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Pesticide and Persistent Organic Pollutants (Pops) Residues in the Environments and Their Effects on Food Safety
2010-12-22
Persistent organic pollutants (POPS) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment (UN Environment Programme). The residues of pesticides and POPs are widely distributed in soil, water, air, living creatures, and crops. POPs such as pesticide chlorinated hydrocarbons (e.g. DDT, drins: aldrin, dieldrin, endrin, etc.), dioxins, and polychlorinated biphenyls (PCBs) are very resistant to natural (biological, chemical and physical) decomposition in the environments, and persistently remain in the soil for decades.

With recent advances in analytical technology, the distribution and dynamics of POPs and ordinary pesticides in the environments can now be traced at their pico- and even nano-levels. Consequently, some POPs have been identified as present in crop produce such as vegetables, fruits, tea leaves, etc. The POPs found in these crops are likely to have been derived from soil, water and air. However, among these three POPs sources, contaminated soil is the most important source. Various pollutants such as POPs and ordinary pesticides are brought intentionally or unintentionally into the soil, and have accumulated through the years. These persistent pollutants remain in the soil for a long time, some of which gradually decompose and are absorbed by the crops, and eventually flow out of the arable land to the surrounding environments.

Global Efforts to Reduce and Eliminate Releases of Pop

With the evidence of long-range transport of POPs to regions where they have never been used or produced and the consequent threats they pose to the global environment, the international community has now, at several occasions called for urgent actions to reduce and eliminate releases of these chemicals. The Stockholm Convention on POPs requires participating parties to develop their respective National Implementation Plan (NIP) to reduce or eliminate releases from unintentional production of POPs, as well as releases from stockpiles and wastes with POPs, for the protection of human health and the environment.

Hence, in 2002, in accordance with the Stockholm Convention, the workshop on "Environment monitoring of POPs in east Asian countries" was held with the participation of 12 Asian countries namely, Cambodia, Indonesia, Japan, Korea, Malaysia, Mongolia, Philippines, Thailand, Singapore, Vietnam and India.

The OECD has likewise proposed a new Chemical Pesticide Guidelines to help member countries in assessing and reducing pesticide risks to human health and the environment. Recently, Japan complied with the new guidelines by drastically revising its Registration of Chemical Pesticide Regulations based upon the concept of "Positive Listing System of Chemical Pesticides." After enforcement of this new registration guideline, the public has become more aware of the need to be vigilant against the increasing presence of pesticide residues in foods. People are now giving more attention to safe foods cultivated with less/no pesticide use, hence, less pesticide residues.

Regional Forum on Pops

Under intensive farming common in Asian small-scale farmers, pesticide spray to the targeted crops also affects other crops and vise versa. Several short-duration crops are planted not far apart from each other on the same plot. Similarly, relay cropping with short-duration crops is common in vegetable production, particularly under protected cultivation. For such mixed culture and relay cropping, pesticides sprayed to the targeted crops can affect not only other crops on the same plot, but also the succeeding crops due to the short time interval. The pesticides applied to the preceding crops cannot be completely decomposed within the Plant Harvest Interval (PHI), and some are left over in soil, and possibly taken-up by the succeeding crops. Thus, the problem of pesticide residue is closely associated with cropping systems adopted in the region, and this will be more serious for Asian small-scale farmers adopting more intensive/complicated cropping systems under the year-round production.

Against this backdrop, FFTC in cooperation with the National Institute for Agro-Environmental Sciences (NIAES), Japan; the Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ), COA, Taiwan ROC; the Taiwan Agricultural Chemicals & Toxic Substances Research Institute (TACTRI); and the National Chung-Hsing University (NCHU), Taiwan ROC, organized the international seminar on Pesticide and Persistent Organic Pollutants (POPs) Residues in the Environments and their Effects on Food Safety in October 2009 in TACTRI, Taiwan ROC. This international seminar aimed to promote a better understanding of the current status of POPs distribution in the environments, particularly in arable soils in the ASPAC region, and to discuss the adverse effects of POPs on food safety based on recent and advanced studies in the region. Standards and appropriate use of chemical pesticides in the context of IPM systems were discussed and recommended for Asian small-scale farmers under intensive farming with short-duration crops such as vegetables.

Prominent pollution sites of POPs in the ASPAC region were identified to be those heavily used for agricultural and industrial purposes. Bio-indicators such as mussel proved to be useful tools for monitoring POPs levels in coastal waters. Mussel samples contain the highest DDT residue in South China coast waters, and much higher PCB residue in developed countries such as Japan than in developing Asian countries. PBDE-polluted regions were closely associated with "e-waste" accumulation.

Half-lives of banned POPs in paddy soils ranged from 3 to 25 years, at first decreasing sharply and then gradually, and remaining in the soil for a long time. This condition requires some measures to reduce the risk exceeding Maximum Residue Limits (MRL) and to minimize surface runoff to aquatic environments. Agricultural products should be managed from farm to table through risk assessment, risk management, and risk communication.

For remediation of polluted soils, aerobic bacteria and fungus decomposing POPs were isolated from soil in Japan, and were proven to decompose more than 50% of various POPs such as triazine, PCNB, PCP, HNB, and drins. Out of 17 plant family entries, only cucurbitaceae accumulated a considerable amount of dieldrin in the shoot. Since more than 80% of grafted seedlings are used in cucumber production in Japan, and varietal differences in dieldrin uptake among Cucurbita spp. were high, it is recommended to use low-dieldrin uptake varieties of squash as rootstock. Zucchini was the greatest accumulator of dieldrin, hence, it is a promising species for phyto-remediation of dieldrin-polluted soils.

Looking Forward

Following are some of the recommendations drawn during the international seminar:

  • 1. Adoption of comprehensive and long-term monitoring of banned POPs for soil, sediment, water, fish, marine mammal, etc., because of their long half-lives and wide distribution through geological and food chains.
  • 2. Hazardous impacts of human exposure by toxic chemicals should be periodically surveyed among people residing in open dump sites in major urban areas, especially those for e-wastes.
  • 3. Quality control of POPs residue analysis should be guaranteed through `Internal Quality Control' and `External Quality Assessment.' However, quality control level should be adjusted according to the purpose, sample, method, sensitivity and precision. A new analytical technique using bioassay has been developed for dioxins and dioxin-like PCBs (DR CALUX) in Taiwan.
  • 4. Proposed simulation models (PADDY, PCPF-1) can be used for `risk assessment' of pesticides on a river basin scale with reasonable accuracy. Practical applications of these models may provide farmers with appropriate water management to minimize the run-off loss of pesticides applied to paddy fields.

The importance of intensifying collaboration among international (FFTC/APO/UNU/UNEP) and national organizations (MARCO-NIAES, etc.) in the ASPAC region was highlighted, toward coming up with long-term on-farm solutions to mitigate the impact of POPs and other pollutants on food safety that are applicable to Asian small-scale farmers under intensive farming systems.

International Seminar on Pesticide and Persistent Organic Pollutants (Pops) Residues in the Environments and Their Effects on Food Safety

  • Held in TACTRI, Taiwan ROC, 26-30 October 2009
  • No. of participating countries: 9 (Australia, Cambodia, India, Japan, Korea, Philippines, Taiwan ROC, Thailand, Vietnam)
  • No. of papers presented: 24
  • No. of participants: 24 paper presenters and about 30 local participants
  • Co-sponsors: National Institute for Agro-Environmental Sciences (NIAES), Japan; Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ), COA, Taiwan ROC; Taiwan Agricultural Chemicals & Toxic Substances Research Institute (TACTRI); National Chung-Hsing University (NCHU), Taiwan ROC

List of Papers Keynote Papers

  • 1. Environmental and biotic contamination by POPs in the Asia-Pacific region
  • - Shinsuke Tanabe, Ehime University, Japan
  • 2. The role of black carbon in environmental fate of persistent organic pollutants (POPs) in soils and effect on food safety
  • - Rai S. Kookana, CSIRO Land and Water Adelaide Laboratory, Australia
  • Resource papers
  • 3. Present and future perspectives on international and domestic POPs situation
  • - Teruo Sato, Ministry of Environment, Japan
  • 4. Pesticide management in Japan and current OECD strategy on pesticide residues in short-term rotational crops
  • - Nobuhiko Nishioka and Mr. Yasuo Kitamura, Food and Agricultural Materials Inspection Center, Japan
  • 5. Temporal changes in POPs of Japanese arable soil
  • - Nobuyasu Seike, National Institute for Agro-Environmental Sciences, Japan
  • 6. Residual characteristics of POPs in soil environment
  • - Oh-Kyung Kwon, National Academy of Agricultural Science, RDA, Korea
  • 7. The control strategies for POPs in Taiwan
  • - Shaw-Ying Yuan, Environmental Protection Administration, Taiwan ROC
  • 8. Long-term monitoring of persistent pesticides in the agricultural environment of Taiwan
  • - Haw-Tarn Lin, Taiwan Agricultural Chemicals and Toxic Substances Research Institute (TACTRI), COA, Taiwan ROC
  • 9. Modeling of pesticide dynamics in rice paddy environments and its risk assessment
  • - Hirozumi Watanabe, Tokyo University of Agriculture and Technology, Japan
  • 10. Distribution of pesticide and POPs in the main rivers in Thai agricultural area
  • - Pakasinee Klaimala, Department of Agriculture, Ministry of Agriculture & Cooperatives, Thailand
  • 11. Persistent organic pollutants in marine organism from South Korea: Potential health risks
  • - Sang Hee Hong, Korea Ocean Research and Development Institute (KORDI), Korea
  • 12. Recent technology on bio-remediation of POPs and pesticides
  • - Kazuhiro Takagi, National Institute for Agro-Environmental Sciences, Japan
  • 13. Recent technology on phyto-remediation and risk mitigation of POPs
  • - Takashi Otani, National Institute for Agro-Environmental Sciences, Japan
  • 14. Quality control of residue analysis of POPs and pesticides
  • - Takashi Yabusaki, Japan Food Research Laboratories, Japan
  • 15. Analysis of POPs residues in food in Taiwan: taking dioxins in milk products as an example
  • - Pao-Chi Liao, National Cheng Kung University Medical College, Taiwan ROC
  • 16. Developing bioassay technique for determination of dioxins and dioxin-like PCBs in feed and egg samples in Taiwan
  • - Tsyr-Horng Shyu, TACTRI, COA, Taiwan ROC
  • Selected country reports
  • 17. Organochlorine pesticide residues in the environment and milk of Philippine buffaloes (Bubalus bubalis) in selected pasture sites in the Philippines
  • - Evangeline Santiago, Natural Sciences Research Institute, UP Diliman, Philippines
  • 18. Risk management of POPs in foods in Taiwan
  • - Ting-Hung Hsieh, Bureau of Food Safety, Department of Health, Taiwan ROC
  • 19. Risk assessment and management for POPs contaminated sites in Vietnam - A case study
  • - Nguyen Anh Tuan, Vietnam Environment Administration, Vietnam
  • 20. POPs pesticide use in Cambodia
  • - Presp Visarto, Department of Plant Protection Sanitary and Phytosanitary, MAFF, Cambodia
  • 21. POPs pesticide contamination in food and environment in India: Study by community groups and monitors
  • - Jayakumar Chelaton, Pesticide Action Network Asia and the Pacific, India

For further information, contact:

Dr. Te-Yeh Ku, FFTC Technical Consultant

Index of Images

  • Figure 1 Dr. Haw-Tarn Lin, TACTRI Associate Specialist, gave an orientation tour of TACTRI's laboratory facilities dedicated to studies and research on pesticide safety use and plant protection techniques in Taiwan ROC.

    Figure 1 Dr. Haw-Tarn Lin, TACTRI Associate Specialist, gave an orientation tour of TACTRI's laboratory facilities dedicated to studies and research on pesticide safety use and plant protection techniques in Taiwan ROC.

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