DSpace at VNU: Persistent organic pollutants in Vietnam: Environmental contamination and human exposure

DSpace at VNU: Persistent organic pollutants in Vietnam: Environmental contamination and human exposure tài liệu, giáo á...

Rev Environ Contam Toxicol 193:213–285 © Springer 2008 Persistent Organic Pollutants in Vietnam: Environmental Contamination and Human Exposure Tu Binh Minh, Hisato Iwata, Shin Takahashi, Pham Hung Viet, Bui Cach Tuyen, and Shinsuke Tanabe Contents I Introduction II Production and Use III Contamination Status A Air, Water, Sediments, and Soils B Biological Samples C Foodstuffs D Human Exposure E Dioxin Contamination IV Environmental Behavior and Bioaccumulation A Transport Behavior in Tropical Environments B Bioaccumulation in Biota V Temporal Trends VI Environmental and Human Health Implications VII Conclusions and Recommendations Summary Acknowledgments References 213 215 216 216 230 242 243 244 269 269 272 273 277 282 284 284 285 I Introduction Global contamination and toxic effects of persistent organic pollutants (POPs) have been an emerging environmental issue and have received considerable attention during the past four decades Although the extent of contamination by POPs has been dominant in industrialized nations, an Communicated by G.W Ware T.B Minh, H Iwata, S Takahashi, S Tanabe ( ) Center for Marine Environmental Studies (CMES), Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan P.H Viet Center for Environmental Technology and Sustainable Development (CETASD), Hanoi National University, 334 Nguyen Trai Street, Thanh Xuan, Hanoi, Vietnam B.C Tuyen Nong Lam University, Linh Trung, Thu Duc District, Hochiminh City, Vietnam 213 214 T.B Minh et al increasing number of recent investigations have highlighted the role of the Asia-Pacifi fic region as a potential source of emission for these chemicals, particularly to pristine areas such as the Arctic and the Antarctic (Tanabe et al 1994; Tanabe 2000, 2002; Tanabe and Subramanian 2006) In view of environmental contamination, Vietnam has been well known as a land of extensive spraying of Agent Orange during the Vietnam War The high degree of dioxin contamination in some military bases and Agent Orange-sprayed areas in South Vietnam has received particular attention during the past 30 years In addition to the dioxin contamination caused by Agent Orange, the rapid agricultural and industrial growth in this country lends credence to the widespread contamination of POPs Vietnam is located at the center of the Southeast Asian region (Fig 1); it has more than 300 km of coastal area and two major agricultural production areas: the Red River Delta in the north and the Mekong River Delta in the south These two deltas are inhabited by more than 30 million people and are two of the most densely populated areas in the world The Mekong River Delta has recently become one of the most productive agricultural regions of Southeast Asia Such a strategic geographical position and the rapid agricultural development of Vietnam made this country an important region where extensive studies on environmental pollution have been carried out during the last two decades This chapter provides a comprehensive review of the studies dealing with POPs in Vietnam Available data on POP contamination in Vietnam are compiled on the basis of various investigations in the framework of the Red River Delta Pacific Ocean China India South China Sea Philippines Malaysia a Indonesia sia a Mekong River Delta Fig Map of Vietnam Vietnam is located at the center of the Southeast Asian region: it has two the largest deltas, Red River Delta and Mekong River Delta Organic Pollutants in Vietnam 215 Asia-Pacifi fic Mussels Watch Program, the 21st Century Center of Excellence Program, and the Core University Program supported by the Japan Society for the Promotion of Science (JSPS), which were conducted in our laboratory during the past decade Results of these comprehensive studies are reviewed, and various issues of POPs contamination in Vietnam are discussed in a comparative point of view with the other countries in the Asia-Pacifi fic region In addition, results from other laboratories are also reviewed to help improve insights into the distribution, transport, bioaccumulation, and possible toxic implications on environmental quality and human health This review focuses on the organochlorine insecticides such as 1,1,1-trichloro-2,2-bis(p ( -chlorophenyl)ethane (DDT) and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), and hexachlorobenzene (HCB) Residue levels of industrially derived contaminants such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p - -dioxins and dibenzofurans (PCDD/Fs), and polybrominated biphenyl ethers (PBDEs) are also reviewed II Production and Use In general, information on the production and usage of POPs, particularly organochlorine (OC) insecticides and PCBs in Vietnam, as well as some other developing countries in the East and South Asian region, is still limited or obscure Systematic inventory of toxic manmade chemicals is lacking in these countries because of their limited capacity to conduct comprehensive monitoring surveys Recently, the United Nations Environment Program (UNEP) has initiated various monitoring programs for POPs at regional and global levels, and the results have been summarized at different workshops According to these reports, the active ingredients for insecticides were not produced in Vietnam In fact, before 1985, pesticides such as DDT and HCB were imported from the former Soviet Union and some socialistic countries up to a quantity of 6,500–9,000 t/yr (Sinh et al 1999) The statistical data showed that the total quantity of DDT imported into Vietnam for malaria control from 1957 to 1990 was 24,042 t During 1986–1990, approximately 800 t was used (Sinh et al 1999) These amounts are still lower than those in some other countries in regions such as Malaysia, Indonesia, and India DDT usage for malaria control ceased in Vietnam in 1995, and other insecticides such as pyrethroid compounds have been used as substitutes for DDT (Sinh et al 1999) The information on PCB usage in Vietnam is still obscure Data indicate that about 27,000–30,000 t of oils contaminated by PCBs were imported from the former USSR, China, and Rumania (Sinh et al 1999) In addition, electrical equipment containing PCBs, such as transformers, was also imported from Australia until the mid-1980s (Kannan et al 1995) Yet another possible source of PCBs in Vietnam are the weapons used extensively during the Indochina War (Thao et al 1993a,b) The major 216 T.B Minh et al source of dioxins in Vietnam in the past was Agent Orange and other herbicides sprayed in South Vietnam during the American war Recently, Stellman and coworkers (Stellman et al 2003) provided revised estimates of the amounts of herbicides used in Vietnam During 1961–1971, at least about 45 million L Agent Orange was sprayed (Stellman et al 2003) 2,4,5T, a constituent of Agent Orange, is known to be contaminated with 2,3,7,8tetrachlorodibenzo-p - -dioxin (TCDD) However, the combustion-derived sources of dioxins in Vietnam are unknown Various kinds of combustion processes may facilitate the widespread contamination of dioxins and related compounds in Vietnam III Contamination Status A Air, Water, Sediments, and Soils Comprehensive monitoring surveys have been conducted to examine the distribution of POPs such as PCBs, DDTs, HCHs, and HCB in air, water, and sediments from estuarine environments from various countries in the Asia-Pacifi fic comprising Japan, India, Vietnam, Thailand, Indonesia, Malaysia, the Philippines, and Australia (Iwata et al 1994) These investigations reported the presence of higher residues of DDTs and HCHs in air and water from coastal and estuarine areas in the developing countries of tropical and subtropical regions (India, Thailand, and Vietnam), than in developed nations (Japan and Australia) A compilation of available data for Vietnam is given in Tables and The distribution in air, water, and sediments from north, middle, and south regions of Vietnam showed relatively higher DDT concentrations, supporting the concept of widespread contamination of this insecticide throughout the country This result suggests extensive use of DDT for agricultural purposes in the past and for malaria control until very recently Interestingly, in a survey conducted about 10 yr later than the survey by Iwata et al (1994) (in 1998/1999) covering an extended area along Red River and Duong River, the two biggest rivers in northern Vietnam, elevated concentrations of DDTs, HCHs, and CHLs were reported (Hung and Thiemann 2002) The levels of DDTs, HCHs, and CHLs in Red River and Duong River were apparently higher than those reported in the early 1990s surveys In addition, wastewater collected from extensive human activity areas such as canals of Tu Liem district, a suburb of Hanoi city (northern Vietnam), and Thi Nghe River, Hochiminh (southern Vietnam) contained elevated concentrations of DDTs (see Table 1) It is also interesting to note that levels found in a recent survey (in suburb Hanoi; Hung and Thiemann 2002) were higher than those reported a decade ago (Iwata et al 1994) Although backgrounds of analytical methods and sampling locations are different among studies, these observations suggest that the use of DDT for malaria control was relatively extensive until very recently in both northern and southern Vietnam 1998–1999 Groundwater Mean (range) 1998/99 River water a 1998/99 Lake water Lakes in Hanoi: West Lake, Thuyen Quang Lak Bay Mau Lake and Ba Mau Lake Dry season Rainy season Irrigation canal, Tu Liem, suburb Hanoi Dry season Rainy season Wells, Gia Lam, suburb Hanoi Dry season Rainy season 1990 25 0.6 0.55 0.68 0.29 1.1 4.7 DDTs a 21 (0.81–110) 27 (1.6–130) 0.16 0.13 0.045 0.21 0.07 0.55 CHLs 7.2 (1.6–1.8) 17 (5.5–26) 6.9 (6.0–7.5) 15 (1.2–25) 0.69 (0.26–2.16) 2.9 (1.1–4.8) 32 (0.69–120) 13 (2–51) 17 (1.6–83) 29 (3.1–97) 19 9.5 5.2 3.2 18 1.9 31 HCHs 0.17 (0.11–0.23) 0.21 (0.19–0.22) 0.17 0.09 0.04 1000 pg TEQs/g should be considered for stronger actions such as health studies, exposure investigations, etc (ATSDR guideline, 1997) The Japanese Government recently issued new standards for dioxins in soil, establishing 1000 pg TEQ/g as the maximum acceptable level and those within 250–1000 pg TEQ/g be kept under surveillance Many soil samples in dumping sites from Asian countries including Vietnam contained TEQ concentrations exceeding 250 pg/g TEQs (Fig 20; Minh NH et al 2003), suggesting the necessity of continuous monitoring Particularly, some soils from Cambodia and Hanoi dumping sites contained TEQ concentrations >1000 pg/g, suggesting their potential for causing adverse health risks for humans and wildlife In the perspective of human health implication, surveys conducted in early 1990s on OCs in foodstuffs provided useful information regarding dietary intake of these compounds by Vietnamese (Kannan et al 1992) The estimated average daily intakes based on exposure through foodstuffs to PCBs in Vietnam were higher than India and Thailand, comparable to those reported for developed nations such as the U.S and Germany Particularly, average daily intake of DDTs by Vietnamese was estimated to be 19 μg/person/d, and this value was the highest of countries in the region and in developed nations (Kannan et al 1992) Although the data used for this estimation were reported a decade earlier, this fact clearly suggests elevated exposure to DDTs and PCBs by Vietnamese and that the usage of DDT has been extensive during the past 10 yr Surveys in the framework of the recent Asia-Pacific fi Mussel Watch Program indicated that dietary intakes of DDTs and PCBs from fish fi in Vietnam were higher than those in Cambodia and Thailand, but still lower than those in industrialized nations such as Australia, Japan, and Hong 280 T.B Minh et al Fig 20 Concentrations of PCDD/Fs in soils from dumping sites in developing Asian countries compared with various environmental guideline values (Minh NH et al 2003) Kong (Monirith et al 2000) On the basis of data of average seafood consumption reported by the Food and Agriculture Organization of the United Nations, the average daily intakes of PCBs and DDTs from seafood for different countries in the Asia-Pacific fi region were estimated (Table 6) Interestingly, results again showed that intakes of DDTs by Vietnamese were apparently higher than those reported in other countries examined In addition to the elevated exposure of DDT via seafood to the Vietnamese general population, certain cohorts living near municipal dumping sites may be at a higher risk from dioxins and dibenzofurans A methodical approach has been developed to evaluate the risk of exposure to PCDD/Fs via soil ingestion and dermal absorption (Minh NH et al 2003) Human exposure to PCDD/Fs in soil is considered to be different for children and adults because of differences in ingestion rates as well as body weights of children and adults Intakes of dioxins were estimated to be the highest in people of the Philippines, followed by Cambodia, India, Hanoi (North Vietnam), and Hochiminh (South Vietnam) Intakes of PCDD/Fs by those living near dumping sites in Vietnam were about 2- to 200 fold greater than those of residents in control sites, thus emphasizing greater health risks In addition, it is important to note that the estimated intakes of dioxins via soil ingestion and dermal exposure by children were higher than those for adults, suggesting greater risk of dioxin exposure for Organic Pollutants in Vietnam 281 Table Estimated Daily Intakes of Persistent Organochlorines Via Mussels by Different Populations in Asia-Pacifi fic Region Country Cambodia China Hong Kong India Indonesia Japan South Korea Malaysia Philippines Russia Vietnam Survey year Seafood consumptiona (g person−1 d−1) Intake of PCBsb (ng person−1 d−1) Intake of DDTs (ng person−1 d−1) Intake of HCHs (ng person−1 d−1) 1998 1999–2001 1998–1999 1998 1998 1994 1998 1998 1998 1999 1997 20 71 69 13 52 196 114 156 77 54 47 15 180 260 49 68 5,900 420 160 440 3,400 66 6.6 17,000 8,300 55 52 690 400 220 31 650 1,900