Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines.

This volume documents the proceedings of the meeting convened by SEAFDEC/AQD, FAO/UNDP and CIDA in 20-22 May 1996. Country and area papers on the use of chemicals in various aquaculture systems, and the country regulations regarding their distribution and usage are included. This volume also covers the effect of chemicals on human health and environment, problems with drug-resistant fish pathogens, and the delivery of chemicals through feeds and water.

Recent Submissions

  • Conference paper

    The use of chemicals in aquaculture in Thailand 

    K Tonguthai - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    In Thailand, many chemicals are used to treat diseases of cultured aquatic animals and to improve water quality in culture facilities. Along with the intensification of aquaculture practices that has occurred in recent years in Thailand, chemical use has also increased, particularly in marine shrimp culture. This paper summarizes information on the types of chemotherapeutants commonly used in Thailand, their sources and costs, the treatment regimes used, the adverse impacts that have resulted and the hazards posed. Also included is information on national regulations, a summary of on-going research, and recommendations to aquaculturists, producers and suppliers of chemicals, government agencies and scientists. It is concluded that although chemicals and drugs will continue to play an important role in the development of Thai aquaculture, they must be used with caution to avoid adverse effects such as environmental damage and the development of resistant strains of pathogens. To minimize chemical usage, additional emphasis needs to be placed on developing good management practices for aquaculture systems.
  • Conference paper

    The use of chemicals in aquaculture in Taiwan, Province of China 

    IC Liao, JJ Guo & MS Su - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Aquaculture in Taiwan has a history of more than three centuries. To satisfy consumer preferences, a wide variety of aquatic species, 71 in 1993, are being cultured in Taiwan. It is difficult to control diseases when many species are cultured and stocking densities are high. At present, it is important to manage the use and application of chemotherapeutants effectively. Many aquatic animal diseases fall under the category of potentially curable illnesses. These include diseases of bacterial, protozoan, fungal, and environmental etiologies. This paper summarizes the chemicals used in aquaculture, farm management practices, alternative disease prevention methods, national regulations, and the current research on chemical use for aquaculture in Taiwan.
  • Conference paper

    Workshop summary. 

    JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.) - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Prepared by Rohana P. Subasinghe, Uwe Barg, and Celia Lavilla-Pitogo, Rome, Italy and Iloilo, Philippines, September 1999.
  • Book | Conference publication

    Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia. 

    JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.) - 2000 - SEAFDEC Aquaculture Department
    The use of chemicals is common in various aquaculture systems, as it is in many agricultural practices. However, with growing worldwide awareness of the need for responsible practices in aquaculture, governments and aquaculturists are increasingly concerned with the effects of the use of chemicals in aquaculture, especially those which appear likely to be hazardous to man, cultured stock and/or the environment. The need to synthesize and disseminate information on the use and management of double prime aquachemicals double prime was recognized by the Fishery Resources Division of the Food and Agriculture Organization of the United Nations (FAO) and the Southeast Asian Fisheries Development Center (SEAFDEC) Aquaculture Department, who convened double prime The Expert Meeting on the Use of Chemicals in Aquaculture in Asia, double prime which was held 20-22 May 1996 at the SEAFDEC facilities in Tigbauan, Iloilo, the Philippines. Support was provided by FAO, SEAFDEC and the Canadian International Development Agency s (CIDA) ASEAN Fund. The World Health Organization (WHO) supported the participation of a human health expert. The meeting was attended by 27 participants and more than 70 observers from the public and private sectors of 20 countries. Among the attendees were representatives from the Network of Aquaculture Centres in Asia-Pacific (NACA), the Fish Health Section of the Asian Fisheries Society (FHS/AFS), the Japan International Research Center for Agricultural Sciences (JIRCAS), the GESAMP Working Group on Environmental Impacts of Coastal Aquaculture, and the ICES Working Group on Environmental Interactions of Mariculture. The results of this expert workshop are presented in this volume. They include the texts of presentations on a wide range of topics (thematic reviews) related to the use of chemicals in aquaculture, with emphasis on the Asian Region, as well as country overview papers summarizing the use of aquachemicals in Asian countries. The contributions of the selected participants during the meeting are contained in this volume.
  • Conference paper

    The use of chemicals in aquaculture in Indonesia 

    H Supriyadi & A Rukyani - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Aquaculture systems in Indonesia have developed toward intensive culture. As a result of intensification of fish culture, increased outbreaks of disease have occurred. Various chemotherapeutic agents like antibiotics and other chemicals have been widely used for treatment and prevention of infectious diseases in fish and shrimp farms. Antibiotics such as oxytetracycline, chloramphenicol, neomycin, streptomycin, erythromycin, prefuran and enrofloxacin are used in the treatment of bacterial diseases. Other chemicals such as malachite green oxalate, potassium permanganate, formalin, methylene blue, chlorine and teaseed have been used for the treatment of various diseases. Organic fertilizers, such as chicken manure, and inorganic fertilizers like urea and trisodium phosphate are often applied by shrimp farmers to improve primary productivity in ponds. Bacterial products with trade names like “Multi bacter,” “Enviro star” and “Super NB” have recently been used by shrimp farmers to decompose organic matter resulting from excessive feeding. Feed additives such as vitamin C, “Protec Plus,” and “Super Embak” are used for disease prevention.
  • Conference paper

    The use of chemicals in aquaculture in Malaysia and Singapore 

    S Mohamed, G Nagaraj, FHC Chua & YG Wang - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Aquaculture is an increasingly important force in both the Malaysian as well as the Singaporean economies. In recent years, Singapore has focused on the aquarium fish trade, making it one of the largest ornamental fish production and transhipment centers in the world. Similarly, the Malaysian aquaculture industry has made rapid strides in the last few years and is poised to become a major contributor to the national fish supply by the early part of the next century. A significant trend in both countries has been the growing intensification of culture systems to achieve higher production per unit area. This has led to a greater occurrence of disease, particularly among aquarium fish, shrimp and marine fish farms. To obviate and control these diseases, there has been a concurrent increase in the use of chemotherapeutants. The three major groups of commonly used chemotherapeutants are: topical disinfectants, antimicrobials and probiotics. There is a wide range of topical disinfectants used by aquafarmers. The most common of these include lime, teaseed cake, formalin, benzalkonium chloride, acriflavine, malachite green, hypochlorite and poly-vinyl pyrrolidine. Of these, lime and teaseed cake are used exclusively in ponds, and acriflavine and malachite green only in hatcheries, while the others are used in both systems. Antimicrobials being used include sulfonamides, tetracyclines, nitrofurans, chloramphenicol, oxolinic acid and virginiamycin. A number of other chemotherapeutants are also used, albeit on a limited basis. The current concerns surrounding the use of chemotherapeutants and the legislative framework surrounding their sale and distribution are also discussed.
  • Conference paper

    The use of chemicals in aquaculture in the Philippines. 

    ER Cruz-Lacierda, L De la Peña & S Lumanlan-Mayo - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    The intensification of aquaculture in the Philippines has made the use of chemicals and biological products inevitable. A recent survey conducted nation wide among shrimp and milkfish culture facilities revealed the use of more than 100 products for rearing, prophylaxis, and treatment purposes. The most commonly applied chemicals are disinfectants, soil and water conditioners, plankton growth promoters, organic matter decomposers, pesticides, feed supplements, and antimicrobials. All of these are readily available in the market. The dosages, purposes, patterns of use, origins, and manufacturers of these chemicals and biological products are discussed in this paper.

    The indiscriminate use of chemicals has caused mortalities and morphological deformities in the host and development of antibiotic-resistant bacterial strains. The use of chemicals in aquaculture also poses dangers to public health. Government policies regulating or prohibiting the use ofcertain chemicals for aquaculture have helped curtail the destructive consequences of chemotherapy. Moreover, research institutions have geared their studies towards discovering environmentally safe drugs and other alternatives to disease control. However, these efforts will be futile unless a strong and aggressive campaign on the cautious and restricted use of drugs in aquaculture is conducted among shrimp and fish farmers, drug manufacturers and suppliers.
  • Conference paper

    Government regulations concerning the use of chemicals in aquaculture in Japan 

    MN Wilder - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    In Japan, fisheries research activity is of a very diversified nature and is overseen by the national and prefectural governments. Regarding the use of chemicals in aquaculture, various regulations exist to protect the safety of cultured aquatic animals intended for human consumption. Under Japan’s Drug Laws, certain materials are designated as “medical products” for use in humans and animals, and their usage is strictly regulated. This paper introduces aspects of this legislation as relevant to the aquaculture industry and discusses how they are actually applied on the level of operation. Prefectural fish disease centers and extension services engage in the actual supervision of the use of such designated chemicals. In reference to government research structure, the Ministry of Agriculture, Forestry and Fisheries maintains 29 national research institutes, nine of which are fisheries institutes directly under the Fisheries Agency. The prevention and treatment of fish disease is an important research theme, and programs are being implemented, especially at the National Research Institute of Aquaculture. An auxiliary organ of the Fisheries Agency, the Japan Fisheries Resource Conservation Association operates educational and training programs for employees of prefectural centers and extension services whereby individuals receive certification as fish health specialists.
  • Conference paper

    Ecological effects of the use of chemicals in aquaculture. 

    DP Weston - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Many aquaculture chemicals are, by their very nature, biocidal, and may be released to the surrounding environment at toxic concentrations either through misuse, or in some cases, even by following generally accepted procedures for use. Thus, there is a potential for mortality of nontarget organisms. Illustrations are provided of three classes of aquaculture chemicals and their effects on non-target biota: 1) use of a carbaryl pesticide and mortality of non-target invertebrates; 2) use of an organophosphate parasiticide and suspected effects on nearby biota; and 3) effects of antibacterial residues in aquatic sediments on the associated microbial community. Efforts to assess the risks posed by aquaculture chemicals are often frustrated by a lack of information on environmental fate and effects, and data needs to resolve this situation are identified.
  • Conference paper

    The use of chemicals in aquafeed. 

    M Boonyaratpalin - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    Various chemicals and additives used in fish and shrimp feeds may have impacts on animal health, product quality and the environment. This paper reviews the use and effects of vitamins (vitamins C and E), essential fatty acids, carotenoids, immunostimulants, hormones and attractants added to feeds for cultured fish and shellfish.
  • Conference paper

    Transferable drug resistance plasmids in fish-pathogenic bacteria. 

    T Aoki - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    Chemotherapeutic agents have been developed for treating bacterial infections and have been widely used for cultured fish for the last 30 years in Japan. The extensive use of chemotherapeutants has resulted in an increase in the occurrence of drug resistance in fish-pathogenic bacteria and also in the bacterial flora of the intestinal tract of cultured fish. The kinds of chemotherapeutants used are correlated with the occurrence of the corresponding drug-resistant genes in fish-pathogenic bacteria. Almost all multiple-drug resistant strains are carried on the transferable R plasmid, although resistance in fish pathogens to nitrofuran derivatives and pyridonecarboxylic acids is associated with a chromosomal gene. The DNA sequences of R plasmids generally differ depending on the species of fish pathogen. Exceptions are the R plasmids of Aeromonas hydrophila and A. salmonicida, which have the same resistance markers as chloramphenicol, streptomycin, and sulfonamides (SA); and the R plasmids of A. hydrophila and Edwardsiella tarda, which have the same resistance markers as SA and tetracycline. The fish pathogens A. hydrophila, A. salmonicida, E. tarda, Enterococcus seriolicida, Pasteurella piscicida, and Vibrio anguillarum are all widely distributed in fish farms in various areas, and within each species the R plasmid has an identical DNA sequence. The chloramphenicol resistance (cat) gene of the R plasmid from Gram-negative bacteria was classified into CAT I, II, III, and IV according to the DNA sequence. The cat gene of P. piscicida was classified as CAT I, those of A. salmonicida and E. tarda were classified as CAT II, and that of V. anguillarum was classified as CAT II or IV, depending on the time the strains were isolated. The tetracycline-resistance determinants (Tet), which occur in six classes (Tet A through Tet G), were class D in the R plasmids obtained from strains of V. anguillarum that were isolated from 1989 to 1991. The Tet for strains of V. anguillarum isolated from 1973 to 1977 was classified as Tet B, while for strains isolated from 1980 to 1983 it was classified as Tet G.
  • Conference paper

    Chemicals in Asian aquaculture: need, usage, issues and challenges 

    RP Subasinghe, U Barg & A Tacon - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    This paper outlines the opening introductory presentation made at the “Expert Meeting on the Use of Chemicals in Aquaculture in Asia,” which was held 20-22 May 1996 at the SEAFDEC facilities in Tigbauan, Iloilo, the Philippines. Its purpose is to provide a balanced and realistic perspective on the needs, issues and challenges with respect to the use of chemicals in Asian aquaculture. We hope to assist participants in identifying development opportunities and in differentiating real hazards from hypothetical threats to cultured organisms, end-users and the environment as a consequence of chemical use. We do not attempt to provide answers to issues related to chemicals in Asian aquaculture, but rather offer some basic directives and opportunities to the workshop participants to assist them in their discussions and in the compilation of realistic recommendations.
  • Conference paper

    The use of chemicals in aquaculture in India 

    SC Pathak, SK Ghosh & K Palanisamy - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    A review of the use of chemotherapeutants and other chemicals and drugs in Indian aquaculture is presented. A large number of products are used for various purposes such as soil and water treatments, disinfectants, piscicides, herbicides, organic and inorganic fertilizers, feed additives, therapeutants, and anesthetics. Farm management techniques for the use of chemicals are discussed, as are the hazards posed by, and impacts resulting from chemical use. Other approaches to disease prevention (crop holiday, pond preparation, regulating stocking density, effluent treatment systems) are considered, and national regulations on the use of chemicals in aquaculture and current research being conducted in India are summarized. Recommendations for the improved use of chemicals in Indian aquaculture are provided for farmers, government and aquaculture institutions, the chemical industry, regional and international agencies, and research institutions.
  • Conference paper

    The use of chemicals in aquaculture in the People's Republic of China. 

    J Yulin - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    Aquaculture in China has developed very rapidly in recent years. Chemicals have become important tools in the control of disease and prevention of losses in various culture systems. The occurrence of diseases stimulated the development and production of drugs for aquatic culture systems, and promoted research on chemicals and their applications. Meanwhile, there exist some problems in the application of chemicals; and there are some potential risks in their usage in aquaculture which should not be neglected.

    This paper describes the use of chemicals for the prevention and control of diseases in aquaculture in China. Their production, marketing, and usage, as well as associated problems and adverse impacts are also discussed. Approaches and practices to prevent diseases are also given. National regulations, on-going research and other aspects of the use of chemicals in aquaculture in China are also highlighted.
  • Conference paper

    Antibacterial chemotherapy in aquaculture: review of practice, associated risks and need for action 

    V Inglis - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    This paper briefly reviews the use of chemicals to prevent and treat bacterial diseases in aquaculture, and provides a detailed summary of the current state of knowledge on the development of bacterial resistance to antimicrobial agents in fish and shellfish. The topics covered include mechanisms of resistance, resistance of bacterial fish pathogens, resistance to antibacterial agents associated with use in aquaculture, and factors causing selection of resistant variants. Emphasis is placed on avoiding and solving problems related to bacterial resistance in aquaculture, and recommendations on antibiotic usage in aquaculture are made.
  • Conference paper

    The use of chemicals in carp and shrimp aquaculture in Bangladesh, Cambodia, Lao PDR, Nepal, Pakistan, Sri Lanka and Viet Nam. 

    M Phillips - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    This paper provides an overview on the use of chemicals in seven countries in Asia (Bangladesh, Cambodia, Nepal, Laos PDR, Pakistan, Sri Lanka and Viet Nam), with an emphasis on coastal shrimp aquaculture and inland carp farming systems. The data come primarily from a recently completed survey of aquaculture farms in Asian countries conducted under the ADB/NACA Regional Study and Workshop on Aquaculture Sustainability and Environment. The issues discussed include the types and uses of chemicals in shrimp and carp culture, farm management practices and use of chemicals, hazards and adverse impacts associated with chemical use, alternative approaches to chemical use, and research recommendations. In inland carp farming, apart from lime and fertilizers, which are unlikely to give rise to any significant negative environmental impact, the overall use of chemicals is extremely low. Piscicides are used in some countries to control predators prior to stocking of ponds, but the use of antimicrobials and disease-control chemicals is limited to a small percentage (<5%) of producers. Most small-scale producers, who dominate aquaculture production in these countries, simply do not have the resources or need for such chemicals. The situation is similar in shrimp culture, with lime and fertilizers, followed by piscicides, being the most common chemicals used. The use of antimicrobials increases with intensification in shrimp culture, and these chemicals are mostly used in more intensive shrimp farming. In both shrimp and carp culture, promotion of “primary” health management practices probably offers greatest scope for prevention of aquatic animal disease outbreaks and the need for chemical use.
  • Conference paper

    The use of chemotherapeutic agents in shrimp hatcheries in Sri Lanka. 

    PKM Wijegoonawardena & PPGSN Siriwardena - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDEC
    In Sri Lanka, the active promotion of chemical products to prevent disease in shrimp hatcheries has led to an increase in the use of drugs and chemicals without much emphasis on understanding their efficacies. A survey was carried out to evaluate trends in the use of drugs and chemicals as therapeutic treatments for shrimp-hatchery diseases. A wide range of chemicals and drugs are being used, both for prophylactic treatment and to prevent or control parasitic, fungal and bacterial diseases in hatcheries. Without proper scientific investigation into treatment regimes, there has been a tendency for individual hatcheries to select their own treatment regimes and to do their own experimentation. Little knowledge exists among hatchery operators as to the hazardous effects of the chemicals in use. Lack of legislation on the use of chemotherapeutants in aquaculture has led to the uncontrolled use and improper selection of chemicals for use in shrimp hatcheries.
  • Conference paper

    Preliminary review of the legal framework governing the use of chemicals in aquaculture in Asia 

    A Van Houtte - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    This preliminary review looks into legislation governing the use of chemicals in aquaculture in Asia. Brief assessments are made of the legislation relating to chemical contamination and the use of veterinary drugs and feed additives, a section is dedicated to trade in aquaculture products, and a few conclusions are then drawn. While mandatory measures of control are desirable and feasible, soft law instruments, such as codes of practice and conduct, allow an element of flexibility to be maintained while avoiding undue legislative restraints on scientific and technical progress.
  • Conference paper

    Human health aspects of the use of chemicals in aquaculture, with special emphasis on food safety and regulations 

    P Sinhaseni, M Limpoka & O Samatiwat - In JR Arthur, CR Lavilla-Pitogo & RP Subasinghe (Eds.), Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - SEAFDEC Aquaculture Department
    Safe and wholesome food is essential for good health. Therefore, when one considers health issues related to unsafe foods, recorded morbidity and mortality as well as economic losses in a population must be included. Due to their presence in unsafe food, micro-organisms are generally considered to pose a major risk to human health. In aquaculture, chemicals are used mainly in the treatment and prophylaxis of disease problems, which constitute the largest single cause of economic losses. However, the increasing use of chemicals in aquaculture has led to wide-spread public concern. The concerns related to human health due to chemical use in aquaculture are repeatedly found in the published literature. They include allergic reactions in previously sensitized persons triggered by chemical residues, and the potential impacts on human health resulting from the emergence of drug-resistant bacteria caused by the use of sub-therapeutic levels of antibiotics and by antibiotic residues persisting in the sediments of aquaculture environments. This paper discusses the risk evaluation principles, data requirements and the concept of maximum residue limit. The uncertainties inherent in the process include, but are not limited to, the state-of-the-art of toxicological evaluation, the level of understanding of the environmental transport process of chemicals, the exposure data available, and any assumptions and extrapolations.