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Trang 1Open Dumping Site in Asian
Developing Countries: A Potential
Source of Polychlorinated
Dibenzo-p-dioxins and
Polychlorinated Dibenzofurans
N G U Y E N H U N G M I N H ,† T U B I N H M I N H ,†
M A F U M I W A T A N A B E ,†
T A T S U Y A K U N I S U E ,† I N M O N I R I T H ,†
S H I N S U K E T A N A B E , *, † S H I N I C H I S A K A I ,‡
A N N A M A L A I S U B R A M A N I A N ,§
K A R U P P I A N S A S I K U M A R ,§
P H A M H U N G V I E T ,| B U I C A C H T U Y E N ,⊥
T O U C H S T A N A ,# A N D
M A R I C A R S P R U D E N T EO
Center for Marine Environmental Studies, Ehime University,
Tarumi 3-5-7, Matsuyama 790-8566, Japan, Research
Center for Material Cycles and Waste Management,
National Institute for Environmental Studies, Tsukuba, Japan,
Centre of Advanced Study in Marine Biology, Annamalai
University, Parangipettai, India, Center for Environmental
Technology and Sustainable Development, Hanoi National
University, Hanoi, Vietnam, University of Agriculture and
Forestry, Hochiminh City, Vietnam, Social and Cultural
Observation Unit, Cabinet of the Council of Minister,
Phnom Penh, Kingdom of Cambodia, and Science Education
Department, De La Salle University, Manila, Philippines
Open landfill dumping areas for municipal wastes in
Asian developing countries have recently received
particular attention with regard to environmental pollution
problems Because of the uncontrolled burning of solid
wastes, elevated contamination by various toxic chemicals
including dioxins and related compounds in these dumping
sites has been anticipated In this study, concentrations
of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated
dibenzofurans (PCDFs), and coplanar polychlorinated
biphenyls (PCBs) were determined in soils from dumping
sites in the Philippines, Cambodia, India, and Vietnam Residue
concentrations of PCDD/Fs and coplanar PCBs in dumping
site soils were apparently greater than those in soils
collected in agricultural or urban areas far from dumping
sites, suggesting that dumping sites are potential sources
of PCDD/Fs and related compounds Observed PCDD/F
concentrations in soils from dumping sites in the Philippines
and Cambodia were comparable or higher than those
reported for dioxin-contaminated locations in the world
(e.g., near the municipal waste incinerators and open landfill
dumping sites) Homologue profiles of PCDD/Fs in dumping
site soils from the Philippines and, to a lesser extent, from Cambodia and India reflected patterns of samples representing typical emissions, while profiles of agricultural
or urban soils were similar to those of typical environmental sinks This result suggests recent formation of PCDD/Fs
in dumping site areas and that open dumping sites are a potential source of dioxins in Asian developing countries Uncontrolled combustions of solid wastes by waste pickers, generation of methane gas, and low-temperature burning can be major factors for the formation of dioxins
in dumping sites Elevated fluxes of PCDD/Fs to soils in dumping sites were encountered in the Philippines, Cambodia, India, and Vietnam-Hanoi, and these levels were higher than those reported for other countries Considerable loading rates of PCDD/Fs in the dumping sites of these countries were observed, ranging from 20 to 3900 mg/yr (0.12-35 mg TEQ/yr) PCDD/F concentrations in some soil samples from the Philippines, Cambodia, India, and Vietnam-Hanoi exceeded environmental guideline values, suggesting potential health effects on humans and wildlife living near these dumping sites The estimated intakes of dioxins via soil ingestion and dermal exposure for children were higher than those for adults, suggesting greater risk of dioxin exposure for children in dumping sites To our knowledge, this is the first comprehensive study on PCDD/Fs contamination in open dumping sites of Asian developing countries On the basis of the result of this study, we have addressed a new environmental issue that open dumping sites are potential sources of PCDD/Fs and related compounds, and dioxin contamination in dumping sites may become a key environmental problem in developing countries.
Introduction
(PCDDs) and polychlorinated dibenzofurans (PCDFs) is a growing concern because of the toxic effects on human health and wildlife These compounds were unintentionally formed during various combustion processes and are impurities of chlorinated chemicals that were used in large quantities as herbicides and wood preservatives Combustion is believed
to be the major source of PCDD/Fs to the environment (1).
Once emitted, PCDD/Fs undergo various processes such as dispersion and reaction in/through the atmosphere, deposi-tion into the earth’s surface, and eventually accumuladeposi-tion in
human and wildlife tissues (2, 3) In recent years, a number
of extensive investigations have been conducted in some developed nations such as the United States, United King-dom, and Japan to elucidate the transport behavior, global fate, and emission/deposition of PCDD/Fs using soils as a
suitable sampling matrix (3-8) Research in the United States
indicated that municipal waste incineration was a consider-able source of PCDD/Fs to the atmosphere and that a global emission rate derived from municipal waste incineration was
1130 kg/yr (5) In the United Kingdom, Jones and co-workers
measured PCDD/F concentrations in various environmental compartments and suggested that volatilization from soils was one of the major sources of dioxins to the atmosphere
(3).
* Corresponding author telephone/fax: +81-89-946-9904; e-mail:
shinsuke@agr.ehime-u.ac.jp
†Ehime University
‡National Institute for Environmental Studies
§Annamalai University
|Hanoi National University
⊥University of Agriculture and Forestry
#Cabinet of the Council of Minister
ODe La Salle University
10.1021/es026078s CCC: $25.00 2003 American Chemical Society VOL 37, NO 8, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 91493
Trang 2Despite the fact that PCDD/F contamination has been
extensively studied in developed nations, very little is known
about their behavior, fate, and ultimate sources in developing
countries In recent years, public media have voiced concern
regarding the open dumping sites in Asian developing
countries where large amounts of municipal solid wastes
have been dumped Unfortunately, in most of the developing
countries in Southeast Asia, such open dump areas are located
near human habitats; therefore, exposure to various toxic
chemicals that originated from dumping sites are of serious
concern because of the effects on human health, wildlife,
and environmental quality (9) Uncontrolled burning of solid
waste by waste pickers, generation of methane gas, lack of
advanced waste incineration technology, and natural
low-temperature burning are major problems in dumping sites
in Asian developing countries at present These are favorable
factors for the formation of dioxins and dibenzofurans
Because of these reasons, we anticipated elevated
con-tamination by PCDD/Fs in dumping site environments in
Asian developing countries Our laboratory has conducted
a comprehensive research to find an answer to the question
of whether open dumping sites in Asian developing countries
are potential sources of dioxins and related compounds In
this study, soil samples were collected in open dumping sites
from the Philippines, Cambodia, India, and Vietnam, and
concentrations of PCDDs and related compounds such as
PCDFs and coplanar polychlorinated biphenyls (PCBs) were
measured Soils from agricultural and urban areas, located
far from dumping sites, were also examined for PCDD/Fs to
elucidate the differences in dioxin accumulation in dumping
sites and agricultural areas and whether dumping sites are
sources of PCDD/Fs The annual loads of dioxins into
dumping site areas were also estimated to give further insight
into the fate of dioxins in tropical environment
Materials and Methods
Samples Soil samples were collected in open dumping sites
in Manila (Philippines), Phnom Penh (Cambodia), Chennai
(India), and Hanoi and Hochiminh (two cities in Vietnam)
during 1999-2001 Details of samples and characteristic of
dumping sites are given in Table 1 The sampling map and
other relevant information can be found in the Supporting
Information Those open dumping sites are located close to
human habitat, and there are large numbers of people
scavenging in these dump sites for collecting recycling wastes
In dumping sites in Cambodia, uncontrolled burning of solid
wastes was observed Some figures of open dumping sites
in Cambodia and India can be found in the Supporting
Information Soil samples were collected at depths from 0
to 10 cm at five points with an area of approximately 25 m2
and combined together and considered as a representative
sample Urban or agricultural soils were also collected at
some locations far from the dumping site areas (at least 30
km from dumping sites) Soil samples collected from these
locations hereinafter are referred to as “control sites” relative
to dumping sites Soils were kept in clean plastic bags,
maintained at 4°C, transported to laboratory, and stored at
-20°C until chemical analysis
Chemical Analysis Chemical analyses of PCDD/Fs and
coplanar PCBs followed the method of the Environmental
Agency of Japan with some modifications Soil samples were
dried and sieved using a 2-mm sieve before analysis About
10-30 g of dry soil samples was extracted in a Soxhlet
(2378-T4CDD/F, 12378-P5CDD/DF, 123678-H6CDD/F,
coplanar PCBs (77, 81, 118, 126, 156,
CB-167, CB-169, and CB-189 for the respective coplanar PCBs;
dumping sites control sites
area (m
2 ) capacity (t/day)
a More
b More
c na,
Trang 3centrated extract as internal standards For checking the
extraction efficiency, we used repeated Soxhlet extraction
procedure (2 times) for soil samples PCDD/Fs in the second
extracts remained at the residues less than 5% of the
concentrations in samples the used the first extraction The
extract, after adding internal standards, was then applied to
a multilayer silica gel column, and PCDD/Fs and PCBs were
eluted with hexane The hexane was concentrated and further
passed through an activated carbon-impregnated silica gel
column to separate mono-ortho coplanar PCBs and PCDD/
Fs and non-ortho coplanar PCBs The first fraction eluted
with 25% dichloromethane in hexane contained mono-ortho
coplanar PCBs The second fraction eluted with toluene
contained PCDD/Fs and non-ortho coplanar PCBs The first
fraction was then further cleaned up by passing through an
activated alumina column, and PCB congeners were eluted
1234-T4CDD and 123789-H6CDD prepared in decane were
added into the final solutions of first and second fractions,
respectively All fractions were microconcentrated and
injected into a high-resolution gas chromatograph coupled
with a high-resolution mass spectrometric detector
(HRGC-HRMSD) for quantification
Mono-ortho PCBs were quantified using a gas
chromato-graph (Agilent 6980N series, Wilmington, DE) with an
auto-injection system and a benchtop double-focusing mass
selective detector (JEOL, GC-Mate II, Tokyo, Japan) at a
resolving power of >2000 The GC column used was DB-1
fused silica capillary (0.25 mm× 60 m; J&W Scientific Inc.,
Folsom, CA) having 0.25 µm film thickness with deactivated
fused silica guard columns at both ends The quantification
of non-ortho coplanar PCBs and PCDD/Fs was performed
using a GC (Agilent 6890N series) coupled with a
high-resolution mass selective detector (JEOL JMS-700D) at a
J&W Scientific Inc.) fused silica capillary column was used
for separation of non-ortho PCBs and hepta- and octa-CDD/
thickness; Varian, Walnut Creek, CA) capillary column for
tetra- to hexa-CDD/Fs Equipment were operated at an EI
energy of 38 eV, and the ion current was 600 µA PCDD/F
and coplanar congeners were monitored by selective ion
monitoring mode at the two most intensive ions of the
molecular ion cluster, except for P5CDD at ions of M+and
[M + 2]+ All the congeners were quantified using the isotope
dilution method to the corresponding13C12-labeled congeners
if the isotope was within 15% of the theoretical ratio and the
peak area was more than 5 times noise or procedural blank
level Detection limit for tetra- and penta-CDD/Fs was 1 pg/g
dry wt; hexa- and hepta-CDDs was 2 pg/g; OCDD/F was
5 pg/g dry wt; and non-ortho coplanar PCBs was 1 pg/g
dry wt
A procedural blank with every set of 6 samples was
analyzed to check for interfering compounds and to correct
samples values, if necessary Recoveries for 13C12-labeled
PCDD/Fs and coplanar PCBs, which were added prior to
multilayer silica gel column, ranged within 60-120%
Varia-tion of concentraVaria-tions between duplicate analyses of soil
samples was within 15% for congener concentrations with
signal-to-noise (s/n) ratio >50 and was within 30% for those
with s/n ratio of 5-50
Results and Discussion
Residue Levels Average concentrations of PCDD/Fs in soils
from dumping sites were the highest in the Philippines,
followed by soils in Cambodia, India, Hanoi, and Hochiminh,
Vietnam in that order (Table 2) A full database of
concen-trations of individual soil samples from all the surveyed Asian
countries can be found in the Supporting Information
Elevated residues were found in soils from dumping sites in
the Philippines and Cambodia, ranging from 44 000 to 75 000 and from 330 to 200 000 pg/g dry wt, respectively In particular, few soil samples in Cambodia had extremely high concentrations of PCDD/Fs (up to 200 000 pg/g dry wt) Soils from the dumping site in Hochiminh City, Vietnam, ac-cumulated the lowest PCDD/F residues (ranging from 130
to 260 pg/g dry wt) Soils collected from agricultural or urban areas located far from dumping sites were considered as the control samples for corresponding dumping soils Interest-ingly, the control levels of PCDD/Fs ranged from 33 to 370 pg/g dry wt, which was substantially lower than those in soils from dumping sites in most of the countries surveyed, except in Hochiminh (South Vietnam) (Table 2) The magnitude of contamination of dumping site soils was apparently greater than that in control sites, suggesting that open dumping sites are a potential source of dioxins and related compounds in Asian developing countries The trend of contamination by non- and mono-ortho coplanar PCBs was somewhat similar to that of PCDD/Fs with the concentrations ranging from 900 to 42 000 pg/g dry
wt in dumping sites and from 3 to 160 pg/g dry wt in control sites (Table 2) Their contribution to total TEQs was also different between dumping and control sites, which were 10-57% and 5-20%, respectively In dumping sites, the highest coplanar PCBs concentration was found in the Philippines, and the lowest was in Hochiminh, Vietnam However, their concentrations in the control group were the highest in Hochiminh followed by Hanoi (North Vietnam), India, and Cambodia (control site in the Philippines was not investigated) This result indicates considerable background contamination of coplanar PCBs in Vietnam In general, elevated accumulation of PCDD/Fs and coplanar PCBs in landfill soils from the Philippines, Cambodia, and India is of concern and suggests that the formation of dioxins in these dumping site areas was significant in addition to the atmospheric deposition Considering that there were no municipal waste incinerators located near such dumping sites (Table 1), uncontrolled burning of solid wastes by waste pickers and low-temperature burning with the formation of natural (methane) gas are probably the plausible explanations for the formation of dioxins in dumping sites
Observed PCDD/F residue levels in control sites from the Philippines, Cambodia, India, and Vietnam in this study were comparable or lower than levels reported for general soils from other countries, while soils collected in the dumping sites showed much higher levels (Table 3) To our knowledge, this is the first comprehensive data of PCDD/Fs and related compounds in dumping soils from Asian developing coun-tries, which were comparable or greater than those in soils from dioxin-contaminated sites reported in developed na-tions Our result, therefore, highlights the role of dumping sites as a significant source of PCDD/Fs
Residue levels of PCDD/Fs from the soils of dumping sites were also compared with those in soils from other locations around the world that were reported as dioxin-contaminated sites (Table 3) In the present studies, sampling was conducted at the dumping sites (representing the sources) and control sites (representing background loca-tions) The cited data from literature represent the concen-trations in soils from the environments that are impacted from the municipal waste incinerator, open landfill dumping
sites, and HCH manufacturing waste site (11-15) In such
studies, soils were collected from the sources, from the control sites, and along gradients in the vicinity of the sources Nevertheless, these levels also reflect the magnitude of contamination in the source allocations We compared our data to those from these studies to understand the magnitude
of dioxin contamination in dumping sites from Asian developing countries and to demonstrate the role of these dumping sites as significant sources of dioxins and
Trang 4diben-TABLE 2 Concentrations (pg/g dry wt) of PCDD/Fs and Coplanar PCBs in Soils from Dump Sites and Control Sites in Asian Developing Countries
Philippines Cambodia India Vietnam-Hanoi Vietnam-Hochiminh dumping site dumping site control site dumping site control site dumping site control site dumping site control site concn TEQs a concn TEQs concn TEQs concn TEQs concn TEQs concn TEQs concn TEQs concn TEQs concn TEQs
OCDD 12 000 1.2 1 400 0.14 39 0.004 1 900 0.19 21 0.002 480 0.048 270 0.03 220 0.02 100 0.01
total PCDD/Fs 61 000 520 30 000 390 130 1.9 7 400 47 33 0.20 6100 95 370 1 370 2.21 190 1.15
000-75 000
400-630
330-200 000
1.4-1 700
40-370
0.031-4.5
2
200-34 000
9.9-200 18-79
0.05-0.34
125-50 125-500
0.4-850
370 1 21-880
0.02-4.4
130-260
0.36-1.2 non-ortho
coplanar PCBs
2 500 21.00 1 100 11.0 0.9 0.0001 570 4.05 1.8 0.018 410 7.00 6.4 0.081 54 0.36 11 0.103 mono-ortho
coplanar PCBs
39 000 5.50 6 500 1.1 10 0.0016 6 100 1.00 26 0.004 2 200 0.32 120 0.016 860 0.13 150 0.021 total coplanar PCBs 41 500 26 7 600 12.0 11 0.0017 6 670 5.1 28 0.022 2 600 7.30 130 0.097 910 0.49 160 0.124
000-83 000
17-34
590-24 000
1.1-27 10.9 0.0017 1
300-20 000
2.4-10 12.0-52
0.015-0.029
59-7 100
0.22-59 120 0.097
65-2 000
0.01-1.0
46-300
0.027-0.19
a TEQs were calculated using WHO-TEF [Van den Berg et al ( 10)].
Trang 5zofurans Interestingly, concentrations of PCDD/Fs in some
soil samples from Cambodia, the Philippines, and India were
higher than those reported in soils from Ohio, USA (mean
concentration of 15 700 pg/g dry wt), which was near a
municipal solid waste incinerator emitting large amount of
dioxins (1000 g TEQ/yr) Similarly, an open landfill site in
Crete, Greece, where uncontrolled low-temperature
com-bustion was noticed for more than 10 yr, has an extremely
high concentration of PCDD/Fs (92 000 pg/g dry wt) in a site
close to the burning areas (12) Likewise, three soil samples
collected in Cambodia, two in Philippines, and one in Hanoi,
Vietnam, contained PCDD/F concentrations >50 000 pg/g
dry wt Given that there were no industrial or waste
incineration activities in all those areas, elevated
concentra-tions of PCDD/Fs again indicate that open dumping sites
with uncontrolled burning processes are significant sources
of dioxin formation In this context, however, further studies
to examine the extent of PCDD/F contamination along the
gradient in the vicinity of the dumping sites would provide
more detailed insights into the impacts of dumping sites
emissions
Though reaction mechanisms of dioxin formation are believed to be very complex, the combustion, particularly the combustion of chlorinated waste, is the major source of
PCDD/Fs to the global environment (5) Katami and co-workers (17) evaluated the contributions to dioxins formation
from combustion of some polymer materials such as polyethylene (PE), polystyrene (PS), and poly(vinyl chloride) (PVC) Of the examined polymers, PVC contributed signifi-cantly to the formation of PCDD/Fs and coplanar PCBs Under poorly controlled conditions such as low temperature and high CO concentration, a level up to 8920 ng/g PCDD/
Fs was found in emission gases Common applications of plastics in daily use products and industries together with the lack of proper management of waste materials in developing countries have led to huge dumping of chlorinated wastes such as poly(vinyl chloride), chloromethane, chloro-phenols, etc in landfills everyday Given this fact, we suggest the possibility of the considerable formation of PCDD/Fs in those dumping sites
Homologue Profiles To further understand the role of
the dumping sites as a source of PCDD/Fs, we examined the
TABLE 3 Comparison of PCDD/Fs Concentrations (pg/g dry wt) in Soils from Dumping and Control Sites in Asian Developing Countries with Those in General and Contaminated Soils from Other Locations in the World
soils from
(44 000-75 000)c (14-100) uncontrolled burning
nrd
nr
(3-252)e
nr
(31-42)
(2 500-8 650)
(49-1 900)
(6.2-250)
(94-490)
(1600-2400)
(130-500)
(286-300)
(21/1.9 TEQ)b
(647-650)
a Mean concentratration b pg/g WHO-TEQs were reported in mean values if available c Range concentration d nr, not reported e Concentrations were reported as pg/g I-TEQs f Urban/rural soils.
Trang 6homologue profiles of PCDD/Fs in dumping soils and control
soils Their PCDD/Fs homologue profiles were then
com-pared with typical profiles of samples representing
envi-ronmental sources (municipal waste incinerator emissions)
and sinks (urban soils, sediments, or atmospheric deposition
samples) (Figures 1 and 2) Samples representing
environ-mental sources were an emission of a typical municipal waste
incinerator in the United States (5) and an average of 12
different combustion sources (18), while environmental sinks
were soils collected from various locations over the world by
Hites and co-workers in a Indiana University laboratory (18).
In general, the homologue profiles of sample representing
environmental sources are characterized by the
predomi-nance of lower chlorinated dibenzofurans and an increasing
proportion from tetra- to hexachlorinated dibenzo-p-dioxins.
On the other hand, the typical pattern of environmental sink
samples contains OCDD as predominant congener The
differences could be due to the differential losses of PCDD/
Fs through reactions with a hydroxyl radical during
atmo-spheric transport and deposition and the additional
pho-tochemical generation of OCDD and, to lesser extent, HpCDD
from pentachlorophenol (5).
Comparisons of PCDD/Fs homologue pattern of samples
in the investigated areas with these typical patterns of sources
and sinks could provide insight into the sources and status
of formation of PCDD/Fs in dumping sites Interestingly,
homologue profiles of the dumping soils from the Philippines,
India, Cambodia, and one soil sample from Hanoi, Vietnam,
reflect a pattern of emission sources (Figure 1) Profiles of
the control soils, in contrast, were similar to those of typical
environmental sinks (Figure 2) PCDD/F profiles of dumping soils from the Philippines and Cambodia were most similar
to those of emission sources, suggesting recent formation of dioxins in these dumping sites Homologue profiles in soils from Hochiminh, Vietnam, resemble those of environmental sink samples and are also similar to those of soils from control sites in other countries (Figure 2) This fact together with the relatively low residue levels of PCDD/Fs and coplanar PCBs might indicate less dioxin formation in Hochiminh dumping sites
As for coplanar congener patterns, non-ortho congener CB-126 predominantly contributed to total TEQs (>95% of the total TEQs) in most of the soil samples from dumping and control sites in the Asian countries surveyed (see data
in Table 7 in Supporting Information for further details) The formations of coplanar PCBs have been hypothesized through three alternative processes including release from commercial PCBs mixtures, emission from combustions, and to a lesser
extent, solar photolysis of higher chlorinated PCBs (19) In the United Kingdom, Alcock et al (20) reported that TEQ
input of coplanar PCBs from Aroclor formulations into environment was mainly contributed by PCB congeners
CB-77, -105, -118, -156, and to a lesser extent CB-126 Combustion source emissions were dominated by non-ortho PCBs, in which congener CB-126 predominantly contributed to total
TEQs (19) Besides, it should be noted that CB-126 could be also formed during the domestic burning process (21) Our
result suggests that uncontrolled burning of solid wastes in dumping sites in Asian developing countries could be a source
of coplanar PCBs
FIGURE 1 Homologue profiles of PCDD/Fs in soils from dumping sites in Asian developing countries in comparison with the profile of samples representing emission sources (municipal waste incinerators) Vertical bars represent the percentage of each homologue to total PCDD/F concentrations F and D refer to dibenzofurans and dibenzo- p -dioxins, respectively Numbers indicate the degree of chlorination Data for emission source samples were cited from ref 18 Profile of emission sources (a) represents a typical emission of a municipal waste incinerator reported in ref 5 Profile of emission source (b) represents an average of 12 different combustion sources reported in ref 18 Profile of Hanoi (a) was illustrated on the basis of one sample with the highest PCDD/F concentration Profile of Vietnam-Hanoi (b) was illustrated based on the average concentration of other remaining samples See Supporting Information for further details.
Trang 7Flux and Load of PCDD/Fs to the Dumping Sites.
Recently, Hites and co-workers (4-6) have demonstrated
that soil is a useful environmental matrix to estimate the
deposition of PCDD/Fs on a global scale This is because soil
can act as a passive collector of atmospheric deposition and
is easy to collect worldwide In addition, soils are excellent
reservoirs of dioxins and related compounds as these
chemicals are very persistent in soils with long biological
half-lives, approximately 9-15 yr (4) In this study, we used
the same approach that was reported by Hites and co-workers
(4-6) to estimate the flux of PCDD/Fs to the soils and their
load to the dumping site areas in Asian developing countries
Flux to soils can be calculated by the following equation:
where F is depositional flux to soils (ng m-2yr-1); C is the
concentration in soils, M is the mass of soils collected (g),
S is the surface area of soil sample (m2), and t is the
accumulation time of PCDD/Fs in the soil compartment (yr)
For soils in open dumping sites, t values were calculated on
the basis of the time when dumping sites began to be used and the time when soil samples were collected (see Table 1
for further details) Accordingly, we set t values for soils in
dumping sites in the Philippines; Cambodia; India; Hanoi, Vietnam; and Hochiminh, Vietnam, at 7, 21, 15, 3, and 11 yr, respectively
The loading rate (R) of PCDD/Fs to a dumping site
(considered as the annual amount of PCDD/Fs received by surface area of the dumping site; mg TEQs/yr) can be
calculated by multiplying flux value to surface area (A) of the
dumping sites:
Estimated fluxes of PCDD/Fs to soils in dumping sites in the Philippines, Cambodia, India, and Vietnam in comparison with agricultural/urban soils from other countries are given
in Table 5 It is interesting to note that fluxes to dumping site soils from the Philippines and Cambodia were greater than those from other locations in the world, including some contaminated sites in Hong Kong and Indiana, USA (Table 4) This result clearly supports the fact that dumping sites are potential sources of PCDD/Fs Fluxes to control soils were apparently lower than those to dumping site soils Considering the homologue pattern of soils from control sites, it can be suggested that soils from control sites were mainly originated from atmospheric depositions Elevated fluxes observed in dumping sites in the present study could
be attributed to uncontrolled combustion processes in a large open landfill area
The load of PCDD/Fs to the dumping sites, which were estimated using the equation as mentioned above, indicates
FIGURE 2 Homologue profiles of PCDD/Fs in soils from agricultural
and urban areas (control sites) in Asian developing countries in
comparison to the profile of samples representing environmental
sinks (urban soils) Vertical bars represent the percentage of each
homologue to total PCDD/F concentrations F and D refer to
dibenzofurans and dibenzo- p -dioxins, respectively Numbers Figures
indicate the degree of chlorination Data for environmental sink
samples were cited from ref 18 Data for soils in Philippines were
cited from ref 6
TABLE 4 Estimated Flux of PCDD/Fs to Soils in Dumping Sites from Asian Developing Countries in Comparison with Those to Soils from Other Countries in the World
British Columnbia, Canada
Yukon Territory, Canada
TABLE 5 Estimated Load of PCDD/Fs to Dumping Site Areas in Asian Developing Countries
load country
dumping site
Trang 8that dumping sites in the Philippines and India with a huge
area of approximately 23 and 140 ha could receive the highest
annual amount of 3900 and 1400 mg/yr PCDD/Fs (35 and
8.8 mg TEQs/yr), respectively (Table 5) The dumping site in
Hochiminh, Vietnam, had the lowest loading rate due to the
less contamination of PCDD/Fs in soils As for comparison,
total annual fluxes to the Kanto region in Japan, one of the
most polluted areas in the world, were estimated and were
found to range from 50 to 900 g TEQ with a total area of 32r
dumping sites in India is 140 ha, which is 21 000 times smaller
than that of the Kanto region; and this area was estimated
to receive 8.8 mg TEQs/yr These estimation data suggest
that dumping sites in India and the Philippines may be a
significant reservoir for PCDD/Fs Possible impacts on human
health and wildlife living near dumping sites are of great
concern and deserve further comprehensive studies
Risk Assessment The formation of PCDD/Fs in open
dumping sites in Asian developing countries has raised a
considerable public concern to human health for not only
communities living near the dumping sites but also for people
who live far away because PCDD/Fs may undergo
atmo-spheric transport and deposit in such distant areas For risk
assessment of soils contaminated by dioxins and related
compounds, the Agency for Toxic Substances and Disease
Registry (ATSDR) proposed guidelines recommending that
areas having soil concentrations within the range from 50 to
1000 pg TEQ/g should be evaluated for bioavailability,
ingestion rates, community concerns, etc and that soils with
concentrations over 1000 pg TEQs/g should be considered
for stronger actions such as health studies, exposure
inves-tigations, etc (22) The Japanese Government recently issued
new standards for dioxins in soil that established a level of
1000 pg TEQ/g for the maximum acceptable level, and those
within 250-1000 pg TEQ/g must be kept under surveillance
(23) Results of this study revealed that many soil samples
in dumping sites contained TEQ concentrations exceeding
250 pg/g TEQs (Figure 3), suggesting the necessity of
continuous monitoring Particularly, some soils from
Cam-bodia and Hanoi dumping sites contained TEQ
concentra-tions beyond the level of 1000 pg/g, suggesting their potential
for causing adverse health risk for humans and wildlife
It is clear that living in areas contaminated by PCDD/Fs
will lead to exposure to those chemicals via either direct
ways (such as inhalation, dermal absorption) or indirect ways
(e.g., soil ingestion, consumption of food grown or raised in
the areas, etc.) In the present research, we are able to assess
two exposure pathways including soil ingestion and dermal
exposure The assessment was implemented for two
cat-egories: people in dump sites (exposed group) and people
in control sites (control group) because of our observation
during sampling surveys that there have been as much as
hundreds of people daily scavenging in the duping sites (e.g.,
in the Philippines, Cambodia, and India) or even residing
there (e.g., in the Philippines) Humans ingest a small amount
of soil indirectly in food and other sources including
inhalation particles The ingestion rate may be twice as high
for children (63 mg/day) as for adults (26 mg/day) On the
other hand, humans can also be exposed directly to soil and
dust particles in air via dermal absorption, which takes place
on body skin (24) It should be noted that PCDD/Fs are highly
lipophilic; therefore, consumption of possible contaminated
foods may cause much higher dioxins intake than a portion
of soil ingestion and dermal exposure For such reason, our
assessment may only demonstrate a part of the total intake
of dioxins
Human intake of dioxins via soil ingestion was calculated
based on the eq 3, and similarly, absorption by dermal
exposure was estimated from eq 4, which was simplified from
the original descriptions (24) The total intake via ingestion
includes two factions, one is from ingestion of soil and the other is from ingestion of dust:
where DUtotal, DUsoil, and DUdust(pg TEQ kg-1day-1) are total ingestion of contaminant and fraction for soil and dust, respectively; AID (kg/day) is ingestion of soil particle amounts;
respectively; Csoilis TEQs concentration in soil (pg/g dry wt) Total absorption via dermal exposure (DAtotal) similarly is the sum of absorption by soil (DAsoil) and absorption by dust (DAdust):
where DA is dermal absorption (pg TEQ kg-1day-1); DAEout
EFoutand EFinare exposure factors for appropriate absorptions
of outside and inside skin, respectively Those factors
represent for exposing time, ratio of soil/dust, etc (24) See
Appendix I and II in the Supporting Information for details
of calculations
Human exposure to PCDD/Fs in soil is considered to be different for children and adults due to the differences in the ingestion rate as well as body weight of children and adults Various parameters for estimating intake of dioxins through soil ingestion can be found in the Supporting Information, and estimated intakes of dioxins for children and adult are
FIGURE 3 Concentrations of PCDD/Fs (pg/g TEQs dry wt) in soils from dumping sites in Asian developing countries in comparison with various environmental guideline values (1) 50 pg/g TEQs dry
wt, recommended by ATSDR for bioavailability, ingestion rates, pathways, etc.; (2) 250 pg/g TEQs dry wt, recommended by Japanese Government for the continuous monitoring necessity; (3) 1000 pg/g TEQs dry wt, Japanese Standard and level proposed by ATSDR for stronger actions and research on exposure and health studies See text for further details of guideline values.
DUtotal) DUsoil+ DUdust) (AID × IFsoil× Csoil)/
Wt + (AID× IFdust× Csoil)/Wt (3)
DAtotal) DAsoil+ DAdust) (DAEout× EFout× Csoil)/
Wt + (DAEin× EFin× Csoil)/Wt (4)
Trang 9given in Table 6 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 for the exposed group were
about 2-200-fold greater than those for the control and thus
underline greater health risk threatening these people Intake
of dioxins via soil ingestion and dermal sorption contributed
only a small portion to the total intake If people consume
foods (e.g., milk, meat, vegetables) produced in the vicinity
of incinerators, dioxin intake via foods could account for
more than 95% of the total intake (24) It is worth noting that
Nouwen et al (24) classified up to 5 scenarios in their study
based on the different exposure patterns (food consumption,
residence areas, etc.) Thus, exposure levels actually varied
widely from this group to the others Regardless of these
differences, if considering the worst case and assuming that
people in dumping sites have similar habits of food
con-sumption, total dioxin intake was estimated to be in the range
of 3-36 pg TEQ (kg of body wt)-1day-1, which exceeds the
WHO tolerable daily intake (TDI) value of 10 pg TEQ (kg of
body wt)-1day-1 Recently, the WHO intends to lower this
day-1(25) Similarly, The Japanese Government issued a new
TDI of 4 pg TEQ (kg of body wt)-1day-1of dioxins for humans
(23) These recommended TDI values would obviously
increase concern over health risk of people living near
dumping site areas Further investigations should be focused
on children and infant as they are the most susceptible group
and have higher exposure levels to dioxins
Recommendations and Directions for Future Research.
To our knowledge, this is the first comprehensive study on
PCDD/Fs pollution in open dumping sites in Asian
develop-ing countries Our result provides clear evidence that
dumping sites in Asian developing countries are potential
sources of PCDD/Fs and dioxin-like PCBs On the basis of
the results of this study, we have addressed a new
environ-mental issue that open landfill dumping areas in developing
countries may be a “hot spot” of pollution by toxic chemicals
Thus, dioxin contamination may become a key
environ-mental problem in Asian developing countries in the 21st
century Possible toxic effects on human health and wildlife
living near dumping areas should be studied in future, and
this is a critical step for further considerations of the necessary
control measures toward protecting environmental quality
Monitoring studies on exposure to other chemicals such as
organochlorine insecticides, which were used in large
quantities in the past and have been used until very recently
in Asian developing countries, are indispensable Temporal trends of contamination of PCDD/Fs and organochlorine insecticides also deserve comprehensive investigations
Acknowledgments
The authors thank the staff of the Center for Environmental Technology and Sustainable Development, Hanoi National University, Hanoi; of the University and Agriculture and Forestry, Hochiminh City, Vietnam; and of the Centre of Advanced Study in Marine Biology, Annamalai University, India, for their valuable support during our sampling surveys This study was supported by a Grant-in-Aid from the Scientific Research on Priority Areas (Project No 13027101) of the Japanese Ministry of Education, Science, Sports, Culture and Technology and by the Scientific Research (Project No 12308030) of Japan Society for the Promotion of Science Financial assistance was also provided by “Formation and Behavior of Dioxins and their Related Persistent Organic Pollutants in Uncontrolled Combustion Processes” from the Waste Management Research Grants of the Ministry of the Environment; the Sumitomo Foundation; and the Core University Program between Japan Society for the Promotion
of Science (JSPS) and National Center for Natural Science and Technology, Vietnam (NCST) The award of the JSPS Postdoctoral Fellowship for Researchers in Japan to T.B.M (P00323) and M.W (04166) is acknowledged
Supporting Information Available
Additional text, tables, and figures This material is available free of charge via the Internet at http://pubs.acs.org
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TABLE 6 Estimated Intakes of PCDD/Fs for Children and
Adults via Soil Ingestion and Dermal Exposurea
soil ingestion dermal exposure
Dumping Sites
Vietnam-Hanoi 0.3406 0.0299 0.0611 0.0711
Vietnam-Hochiminh 0.0089 0.0008 0.0016 0.0019
Control Sites
Vietnam-Hanoi 0.00365 0.00032 0.00065 0.00076
Vietnam-Hochiminh 0.00406 0.00036 0.00073 0.00085
Waste Incinerators
Wilrijk, Belgiumb 0.06810 0.00787 0.01470 0.00730
a Intakes were estimated using formulars reported by Nouwen et al.
(24), see text for further details b Data were cited from Nouwen et al.
(24).
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Interim Policy Guideline: Dioxins and Dioxin-like Compounds
in soil; U.S Department of Health and Human Services, Public
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(25) WHO Association of the Health Risk of Dioxins: Re-evaluation
of TDI, Exclusive Summary, 1998; International Program on
Chemical Safety, WHO Consultation, May 25-29, 1998; p 22
Received for review August 22, 2002 Revised manuscript received January 28, 2003 Accepted January 29, 2003.
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