Atlas of Contaminated Sites

Notable case, Mae Sot, Tak, Thailand

Mae Tao, Mae Sot (cadmium in rice paddies)

ห้วยแม่ตาว

The paddies below the Padaeng zinc deposit in north-western Thailand, where creeks carried cadmium and zinc from the mining area to the fields. It is South-East Asia's most studied case of cadmium in rice, including trials with accumulator plants.

Phytoremediation

Status
Contained
People affected
7,697 (2004)2
Media
soil, sediment, surface water, living organisms
Kind of site
mining
  1. Area. Paddies irrigated by the Mae Tao and Mae Ku creeks in three sub-districts (Phra That Pha Daeng, Mae Tao, Mae Ku). The sources read give no reliable area. The map point is Mae Sot district.
  2. People affected. Residents aged 15 and over screened for urinary cadmium in 2004; not the total number exposed.

Contaminants

Metals

Status

Contained

Rice growing in the contaminated area has been banned since 2004 and non-food crops are encouraged; zinc mining was halted in the three sub-districts because of its environmental impact. In 2018 affected residents were awarded 16 million baht in compensation (Wikipedia, citing the Bangkok Post). The soils remain contaminated.

Story

The Padaeng zinc deposit, in Mae Sot district, was worked for about thirty years by two mines; the second, owned by Padaeng Industry, was the largest zinc mine in South-East Asia. The Mae Tao and Mae Ku creeks cross the mining area and then irrigate the paddies of the villages below, such as Pha Te and Mae Tao Mai.

Contamination of soil and rice was first reported in 1998; from 2003 surveys by the International Water Management Institute with Thai authorities showed elevated cadmium and zinc in the paddies watered by the two creeks. Around Pha Te farm soils held 0.63 to 30.4 mg/kg of cadmium, against a national mean of 0.03 mg/kg. In 2008 rice eaten by households contained 0.12–1.27 mg/kg of cadmium; the limit proposed by Codex is 0.2 mg/kg.

Since 2004 the government has banned rice growing in the area. Measures taken include promoting non-food crops such as sugar cane, removing contaminated soil, chemically stabilising cadmium with phosphates and amendments, and phytoremediation trials.

Timeline

  1. 1998First report of cadmium in farm soil and rice near the mine.
  2. 2003Surveys show elevated cadmium and zinc in the paddies irrigated by the Mae Tao and Mae Ku creeks.
  3. 2004The government bans rice growing in the area; urinary cadmium survey of 7,697 residents.
  4. 2006Field trial with four vetiver ecotypes in the Padaeng mine area.
  5. 2018Affected residents are awarded 16 million baht in compensation.

Health

In a 2004 survey of 7,697 residents aged 15 and over, those who ate local rice had more cadmium in urine: 4.9% were between 5 and 10 µg/g creatinine and 2.3% above 10 (the WHO threshold for kidney damage is 5.24). Tubular and glomerular kidney dysfunction increased among the exposed; among people aged 40 and over, osteoporosis affected 21.5% of women and 14.7% of men (figures summarised by Akkajit, 2015).

Remediation

  1. 2004crop restrictionBan on growing rice in the contaminated area and promotion of non-food crops.
  2. —chemical stabilisationTrials of cadmium stabilisation with phosphates: triple superphosphate cut cadmium leachability by 94% in three local soil types after 30 days.

Plants and fungi at this site

PhytoremediationField scale

Gynura pseudochina, Chromolaena odorata, Crassocephalum crepidioides, Conyza sumatrensis

Four wild species common around the mine, classed as hyperaccumulators in the greenhouse, were also tested in the field on contaminated farm soil at Mae Sot (Khaokaew and Landrot, field-scale study).

Outcome The review by Akkajit (2015) does not give the amounts removed in the field. For Chromolaena odorata it reports accumulation mainly in the shoots (14.1 mg/kg cadmium and 278 mg/kg zinc), good biomass and no signs of toxicity.

PhytoremediationField scale, 2006

Chrysopogon zizanioides, Chrysopogon nemoralis

Four vetiver ecotypes (two of Chrysopogon nemoralis and two of C. zizanioides) grown in the Padaeng Industry zinc mine area to assess growth in the field on contaminated ground (Roongtanakiat).

Outcome The two C. zizanioides ecotypes grew well with high biomass. The review does not give the amounts of metal taken up.

PhytoremediationField scale

Saccharum officinarum

Sugar cane as a non-food alternative crop on contaminated soil, with sugar-mill by-products (boiler ash, filter cake, vinasse) added at 3% by weight as amendments to immobilise cadmium (Akkajit and colleagues, 2014). The review does not state the scale of the experiment.

Outcome Cane biomass 6 times higher above ground and 3 times in roots; up to 54.5% less cadmium in the most available soil fractions.

From the literature

Species that acted on one of this site's contaminants in at least one study. The list is automatic and takes no account of this site's soil, concentrations or climate.

Plants

Fungi

The rest are on the contaminant pages.

Nearby

Notable case, Lower Klity (Thong Pha Phum district), Thailand

Klity Creek

219 km

  • Lead

Sources

  1. Akkajit P. Review of the Current Situation of Cd Contamination in Agricultural Field in the Mae Sot District, Tak Province, Northwestern Thailand. Applied Environmental Research 37(1): 71–82, Chulalongkorn University, 2015
  2. Mae Sot district, Wikipedia, 2026

Draft compiled from public sources, not yet reviewed.