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Source document:
FAO (2004)

Summary & Details:
GreenFacts (2005)
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6. What contaminants are affecting fisheries?

6.1 What contaminants can find their way into fish and seafood?

The source document for this Digest states:

Several organic and inorganic compounds can find their way into fish and seafood. These compounds can be divided into three major groups:

Many of the inorganic chemicals are essential for life at low concentration but become toxic at high concentration. While minerals such as copper, selenium, iron and zinc are essential micronutrients for fish and shellfish, other elements such as mercury, cadmium and lead show no known essential function in life and are toxic even at low concentrations when ingested over a long period. These elements are present in the aquatic environment as a result of natural phenomena such as marine volcanism and geological and geothermal events, but are also caused by anthropogenic pollution arising from intensive metallurgy and mining, waste disposal and incineration, and acidic rain caused by industrial pollution. This is in contrast with organic compounds, most of which are of anthropogenic origin brought to the aquatic environment by humans.

Increasing amounts of chemicals may also be found in predatory species as a result of biomagnification, which is the concentration of the chemicals in higher levels of the food chain. Similarly, they may be present as a result of bioaccumulation, when chemicals in the body tissues accumulate over the life span of the individual. In this case, a large (i.e. older) fish will have a higher content of the chemical concerned than a small (younger) fish of the same species. The presence of chemical contaminants in seafood is therefore highly dependent on geographic location, species and fish size, feeding patterns, solubility of chemicals and their persistence in the environment.

Source & ©: FAO "The State of World Fisheries and Aquaculture, 2004"
Part 1: World review of fisheries and aquaculture, Box 4 


6.2 What are the risks associated with these contaminants?

The source document for this Digest states:

But what are the risks to human health caused by these contaminants as a result of consuming fish and seafood?

Several studies indicate that in the open seas, which are still almost unaffected by pollution, fish mostly carry only the natural burden of these inorganic chemicals. However, in heavily polluted areas, in waters that have insufficient exchange with the world’s oceans (e.g. the Baltic Sea and the Mediterranean Sea), in estuaries, in rivers and especially in locations that are close to industrial sites, these elements can be found at concentrations that exceed the natural load.

Likewise, several studies have concluded that levels of these chemicals in fish intended for human consumption are low and probably below levels likely to affect human health. Nevertheless, they can be of potential concern for populations for whom fish constitutes a major part of the diet and for pregnant and nursing women and young children who consume substantial quantities of oily fish. These concerns can only be clarified if updated and focused risk assessments are conducted.

While scientists and other experts recognize that certain of these elements are present naturally in fish and seafood, some consumers regard their presence even at minimal levels as a hazard to health. Consequently, food scares can be easily started and further amplified if communication is mismanaged – particularly given the growing speed of communication and information dissemination facilitated by the Internet. A number of such scares concerning fish contaminants have recently led to significant negative impacts on fish trade flows.

Example 1: Mercury in fish 

Example 2: Organic pollutants in salmon 

Source & ©: FAO "The State of World Fisheries and Aquaculture, 2004"
Part 1: World review of fisheries and aquaculture, Box 4 


6.3 How can fish safety be controlled?

The source document for this Digest states:

Globalization and further liberalization of the world fish trade, while offering many benefits and opportunities, also present new safety and quality challenges. Fish safety regulators have been applying a host of control measures, from mandating the use of the Hazard Analysis and Critical Control Point (HACCP) system4 to increasing testing, with varying degrees of success. Improved risk-based scientific tools must be adopted so that the fish safety standards reflect the most current and effective scientific methods available to protect public health.

In establishing maximum levels of fish pollutants, regulators need to ensure the highest level of consumer health protection, but they must also take into account the reality of the current background contamination of the environment in order not to endanger the food supply. Concurrently, strategies must be adopted to reduce gradually the background contamination of the environment and lower progressively the maximum levels in feed and foods to follow this downward trend. In addition, consumer information and awareness programmes will be necessary in order to improve transparency and consumer education.

Progress in this area will require enhanced international cooperation in promoting scientific collaboration, harmonization, equivalency schemes and standard-setting mechanisms that are based on scientific principles. The World Trade Organization’s Agreements on Sanitary and Phytosanitary Measures and Technical Barriers to Trade,5 together with the benchmarking role of the Codex Alimentarius Commission, provide an international platform in this respect. Meeting these challenges will be of the utmost importance for fish trade, both in developed and developing countries, particularly as the latter contribute more than 50 percent (in value) of international fish trade.

Source & ©: FAO "The State of World Fisheries and Aquaculture, 2004"
Part 1: World review of fisheries and aquaculture, Box 4