March 2003 - Chemical crustaceans: pesticides and prawn farming

Most consumers think of shrimp* as coming from the sea – they are harvested by trawlers, brought to shore and then packed for distribution to restaurants, supermarkets, and other retailers. But these days, nearly one-third of shrimp eaten in industrialised nations comes from farms. The US$7 billion shrimp farming industry has experienced massive growth since its advent in the 1970s, and shrimp are now farmed in over 50 countries(1).
    A variety of systems are used, varying in the degree of intensification employed, with the most intensive farms being found in Asia. The unnaturally-high stocking densities used means that a suite of inputs is needed to maintain productivity. One study of shrimp farmers from three different regions of Thailand found that on average they used 13 different products(2).
    Chemicals used in intensive shrimp farming include fertilizers, disinfectants, coagulants, liming materials, feed additives (e.g. steroid hormones, probiotics, feed attractants, vitamins, and immunostimulants), and antibiotics (e.g. sulfonamides, tetracyclines, quinolones, nitrofurans, and chloramphenicol – the latter two banned in the US and EU)(3).
    Additionally, a number of pesticides are used to kill fish and molluscs before stocking the ponds, whilst others are added to pond water to control bacterial and fungal infections and parasitic worms(4,5). These pesticides, many of which are of concern due to threats they pose to health or the environment, hail from a range of chemical classes (see table).

Health threats
The risks to human health from pesticide exposure have been well-documented(6,7). For example, many organophosphates and carbamates are toxic to the nervous system through cholinesterase inhibition. Poisoning may occur through the skin as well as orally and by inhalation.
    Acute symptoms of exposure to these chemicals range from headache, nausea, dizziness, and anxiety through blurred vision and vomiting, to seizures and death (usually from respiratory failure). Chronic exposure can have similar effects. In addition, pesticide exposure has been linked to a range of serious respiratory diseases, cancers, birth defects and reproductive and neurological disorders.
    Of the pesticides used in shrimp farming, a number are of special concern. Prolonged or repeated contact with trifluralin may cause allergic dermatitis, whilst carbaryl is an irritant and direct contact may cause burns(8). Dichlorvos is classified as a possible human carcinogen(9). In powder form, rotenone is toxic by inhalation and may cause respiratory paralysis(10). Formalin is severely irritating to the eyes, skin and respiratory tract; repeated or prolonged contact may cause skin sensitisation, prolonged inhalation may cause asthma-like symptoms, and it may also be carcinogenic to humans(11).
    Those handling chemicals on shrimp farms in developing countries are generally poor, vulnerable and often lacking education. Inadequate labelling often contributes to a general lack of information about safe and effective use of chemicals in shrimp farming, which can lead to unsafe handling practices such as mixing chemicals with bare hands, overdosing, and not observing withdrawal periods before harvest(12,13). There exists, as a consequence, a real and widespread risk of harm to human health.

Environmental impacts
The effects of these chemicals on the wider environment are largely unknown because their use in shrimp farming is poorly-regulated and monitored. Many of the pesticides (e.g endosulfan, dichlorvos, copper sulphate) used in shrimp farming are very highly toxic to fish and other aquatic organisms.
This is of grave concern given the widespread discharge of untreated shrimp farm effluent into surrounding waters. Intensive shrimp farms require considerable water exchange and organophosphate bath treatments result in the release into the surrounding waters of significant quantities of toxic material liable to affect fish, molluscs and crustaceans, particularly larval stages.
Further effects on non-target organisms may occur as a consequence of the tendency of some of these pesticides (e.g. endosulfan, azinphos-ethyl, trifluralin) to bioaccumulate in fish and marine invertebrates, thus posing threats to organisms higher up the food chain.

Farmed shrimp – the human cost

Shrimp are farmed largely in developing countries but exported for consumption in the industrialised West. Previously a luxury, prices have fallen in recent years but the true cost is much higher and is often transferred to some of the poorest and most vulnerable communities in producer countries. In many cases, the advent of shrimp farming has had serious consequences for such communities. Shrimp farms have polluted agricultural land and water supplies with chemicals and salt. In Indonesia, illnesses have resulted(14) and people have resorted to drinking rainwater. Skin rashes from polluted water are a common problem in such communities. ‘You see this water everywhere, we cannot drink it – we cannot even touch it, because it’s given us skin diseases from the salt and the chemicals in it. The wells are poisoned. If we want drinking water, we have to go to another village to get it’ said Sitalakshmi, whose village in India is surrounded by shrimp farms(15).
Toxic effluent from shrimp farms threatens the wild species, further impacting local communities dependent upon them for food. For example, shrimp farming has been linked to fish deaths and deformities in the Philippines(16) and mass deaths of crabs in Brazil, where one traditional crab collector said ‘How sad it is to wake up and not to have enough food for the children and grandchildren’(17).
Shrimp farms have physically blocked access to traditionally-used coastal resources and, as mangrove forests have been cleared to create shrimp ponds, catches of fish and shell-fish have declined. In some places, land has been seized by force. People have died in at least 11 countries through conflict directly related to shrimp farming, with over 150 deaths in Bangladesh alone(18).

Concluding remarks
Mention pesticide problems and most readers of this journal think of farmers in developing countries being exposed to toxic chemicals as they spray fields. The poorly regulated use of chemicals in shrimp farming world-wide is a little-known hazard that deserves urgent attention.
Research is needed to elucidate the extent of impacts on those handling chemicals, and to the wider environment, especially aquatic ecosystems. The shrimp farming industry must be subjected to scrutiny regarding the types of chemical inputs used and the manner in which they are employed. A precautionary approach should be adopted and the most dangerous (WHO Class Ia and Ib) chemicals should be prohibited immediately. Finally, potential risks to consumers should be considered and responsible authorities should ensure that shrimp are thoroughly screened for dangerous pesticide residues.

* Many people use the words ‘shrimp’ and ‘prawn’ interchangeably, EJF makes no distinction between the two.

New campaign

The Environmental Justice Foundation has recently launched a campaign highlighting the serious environmental and social impacts of shrimp production world-wide. EJF has spent 18 months researching these issues in depth and will shortly be publishing their findings in a series of authoritative reports. Currently, consumers have no guarantee that the shrimp they buy have not been produced in an ecologically devastating or socially unacceptable manner. EJF is raising consumer awareness whilst seeking practical solutions to the problems of shrimp production.

More information can be found at www.ejfoundation.org/shrimp.

Contact: Mike Shanahan (Project Coordinator) or Steve Trent (Director), Environmental Justice Foundation, 5 St Peter’s Street, London N1 8JD, UK. Tel: +44 (0)207 359 0440, Fax: +44 (0)207 359 7123, Email: info@ejfoundation.org,
Website: www.ejfoundation.org

Chemical crustaceans: pesticides and prawn farming

Prawn or shrimp farming is a massive industry located largely on the coasts of developing countries. As the demand for farmed shrimp has increased, the industry has proliferated and use of chemicals has intensified. Mike Shanahan and Steve Trent of the Environmental Justice Foundation report.

Subscriptions

Publications

Email the Editor