Persistent Toxic Substances in Vietnam: A Review of Environmental

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Chapter 3

Persistent Toxic Substances in Vietnam: A Review of Environmental Contamination and Human Exposure Nguyen Hung Minh,1 Duong Hong Anh,2 Tran Manh Tri,3 Hoang Quoc Anh,3 Pham Thi Ngoc Mai,3 Vu Duc Nam,4 Pham Hung Viet,2 and Tu Binh Minh*,3 1Center for Environmental Monitoring, Vietnam Environment Administration, Ministry of Natural Resources and Environment, 556 Nguyen Van Cu Street, Hanoi, Vietnam 2Center for Environmental Technology and Sustainable Development, VNU University of Science, 334 Nguyen Trai Street, Hanoi, Vietnam 3Faculty of Chemistry, VNU University of Science, 19 Le Thanh Tong Street, Hanoi, Vietnam 4Center for Training, Consultancy and Technology Transfer, Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam *E-mail:[email protected]

This chapter provides an overview of studies conducted during the last two decades on the environmental contamination and human exposure of persistent toxic substances (PTS) from classic legacy compounds to emerging contaminants, and the emission of unintentionally produced chemicals derived from industrial sectors. While the contamination of classic persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) exhibited relatively low levels as a result of long-term and effective ban, elevated residues were still encountered in some locations within the densely populated metropolitan and industrialized areas such as Hanoi, Hochiminh city and Bien Hoa - Dong Nai industrial zone. A number of recent systematic investigations have also highlighted several hotspots of pollution with elevated concentrations of various PTS

© 2016 American Chemical Society Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


groups. In this context, open landfill dumping sites for municipal wastes and trade villages with informal recycling practices such as e-waste dismantling are remarkable sources of toxic contaminants and their high emission potential has been quantitatively demonstrated. A high degree of environmental contamination and human exposure to polybrominated diphenyl ethers (PBDEs) has been reported in some informal e-waste recycling trade villages in northern Vietnam. In addition, the presence of new and emerging chemicals such as organophosphorous flame retardants, polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) in e-waste recycling sites further substantiated the importance of those recycling areas in terms of posing high risk to human health and natural ecosystem. Polychlorianted dibenzo-p-dioxins and furans (PCDD/Fs) contamination derived from Agent Orange (AO) exhibited considerable decreasing trends in sediments and soils at AO/dioxin contaminated hotspot areas as the result of three decade remediation efforts. However, newly identified sites within the former Airbases in Da Nang and Bien Hoa were still highly contaminated with dioxins and related compounds. Preliminary surveys for unintentionally produced PCDD/Fs and polychlorobenzene compounds [pentachlorobenzene (PeCB) and hexachlorobenzene (HCB)] indicated that waste incineration, steel making and cement production kiln in Vietnam are potential sectors with relatively high emission levels as compared to other countries in the world. Human exposure studies have emphasized the importance of non-dietary exposure pathways such as dust ingestion and air inhalation with relatively high contribution to total intakes, particularly for children as a more susceptible group. Future studies should be focused on the systematic time trends and toxic impacts of PTS in the above pollution hotspots in order to explore preventive measures towards protecting human health and ecosystems.

Introduction Global contamination and negative effects on ecosystem and human health by persistent toxic substances (PTS) are among the most important environmental issues and have received considerable attention during the past four decades. An increasing number of investigations since the early 1990s have highlighted the role of the Asia-Pacific region as a potential source of emission for these chemicals, particularly to pristine areas such as the Arctic and the Antarctic (1, 2). Vietnam is located at the center of the Southeast Asian region; it has more than 3000 km of coastal lines and two major agricultural production areas: the Red River Delta in the north and the Mekong River Delta in the south. 56 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


These deltas, inhabited by approximately more than 30 million people, are two of the most densely populated areas in the world. Because of this strategic geographical position and recent rapid development in agriculture and industry, Vietnam has become an important subject for studies dealing with environmental contamination during the last decade. Dioxin contamination by Agent Orange (AO) has become the most interesting topic for both research and management in Vietnam since mid-1980s. As an agriculture-based country, a high degree of pollution by oganoclorine pesticides (OCPs) has been of concern in Vietnam due to their late ban and extensive usage in both agricultural and vector-born disease eradication purposes. Environmental pollution and human exposure by classic persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) originated from Agent Orange, OCPs and polychlorinated biphenyls (PCBs) in hotspot and point source areas in Vietnam in the context of the entire Asia-Pacific region have been reviewed in terms of spatial and temporal trends, bioaccumulation features and toxic implications (3–5). In recent years, the increasing activities of electrical and electronic waste (e-waste) recycling in developing countries have received global attention because of the release of a wide range of toxic chemicals resulting from the informal and hazardous recycling practices. E-waste recycling sites in Asian developing countries have been identified as hotspots of contamination by different PTS including PCBs (6), brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) (7, 8), and dioxin-related compounds (DRCs) (9, 10). Following these research strategies, a number of in-depth investigations has been conducted during the last two decades in Vietnam to further elucidate and characterize the status of contamination in the environment and the degree of exposure to humans, particularly focused on emerging PTS such as BFRs, perfluorinated compounds (PFCs) and related chemicals. Particular attention has been given for some hotspots areas such as open landfill dumping sites for municipal wastes and informal trade villages for e-waste recycling. As for PCDD/Fs and related compounds, studies on the present status of dioxin in former contaminated hotspots in southern Vietnam have been conducted to understand the present status of contamination and possible improvement of AO derived dioxin contamination status after decades of remediation efforts. In addition, the issue of PCDD/Fs emission from industry has been initiated by Vietnamese laboratories in collaboration with international organizations. Preliminary results of PCDD/Fs emissions and patterns in some potential sectors have been obtained in very recent investigations. This chapter provides a review of the studies dealing with these above-mentioned issues as the most updated information on the status of PTS research in Vietnam during the last two decades. Given that this themed issue features scientific contributions of Vietnamese scientists, this review article is mainly based on the studies implemented in different laboratories in Vietnam in close collaborations with international researches and organizations. However, in view of assessing environmental pollution and human exposure in Vietnam in the context of the entire Asia-Pacific region, data of published studies from other countries/areas in the region were also synthesized to provide an in-depth 57 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

understanding on the possible changes and update on the pollution sources, spatial distributions, inventory and pattern of unintentionally emissions of PTS.


Status of Contamination and Distribution Contamination and distribution of classic POPs such as DDTs, HCHs, PCBs in different countries in the Asia-Pacific region, including Vietnam, have been previously reviewed (3–5). Results from the Asia-Pacific Mussel Watch Program during the period from early 1990s to the early 2000s demonstrated that in general, developed countries and regions with rapid growth in economic and industrialization are significant source of PTS. This feature of contamination was also observed in Vietnam, where high contamination was found in densely populated urban and industrial areas. After 2005, studies started to focus on the fate, accumulation and human exposure of newly emerging PTS such as brominated flame retardants and their alternatives such as oligomeric organophosphorus flame retardants, brominated dioxins and furans (8–12). A comprehensive compilation of residue concentrations of PBDEs, the most important group of brominated flame retardants, in different environmental samples and at different locations in Vietnam, is illustrated in Figure 1. The spatial distributions of OCPs, PCBs and PBDEs were comprehensively examined throughout various lakes and rivers in Hanoi Metropolitan areas (15, 19). The distribution pattern of PBDEs was similar to those of PCBs and DDTs, showing elevated levels in some locations near canals of the Kim Nguu River, flowing through the densely populated area and being affected by local industrial workshops. Unlike DDTs and PCBs, PBDEs residues in sediments of the lakes that receive discharge from the river system were generally lower than those in sediments of rivers. However, the accumulation pattern of all examined PTS along the To Lich River showed relatively uniform distributions with higher levels found in lower streams near densely populated and industrial areas in the center of Hanoi City. The distribution of PTS in lake and river systems in Hanoi suggests the role of human and industrial activities as major factors controlling their transport and fate. To a larger extent, a systematic survey was conducted in Saigon - Dong Nai River on the spatial distribution of PCBs, DDTs and brominated flame retardants comprising PBDEs and hexabromocyclododecane isomers (HBCDs) (13, 20). Relatively similar distribution patterns were observed for all PTS examined, showing higher levels in sediment from canals of the open sewer system of the Hochiminh city metropolitan area and a decreasing gradient towards river and coastal areas (Figure 1). In general, spatial distributions of PTS in sediment indicate the remarkable impacts of human and industrial activities to the occurrence of persistent semivolatile organic contaminants in both small and large scale of aquatic environment. Unlike metropolitan and industrial areas, the distribution of PCBs and PBDEs in lagoon systems in central Vietnam showed generally low and uniform distributions (14). PBDEs in sediment from lagoons were in lower range if compared with other locations in Vietnam, which could be due to the effectiveness of the degradation process, re-suspension and removal (14). In general, recent studies on the spatial distribution of PBDEs showed that 58 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


the occurrence and fate of these substances were similar to those of industrialized chemicals such as PCBs, and are likely affected by extensive human and industrial activities (13, 15).

Figure 1. A compilation of PBDEs residue concentrations in environmental samples from different locations in Vietnam. Data were cited from the following sources: sediment samples: refs. (11–15); indoor dust samples: ref. (12); biota samples: ref. (12, 16–18). 59 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Next to urban areas with high industrial and human activities, the open municipal waste dumping sites and informal trade villages such as e-waste recycling sites have been also regarded as potential sources of various toxic contaminants. In the course of comprehensive programs on POPs contamination in dumping sites of Asian developing countries, the contamination of different groups of PTS, including organochlorine insecticides (DDTs, and HCHs), PCBs, PCDD/Fs and brominated flame retardants (BFRs) in environmental and human samples in dumping sites in Vietnam, have been investigated (17, 21–23). As a result, concentrations of all the examined contaminants (DDTs, HCHs, PCBs, and PCDD/Fs and PBDEs) in soils at dumping sites were apparently greater than in soils collected far from dumping sites (control sites) (17, 24). Among the Asian developing countries surveyed, soils at dumping sites in Can Tho City, Mekong River delta in southern Vietnam contain the highest PBDE levels (25). Evidence for specific accumulation of PBDEs in dumping sites was also encountered in catfish samples collected near dumping sites in Can Tho City (17). DDTs, PCBs and PBDEs concentrations in catfish collected near dumping sites were significantly higher than those in farmed catfish in Mekong River. Specific accumulation patterns of PBDEs were observed in fish collected near dumping sites, indicating possible source of these compounds in open dumping sites (17). These above results suggest the role of the dumping sites as a remarkable source of contaminants. To further elucidate the role of other hotspots as sources of contaminants, residue concentrations of different groups of PTS, including brominated flame retardants (PBDEs and HBCD) and their alternative substitutes such as bisphenol A bis(diphenyl phosphate) (BPA-BDPP), tetrabromobisphenol A (TBBPA), triphenyl phosphate (TPHP), 1,3-phenylene bis(diphenyl phosphate) (PBDPP); PCDD/Fs and dioxin-like PCBs, and brominated dioxins and furans in sediment, indoor dust and breast milk samples reported for some typical e-waste recycling sites in northern Vietnam were compiled in Figure 2. A recent study on human breast milk samples collected from trade villages specializing on collecting and recycling of e-wastes in sub-urban areas of Hanoi has further substantiated the role of the e-wastes as a significant source of BFRs (8). Breast milk collected from women who were directly involved in recycling activities at e-waste dismantling sites contained much higher levels of PBDEs and HBCDs than woman from other locations. PBDEs levels in recyclers from dismantling areas (20 - 250 ng/g lipid wt, mean: 84 ng/g lipid wt) were in the similar range with the highest levels among non-occupationally exposed populations in the USA. Interestingly, PBDEs levels in breast milk of these recycles even exceeded PCBs concentrations, a longer legacy POPs (8). This specific feature of accumulation is only observed in uncontrolled e-waste recycling in Guiyu, southern China (7).

60 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 2. Concentrations of different groups of PTS in indoor dust, sediment and human breast milk samples from informal e-waste recycling sites in Vietnam. Data from ref. (8–12, 26). Abbreviations: MoBPCDD/Fs: monobromo polychlorinated dibenzo-p-dioxins and furans; BTBPE: 1,2-bis-(2,4,6-tribromophenoxy)ethane); DBDPE: decabromodiphenyl ethane; BPA-BDPP: bisphenol A bis(diphenyl phosphate); TPHP: triphenyl phosphate; TBBPA: tetrabromobisphenol A; PBDPP: 1,3-phenylene bis(diphenyl phosphate).



A recent comprehensive survey covering a wide range of samples collected from e-waste trade villages, including obsolete plastic parts, indoor dust, sediment and fish samples, has been conducted to elucidate the integrated picture of contamination and estimate the emission potential from e-waste recycling activities and human exposure through different pathways (12). Accumulation patterns of PBDEs in different kinds of samples collected from e-waste recycling areas indicate the predominance of deca-BDEs in all samples from sources (obsolete plastic parts) to the receiving environment (dust, sediment, and fish). Estimated emission rates of PBDEs from plastic products to dust ranged from from 2.9 × 10-7 to 7.2 × 10-6 (year-1) with a mean value of 2.8 × 10-6 (year-1) (12). These emission factors from the recycling activities in Hung Yen, Vietnam were comparable to those of deca-BDE from the usage of TVs in Japan reported by Sakai et al. (27), indicating high emission potential from obsolete e-waste recycling activities. Overall, these results indicated a long term accumulation of brominated flame retardants in various environmental compartments within recycling areas as a result of emissions from informal dismantling activities. In addition to brominated flame retardants, elevated accumulations of PBDEs alternatives flame retardants such as 1,3-phenylene bis(diphenyl phosphate) (PBDPP), triphenyl phosphate (TPHP) and tetrabromobisphenol A (TBBPA) have been reported (11). This indicates that the types of flame retardants incorporated into the plastic parts of electronic products have been shifted in response of the international regulations of PBDEs. Nevertheless, elevated accumulations of PBDEs, particularly deca-BDEs were found to be ubiquitous in most kinds of samples from recycling sites, and the PBDE levels were markedly higher than those of other contaminants measured from e-waste sites. In particular, PBDEs levels in indoor dust samples from three typical e-waste recycling sites were at least one order of magnitude higher than those of their alternative organophosphorous flame retardants, HBCDs and PCBs; and two orders of magnitude higher than those of PCDD/Fs and PBDD/Fs (Figure 2) (9, 12, 25). It is interesting that PBDD/Fs residue levels in indoor dust were also significantly greater than those of PCDD/Fs, indicating the predominant accumulation and release of brominated toxic chemicals in e-waste recycling sites. Informal dismantling practices and crude thermal processes are considered to be major pathways for the formation and releases of these brominated contaminants (Figure 2) (9). Perfluorinated compounds (PFCs) have recently been investigated extensively worldwide and their accumulation has been reported in water, particulate phase, airborne particulates, sediment, soils, and animals including humans. In Vietnam, information on PFCs contamination in the environment is still limited. Studies are often scattered, and most of them focused on the occurrence of PFCs in surface water environment. Few studies were conducted on human exposure in breast milk and blood in Vietnam within the framework of larger comprehensive investigations, including other countries such as Japan, Korea, China. A compilation of PFCs residue concentrations in different samples is given in Table 1.


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Table 1. Concentrations of perfluorinated compounds (PFCs) in environmental and human samples from Vietnam Samples

Location

n

Unit

PFOS

PFOA

PFNA

Surface water

Hanoi, Da Nang

28

ng/L

0.27 (0.18 - 0.53)

0.78 (0.09 - 18)

0.27 (0.12-0.93)

(28)

ng/L

0.21

0.22 (0.16-0.52)

0.2 (0.1-0.53)

(28)

ng/L

0.1

0.9

Rural site, near Hanoi

ng/L

Persistent Toxic Substances in Vietnam: A Review of Environmental

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