil (UNEP 2002). Elevated levels of PAHs have according to Fernandez et al (2007) been observed throughout the Wider Caribbean Region. According to UNEP (2002) Barbados was the only country reporting that open burning of garbage disposal was illegal and Jamaica was the only country having a legal control of dioxin and furan emission. However, according to Corbin (2008) there are several other countries that have developed legislation that prohibit/restrict open burning of waste.

 

Figure 1; May 28, 1999 satellite image of SE United States, Central America, and the Amazon region showing a African dust cloud over the Caribbean

pop-dust-cloud.pngInformation obtained from Barbados Trinidad and Tobago, and Jamaica indicated that PTSs may be transported by the Northeast Trade Winds (UNEP 2002). This is also supported by Adolfo Fernandez (et al 2007) who further suggests that organic pollutants can be found in most parts of the region including locations that are far from the pollution sources which indicates long-range transport of these contaminants. The countries of North Africa in the Sahel region apply large amounts of pesticides, including those banned in the Caribbean and the United States. These pesticides are present in dust reaching the Caribbean and southern United States from North Africa, as shown in Figure1(USGS 2000, EP/GEF 2002).

One of the newer persistent substances in the Wider Caribbean region is tributyl tin.  Antifouling paints used on vessel hulls is the primary source of tributyl tin (UNEP 2002). In boatyards in Trinidad and Tobago and in the US Virgin Islands, tributyl tin levels recorded are considered to be unsafe for invertebrate organisms (UNEP 2002). Panama, Cuba and Guatemala have also reported the use of organic tin compounds in agriculture (UNEP 2002).

According to the 2006 study “GIWA Regional Assessment 3a for the Caribbean Small Island subsystem”, the impact of chemical pollution in this region was considered moderate. Some findings presented in this study include; in most countries land clearance practices, inefficient irrigation, and use of agrochemicals damage surface and groundwaters; the use of low lying wetlands for rice cultivation requires heavy pesticide use; in St Kitts and Nevis water resources are susceptible to agricultural pollution due to its low lying position; industrial pollution (sugar, rum, petrochemical, paint, agroprocessing and metal) is particularly a problem in Trinidad and Tobago.

According to the 2004 “GIWA Regional Assessment 3b, 3c done for Colombia, Venezuela, Central America & Mexico”, there are moderate impacts from chemical pollution in the Colombian and Venezuelan sub-system but severe impacts in Central America and Mexico. Some findings from Colombia and Venezuela include: in Venezuela dioxins and furans are discharged from paper bleaching and incineration plants; in the Catatumbo delta extensive amounts of pesticides have been used to fumigate illegal crops posing an threat to the environment (El País 2002); the mangroves of the Atlantico Department, Cienaga de Mallorquin (Magdalena Basin), are being degraded by chemical pollutants discharged by Barranquilla industries impacting the mangroves and the fisheries industry.

For Central America and Mexico it was reported that: Central America is the largest user of pesticides per capita in Latin America and, as a result of the current economic model, its use will increase further (CATHALAC 1999); in Honduras, pesticides and organic waste, mainly from coffee productions, are the most common sources of water pollution; in Nicaragua pesticide pollution mainly from cotton crops have been found in aquifers; DDT has been found to be used in sugar cane production within the region;  In Chetumal Bay mass fish mortalities have been recorded due to contamination by agrochemicals and pesticides transported there by Río Hondo.

According to the 2004 “GIWA Regional Assessment 4, done for the Islands of the Greater Antilles”, the impact of chemical pollution in this region was also considered moderate. Some findings from this region include; Dominican Republic has minor chemical pollution from mining, urban, energy and industrial activities; In Haiti activities generating toxic chemical residuals do not exist (PNUMA/ORPALC/Cimab in press); Bahamas has experienced slight impacts from chemical pollution mainly from shipping (BEST 2001); each year over 1.2 million tonnes of industrial hazardous waste is produced in Cuba and only some of the waste receives minimal treatment; based on internationally accepted standards Cuban scientists estimate that this volume of industrial liquid waste pollutes 1.84 billion m3  of freshwater per year (Portela 1998 in Portela & Aguirre 2000); in Cuba 30 000 tonnes of pesticides and herbicides were used annually over a 25 year period (Herrera & Seco 1986 in Portela & Aguirre 2000).

 

Laws, Regulations, and Policy Responses on POPs and Pesticides

There is a lack of legislation and regulations on the import, export, transport, use, production, emission, storage and disposal of PTSs in the region (UNEP 2002). Ratification of International Conventions relevant to PTS and harmonization of legislation within the Region has taken place to some extent (UNEP 2002). With specific reference to the management of pesticides, regional Governments have promulgated a number of laws, decrees, regulations and standards.  These have focused primarily on regulations relating to importation, licensing and conditions of usage but very little on education and awareness.  For other PTSs, there are fewer regulations on their import, export and/or use and Cuba, Jamaica, Barbados, Trinidad and Tobago and Colombia have developed regulations on industrial PTSs.

The most important regional legal framework in the Wider Caribbean Region for the protection of the Caribbean Sea from pollution is the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (Cartagena Convention). The Convention entered into force in 1986 and is a legally binding, regional multilateral environmental agreement for the protection and development of the Wider Caribbean Region. The Cartagena Convention deals with the management of POPs and Pesticides through its Protocol concerning Pollution from Land-based Sources and Activities (LBS Protocol).

In this LBS Protocol, Annex I lists Primary Pollutants of Concern, which include, but are not limited to, organotin compounds, polycyclic aromatic hydrocarbons, biocides and their derivatives and compounds with hormone-like effects.

Regarding pesticides, Annex IV of the LBS Protocol refers to Agricultural Non-point Sources of Pollution and states that the Parties shall develop plans for the prevention, reduction and control of agricultural non-point sources of pollution.  These plans should include:

 

    1. An evaluation and assessment of agricultural non-point sources of pollution that may affect the Convention Area, which may include:
  • an estimation of loadings;
  • an identification of associated environmental impacts and potential risks to human health;
  • the evaluation of the existing administrative frameworks to manage agricultural non-point sources of pollution;
  • an evaluation of existing best management practices and their effectiveness, and
  • the establishment of monitoring programmes.

 

  1. Education, training and awareness programmes, which may include:
    • the establishment and implementation of programmes for the agricultural sector and the general public to raise awareness of agricultural non-point sources of pollution and their impacts on the marine environment, public health and the economy;
    • the establishment and implementation of programmes at all levels of education on the importance of the marine environment and the impact of pollution from agricultural activities.

 

There are also a number of International Conventions dealing with POPs and Pesticides:

  • Stockholm Convention on Persistent Organic Pollutants (POPs). Aims to reduce releases of POPs chemicals on a global basis. The convention entered into force on May 17th, 2004. Read more at http://chm.pops.int/.
  • Rotterdam Convention on the Prior Informed Consent (PIC) Procedure for Certain Hazardous Chemicals and Pesticides in International Trade. Aim to promote shared responsibilities in relation to importation of hazardous chemicals and contribute safe use. The Convention entered into force on 24 February 2004. Read more at http://www.pic.int/home.php?type=t&id=5&sid=16.
  • The Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal. Aims to protect human health and the environment against the adverse effects resulting from the generation, management, transboundary movements and disposal of hazardous and other wastes. It has 170 Parties and came into force in 1992. Read more at http://www.basel.int/.

 

  • Convention on Long-Range Transboundary Air Pollutants (LRTAP), Protocol on Persistent Organic Pollutants (POPs). The aim of the Convention is that Parties shall endeavor to limit and, as far as possible, gradually reduce and prevent air pollution including long-range transboundary air pollution. The aim of the protocol on POPs is to control, reduce, or eliminate discharges, emissions, and losses of persistent organic pollutants. The protocol entered into force on 23 October 2003. Read more at http://www.unece.org/env/lrtap/.

 

  • Globally Harmonized System (GHS) for Classification and Labelling of Chemicals. Is a Globally Harmonized System (GHS) of Classification and Labelling of Chemicals promoting standard criteria for classifying chemicals according to their health, physical and environmental hazards. Read more at http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html.

 

  • International Convention on the Control of Harmful Anti-fouling Systems on Ships.  Aim to prohibit the use of harmful organotins in anti-fouling paints. Will enter into force on 17 September 2008. Read more at http://www.imo.org/conventions/mainframe.asp?topic_id=529.

 

  • The Vienna Convention for the Protection of the Ozone Layer & The Montreal Protocol on Substances that Deplete the Ozone Layer. Aims protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. Entered into force on January 1, 1989. Read more http://ozone.unep.org/.

 

Many of the countries in the Wider Caribbean Region have signed and/or ratified the Stockholm Convention.  Few countries have signed (Barbados, Colombia, Costa Rica, Saint Lucia) and some countries have  ratified (Belize, Cuba, Dominican Republic, Jamaica, Panama, Venezuela) the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade.

 

What is the Caribbean Environment Programme (CEP) doing?

Examples of on-going activities relating to the management of the use and disposal of POPs and pesticides include:

With financing provided by the Global Environment Facility (GEF), a project entitled "Reducing Pesticide Runoff to the Caribbean Sea" is currently on-going in Colombia, Costa Rica and Nicaragua. This project provides the opportunity for the collaborating countries to implement comprehensive management practices and specific measures to control the use and application of pesticides in the agricultural sector thereby reducing pesticides run-off to the Caribbean Sea. The project is a cooperative effort of national, regional and local stakeholders.  As Secretariat to the Cartagena Convention, UNEP-CAR/RCU is responsible for overall carrying out of the project and co-ordination at the regional level.  At the national level, the executing agencies are the Ministries of Environment in Nicaragua, Costa Rica and Colombia.  The main stakeholders for this project are the farmers, agrochemical distributors, health, agricultural and environmental ministries and agencies, environmental NGOs and other community-based organizations, relevant international organizations and academic institutions. The project contains a significant number of activities. As approved by the GEF Council, the project contains six main elements that will be implemented through three project components and various subcomponents. The six (6) elements are:

 

  1. Monitoring and Assessment of Impact
  2. Technology Transfer and Alternatives
  3. Education and Training
  4. Development of Incentives
  5. Institutional Strengthening
  6. Information Management and Dissemination

 

The activities to be financed over a 4-year period will include the development of 12 pilot projects in 6 relevant crops as a basis for the validation of technologies, for the assessment of environmental and socio-economic impact of different practices and as a tool for capacity building in pesticides management and a train-the-trainer programme. The project will also establish a regional coastal monitoring programme and database. Special efforts will be made to foster policy and legislative reforms and recommend incentives to discourage the use of toxic pesticides. The pilot projects will have an integrated design, incorporating the six elements mentioned above.

 

In collaboration with Earth University in Costa Rica, the CEP has supported activities under the project “Best Management Practices in Agriculture”. These include pilot projects in Guatemala and Costa Rica demonstrating best practices in organic farming techniques and dairy farming, sustainable farming practices including proper fertilization and the use of environmentally friendly techniques and alternatives in pest control. LINKS to  two of the pilots reports in Costa Rica.

 

The CEP in collaboration with the UNEP GPA facilitates the development and implementation of National Programmes of Action (NPAs) for the prevention of pollution from land based sources and activities including agricultural run-off of pesticides and direct or indirect discharges of POPs . In 2007, direct support was provided to Jamaica, Saint Lucia, Trinidad and Tobago and Barbados for completion of these plans. Ongoing efforts are focused on strategic planning and sustainable financing to enable these NPAs to be mainstreamed into development planning processes and implemented

 

One of CEP’s collaborating partner is Croplife International (www.croplife.org), which is a global federation representing the plant science industry and a network of regional and national associations in 91 countries. Members include BASF, Bayer CropScience, Dow Agrosciences, Dupont, FMC, Monsanto, Sumitomo and Syngenta. These companies are committed to sustainable agriculture through innovative research and technology in the areas of crop protection, pest control, and biotechnology. Together with the member companies, Croplife works to improve for example the safety of pesticides, management practices of pesticides and regulatory issues related to pesticides.

 

What can you do?

  • Stay informed and act responsibly.
  • Always read the labels and follow instructions.
  • Protect you children from all chemicals since they are more sensitive to toxic substances.
  • Protect pregnant women since exposure could harm the fetus’/baby’s health. Exposure to pesticides can cause miscarriage and birth defects.
  • Eat ecological grown vegetables and meats whenever possible.
  • Support companies that make clean products. Ask before buying.
  • Recycle batteries.
  • Recycle remains of paint, garden pesticides, and all other chemicals.
  • Recycle oil from vehicles.
  • Recycle medicines.
  • Recycle all electronic equipment.
  • Pesticides are poisons. Avoid using them whenever you can.
  • If you decide that you must use a pesticide, always choose the least-toxic product.
  • Use environmentally friendly cleaning products for cleaning and washing.
  • Landscape with native plants.

 

 

 

References

  • BEST, 2001, First National Communication on Climate Changes, Bahamas Environment Science and Technology Commission, The Government of The Bahamas, Nassau, New Providence.,The Bahamas
  • CATHALAC, 1999, Vision on Water, Life and the Environment for the 21st Century, Regional Consultations for Central America and the Caribbean Water Centre for the Humid Tropics of Latin America and the Caribbean (CATHALAC), Panama City.
  • Chin Sue H, 2002, Jamaica Country Report on Persistent Toxic Substances, Region X IRET/CSUCA, Regionally Based Assessment of Persistent Toxic Substances, GF/XG/XG/4030-00-20, FMAM/UNEP
  • Corbin C, 2008, personal communication on this subject
  • El País, 2002, El Río Catatumbo está mal herido, Retrieved Aug. 2002 from: http://elpais-cali.terra.com.co/historico/ago112002/NAL/D1411N2.html (In Spanish).
  • Fernandez  A, Singh A, and Jaffé R, 2007, A literature review on trace metals and organic compounds of anthropogenic origin in the Wider Caribbean Region, Marine Pollution Bulletin 54 (2007) 1681–1691, Southeast Environmental Research Center, Florida International University, 11200 SW 8th St, Bldg OE 148, Miami, FL, USA
  • Gesamp, 2001, Protecting the oceans from land-based activities – Land-based sources and activities
  • affecting the quality and uses of the marine, coastal and associated freshwater environment, Rep. Stud.
  • gesamp No. 71. United Nations Environment Programme, Nairobi
  • Lee DH, Lee IK, Song K, Steffes M, Toscano W, Baker BA, and Jacobs DR Jr, 2006, A Strong Dose-Response Relation Between Serum Concentrations of Persistent Organic Pollutants and Diabetes, Diabetes Care, 29:1638-1644
  • PNUMA/ORPALC/Cimab (in press). Estado del Medio Ambiente Marino y Costero del Caribe, Proyecto Regional, Officina Regional para América Latina y el Caribe
  • Portela  A, & Aguirre BE, 2000, Environmental degradation and vulnerability in Cuba, Natural Hazards Review 1 (August):171-179
  • Singh A, 2005, SIDS Sustainability and the Caribbean Sea, PhD Thesis, University of Plymouth, Plymouth, 450pp
  • The World Bank, Taken 2008-0510 from http://web.worldbank.org/WBSITE/EXTERNAL/TOPICS/ENVIRONMENT/EXTPOPS/...
  • UNEP, 2003, Global Report 2003-Regionally Based Assessment of Persistent Toxic Substances, Geneva Switzerland
  • United Nations Economic Commission for Europe, Taken 2008-05-15 from http://www.unece.org/spot/s01.htm
  • UNEP, 1994, Regional Overview of Land-based Sources of Pollution in the Wider Caribbean Region, vol. 33, UNEP/CEP, Kingston, 89pp.
  • UNEP, 2002, Central America and the Caribbean Regional Report, Regionally Based Assessment of Persistant Toxic Substances, Geneva Switzerland
  • UNEP/GEF, 2002, Evaluación Regional Sobre Sustancias Tóxicas Persistentes, Informe Regional De América Central y El Caribe. http://www.chem.unep.ch/pts/regreports/Translated%20reports/Central%20America%20
  • &%20Caribbean%20sp.pdf.
  • UNEP/GEF/Kalmar Högskola 2006, Global International Water Assessment (GIWA), Caribbean Sea/Small Islands GIWA Regional assessment 3a, Kalmar Sweden 2006
  • UNEP/GEF/Kalmar Högskola,Invemar, 2004, Global International Water Assessment (GIWA), Caribbean Sea/Colombia & Venezuela, Central America & Mexico GIWA Regional Assessment 3b, 3c, Kalmar Sweden
  • UNEP/GEF/Kalmar Högskola/Cimab 2004, Global International Water Assessment (GIWA), Caribbean Islands Bahamas, Cuba, Dominican Republic, Haiti, Jamaica, Puerto Rico Regional Assessment 4, Kalmar Sweden
  • UNEP/GPA, 2006a, The State of the Marine Environment: Trends and processes, The Hague
  • UNEP/GPA, 2006b, The State of the Marine Environment: A regional assessment,The Hague
  •  U.S Environmental Protection Agency (EPA), Taken 2008-05-17 from   http://www.epa.gov/international/toxics/pop.htm#affect).
  • USGS, 2000, African Dust Causes Widespread Environmental Distress, http://coastal.er.usgs.gov/african_dust/dust-infosheet.pdf.
  • Wikipedia the free encyclopedia, Taken 2008-04-29 from http://en.wikipedia.org/wiki/Persistent_Organic_Pollutant