Arsenic Contamination of
Bangladesh Paddy Field Soils:
Implications for Rice Contribution to
Professor：Pao-Nuan Hsieh ,Ph.D.
Nov 19th, 2009
• Materials and Methods
• Results and Discussion
• 世界各地砷污染之分佈（Smedley and kinniburgh, 2002）
（Smedley and kinniburgh, 2002）
• Arsenic contaminated groundwater is used
extensively in Bangladesh to irrigate the
staple food of the region, paddy rice.
• A survey of arsenic levels in paddy soils and
rice grain was undertaken.
• Regression of soil arsenic levels with tube-
well age was significant.
• The digging of tube-wells for drinking water
supply into aquifers elevated in arsenic in
Bangladesh and West Bengal has been
described as the greatest mass poisoning in
human history. ---36 million people exposed
• Groundwater arsenic concentrations
approaches 2mg L-1, 200,000-270,000
people will die of cancer from drinking
arsenic contaminated drinking water
• Arsenic contaminated groundwater is not just used
for drinking water but is also widely used for
irrigation of crops,and particularly for the staple
food paddy rice,~provides 73% of calorific intake
• Groundwater is used extensively to irrigate rice
crops in Bangladesh, particularly during the dry
season with 75% of the total cropped area given
over to rice cultivation and 83% of the total irrigated
area used for rice cultivation.
• Levels of arsenic in rice grain are typically
0.05-0.4 μg g-1 for North America, Europe,
and Taiwan(0.074 μg g-1 ).
• Arsenic levels in rice grain reached 0.7 μg g-1
in rice grown on paddy soils containing 68 μg
g-1 arsenic in China , showing the potential
for arsenic contamination of rice grain from
contaminated paddy soils.
• Contamination of soil was related to tube-
well arsenic levels, depth, and age to
understand the mechanism of soil
contamination by arsenic.
• Arsenic levels in Bangladesh produced rice,
were determined to calculate baseline
exposure of the population to rice derived
• Dietary arsenic exposure was then modeled
using these data.
Materials and Methods (1/3)
• Collection of Soil and Rice Grain Samples：
Soil and rice samples were collected during the period of
Soil samples were collected from 27 administrative districts
of Bangladesh, and a total of 71 samples were obtained.
Materials and Methods (2/3)
soil and rice grain(husk)→oven dry(70 ºC)→grinding
→digested→nitric acid-hydrogen peroxide
→heating block(60 ºC)→cooled →diluted in deionized water
→filtered(Whatman no. 42 filter paper)
→rice grain(Perkin-Elmer Aanalyst 300、FIAS 100 hydride generator)
Materials and Methods (3/3)
• Tube-Well Data：year constructed, depth,
arsenic levels obtain from the British
Geological Survey (BGS) web-site.
• The BGS tube-well data was similarly
averaged per district for comparison with the
• Statistics：Minitab v.13
Results and Discussion (1/9)
• Arsenic in Paddy Soils：
‧surface paddy soils 3.1 to 42.5 μg g-1
‧ the age and depth of the tube-wells need to be
considered as arsenic will accumulate in the
soil with long period of time
‧ the soils had become contaminated through
irrigation with arsenic contaminated water
Results and Discussion (2/9)
well age vs arsenic levels(soil)
Results and Discussion (3/9)
• Continuous variable
• Two continuous variable →covariance
• Linear regression
• Linear regression of tube-well age against paddy
soil arsenic levels was significant (P=.048)〈.05
• Similar regressions with tube-well depth (P=.505) 〉.05 and
tube-well arsenic levels (P =.684) 〉.05 were not significant n equation
Results and Discussion (4/9)
• tube-well depth and arsenic concentrations in the
well water were not significantly
Results and Discussion (5/9)
• Arsenic Levels in Rice：
Samples collected from Gazipur District at the
Bangladesh Rice Research Institute had an
average level of
0.092 μg g-1 dry wt,
highest 0.21 μg g-1
10.9,14.6 μg g-1
Results and Discussion (6/9)
• Western Bangladesh Districts arsenic levels
ranging from 0.058 to 1.83 μg g-1
arsenic levels within the same range as the
field trials at Gazipur
Results and Discussion (7/9)
• 113.5 mg╱kg(as soil), 0.074 mg╱kg(rice grain),at Guandu,
Results and Discussion (8/9)
• calculate daily human intake of arsenic from rice.
• With a drinking water intake of 0.1 mg L-1, arsenic
intake from rice will account for 17.3 and 29.6% of
arsenic consumption if rice contained 0.1 and 0.2 μg g-1
of arsenic, respectively.
• These grain values are typical of what has been observed
in a range of studies in Asia, Europe, and N. America
Results and Discussion (9/9)
• the bioavailability of arsenic in rice
• arsenic in rice grain →inorganic arsenic→toxic
and readily assimilated into the blood stream
• provide a safe water source
• decrease dietary exposure from arsenic still exists.
Meharg, A. A., and Rahman A. A., 2003.
“Arsenic Contamination of Bangladesh
Paddy Field Soils: Implications for Rice
Contribution to Arsenic Consumption,”
Environmental Science Technnology, 37(2)：
Thanks for your attention!!