Health risk management for cadmium contamination i Quản lý rủi ro sức khoẻ đối với ô nhiễm Cadmium ở Thái Lan: Có phải những thách thức khắc phục?

Health Risk Management for Cadmium Contamination in Thailand : Are Challenges Overcome ?
Pensiri Akkajit
Prince of Songkla University
Some of the authors of this publication are also working on these related projects


2
Health Risk Management for Cadmium Contamination in Thailand : Are Challenges
Overcome ?
Chantana Padungtod MD, DrPH1 , Wittaya Swaddiwudhipong MD, MSc2, Muneko Nishijo MD,
PhD3, Werawan Ruangyuttikarn PhD4, Thawangon Inud BSc, MSc.5
1

Bureau of Occupational and Environmental Disease, Department of Disease Control, Ministry of Public
Health, Nonthaburi, Thailand, 2 Mae Sot Hospital, Mae Sot, Tak, Thailand, 3Department of Public Health,
Kanazawa Medical University, Kanazawa, Japan, 4 Department of Forensic Medicine, Faculty of Medicine,
Chiang Mai University, Chiang Mai, Thailand, 5 Tak Provincial Health Office, Tak, Thailand.

Abstract
This report addresses the challenges encountered and, to a certain extent, overcome,
while health risk assessment and management were being conducted in Mae Sot, Thailand
following cadmium contamination to rice, the main diet of Thais.
In November 2003, Department of Agriculture (DOA), Ministry of Agriculture (MOA)
sent a summary report of a 6-year study revealing serious contamination of cadmium to soil and
rice grown in the vicinity of a large zinc mine to Department of Pollution Control (DPC). The
report concluded that level of rice contamination warranted immediate attention to prevent
cadmium poisoning among the exposed population. A team of DPC experts initiated a risk
assessment plan and Department of Disease Control (DDC) was among the 6 central
governmental offices contacted to join this effort.
Department of Disease Control (DDC) staffs and Mae Sot Hospital team initiated a rapid
survey to assess exposure situation among the 100,000 residents in the affected municipality.

Using GIS data, health staffs mapped contaminated rice fields with consumers. By the end of
2004, affected population was classified according to their exposure statuses. Toxicologists from
Chiang Mai University Medical School and Japanese cadmium experts from Kanazawa Medical
University started a research project to assess the effect of cadmium on kidneys, the major target
organ of cadmium. It is expected that a 10-year surveillance is needed to reduce health risks
among 800 people, who had high urinary cadmium level (> 5 µg/g creatinine) and were at risk of
having cadmium-induced renal failure, to acceptable level.
Challenges encountered during health risk management included; unclear source of
contamination, between natural and man-made origins, rendering it difficult to claim
accountability from the sole zinc mine, discontinuation of rice growing on contaminated land
against local cultural beliefs, compensation for rice growing without alternative crops cultivation
solution, and human rights issues for Karen population in the affected area. All these issues
prompt public staffs to search for alternative ways to manage health risks more economically,
socially and culturally acceptable.


Introduction
Heavy metal contamination caused by mining and
ore processing [1] is of major concern among the
range of environmental impacts associated with
Thailand’s economic development. For the past 30
years, zinc ore (Zn) has been exploited from the
Padaeng deposit in Mae Sot District, Tak Province,
Northwestern Thailand [2]. Two Zn mines were
operated; the first is no longer active, while the
second is owned and operated by

the Padaeng Industry Public Company Limited. It is
the largest Zn mine in Southeast Asia [3], with an
overall production capacity of 110,000 metric tons

of Zn metal per year [4].
The mining activities generated a large amount of
waste and tailings, resulting in heavy metal
contamination of the soils. Cadmium (Cd) contamination in agricultural soils and rice in the
vicinity of the mine was first reported in 1998
(Figure 1). Since 2003 it was found that paddy


4App. Envi. Res. 37 (1): 71-82
fields receiving irrigation from the Mae Tao and
Mae Ku creeks passing through the Zn deposit area
contained elevated Cd and Zn levels [5]. It was
reported that 1,600 m2 of paddy fields at the Mae
Sot District were contaminated with Cd and Zn
[3].
The objective of this study was to assess the
contamination status of Cd in soils, sediments and rice
plants in the vicinity, and propose technolo- gical
options for remediation, including chemical
remediation and phytoremediation.
Cadmium contamination in an environment Cd is
a particularly hazardous heavy metal because it can
be accumulated by plants to levels toxic to humans
and animals when consumed even in small
amounts [6, 7]. The transfer of Cd to agricultural
areas in the vicinity of the mine therefore poses a
major human health risk and
also impacts on the environment [7, 8].
1) Soil and sediment
Several studies have been conducted to

determine Cd levels in soils and identify the
origin of Cd in the vicinity of the mine [9, 10,
11]. Soil total Cd and Zn in Thailand ranges from
0.01 to 1.3 mg Cd kg -1 [12] and 5 to 158 mg Zn
kg-1 [13] with a mean value of 0.03 mg Cd kg-1 and
45 mg Zn kg-1, respectively [12, 13]. However, soil
samples from agricultural areas around the Pha Te
village, the Mae Sot District, have total soil Cd and
Zn concentrations rang- ing from 0.63 to 30.4 mg
Cd kg-1 and 14.4 to 594 mg Zn kg-1, respectively.
The upper-paddy soils that receive irrigation water
through a canal from the Mae Tao creek and that
flow into the lower-paddy soils showed high Cd
and Zn concentrations (5.93 to 30.4 mg Cd kg-1 and
286 to 594 mg Zn kg-1, respectively) [10]. Mae Tao
creek originates in the mountains of Northwestern
Thailand and is directly influenced by mining
activities. The Mae Tao creek passes through the
mine area, Pha Te and Mae Tao Mai Villages, then
Mae Sot city, in turn [13]. Soil

App. Envi. Res. 37 (1): 71-82
4

samples from the Mae Tao creek were found to have
low Cd levels upstream (8.45 mg Cd kg-1),
increasing to 22.5 mg Cd kg-1 at Mae Tao Mai
Village. Mae Ku creek, on the other side of the
mountain with Zn mining, showed high Cd levels
(7.55 to 34.95 mg Cd kg-1). The Mae Tao Ngae Sai

and Nong Khiao creeks in the northeastern and
southwestern highlands of the mine area had Cd
levels of 3.05 mg Cd kg-1 and 1.1 mg Cd kg-1,
respectively [14]. The data indicate that these soils are
contaminated with Cd and Zn, and the source of
contaminant is located upstream from the Mae Tao
creek [14]. Figure 2 illustrates the location of the
creeks in relation to the mine.
Cadmium concentrations in sediments in Mae
Sot District have been studied extensively, and have
been found to exceed the Thai standard for Soil
Quality for Habitats and Agriculture of 37 mg Cd
kg-1 [15]. The highest concentrations of Cd and Zn
(73.1 mg Cd kg-1 and 1,330 mg Zn kg-1,
respectively) were detected in the creek sediment
collected from Mae Tao creek [10]. Thailand’s
Pollution Control Department [16] reported Cd
concentrations in sediments along Mae Tao creek
and in the Zn mine area rang- ing from 44 to 63
mg Cd kg-1 and 82 to 326 mg Cd kg-1, respectively.
During April 2011 and February 2012, Cd
concentrations in sediments upstream and
downstream of Mae Tao creek ranged between 0.84
to 7.86 mg Cd kg-1, exceed- ing the European
maximum level of 3.0 mg Cd kg-1 for agricultural
soils [17]. The highest total Zn and Cd
concentrations in Mae Tao creek were found in
stream sediments (1,231 mg Zn kg-1and 37.11 mg
Cd kg-1) and suspended solids (7,767 mg Zn kg-1and
18.27 mg Cd kg-1). In the Mae Ku creek stream

sediments contained 316.55 mg Zn kg-1 and 7.99 mg
Cd kg-1, whilst suspended solids contained 7,723 mg
Zn kg-1 and 7.75 mg Cd kg-1, respectively) [18].
Since soil is an extremely heterogeneous system, the chemistry of metals has been shown to
vary from place to place. Metals exist as a variety
of chemical species and exhibit different


behavior in terms of chemical interaction, mobi- lity,
to a variety of matrices including sediments, soils;
biological availability and potential toxicity.
sewage sludge, mining wastes, with some modifiBioavailability can be defined as the fraction of the
cations [20]. Various studies have been conducted to
total metal that is readily available for uptake by
determine element behavior in order to estimate the
living organisms. It is therefore important to
risk associated with Cd movement [10, 11, 21]. In
understand the processes of distribution and
2007, Cd in soils from the Mae Tao and Mae Ku
transformation of metals under the prevailing soil
sub-catchments showed the highest mobility
environments, in order to understand the migra- tion with the highest content in the first (exchangeableand movement of Cd into uncontaminated soils. BCR1) (25 to 30%) and the second (reducible-BCR2)
Assessment of the changes in the Cd forms and
fractions of the three-step BCR sequential extraction
measurement of soil parameters would allow more
[21]. The major proportion of Cd and Zn in soils
insight into mechanisms that might be responsible
collected from the Pha Te village, the Mae Sot
for Cd immobilization and/or metal movement.
District, was dominantly associated with the

The three-step BCR sequential extraction proposed
exchangeable fraction (40 to 70% of total Cd and 37
by the Standards, Measure- ments and Testing to 46% of total Zn, respectively) [10]. In the stream
Programme of the European Union [19] has been sediments from Mae Tao creek, Cd is distributed
used extensively to deter- mine the bioavailability of
mostly in extractable forms (BCR1 and BCR2);
metal in this parti- cular area. The extraction
on the other hand, Cd from Mae Ku creek are
procedures are useful under defined conditions for
dominated by the less extracta- ble forms of BCR2
predicting metal transformation with respect to
and BCR4 [20]. Significantly, 70 to 90% of Cd in
their extraction capacity. Sequential extraction
the paddy fields was found to be present in the
techniques estimate the amounts of metals in various
exchangeable fraction (BCR1) [11]. The
solid fractions which can be operationally categorized
exchangeable fraction is only weakly absorbed, is
as follows: easily soluble (exchangeable-BCR1), Fe- easily solubilized and thus is readily bioavailable for
Mn oxide bound (reducible-BCR2), organic (oxidizableplant uptake. This poses signi- ficant risks to the
BCR3), and organic and silicate bound (residual- ecosystem and has significant potential to affect the
BCR4). This procedure has been standardized and
environment via transfer
applied
of Cd through the food chain.


Thailand context
Located on the Thai-Myanmar border, Mae Sot district in Tak province is hidden in
mountainous area. With the abundant supplies of water from Moei River and smaller

canalization, local residents of Mae Sot have depended on rice, soybean and garlic cultivations
for at least 3 generations. Rice grown in the area has yielded national award-winning products
for many consecutive years.
Around 1977, zinc mining activities of 3 companies were started after the Department of
Mineral Reources, Ministry of Industry 1 classified this area as the richest source of zinc minerals
in Thailand. However, at present, only one company has remained in the area and its gross
income and profit is shown in table 1.
Table 1 : Gross income and profit of the only zinc mining company in Mae Sot, Tak, 1999 – 2004
(Social Research Institute, Chiang Mai University, Thailand 2006)
Year
1999
2000
2001
2002
2003
2004

Gross Income in Millions Bahts
(US$ : 1 US$ = 40 Bahts)
4,462 (110,550,000)
5,315 (132,875,000)
5,222 (130,550,000)
4,406 (110,150,000)
4,932 (123,300,000)
5,715 (142,875,000)

Net Profit in Millions Bahts
(US$ : 1 US$ = 40 Bahts)
145 (3,625,000)
211 (5,275,000)

335 (8,375,000)
-29 (-725,000)
284 (7,100,000)
217 (5,425,000)

With regard to pollution control in Thailand, the Office of Environmental Policy and
Planning, Ministry of Natural Resource and Environment (MNRE) is mandated to review and
approve the environmental impact assessment (EIA) of 22 hazardous industries. This activity can
be considered as primary prevention of industrial pollution. Meanwhile, once pollution is
suspected, the Department of Pollution Control (DPC) is called for investigation and control
activity. Generally, the DPC staffs conduct their work independently and Ministry of Public
Health (MOPH) is consulted for diagnosis and treatment of the diseases or clinical symptoms
presented. In addition, after a certain period of time, follow up of environmental contamination
and adverse health effects are both discontinued.
Collaboration between Thai MOA and IWMI
The discovery of cadmium contamination to rice and soil in Thailand began in 1998 (1,2).
Dr. Robert W. Simmons, a senior researcher at International Water Management Institute (IWMI)
and his team decided to conduct a study in Mae Sot district, Tak province, Thailand. Based on
their experiences from water and soil contamination studies in China and other Asian countries,
they foresaw that rice growing in the vicinity of zinc mine could lead to cadmium, which coexists naturally with zinc, contamination to rice and would inevitably cause adverse health effect,
particularly itai-itai disease, or chronic cadmium poisoning, among the exposed population.
IWMI jointly quantified soil and rice cadmium contamination in Mae Sot district with
Dr.Pichit Pongsakul, a soil and plant expert at Department of Agriculture, Ministry of Agriculture,
Thailand. From 1998 – 2000, the first phase of the study was done in the most potentially
polluted area where water was naturally supplied by Mae Tao Creek in which sediment was
suspected of having high contamination of cadmium.

1

Since October 2002, this department has branched into Department of Mineral Resources, Ministry of

Natural Resources and Environment and Department of Primary Industries and Mine, Ministry of Industry.


It was concluded that source of cadmium contamination was soil containing high level of
cadmium, which evidences were not sufficient to confirm that whether cadmium was from natural
zinc mineralized area or contamination by zinc mining activities, flooded or eroded into natural
and man-made water supplies which was, then, irrigated into rice paddy fields. Cadmium was
eventually transferred from soil into rice, the only plant known to absorb cadmium completely.
Results showed that cadmium levels in 154 soil samples ranged from 3.4 – 284 mg Cd/kg
soil which was 1.13 – 94 times European Economic Community (EEC) Maximum Permissible
(MP) soil cadmium concentration of 3.0 mg Cd/kg soil and 1,800 times the Thai standard of 0.15
mgCd/kg soil. Moreover, rice samples from 90 fields were found to be contaminated with
cadmium ranging from 0.1 to 4.4 mg/kg rice while the mean background Thai rice Cd
concentrations as reported by Pongsakul and Attajarusit (1999) was 0.043 ± 0.019 mg/kg rice.
With this amount of cadmium presented in rice and based on Thai daily rice consumption,
it was estimated that local residents would have been exposed to cadmium 14 – 30 times higher
than the Joint FAO/WHO Expert Committee on Food Additives (JECFA) Provisional Tolerable
Weekly Intake (PTWI) of 7 µg Cd / kg body weight (BW) per week.
The second phase of the study, from 2001 – 2003, was expanded to cover the
downstream part of Mae Tao Creek. Cadmium level in soil samples was found to be 72 times
European Union (EU) standard and 80 % of rice samples were contaminated with cadmium at the
level higher than Food and Agriculture Organization (FAO) and Japanese standards. This
concentration of cadmium could lead to 2.8 – 11 times higher than the aforementioned PTWI set
by JECFA.
Risk Assessment
Due to the Department’s roles and functions, Department of Pollution Control (DPC),
MNRE was the first governmental office invited to attend MOA/IWMI research result
dissemination meeting in October 2003. DPC staffs, then, initiated a plan to investigate the
extent and severity of cadmium contamination in Mae Sot. However, contradicted to the general
practice, Department of Disease Control (DDC) was asked to join the effort at that early stage.

From January to April 2004, using GIS mapping based on cadmium concentration
gradient in soil and rice provided by MOA/IWMI research team, DPC staffs collected
environmental samples from Mae Tao Creek, surface water, underground water, well water and
soil. Rice and fish were also sampled. Concurrently, MOPH staffs located the exposed population
and biological samples were collected for cadmium measurements.
Environmental samplings
Table 2 summarized standards used for all environmental samplings conducted under the
auspice of a special technical task force led by DPC (3).
• The Department of Underground Water found that all underground and surface water
samples contained cadmium less than 0.001 mg/L which was considered safe for drinking
according to international standard of < 0.01 mg/L.
• The Department of Water Resources reported that all samples throughout the creek length
contained cadmium between 0.00281 – 0.001 mg/L which was also considered safe for
consumers (<0.05 mg/L at water hardness >100 mg/L).
• The Department of Fisheries found that all fish samples had cadmium concentration
within safe limit for consumption of < 2 mg/Kg.
• The Department of Mineral Resources found that 88 % of sediment samples from Mae
Tao Creek contained high concentration of cadmium. The highest level was 93 times the
lowest contamination concentration (326 mg Cd /Kg soil).
• DPC reported that 86 % of soil samples were contaminated ranging from 61 – 207 mg Cd
/Kg soil.


•

Rice samples from household storage were found to contain cadmium from trace to 5 mg
Cd/Kg rice with the average of 1.33 mg Cd/Kg rice. In other words, 91 % of rice
samples exceeded Codex Committee on Food Additives and Contaminants (CCFAC) of
0.2 mg Cd/Kg rice.

Table 2 : Standards of cadmium concentration used by Department of Pollution Control for
environmental samplings in Mae Sot area (January – April 2004)
Type of samples
Underground and
surface water
Water from Mae
Tao Creek
Sediment in Mae
Tao Creek
Soil from rice
paddy fields
Rice grown on
contaminated
soil

Low
contamination
≤ 0.01
mg/L
≤ 0.05
mg/L
≤ 3.5
mg Cd /Kg soil
≤3
mg Cd / Kg soil
≤ 0.2
mg Cd / Kg rice

Medium
contamination

0.01 - < 0.1
mg/L
0.05 - < 0.5
mg/L
3.5 - < 35
mg Cd / Kg soil
3 - < 30
mg Cd / Kg soil
0.2 - < 1
mg Cd / Kg rice

High
contamination
≥ 0.1
mg/L
≥ 0.5
mg/L
≥ 35
mg Cd / Kg soil
≥ 30
mg Cd / Kg soil
≥1
mg Cd / Kg rice

The environmental samplings revealed similar results to MOA/IWMI research except the
conclusion on pollution source. DPC reported a significant difference of cadmium concentration
in sediments sampled along Mae Tao Creek (Table 3). From this report, it was evident that
cadmium contamination in natural water supply could be attributed to zinc mining activity.
Table 3 : Cadmium concentration found in sediments of Mae Tao Creek as reported by
Department of Pollution Control (April 2004)

Location along Mae Tao Creek
Tham Sue village (creek origin)
Zinc mining area
Small dam near Zinc mining area
Towards the end of creek

Cd concentration in sediments
(mg Cd/Kg soil)
0.5
82 – 326
80 – 104
44 – 63

Population survey
Mae Sot hospital staffs, supported by health staffs from Tak Provincial Health Office and
Bureau of Occupational and Environmental Disease, Department of Disease Control, classified
approximately 100,000 residents in Mae Sot district into exposed and non-exposed group based
on the duration of living in the area and rice consumption habit (4). Among the exposed, 7,697
residents aged 15 years and older were asked to donate urine samples for cadmium concentration
measurement.
Using World Health Organization (WHO) standard of 2 µg/g creatinine for environmental
exposure, 5 µg/g creatinine for occupational exposure and > 10 µg/g creatinine for possible renal
damage caused by cadmium, it was found that 45.6 % of surveyed population had urinary
cadmium levels < 2 µg/g creatinine while 4.9 % had cadmium between 5 and 10 µg/g creatinine
and 2.3 % had cadmium concentration > 10 µg/g creatinine.


When classified by the origin of rice that the exposed population habitually consumed, it
was shown in table 4 that those who ate rice grown in contaminated area had significantly higher
level of urine cadmium concentration compared to those eating rice purchased from markets or

other districts.
Table 4 : Mean urinary cadmium of adult population surveyed classified by origin of rice
consumed* (2004)
Rice-producing
Area

Urinary cadmium (µg/g creatinine)
No.
<2 2 – 4.9 5 –10
>10
surveyed

Mean + SD** P-value

Rice grown locally in 6,770
contaminated areas
Rice purchased from
858
Mae Sot markets
Rice purchased from
69
other districts

44.5

47.7

5.2

2.6

2.1 + 3.0

52.6

44.1

3.0

0.3

1.8 + 2.7

62.3

37.7

0.0

0.0

1.5 + 2.4

Total

45.6

47.2

4.9

2.3

2.1 + 2.9

7,697

< 0.01

* Expressed as a percentage of the number surveyed
**Geometric mean + standard deviation
Table 5 showed urinary cadmium concentration classified by age and gender. Older
population appeared to have, significantly and in a dose-response manner, higher urinary
cadmium levels compared to younger population and females had significantly higher level of
urinary cadmium than males.
Table 5 : Mean urinary cadmium of exposed adult population classified by age and gender*
(2004)
No.
surveyed
Total
Age (years)
15-24
25-34
35-44
45-54
> 55
Sex
Male
Female

Urinary cadmium ( µg/g creatinine)
<2
2 – 4.9
5 –10
>10

Mean + SD** P-value

7,697

45.6

47.2

4.9

2.3

2.1 + 2.9

983
1,296
1,983
1,518
1,917

66.8
56.2
44.1
40.8

32.9

31.9
39.7
49.4
49.9
55.6

0.8
3.1
4.6
6.0
7.6

0.2
0.8
1.9
3.2
4.0

1.4 + 2.2
1.6 + 2.6
2.1 + 2.9
2.3 + 3.0
2.9 + 3.2

3,667
4,030

49.6

42.0

44.7
49.5

3.7
5.9

2.0
2.6

1.9 + 2.8
2.3 + 3.0

* Expressed as a percentage of the number surveyed
**Geometric mean + standard deviation

<0.01

<0.01


Smoking is known to increase body burden of cadmium. When classified exposed
population by smoking status, current smokers had significantly higher concentration of urinary
cadmium (1.8 + 2.8 µg/g creatinine) compared to former (2.3 + 3.1 µg/g creatinine) and nonsmokers (2.5 + 3.1 µg/g creatinine).
Clinical assessment
The aforementioned epidemiological survey in 2004 could be concluded that
consumption of contaminated rice was associated with elevated urinary cadmium levels. The
next step was to assess the renal and bone effects caused by cadmium.
Mae Sot Hospital registered 800 exposed population having urinary cadmium > 5 µg/g

creatinine as “high risk group” and provided follow up by an internist every 3 months at a special
clinic. This high risk group was also further investigated as followed;
• Bone density measurement of both wrists (data is being analyzed)
• Renal function test (BUN, creatinine) revealed that 5% (n=40) of the high risk group
could have early stage renal failure.
In 2005, toxicologists from Chiang Mai University Medical School and Kanazawa
Medical University, Japan, jointly measured selected renal markers related to cadmium-induced
renal failure namely urinary protein, urinary β2-microglobulin and Urinary N-acetyl-βglucosaminidase (NAG)(5).
It was found that the proportion of the high risk group having β2-microglobulin ≥ 1,000
µg/g creatinine, Japanese cut-off level for people living in cadmium-polluted area, was 22.5%
and 17.2% among males and females respectively. The proportion of the high risk group having
NAG ≥ 10 U/g creatinine, the upper limit of that measurement, was 7.7% and 28.7% in men and
women respectively. Lastly, positive rate for urinary protein, measured by urinary strip, was
39.8% and 28.7% in men and women respectively.
These results showed that the exposed population with renal tubular disturbance could
potentially exist in Mae Sot and that the positive rates found were as high as those found among
residents of polluted areas in Kakehashi River Basin, Japan. It was anticipated that a 10-year
surveillance would be needed to reduce health risks among 800 high risk people, who had high
urinary cadmium level (> 5 µg/g creatinine) and were at risk of having cadmium-induced renal
failure, to acceptable level.
Conclusions
The results of environmental samplings, population survey and clinical assessment led to
the conclusion that selected areas of Mae Sot district were highly contaminated with cadmium
and that this level of contamination has already posed excessive risk of having cadmium-induced
renal failure among the local residents who habitually consumed contaminated rice.
Risk management
To reduce risk posed by cadmium contamination among Mae Sot residents, a twopronged approach was needed. The so-called “main” part was environmental and behavioral
modification to reduce cadmium intake while the supportive part was long term health
surveillance to detect, as early as possible, renal damage caused by cadmium.
Bright start in 2004

In 2004, after data on environmental samplings from DPC and preliminary results of
population survey from Mae Sot Hospital were available, an initial risk management plan was set
up under auspice of special committee led by DPC. Based on the cadmium level found in soil,
DPC suggested discontinuation of rice cultivation in the area. This solution was fully supported


by health staffs, who, further added that contaminated rice consumption should also be stopped.
However, if this option was to be adopted, alternative crops cultivation, or even alternative
occupation, should have been suggested or provided for the local residents who had depended on
rice and other edible crops cultivation through out their lives.
Instead of offering alternative crop cultivation, the MOA suggested cadmium absorption
by a plant which was known as cadmium accumulator. At the same time, to encourage local
residents to stop rice growing, local administration gave financial compensation to the residents
based on the amount of rice stored from 2003 cultivation and the number of rice paddy fields
owned.
Difficult 2005
In 2005, rice cultivation was halted while MOA was still searching for alternative crops
cultivation solution. Residents began to protest that compensation was unjustly allocated
particularly among the Karen population, a minority tribe living along Thai-Myanmar border
including Mae Sot area. This dissatisfaction eventually bloomed into human rights debates and
the Office of the National Human Rights Commission of Thailand stepped in to investigate and
settle this issue.
Rumor was spreading that all exposed population would eventually suffer and die from
renal damage and that hospital was not prepared for this increasing demand. Mae Sot Hospital
was, then, pushed to seek for additional financial resources to expand the existing renal dialysis
unit and to set up laboratory for cadmium and renal markers measurement needed for long term
health surveillance.
On the other hand, the sole zinc mining company in the area was suspected as polluter
and accountability was asked for. However, the unclear source of contamination, between natural
and man-made origins, rendering it difficult to claim accountability from the zinc mine. The

company itself has hired several research teams from academic institutions to study in the area
and none of the studies had revealed positive correlation between cadmium in the environment
and mining activities.
Meanwhile, faced with these difficulties, Ministry of Interior (MOI) has worked closely
with key advocacy groups, particularly the Mae Sot Civil Society, to alleviate the problems.
Several town meetings were organized by the Civil Society group to improve local residents’
understanding of the situation. Emphasis was also placed on the collaboration between
governmental offices and local residents to successfully reduce cadmium exposure.
Difficulty continued for 2006
MOA suggested sugar cane, decorative palm and rubber plantation to replace rice
cultivation. However, up to present, these plants are still in experimental phase.
A social survey among 312 household leaders from 6 villages located in contaminated
area in March 2006 (6) showed that residents who had better access to information could adjust
and cope more positively with cadmium contamination compared to those neglected or having
limited access. It was also noted that social and spiritual health was interrupted after
discontinuation of rice cultivation. Mae Sot residents had a cultural calendar closely tied with
rice cultivation cycle and it had been difficult for them to stop these activities and, to a certain
extent, to change their agricultural habits.
A 3-year Mae Tao Creek area Development Plan was proposed to the cabinet, by MOI,
early in September 2006. If approved, a 195 millions Bahts (4.8 millions US$) -budget would be
allocated for 14 projects classified under 4 strategies as followed.
• Strategy 1 : Soil rehabilitation
o cadmium absorption by cadmium accumulating plant
• Strategy 2 : Pollution prevention and control


•

•

o environmental monitoring
Strategy 3 : Economic development for security, health and quality of life
o Alternative occupation promotion such as mushroom plantation
o Fund for occupation changes
o Fund for chronic renal failure patients
o Hospital laboratory capacity building
o Long term health surveillance
o Alternative crops cultivation for ethanol production such as sugar cane and others
o Animal health risk assessment
o Detection of cadmium concentration in animal feedings
o Decorative palm plantation promotion
Strategy 4 : Capacity building for risk management
o Funding for Mae Sot Civil Society activities
o Mae Tao Creek Development Center
o GIS of contaminated area

Conclusions
Although multidisciplinary approach was used for environmental health risk management,
public, in particular public health, staffs needed to search for alternative ways to manage health
risks more participatory, economically, socially and culturally acceptable.
Acknowledgement
Special appreciation to Dr.Suwit Wibulpolprasert, IFCS president, for his continuous support to
younger colleagues.
References
(1) International Water Management Institute, South East Asia Region. Briefing note :
Cadmium Contamination in Soil and Crops of Tambon Phathat Padaeng and Tambon
Mae Tao, Amphur Mae Sot, Tak Province, Thailand : Implications for Public Health.
2003
(2) R.W.Simmons, P.Pongsakul, D.Saiyasitpanich and S.Klinphoklap. Elevated levels of
cadmium and zinc in paddy soils and elevated levels of cadmium in rice grain

downstream of a zinc mineralized area in Thailand : Implications for public health.
Environmental Geochemistry and Health (2005) 27:501-511.
(3) Department of Pollution Control, Ministry of Natural Resources and Environment,
Thailand. Summary of Environmental Samplings in Mae Sot after cadmium
contamination. April 2004.
(4) Wittaya Swaddiwudhipong, Pisit Limpatanachote, Pranee Mahasakpan and Somyos
Krintratun. Cadmium-exposed Population in Mae Sot District, Tak Province : Prevalence
of High Urinary Cadmium levels in the Adults. Submitted for publication 2006.
(5) Muneko Nishijo. Report on Urinary beta-2-microglobulin and NAG levels among the
Mae Sot residents found to have urinary Cd ≥ 5 µg/gCr from 2004 survey. December
2005.
(6) Thawangon Inud. Adjustability to Environmental Impact among Residents in Mae Tao,
Tak, Thailand. Thesis submitted 2006.

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