Heavy Metals


Several definitions of heavy metals exist. There are about 40 heavy metals but the exact number depends on the definition used. Definitions are based on the density, atomic number or weight and/or toxicity. (http://en.wikipedia.org/wiki/Heavy_metals#Heavy_metal_pollution).

Heavy metals normally occur in nature and are essential to life but can become toxic through accumulation in organisms. Arsenic, cadmium, chromium, copper, nickel, lead and mercury are the most common heavy metals which can pollute the environment. Mercury, lead and cadmium are of greatest concern because of their ability to travel long distances in the atmosphere (http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xOTE3NSY2PWVuJjMzPSomMzc9a29z).

Sources of heavy metals include mining, industrial production (foundries, smelters, oil refineries, petrochemical plants, pesticide production, chemical industry), untreated sewage sludge and diffuse sources such as metal piping, traffic and combustion by-products from coal-burning power stations. According to UNEP/GPA (2006a), an increasingly serious global problem is the management of electronic waste (e-waste), particularly the disposal of used computers and mobile phones, which contain over 1 000 different materials, many of which are toxic to humans.



The effects on human health and the environment from exposure to the three most common heavy metal pollutants (mercury, lead and cadmium) include:

  • Mercury exposure can harm the brain, heart, kidneys, lungs, and immune system of people of all ages. In babies and young children, the nervous system can be affected making the child less able to think and learn (http://www.epa.gov/mercury/about.htm). Some studies have suggested that methylmercury may cause cancer in humans, but the results are inconclusive. (http://www.greenfacts.org/en/mercury/mercury-1.htm#1).
  • Mercury accumulation in fish may harm the fish and other animals that consume them. Birds and mammals that eat fish are more exposed to mercury than other animals which live in aquatic ecosystems. Effects on wildlife can include reduced fertility, damaged kidneys, slower growth and development, abnormal behavior and even death (http://www.epa.gov/mercury/about.htm). Whales and dolphins may also be at high risk from mercury exposure (UNEP 2002b).
  • Lead may, according to UNEP (2008a), cause neurodevelopmental effects in children, even at low levels of exposure. Other effects include cardiovascular, renal, gastrointestinal, hematological and reproductive effects UNEP (2008a). Children six years old and under are most at risk (http://www.epa.gov/lead/). There is presently no known threshold for the effects of lead (UNEP 2008a).
  • In the environment, lead bioaccumulates in most organisms and is toxic to plants, animals and micro-organisms. Young fish are more susceptible to lead poisoning than mature fish or eggs. Symptoms of lead toxicity in fish include spinal deformity and blackening of the caudal region (rear part of the fish) (UNEP 2008a).
  • Cadmium is toxic to humans and exposure can cause pulmonary irritation, kidney disease, bone weakness and possibly lung, prostate, and kidney cancer. Food and cigarette smoke are the largest potential sources of cadmium exposure for the general population     (http://www.e-b-i.net/ebi/contaminants/cadmium.html). According to UNEP (2008b), food accounts for approximately 90 per cent of Cadmium exposure in the general, non-smoking population, of which agricultural crops (particularly irrigated rice) account for most of the intake. Additionally, people with a high intake of shellfish and organ meat from marine animals may have a higher intake of cadmium.
  • Cadmium is also toxic to plants, animals and micro-organisms. Cadmium accumulates mainly in the kidney and liver of vertebrates and in aquatic invertebrates and algae (UNEP 2008b). Acute toxic effects on fish, birds and other animals may include death or fetal malformations (http://www.e-b-i.net/ebi/contaminants/cadmium.html). Cadmium can affect plants resulting in decreased growth rate and even death.


Global versus Caribbean Studies on Mercury, Lead and Cadmium


According to UNEP (2002b), mercury is one of the most studied environmental pollutants but there are still gaps in the basic understanding of its pathways and impacts on human health and environment. Mercury levels have increased considerably since the beginning of the industrial age and are now present in the environment and in food all over the globe. Even regions with few mercury releases, such as the Arctic are affected due to the global transport. According to Greenpeace (1998), 40 000-80 000 people globally may be suffering from mercury poisoning as a result of the consumption of contaminated seafood.

Recent studies suggest that anthropogenic activities have increased the overall level of mercury in the atmosphere by a factor of 3. In and around industrial areas, the deposition rates have increased by 2 to 10 times during the last 200 years (UNEP 2002b).

Combustion of fossil fuels and incineration of waste material accounts for approximately 70% of the total quantified atmospheric emissions from major anthropogenic sources (UNEP 2002b). Since combustion of fossil fuels is increasing, mercury emissions can, according to UNEP (2002b), be expected to increase accordingly. Global climate change may also have impacts as there have been indications of increased formation of methylmercury in small, warm lakes and in new flooded areas (http://www.greenfacts.org/en/mercury/l-2/mercury-3.htm#0. According to UNEP (2002b), many countries lack basic information on the use, release and levels of mercury in the environment.

According to the UN Atlas of the Oceans, high levels of mercury have recently been recorded in a number of seafood products including sharks, swordfish, marlins and tunas. Some countries have warned pregnant women to avoid all consumption of these seafoods.



Lead is mined in more than 40 countries worldwide and in 2004 world production of lead was  3 150 000 tonnes (UNEP 2008a). According to UNEP (2008a), lead exposure occurs in nearly all countries of the world. On a global scale, Latin America, the Middle East, Asia, parts of Eastern Europe and the Commonwealth of Independent States are the regions whose peoples have the highest blood levels of lead. According to Greenpeace (1998), as many as 200 million people globally are at risk of lead poisoning.

Data from ice core drillings in Greenland demonstrated that lead levels increased significantly following the industrial revolution and lead deposited between the 1960s and 1990s was eight times higher than in pre-industrial times. Nevertheless, since the decreased use of leaded petrol in the 1970s and the increased emission controls, levels of lead in ice cores have decreased. According to UNEP (2008a), the global consumption of lead for manufacturing of petrol additives decreased from 310 000 tonnes in 1970 to 14 400 tonnes in 2003.

According to UNEP (2008a), the quantified global anthropogenic emissions of lead decreased from 330 000 tonnes to 120 000 tonnes between 1983 and mid-1990s. The total emissions of lead have been decreasing in most industrialized countries and the release to the aquatic environment decreased due to improved treatment of wastewater.

However, lack of public awareness and limited industrial waste management capacity in many developing countries, including Latin America and small developing island states (SIDS), cause lead containing products to be inappropriately disposed of. Open burning of waste products containing lead is probably an important source of local and regional lead emissions to the atmosphere as well as illegal dump sites and disposal in wetlands and rivers (UNEP 2008a). The use of lead in some developing countries has continued or increased in, for example, the the manufacture of plastics and paints. According to UNEP (2008a), the health effects from lead exposure and impact on development may cause significant economic losses for society.



Human activities have resulted in elevated cadmium concentrations in the environment. The global cadmium production has almost doubled between 1950 and 1990. Since then, the global consumption has remained constant, at about 20 000 tonnes per year (UNEP 2008b),


Cadmium deposition in the 1960’s and 1970’s, based on analysis of Greenland ice cores, was eight times higher than in pre-industrial times. However, according to recent data, cadmium deposition levels have declined since the 1970’s (UNEP 2008b). Between 1990 and 2003, data show that the anthropogenic emission of cadmium decreased by an average of 50% in developing countries.


According to UNEP (2008b), a study done in the mid 1990’s estimated a global anthropogenic atmospheric emission of  2 983 tonnes. The main sources of emissions are non-ferrous metal production and fossil fuel combustion.  Global atmospheric cadmium deposition to the aquatic environment, originating from anthropogenic sources, is estimated to be between 900 and 3 600 tonnes (UNEP 2008b).


In some developing countries, the use of cadmium has continued or increased. Regulations and restrictions are less comprehensive and hazardous disposal practices like open burning or dumping in rivers and wetlands have resulted in health and environmental risks (UNEP 2008b). According to Greenpeace (1998), some 250 000-500 000 humans may suffer from renal dysfunction as a result of cadmium exposure.


In agricultural soils, cadmium is mainly deposited through atmospheric deposition, phosphate fertilizers and sewage sludge. Since plants are taking up cadmium this can result in an increase concentration in food products (UNEP 2008b).



Mercury, Lead and Cadmium in the Wider Caribbean Region

Many of the Central American and Caribbean countries have high volcanic activity which is a significant natural source of mercury. While the use of Mercury in fungicides and insecticides has been banned in most countries of the region it is still produced as a by-product in gold mining, non metal extraction, dental laboratories and hospitals, fish canning, municipal waste, mercury lamps, batteries and electrical components (de la Cruz 2002). According to Carré (2002) found in UNEP (2002a), organic mercury components are imported by paint companies in Haiti. In a Venezuelan gold mining area, 69% of the miners and 37% of non-miners were contaminated with mercury in 1990 (UNEP 2002a).


According to UNEP (2008c), leaded gasoline was still used in Trinidad and Tobago until April 2004. In Panama, lead was added to petrol until 2001, in Dominican Republic until 1999 and in Guyana until 2000 (UNEP 2002a). At the end of 2005, Cuba prohibited future import and use of Lead Tetraethyl (UNEP 2008c). However, according to UNEP (2008c), tetraethyl lead in gasoline is present in 0.44% of the produced gasoline in Cuba. According to UNEP (2002a), leaded petrol was also banned in Jamaica and Costa Rica but information regarding this issue was not available for the other countries in the region. (Leaded gasoline has actually been phased out in most if not all of the English Speaking Caribbean Countries as part of that global phase out effort – I am sure we can find a reference for that somewhere)


A source of lead in all countries within the region is lead-acid batteries used in vehicles and various industrial applications. In Trinidad and Tobago slag from a secondary lead smelter was deposited at landfills and used in road constructions resulting in lead levels as high as 12% around homes and high blood levels of some residents (UNEP 2002a).  According to UNEP 2006b coastal areas near to oil installations show significant heavy metal concentrations in sediments. At the coast of Santo Domingo (Dominican Republic) and Havana Bay (Cuba), which have petrochemical complexes in the proximity of the coasts, lead values of up to 113 mg/kg and 340 mg/kg respectively were observed (GEF/UNDP/UNEP 1998, Beltrán et al 2002).  Other lead contaminated sites have been identified in the parishes of St.Catherine and St.Andrew in Jamaica, where the source was illegal dumping of used lead acid batteries (Chin Sue 2002).


In the port of Cartagena (Colombia), the sediments contain heavy metals including copper, cadmium, chromium, lead, zinc and mercury which have accumulated as a result of previous activities and discharges. Marine activities like dredging in ports, disturb the polluted sediments so that they are suspended in the water column where they are ingested by marine organisms, such as mollusks, and then passed through the food chain (UNEP et al 2006).


Antifouling paints used on vessels is also a concern, considering the growing recreational boating sector and servicing facilities in the region (UNEP 2006b). Antifouling paints, containing copper or tributyltin, discourages the growth of life on submersed hulls boats.



Laws, Regulations, and Policy Responses on Heavy Metals

According to UNEP (2002a) there is lacking legislation and regulations concerning the import, export, transport, use, production, emission, storage and disposal of Persistante Toxic Substances (PTS) including heavy metals in the region. Ratification of International Conventions relevant to PTS and harmonization of legislation within the Region has taken place to some extent (UNEP 2002a).


The most important regional legal framework 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 reducing pollution by heavy metals 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 includes heavy metals and their compounds. By ratifying/acceding to the LBS Protocol, governments agree to, e.g. establish assessment and monitoring programmes, carry out environmental impact assessments, develop information systems, consider transboundary movements of pollution, and promote education and awareness for pollution prevention, reduction and control.

There are a number of International Conventions dealing with heavy metals:

  • Convention on Long-Range Transboundary Air Pollutants (LRTAP), Protocol on Heavy Metals. 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 Protocol targets three particular harmful metals: mercury, lead and cadmium. The Protocol entered into force on 29 December 2003. Read more at http://www.unece.org/env/lrtap/.
  • 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/.
  • 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 entry into force the 17 September 2008. Read more at http://www.imo.org/conventions/mainframe.asp?topic_id=529.


What is the Caribbean Environment Programme (CEP) doing?

The CEP promotes the ratification and implementation of the LBS Protocol. In collaboration with the UNEP GPA, CEP collaborates with the Governments of the Wider Caribbean Region in the development and implementation of National Programmes of Action (NPAs) for the prevention of pollution from land based sources and activities. 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.

In various projects implemented by the CEP, coastal water quality monitoring is taking place in 2008 and 2009 to establish environmental baselines and track changes over time and space. Heavy metal concentrations are measured in coastal waters and sediments of selected hotspots across the region. LINKS to projects:



CEP, in collaboration with the Regional Activity Centre for the LBS Protocol, LBS/RAC-Cimab, is currently updating CEP Technical Report No. 33, dating from 1994, providing a regional overview of land-based sources of pollution. The goal is to update with the best available data the pollutant loadings from industrial, domestic and agricultural sources affecting the marine environment. This project is to be complete by the end of 2008.

Moreover, CEP has collaboration with the BASEL Convention in the development of a Used Lead Acid Battery Strategy for Caribbean and in the promotion of an integrated strategy for managing chemicals and hazardous wastes. LINKS Additionally CEP have a formal MOU with the Basel Convention to promote collaboration on areas of joint interest.CEP is also seeking to strengthen relationships with the LBS RAC for Cleaner Production based in Barcelona, Spain under the Barcelona Convention and Mediterranean Action Plan.


What can you do?

  • Keep yourself informed on the impacts of heavy metals and products containing them and act responsibly in their use and disposal.
  • Always read the labels of products that may contain heavy metals e.g. paints that may contain lead and follow usage and disposal instructions carefully.
  • Protect children from exposure to all heavy metals since babies and young children are more sensitive to such toxic substances.
  • Avoid mercury-silver dental amalgams.
  • Only drink clean water and if possible use a high quality water filtration unit that removes heavy metal impurities.
  • Avoid regular consumption of fish and seafood especially the largest fish (shark, swordfish, tuna) that may have been exposed to industrial discharges especially those containing heavy metals This is particularly important for pregnant women and children.
  • Reduce your exposure to harmful chemicals by eating organically grown food crops and using natural cleaning products.
  • Wash all fruits and vegetables carefully with fresh water to remove traces of pesticides and fertilizers which may contain heavy metals.
  • Buy environmental friendly products whenever possible.
  • Support companies that use less toxic materials in their production processes and demonstrate good corporate environmental stewardship.
  • Support industrial recycling activities such as those for used batteries, used paint, used pesticides, used oil, and electronic wastes such as used computers and cell phones.