ArticlePDF Available

Cooking rice in a high water to rice ratio reduces inorganic arsenic content

Authors:

Abstract and Figures

Total arsenic and arsenic speciation was performed on different rice types (basmati, long-grain, polished ([white] and wholegrain [brown]) that had undergone various forms of cooking. The effect of rinse washing, low volume (2.5 : 1 water : rice) and high volume (6 : 1 water : rice) cooking, as well as steaming, were investigated. Rinse washing was effective at removing circa. 10% of the total and inorganic arsenic from basmati rice, but was less effective for other rice types. While steaming reduced total and inorganic arsenic rice content, it did not do so consistently across all rice types investigated. Low volume water cooking did not remove arsenic. High volume water : rice cooking did effectively remove both total and inorganic arsenic for the long-grain and basmati rice (parboiled was not investigated in high volume cooking water experiment), by 35% and 45% for total and inorganic arsenic content, respectively, compared to uncooked (raw) rice. To reduce arsenic content of cooked rice, specifically the inorganic component, rinse washing and high volume of cooking water are effective.
Content may be subject to copyright.
Cooking rice in a high water to rice ratio reduces inorganic arsenic content
Andrea Raab,
ab
Christina Baskaran,
c
Joerg Feldmann
b
and Andrew A. Meharg*
a
Received 29th September 2008, Accepted 12th November 2008
First published as an Advance Article on the web 20th November 2008
DOI: 10.1039/b816906c
Total arsenic and arsenic speciation was performed on different rice
types (basmati, long-grain, polished ([white] and wholegrain
[brown]) that had undergone various forms of cooking. The effect of
rinse washing, low volume (2.5 : 1 water : rice) and high volume (6 : 1
water : rice) cooking, as well as steaming, were investigated. Rinse
washing was effective at removing circa. 10% of the total and
inorganic arsenic from basmati rice, but was less effective for other
rice types. While steaming reduced total and inorganic arsenic rice
content, it did not do so consistently across all rice types investi-
gated. Low volume water cooking did not remove arsenic. High
volume water : rice cooking did effectively remove both total and
inorganic arsenic for the long-grain and basmati rice (parboiled was
not investigated in high volume cooking water experiment), by 35%
and 45% for total and inorganic arsenic content, respectively,
compared to uncooked (raw) rice. To reduce arsenic content of
cooked rice, specifically the inorganic component, rinse washing and
high volume of cooking water are effective.
Introduction
Rice is the only staple crop grown under flooded soil conditions.
Under anaerobic conditions, arsenic in soil is converted readily to
arsenite which is mobile, leading to arsenic in rice grain being around
10-fold higher than for other crops.
1
This occurs in soils which have
no or limited anthropogenic contamination. Rice grain arsenic levels
are elevated further when grown in soils subject to anthropogenic
contamination such as: arsenical pesticide use, base and precious
mining and smelting impacted soils, and contaminated water irri-
gated soils.
2–8
Inorganic arsenic, a class 1 non-threshold carcinogen,
9,10
and
dimethyl arsinic acid (DMA) constitute the dominant arsenic species
present in rice while traces of monomethyl arsonic acid (MMA) are
sometimes reported,
11
as well as a residual fraction that is either not
extractable or does not elute from the chromatographic column.
Inorganic arsenic can constitute up to 90% of total arsenic present in
grain, but on average accounts for around 50% of total grain
arsenic.
11
A number of previous studies had suggested that rice cooking was
important to the arsenic content of the cooked grain.
12–18
Some of
these studies focus on how cooking techniques may reduce rice
arsenic content,
12,13
while others focus on how arsenic in cooking
water affects arsenic content of cooked rice.
14–18
Rinsing rice before
washing and then cooking the rice in a high water : rice ratio (6 : 1)
and not allowing the water to evaporate to dryness significantly
reduced the arsenic burden of the rice,
12,13
with one study suggesting
that the arsenic was primarily lost as inorganic arsenic, specifically
arsenite.
12
Previous studies on rice cooking
12–18
had not systematically
looked at: (a) differences between wholegrain (brown) or polished
(white) rice or (b) commonly used cooking techniques such as low
and high water : rice volume and steaming. Similarly, systematic
speciation and/or mass balances are inconsistent or absent between
previous studies.
13–8
Par-boiledricealsoneedstobeconsidereddueto
its widespread utilization. This current study sets out the systematic
determination of the effect of cooking on the concentrations of
arsenic species in rice.
Experimental
Rice samples were purchased from major UK retailers. Two varieties
of basmati, one wholegrain (packed in 1 kg portions, 4 portions were
mixed before use) and one polished (packed in 2 kg portions, 2
portions, mixed before use) were of Indian origin. Wholegrain long-
grain (4 times 1 kg portions, mixed before use) and polished long-
grain (4 times 1 kg portions mixed before use) originated according to
label from more than one country. The same origin was given for the
long-grain easy cook (par-boiled) rice (2 times 2 kg portion, before
use). The easy cook short-grain rice (4 times 1 kg portions mixed
before use) was of Italian origin.
Raw rice was first rinse washed by placing 100 g portions of rice
(packet weight) in an acid washed 800 mL beaker and then adding
600 mL of double distilled deionised (Milli-Q) water. The sample was
allowed to sit for 3 min with routine agitation. The water was dec-
anted and then the process repeated again with another 600 mL of
water. The decanted water was then freeze dried. Dry weight deter-
mination was then made on both the raw and rinsed rice by oven
drying at 80 C until constant weight was reached. The quantity of
freeze dried residue was recorded. Rinse washed rice was used in all
subsequent cooking experiments.
In all boiling experiments the quantity of packet weight used was
100 g. Double distilled deionised water was used for the cooking
water. All rice, including par-boiled, was subject to 2.5 : 1 (low
volume) water to rice (packet weight) cooking, where the water was
cooked to dryness. All rice with the exception of par-boiled, were also
subject to 6 : 1 (high volume) water : rice cooking, where the rice was
cooked to eating texture. The residual water was drained off and then
freeze dried.
For the steaming experiments, rinse washed rice (100 g packet
weight) was soaked for 2 h in an acid washed 400 mL beaker with 200
mL of double distilled deionised (Milli-Q) water. On termination of
a
Institute of Biological and Environmental Sciences, University of
Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen, UK AB4
3UU
b
Department of Chemistry, University of Aberdeen, Meston Building,
Meston Walk, Aberdeen, UK AB24 3UE
c
Foods Standards Agency, Aviation House, 125 Kingsway, London, UK
WC2B 6NH
This journal is ªThe Royal Society of Chemistry 2009 J. Environ. Monit., 2009, 11, 41–44 | 41
COMMUNICATION www.rsc.org/jem | Journal of Environmental Monitoring
Published on 20 November 2008. Downloaded by 391533 on 21/04/2016 09:52:38.
View Article Online
/ Journal Homepage
/ Table of Contents for this issue
soaking, the water was decanted and freeze dried. The steamer was
filled with 200 mL of double distilled deionised (Milli-Q) water and
the soaked rice placed on arsenic and lint-free cotton-cloth. Steaming
time was 2 times 15 min with stirring in between. The residual water
was drained off and then freeze dried.
All cooked rice was then dried at 80 C until constant weight was
reached and then milled using a coffee/spice grinder prior to analysis.
All experiments were conducted with triplicate replication.
For total arsenic analysis 0.5 g dry weight of sample (rice or freeze
dried residual washes or residual liquor) was placed into 50 mL
polypropylene centrifuge tubes and 2.5 mL of Aristar nitric acid and
4 mL of hydrogen peroxide suprapur was added, followed by
microwave digestion using a CEM Mars5 Microwave system. On
digestion the sample was diluted to 25 mL using double distilled
deionised water with rhodium (0.02 mL 10 mg Rh/L) as an internal
standard. CRM NIST 1568a rice powder was used throughout for
the totals determination. Arsenic content was measured using an
Agilent 7500c ICP-MS with hydrogen as the collision/reaction gas.
The ICP-MS operating conditions are given in Williams et al.
1
Samples (rice or freeze dried residual washes or residual liquor) for
speciation analysis were extracted in 1% Aristar nitric acid and 1%
(vol/vol) hydrogen peroxide suprapur using a CEM Mars5 micro-
wave system. The supernatant was used for determination of
extractable arsenic and As-speciation. This oxidises arsenite to arse-
nate, improving chromatographic resolution as arsenate elutes at
some distance to MMA and DMA, where arsenite elutes adjacent to
MMA and DMA. Arsenic species were separated on a Hamilton
PRP 100 anion exchange column using phosphate buffer and the
LC-system was an Agilent 1100 system directly coupled to the Agilent
7500c ICP-MS for arsenic determination. Indium (0.01 mg/kg) in 1%
(v/v) nitric acid was added during the analysis via a T-piece as an
internal standard. CRM NIST 1568a rice powder was used
throughout for speciation determinations. There is no CRM avail-
able for inorganic and organic arsenic in rice, but NIST 1568a has
been used routinely in previous studies as a reference (Table 1).
Solutions (0.1 mL) containing known amounts of DMA (10 to 100
mg/kg) were subjected to LC-ICP-MS under the same conditions as
the supernatants. Peak areas from these measurements were used to
construct a calibration curve. Single species standards DMA, MMA
and As(V) were used for identification of species by retention time.
The supernatants (0.1 mL) were used as they were and injected onto
the column. Peak areas were used for quantification of As-species.
Every 10
th
sample was digested in duplicate and measured. Each
analytical batch contained procedural blanks, spiked samples (for
recovery estimate purposes) and CRM.
Results
The reported mean value and standard error for total arsenic in the
CRM was 0.280 mg/kg 0.007 mg/kg (n¼11) compared to its
certified value of 0.29 mg/kg with a 95% confidence interval of 0.03
mg/kg, so the CRM recovery reported here is well within the 95%
confidence interval. Spike recovery was 103.8% 5.7% (n¼12).
Limits of detection where 0.0004 mg/kg expressed on a sample weight
basis.
Table 1 reports arsenic speciation of the rice flour CRM and
compares the results of this study with those previously published in
the literature as no cereal flour CRM has certified arsenic speciation
reported for it. The results of this CRM analysis from the present
study compare favourably with previously reported studies. Spike
recoveries for arsenate and DMA are 110% 6.2% (n¼5) and 103%
4.3% (n¼5), respectively. Limits of detection for DMA are 0.004
mg/kg when expressed on a flour dry weight basis.
Total, inorganic and organic arsenic concentrations in raw, washed
and cooked rice are presented in Table 2. Mass balances, i.e.
summation of the individual measured components with respect
to the initial arsenic in raw rice, are also presented. The average
mass balance for all the data the standard error was 100.8 1.3%
(n¼20).
There was variation in the effectiveness of rinse washing in
removing total/inorganic arsenic from raw rice (Table 2). Washing
removed more total arsenic for both the polished (to 87% of raw rice
content) and wholegrain (to 85% of raw rice content) basmati, while
for all other rice percentage arsenic remaining ranged only from
96–99% of raw rice content, including parboiled. It appears that rinse
washing is more effective for basmati rice than for other types of rice,
though more samples would need to be analysed to confirm this.
Virtually all the arsenic lost through washing was inorganic (91% on
average of raw rice concentration), while negligible DMA was lost
(99% on average of raw rice concentration).
Table 1 Performance of CRM speciation compared to previous studies. As
i
refers to inorganic arsenic (arsenate and arsenite). As
o
refers to organic
arsenic (DMA and MMA). Numbers in italics are the standard error of the mean from the current study. Column recovery is the sum of species
expressed as a percentage of total arsenic determined in that solution
Extraction As
o
(mg/kg) As
i
(mg/kg) Pof species (mg/kg) Extraction efficiency (%) Column recovery (%) Reference
2M TFA 180 87 267 95 96 14
Enzymatic digest, pepsin
and pancreatin
159 101 260 * * 14
2M TFA 182 92 274 112 84 19
2M TFA 162 80 240 * * 11
Methanol : water with
sonication
180 109 288 99 * 20
Enzymatic hydrolysis, a-
amylase
171 106 277 * * 21
Ultrasonic & enzy. hydrol.,
protease & a-amylase
143 88 231 99 81 22
1MH
3
PO
4
with sonication 164 102 267 * * 23
1% HNO
3
185 99 284 104 98 This study
324 1 1
42 | J. Environ. Monit., 2009, 11, 41–44 This journal is ªThe Royal Society of Chemistry 2009
Published on 20 November 2008. Downloaded by 391533 on 21/04/2016 09:52:38.
View Article Online
Cooking rice to dryness in a 2.5 : 1 water : rice ratio, for all rice
types, resulted in no loss of arsenic from the cooked grain throughout
for all four rice types. All rice types tested for high volume cooking
(6 : 1 water to rice ratio), that is all the non-parboiled types tested,
considerably reduced both total and inorganic arsenic content. There
was no reduction in organic arsenic content on high volume cooking.
Total arsenic content was reduced to a mean of 65% of raw rice
content following rinsing and high volume cooking (Table 2), ranging
from 55% in whole grain basmati to 72% in polished long-grain. This
reduction was on average 55% for inorganic arsenic content, ranging
from 51% for polished long-grain to 60% for polished basmati. Even
though the rinse washing was ineffective for both types of the long-
grain rice, high volume cooking water reduced inorganic arsenic
content to those of basmati rice, where rinsing was more effective.
This suggests that high volume cooking by itself is enough to reduce
total and inorganic arsenic content, though rinse washing is normally
recommended as part of the preparation of rice per se.
Steaming did reduce mean total and inorganic arsenic content to
83% and 78% of the raw rice values, respectively. However, the effects
were variable, ranging from 91% for wholegrain basmati to 75% for
polished basmati for total arsenic. Percentage inorganic arsenic was
reduced lower compared to total arsenic content, with inorganic
concentrations ranging from 85% in polished long-grain to 60% in
polished basmati. While steaming did reduce total and inorganic
arsenic content it did not do so as effectively or as consistently as high
volume cooking.
Discussion
The most comparable to the present study, though more limited in
cooking treatments and rice types, was a high water rice (6 : 1)
investigation conducted by Mihucz et al.
12
Two Hungarian and one
Chinese rice types, for none of which was it recorded if the rice was
wholegrain or polished, were used in that study. They found a
42–63% reduction in total arsenic in cooked rice, with the cooking
liquor containing most of the removed arsenic from the rice (26–49%),
while the quantity removed by rinse washing was less (8–17%). It was
found that raw rice contained both arsenate and arsenite, and it was
primarily arsenite that was removed from the rice on rinsing and
boiling. Arsenite is uncharged at physiological pHs and hence more
mobile than arsenate or DMA, both of which are anionic. The DMA
findings in that study
12
confirm our results. As the present report only
records total inorganic arsenic, because the extraction process oxidises
arsenite to arsenate, the observation that primarily arsenite was
removed from the rice could not be confirmed.
In another comparable study, three West Bengali samples where
rinse washed and then cooked in a large water volume.
13
Total
arsenic, not speciation, was determined. The rinse washing step was
more exhaustive, involving 5–6 rinses until the rinse water discarded
was clear, the traditional Indian preparation, rather than the double
rinse wash step used in the experiments reported here. The rinse wash
step removed 28% of the arsenic compared to raw rice. Combined
rinse washing and large volume (6 : 1 water : rice) reduced arsenic up
Table 2 Summary of As
T
(total), As
i
(arsenate and arsenite) and As
o
(DMA and MMA) concentrations, in rice cooked in various ways. Percentage of
As
T
,As
i
and As
o
concentrations in the processed rice compared to raw rice are shown in parenthesis. Mass balances were obtained by summing the rice
with rinse wash and cooking liquor. Note all rice was rinse washed with the exception of raw rice. Data are the averages of 3 replicates. Numbers in italics
are the standard deviation (s.e.) of the mean
Rice type Cooking technique As
T
(mg/kg) s.e. As
i
(mg/kg) s.e. As
o
(mg/kg) s.e. Mass balance (%) s.e.
Polished basmati Raw 162 393 118 1
Raw washed 141 (87) 586 (92) 219 (106) 1 (96) (6)
2.5 : 1 water to rice 141 (87) 190 (92) 318 (106) 1 (93) (2)
6 : 1 water to rice 103 (64) 556 (60) 518 (100) 1 (98) (6)
Steamed 122 (75) 861 (66) 215 (83) 2 (103) (3)
Wholegrain basmati Raw 131 889 318 1
Raw washed 111 (85) 380 (90) 116 (89) 3 (88) (5)
2.5 : 1 water to rice 119 (85) 382 (90) 121 (89) 2 (97) (5)
6 : 1 water to rice 72 (55) 348 (54) 219 (106) 1 (96) (3)
Steamed 119 (91) 12 76 (85) 322 (122) 2 (100) (19)
Polished long-grain Raw 229 2138 158 2
Raw washed 222 (97) 13 131 (95) 559 (102) 3 (103) (13)
2.5 : 1 water to rice 238 (97) 6144 (95) 20 50 (102) 6 (110) (5)
6 : 1 water to rice 165 (72) 270 (51) 353 (91) 2 (113) (1)
Steamed 177 (77) 4107 (78) 252 (90) 1 (99) (4)
Wholegrain long-grain Raw 314 9183 14 87 2
Raw washed 311 (99) 18 157 (86) 386 (99) 2 (104) (11)
2.5 : 1 water to rice 324 (99) 7165 (86) 3109 (99) 2 (108) (5)
6 : 1 water to rice 219 (70) 5102 (56) 987 (100) 5 (104) (3)
Steamed 280 (89) 5156 (85) 24 76 (87) 6 (102) (4)
Italian parboiled Raw 211 5157 254 3
Raw washed 203 (96) 7149 (95) 354 (100) 4 (100) (5)
2.5 : 1 water to rice 211 (96) 7157 (95) 454 (100) 2 (97) (9)
Long-grain parboiled Raw 186 2115 256 3
Raw washed 180 (97) 199 (86) 257 (102) 1 (104) (1)
2.5 : 1 water to rice 163 (97) 10 86 (86) 13 39 (102) 6 (95) (12)
AVERAGE of ALL RICE
TYPES
Raw washed (93) (2) (91) (2) (99) (2) (99.2) (2.6)
2.5 : 1 water to rice (93) (2) (91) (2) (99) (2) (100.0) (2.9)
6 : 1 water to rice (65) (4) (55) (2) (99) (3) (102.8) (3.8)
Steamed (83) (4) (78) (5) (96) (9) (101.0) (0.9)
This journal is ªThe Royal Society of Chemistry 2009 J. Environ. Monit., 2009, 11, 41–44 | 43
Published on 20 November 2008. Downloaded by 391533 on 21/04/2016 09:52:38.
View Article Online
to 58% of the raw rice content. This is compared to an average of 35%
removal (maximum of 45%) or total arsenic reported in the current
study (Table 1). The increased efficiency of removal for the Indian
rice of that study
13
may be due to more exhaustive rinse washing, or
due to the intrinsic nature of the rice used in that study.
Other studies have been conducted on the effects of cooking rice on
arsenic content, but have focused on the impact of arsenic contami-
nated cooking water on rice arsenic burdens.
14–18
While relevant to
S.E. Asian and US scenarios where cooking and drinking water is
arsenic contaminated, they are not relevant to many parts of the globe.
It was found here that cooking rice in a large volume of water (6 : 1,
water : rice) had the greatest effect with regards to lowering arsenic
levels in cooked rice. Specifically, it preferentially reduced the inor-
ganic arsenic content by 45% of that in the raw rice, when combined
with rinse washing. It is recommended that to reduce total and
inorganic arsenic content of rice, that rice is rinse washed and cooked
in a 6 : 1 water to rice ratio. Exhaustive rinse washing, as practised in
India, may reduce arsenic content even further when combined with
large cooking water volume.
Acknowledgements
This project was funded by a Food Standards Agency grant C01049.
Notes and references
1 P. N. Williams, A. Villada, C. Deacon, A. Raab, J. Figuerola, A. J. Green
and A. A. Meharg, Environ. Sci. Technol., 2007, 41, 6854–6859.
2 Y. J. Zavala and J. M. Duxbury, Environ. Sci. Technol., 2008, 42,
3856–3860.
3 S. Lee, Geoderma, 2006, 135, 26–37.
4 Y.-G. Zhu, G.-X. Sun, M. Lei, M. Teng, Y.-X Liu, N.-C. Chen,
L.-H. Wang, A. M. Carey, C. Deacon, A. Raab, A. A. Meharg and
P. N. Williams, Environ. Sci. Technol., 2008, 42, 5008–5013.
5 H. Liu, A. Probst and B. Liao, Sci. Total Environ., 2005, 339,
153–166.
6 A. A. Meharg and M. Rahman, Environ. Sci. Technol., 2003, 37,
229–234.
7 P. N. Williams, M. R. Islam, E. E. Adomako, A. Raab and
S. A. Hossain, Environ. Sci. Technol., 2006, 40, 4903–4908.
8 P. N. Williams, A. Raab, J. Feldmann and A. A. Meharg, Environ.
Sci. Technol., 2007, 41, 2178–2183.
9 NRC(National Research Council). Arsenic in drinking water – 2001
Update. National Academy Press, Washington, D.C. 2001.
10 IARC. 84 Some drinking-water disinfectants and contaminants,
including arsenic, Geneva. 2004.
11 P. N. Williams, A. H. Price, A. Raab, S. A. Hossain, J. Feldmann and
A. A. Meharg, Environ. Sci. Technol., 2005, 39, 5531–5540.
12 V. G. Mihucz, E. Tatar, I. Virag, C. Zhao, Y. Jao and G. Zaray, Food
Chemistry, 2007, 105, 1718–1725.
13 M. K. Engupta, M. A. Hossain, A. Mukherjee, S. Ahamed, B. Das,
B. Nayak, A. Pal and D. Chakraborti, Food Chem. Toxicol., 2006,
44, 1823–1829.
14 A. H. Ackerman, P. A. Creed, A. N. Parks, M. W. Fricke,
C. A. Schwegel, J. T. Creed, D. T. Heitkemper and N. P. Vela,
Environ. Sci. Technol., 2005, 39, 5241–5246.
15 M. Ae, C. Watanabe, T. Inaoka, M. Sekiyama, N. Sudo, M. H. Bokul
and R. Ohtsuka, Lancet, 2002, 360, 1839–1840.
16 J. G. Aparra, D. Velez, R. Barbera, R. Farre and R. Montoro, Agric.
Fd. Chem., 2005, 53, 8829–8833.
17 S. Torres-Escribano, M. Leal, D. Velez and R. Montoro, Environ. Sci.
Technol, 2008, 42, 3867–3872.
18 A. Ignes, K. Mita, F. Burlo and A. A. Carbonell-Varrachina, Fd.
Addit. Contam., 2007, 25, 41–50.
19 D. T. Heitkemper, N. P. Vela, K. R. Stewart and C. S. Westphal,
J. Anal. At. Spect., 2001, 16, 299–306.
20 M. D’Amato, G. Forte and S. Caroli, J. AOAC Intern., 2004, 87,
238–243.
21 U. Ohlmeyer, E. Jantzen, J. Kuballa and S. Jakubik, Anal. Bioanal.
Chem., 2003, 377, 6–13.
22 E. Anz, R. Munoz-Olivas and C. Camara, Anal. Chim. Acta, 2005,
535, 227–235.
23 M. N Matosreyes, M. L. Cervera, R. C. Campos and M. De la
Guardia, Spectrochim. Acta, Part B, 2007, 62, 1078–1082.
44 | J. Environ. Monit., 2009, 11, 41–44 This journal is ªThe Royal Society of Chemistry 2009
Published on 20 November 2008. Downloaded by 391533 on 21/04/2016 09:52:38.
View Article Online
... A study reported that up to 57% of As can be removed when rice is washed until clear, then cooked with 1:6 rice and water, and excess water is discarded after cooking [21]. Another study reported that cooking rice with deionized water (1:6 ratio) can remove around 35% and 45% of total and inorganic As concentrations from long-grain and basmati rice, respectively [25]. Similarly, cooking of rice with excess water (1:10 rice: water ratio) removed inorganic As by 50%, 60%, and 40% in brown rice, parboiled, and long grain polished rice, respectively [26]. ...
... We found 1-17% reduction in inorganic As from raw rice when cooked in a rice cooker with a 1:2 rice to water ratio after washing three times, while a 20-39% reduction was observed in traditional cooking using a 1:6 rice to water ratio after washing five times. Atiaga, et al. [38] reported a 1:6 rice to water ratio reduced inorganic As by 80% from brown and 60% from white rice, while [25] reported a 44 and 49% reduction in inorganic As from brown and white rice, respectively, when cooked with excess water. Similarly Gray, et al. [26] reported a reduction in inorganic As by 40 and 50% from white and brown rice in cooking with 1:6-10 rice to water ratios. ...
... Mwale, et al. [18] reported a 4.5% and 30% reduction in total As from raw rice when cooked with 1:3 and 1:6 rice to water ratios, respectively. Cooking of rice with 1:6 rice to water ratio was reported to remove As by 35% [25], 15 to 50% [26], and up to 63% [63]. Cooked rice As levels may vary from uncooked rice based on the As content in the cooking water [53,64,65]. ...
Article
Full-text available
This study determined the influence of different cooking procedures on the removal of toxic elements (TEs) including arsenic (As), cadmium (Cd), and lead (Pb) along with other nutrient elements from different commercially available rice brands sold in Bangladeshi markets. We observed 33%, 35%, and 27% average removal of As, Cd, and Pb accordingly from rice when cooked with a rice to water ratio of 1:6 after washing 5 times. We also found a significant reduction in essential elements: Zn (17%), Cu (10%), Mn (22%), Se (49%), and Mo (22%), when rice cooking was performed as in traditional practice. Daily dietary intakes were found to be between 0.36 and 1.67 µg/kgbw for As, 0.06 and 1.15 µg/kgbw for Cd, and 0.04 and 0.17 µg/kgbw for Pb when rice was cooked by the rice cooker method (rice:water 1:2), while in the traditional method (rice:water 1:6) daily intake rates ranged from 0.23 to 1.3 µg/kgbw for As, 0.04 to 0.88 µg/kgbw for Cd, and 0.03 to 0.15 µg/kgbw for Pb for adults. The HQ and ILCR for As, Cd, and Pb revealed that there is a possibility of noncarcinogenic and carcinogenic risk for As but no appreciable risk for Cd and Pb from consumption of rice.
... When the rice is boiled using sufficient water where no extra water is left after the rice is cooked results in the presence of high As levels in cooked rice. Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. ...
... Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. Recent studies suggested that washing three times with deionized water reduces tAs content in both white as well as brown rice by up to 81-84% and 71-83%. ...
Article
Full-text available
Citation: Khan, M.I.; Ahmad, M.F.; Ahmad, I.; Ashfaq, F.; Wahab, S.; Alsayegh, A.A.; Kumar, S.; Hakeem, K.R. Arsenic Exposure through
... When the rice is boiled using sufficient water where no extra water is left after the rice is cooked results in the presence of high As levels in cooked rice. Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. ...
... Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. Recent studies suggested that washing three times with deionized water reduces tAs content in both white as well as brown rice by up to 81-84% and 71-83%. ...
Article
Full-text available
Dietary arsenic (As) contamination is a major public health issue. In the Middle East, the food supply relies primarily on the import of food commodities. Among different age groups the main source of As exposure is grains and grain-based food products, particularly rice and rice-based dietary products. Rice and rice products are a rich source of core macronutrients and act as a chief energy source across the world. The rate of rice consumption ranges from 250 to 650 g per day per person in South East Asian countries. The source of carbohydrates through rice is one of the leading causes of human As exposure. The Gulf population consumes primarily rice and ready- to-eat cereals as a large proportion of their meals. Exposure to arsenic leads to an increased risk of non-communicable diseases such as dysbiosis, obesity, metabolic syndrome, diabetes, chronic kidney disease, chronic heart disease, cancer, and maternal and fetal complications. The impact of arsenic-containing food items and their exposure on health outcomes are different among different age groups. In the Middle East countries, neurological deficit disorder (NDD) and autism spectrum disorder (ASD) cases are alarming issues. Arsenic exposure might be a causative factor that should be assessed by screening the population and regulatory bodies rechecking the limits of As among all age groups. Our goals for this review are to outline the source and distribution of arsenic in various foods and water and summarize the health complications linked with arsenic toxicity along with identified modifiers that add heterogeneity in biological responses and suggest improvements for multi-disciplinary interventions to minimize the global influence of arsenic. The development and validation of diverse analytical techniques to evaluate the toxic levels of different As contaminants in our food products is the need of the hour. Furthermore, standard parameters and guidelines for As-containing foods should be developed and implemented.
... When the rice is boiled using sufficient water where no extra water is left after the rice is cooked results in the presence of high As levels in cooked rice. Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. ...
... Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. Recent studies suggested that washing three times with deionized water reduces tAs content in both white as well as brown rice by up to 81-84% and 71-83%. ...
Article
Full-text available
Dietary arsenic (As) contamination is a major public health issue. In the Middle East, the food supply relies primarily on the import of food commodities. Among different age groups the main source of As exposure is grains and grain-based food products, particularly rice and rice-based dietary products. Rice and rice products are a rich source of core macronutrients and act as a chief energy source across the world. The rate of rice consumption ranges from 250 to 650 g per day per person in South East Asian countries. The source of carbohydrates through rice is one of the leading causes of human As exposure. The Gulf population consumes primarily rice and ready-to-eat cereals as a large proportion of their meals. Exposure to arsenic leads to an increased risk of non-communicable diseases such as dysbiosis, obesity, metabolic syndrome, diabetes, chronic kidney disease, chronic heart disease, cancer, and maternal and fetal complications. The impact of arsenic-containing food items and their exposure on health outcomes are different among different age groups. In the Middle East countries, neurological deficit disorder (NDD) and autism spectrum disorder (ASD) cases are alarming issues. Arsenic exposure might be a causative factor that should be assessed by screening the population and regulatory bodies rechecking the limits of As among all age groups. Our goals for this review are to outline the source and distribution of arsenic in various foods and water and summarize the health complications linked with arsenic toxicity along with identified modifiers that add heterogeneity in biological responses and suggest improvements for multi-disciplinary interventions to minimize the global influence of arsenic. The development and validation of diverse analytical techniques to evaluate the toxic levels of different As contaminants in our food products is the need of the hour. Furthermore, standard parameters and guidelines for As-containing foods should be developed and implemented.
... When the rice is boiled using sufficient water where no extra water is left after the rice is cooked results in the presence of high As levels in cooked rice. Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. ...
... Raab et al. determined tAs and iAs content in a variety of basmati, long grain, polished, and whole rice by washing, rinsing, and boiling/steaming methods in low-volume (rice-to-water ratio 1:2.5) and high-volume (ratio of water to rice: 1:6) uncontaminated water [185]. Findings suggested that a high volume of water during preparation reduces both tAs and iAs by 35% and 45%, respectively, in long-grain basmati rice as compared to raw rice [185]. Recent studies suggested that washing three times with deionized water reduces tAs content in both white as well as brown rice by up to 81-84% and 71-83%. ...
Article
Full-text available
Citation: Khan, M.I.; Ahmad, M.F.; Ahmad, I.; Ashfaq, F.; Wahab, S.; Alsayegh, A.A.; Kumar, S.; Hakeem, K.R. Arsenic Exposure through
... Our study shows that preparations of rice as used in the consumer's kitchen can result in a significant reduction of the arsenic concentration, which is in agreement with data from experiments performed in a more laboratorial setting, with reductions of 40-50% for white rice and 30% for brown rice [10][11]. In case the ratio of water to rice is too small (< 2.5:1), as e.g. in steaming of rice, significantly less arsenic is removed [12]. It has to be noted that by using a lot of water in the cooking process, not only arsenic, but also a number of beneficial nutrients like vitamins will be removed as well [13]. ...
Article
Full-text available
Rice is the most widely consumed food for a large part of the world containing a variety of essential nutrients, but can also be contaminated with toxics like arsenic. This study analyzes the effect of cooking and frying, processed in the consumer’s kitchen, on arsenic concentrations Firstly, arsenic concentrations were measured in a number of rice species from Thailand and Turkey, available in supermarkets. The effect of cooking was studied in both white and brown rice with time of cooking and rice: water ratio as recommended by the producer. Part of the cooked rice was fried together with other ingredients for the preparation of the popular dish nasi goreng. Arsenic concentrations were measured with instrumental neutron activation analysis. Only one of the ten analyzed species contained an arsenic concentration beyond the European maximum limit of 0.3 mg/kg. Cooking of white rice resulted in a decrease of the arsenic concentration by 46%, while the concentration in brown rice was reduced by 27%. The preparation of the fried rice dish nasi goreng resulted in an additional reduction by 20% per weight unit, which should be attributed for the most part to a diluting effect by the addition of the other ingredients. Heating of rice without water reduced the arsenic concentration only by 10%. Cooking and frying of rice according to recommendations by the producer, result in a significant reduction of the arsenic concentration.
... As for people in different age groups, the people aged 45-55 consumed more rice than that of other groups; however, there were no statistically differences. Research (Raab et al., 2008) showed that washing and cooking were effective at removing part of the inorganic arsenic in rice, but only whole wheat rice and basmati (a kind of indica rice) had a higher removal efficiency, and a higher water-to-rice ratio helped to remove the arsenic in rice. Researches (Mondal et al., 2010;Mantha et al., 2017) found that drinking water was the main source of human arsenic exposure, but for people who consume rice extensively, recent studies have reported significant exposure from rice intake for the exposed population, which in some cases exceeds that from drinking water. ...
Article
Full-text available
As a well-known human carcinogen, arsenic (As) could pose various detrimental health effects to humans mainly through the exposure pathway of food ingestion. In comparison with other foods, rice can accumulate more arsenic due to its tissue specificity. Thus, it is of great significance to assess the health risk of As due to rice ingestion. However, the study on risk assessment from exposure to As in rice is still in an early stage and lack accuracy to date. In this study, after obtaining the rice exposure behavior patterns based on a questionnaire survey, a total of 160 rice samples, which consisted of 4 types (i.e., japonica, indica, glutinous and brown rice), rice from 4 areas and consumed by most of the population in Beijing, were collected. On the basis of the actual intake rate and the species weighted average concentration of consumed rice, average daily exposure dose and health risks of inorganic As (iAs) from rice ingestion were assessed for the population among different genders and ages in Beijing. The results show that japonica rice and rice from Northeast China had higher As content, with the same value of 0.064 mg kg⁻¹. And, they were the most popular rice consumed by people, with the intake rates of 75.50 g d⁻¹, and 67.91 g d⁻¹, respectively. The proportion of iAs to total As (tAs) was 58.34%, with a range of 43.18–71.88%. The average daily dose of iAs for the population was 1.15 × 10–4, which mainly came from japonica rice and the rice from Northeast China ingestion. In comparison with the acceptable non-cancer risk, which had a HQ value of 0.38, the carcinogenic risk of the population in Beijing was 1.73 × 10–4 on average. Furthermore, males had higher carcinogenic risk (1.88 × 10–4) than females (1.62 × 10–4), and the people in the age of 45–55 suffered from the highest carcinogenic risk (2.22 × 10–4), which mainly was attributed to the japonica rice and the rice from Northeast China. This study strengthened that appropriate dietary patterns should be paid more attention in order to control the health risk due to As exposure.
Article
Health effect and future risk assessment have been evaluated for a year on a group of arsenicosis patients (n = 24) examining the impact of treated surface water with continuous consumption of arsenic-contaminated dietary foodstuffs. The daily dietary intake rate of arsenic through cooked rice is 5.50 μg/kg bw/day, which is much higher than PTDI recommended value compared to cooked vegetables and treated drinking water. The effect of acute toxicity showed a decreasing trend of 42.9% arsenic in urine (n = 24) after 6 months. Scalp hair (n = 19) and nail (n = 18) arsenic concentration showed a decreasing trend of 39.3% (range: 1.34–86.2%) and 36.9% (range: 0.88–85%), respectively after 12 months. The body hair (hand and leg) and skin scale arsenic accumulation showed high and diverse distribution pattern. Excretion of arsenic through sweat was higher than urine with a mean concentration of 34.7 μg/L (range: 4.76–65 μg/L). Chronic arsenic exposure for a long period of time is the considerable pathway to severe dermatological skin manifestations in the arsenical patients. One-way ANOVA (Tukey-test) interpretation showed a significant relationship between arsenic intakes, biological tissues and dermatological manifestations within the studied groups. Linear mixed modelling showed differential temporal trends of arsenic levels through biomarkers for both studied male and female patients. The SAMOE value for treated drinking water and cooked vegetables showed low to moderate concern level (class 3), whereas, high concern level (class 5) was observed for cooked rice. The future cancer and non-cancerous risk predominantly exists through consumption of rice compared to vegetables and treated drinking water. Supplementation of arsenic-safe drinking water and nutritional food is highly recommended for the arsenic patients to fight against the devastating arsenic calamity.
Article
Rice (Oryza sativa L.) is considered as the staple food for 50% of the world's population. Humans are exposed to arsenic (As) through rice consumption, which is a global health issue that requires attention. The present review reflects the scenario of rice grown in As endemic regions of Asia that has a significant portion of inorganic As (iAs) compared to other rice grown areas around the world. Post-harvesting, pre-cooking, and cooking procedures in South and South-East Asian countries employ As-contaminated groundwater. Polishing of brown rice and parboiling, washing and cooking with As-safe water can reduce As concentration and nutrient level in cooked rice. However, in rural parts of South-east Asia, rice is usually cooked using As-contaminated groundwater and consumption of this As enriched rice and water may cause a significant health exposure in humans. Bioaccessibility and bioavailability of As can be determined using in-vitro and in-vivo techniques that can be utilized as a tool to assess As exposure in humans. Arsenic in cooked rice may be reduced by using newly developed cooking procedures such as Kateh cooking, steam percolating, and the parboiled and absorbed (PBA) method. For individuals living in rural regions, using rainwater or treated surface water for drinking and cooking is also an alternative. Although this study examined the processes involved in the post-harvesting, pre-cooking, and cooking stages, there are still significant research gaps in this area that must be addressed in near future.
Article
Full-text available
This review summarizes the current knowledge on essential vitamins B1, B2, B3, and B5. These B-complex vitamins must be taken from diet, with the exception of vitamin B3, that can also be synthetized from amino acid tryptophan. All of these vitamins are water soluble, which determines their main properties, namely: they are partly lost when food is washed or boiled since they migrate to the water; the requirement of membrane transporters for their permeation into the cells; and their safety since any excess is rapidly eliminated via the kidney. The therapeutic use of B-complex vitamins is mostly limited to hypovitaminoses or similar conditions, but, as they are generally very safe, they have also been examined in other pathological conditions. Nicotinic acid, a form of vitamin B3, is the only exception because it is a known hypolipidemic agent in gram doses. The article also sums up: (i) the current methods for detection of the vitamins of the B-complex in biological fluids; (ii) the food and other sources of these vitamins including the effect of common processing and storage methods on their content; and (iii) their physiological function.
Article
Concern has been raised by Bangladeshi and international scientists about elevated levels of arsenic in Bengali food, particularly in rice grain. This is the first inclusive food market-basket survey from Bangladesh, which addresses the speciation and concentration of arsenic in rice, vegetables, pulses, and spices. Three hundred thirty aman and boro rice, 94 vegetables, and 50 pulse and spice samples were analyzed for total arsenic, using inductivity coupled plasma mass spectrometry (ICP-MS). The districts with the highest mean arsenic rice grain levels were all from southwestern Bangladesh: Faridpur (boro) 0.51 > Satkhira (boro) 0.38 > Satkhira (aman) 0.36 > Chuadanga (boro) 0.32 > Meherpur (boro) 0.29 microg As g(-1). The vast majority of food ingested arsenic in Bangladesh diets was found to be inorganic; with the predominant species detected in Bangladesh rice being arsenite (AsIII) or arsenate (AsV) with dimethyl arsinic acid (DMAV) being a minor component. Vegetables, pulses, and spices are less important to total arsenic intake than water and rice. Predicted inorganic arsenic intake from rice is modeled with the equivalent intake from drinking water for a typical Bangladesh diet. Daily consumption of rice with a total arsenic level of 0.08 microg As g(-1) would be equivalent to a drinking water arsenic level of 10 microg L(-1).
Article
Soil solution samples were extracted from paddy soil near mine tailing dumps in an abandoned mine in Korea. Trace metals in the soil solution and soil solid (As, Cd, Cr, Cu, Ni, Pb and Zn) were analysed, along with the mineralogical composition of the soil, using XRD. Sequential extraction was also undertaken for speciation of different fractions bound to the soil solid. Kaolinite was the main clay minerals and the CEC value was relatively low, recording between 11.0 and 27.5 meq/100 g. Comparison of the paddy soil with the control soil samples collected from an uncontaminated area revealed that nearly all the paddy soil samples were enriched for trace metal contents. Cadmium, Pb and Zn concentrations exceeded the intervention values of the Dutch standards, which requires remediation action. Arsenic, Ni and Cr were below the values, indicating little or no contamination for these metals. The trace metal contents in the paddy varied with distance from the mine tailing site. In addition to the changes with distance, higher proportions of relatively easily releasable fractions, such as exchangeable forms, were found to be proportional to the total trace metal contents in the soil sample. Although most paddy soil samples were enriched with respect to some trace elements, concentrations of Cd, Cu, Ni and Pb in the solution were very low, recording maximum levels of up to only several milligrams per liter. Geochemical equilibrium modelling using PHREEQC indicates the presence of solubility controlling solid phases for Cd and Pb, whereas Zn and Cu seem to be controlled by adsorption/desorption processes. We presumed that either iron sulphides or oxides removed dissolved trace elements. Under reducing conditions, iron may be dissolved as Fe2+ in the soil solution and then the reduced iron possibly would form iron sulphide precipitates with sulphur from the mine tailings. On the contrary, in an oxidizing condition, iron exists as the oxidised form, Fe3+, and again forms iron oxides, which is a good adsorbent for trace elements in soil environments. A Cycle of dry and flooded conditions is characteristic for paddy fields. Therefore, either iron sulphide or iron oxide is believed to provide a good adsorbing site for trace metals and so explains the subsequent low concentrations in the soil solution. Despite the low trace metal concentrations in the soil solution, higher portions of the trace metals still exist as relatively easily available form in the soil solid. It should be stressed that controlling of the redox condition and pH would be important in managing the transport of trace metals in the paddy soil that was affected by the mine tailings.
Article
A method is presented for arsenic speciation analysis in rice using ion chromatography coupled to inductively coupled plasma mass spectrometry. Several procedures for the extraction of arsenic species from rice were investigated and compared. Treatment of the samples with 2 M trifluoroacetic acid for 6 h at 100°C provided good extraction efficiency. Fortification recoveries were 83, 88, 100, and 93% for arsenite (100 ng As g−1), arsenate (100 ng As g−1), methylarsonic acid (MMA, 50 ng As g−1), and dimethylarsinic acid (DMA, 200 ng As g−1), respectively. The arsenate fortification recovery was calculated using the sum of the increase in arsenate and arsenite concentrations because arsenate was partially reduced to arsenite during the extraction process. Thus the sum of their concentrations is reported in this method as total inorganic arsenic. The sum of the arsenic species determined in NIST SRM 1568a rice flour (0.27 µg g−1 As), compared well with the certified total arsenic value (0.29 µg g−1 As). The speciation results obtained for 5 samples of long grain rice and one sample of wild rice are compared with total arsenic concentrations as determined by ICP-MS. The total arsenic concentrations ranged from 0.11 to 0.34 mg kg−1. The sum of the arsenic species extracted and determined by IC-ICP-MS ranged from 84 to 99% of the measured total arsenic concentrations. Inorganic arsenic accounted for 11–91% of the arsenic detected while DMA accounted for most of the remaining arsenic in the samples.
Article
Two Hungarian and one Chinese rice samples were selected in order to establish the extractable arsenic content by washing and cooking in water in a ratio of 6:1, water:rice (cm3:g) by inductively coupled plasma sector field mass spectrometry (ICP-SF-MS). Total arsenic concentration of the Zhenshan 97, Risabell and Ko˝röstáj-333 samples were 171.3 ± 7.1 ng g−1, 116.0 ± 3.7 ng g−1 and 139.0 ± 6.1 ng g−1, respectively, which did not exceed the toxic limits established for As in Hungary (0.3 μg g−1) or in China (0.7 μg g−1). The predominant chemical form of As in the raw rice samples determined by on-line high performance liquid chromatography and ICP-MS was arsenite. Moreover, enzymatic hydrolysis with α-amylase + protease and microprobe focused sonication proved that arsenite could be removed in the highest extent by washing and cooking, meanwhile the main As form remaining in the cooked rice was As(V). Thus, it is recommended to prepare rice-containing dishes in abundant water, which should be discarded after washing and cooking. The results were validated with a NIST SRM 1568a.
Article
A fast, sensitive and simple non-chromatographic analytical method was developed for the speciation analysis of toxic arsenic species in cereal samples, namely rice and wheat semolina. An ultrasound-assisted extraction of the toxic arsenic species was performed with 1 mol L− 1 H3PO4 and 0.1% (m/v) Triton XT-114. After extraction, As(III), As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) concentrations were determined by hydride generation atomic fluorescence spectrometry using a series of proportional equations corresponding to four different experimental reduction conditions. The detection limits of the method were 1.3, 0.9, 1.5 and 0.6 ng g− 1 for As(III), As(V), DMA and MMA, respectively, expressed in terms of sample dry weight. Recoveries were always greater than 90%, and no species interconversion occurred. The speciation analysis of a rice flour reference material certified for total arsenic led to coherent results, which were also in agreement with other speciation studies made on the same certified reference material.
Article
This work proposes an arsenic speciation method, which reduces the sample treatment time from several hours, required by other extraction procedures, to only a few minutes. No organic solvents have to be used and several extraction steps can be avoided, thus diminishing possible sources of error. Total As was determined by ICP–MS and major arsenic species present in rice (As (III), As (V), methylarsonic acid (MMA) and dimethyarsinic acid (DMA)) were quantified by LC–ICP–MS. Different treatments for extraction were evaluated: aqueous, methanol and tetramethyl ammonium hydroxide (TMAH) extraction as well as enzymatic hydrolysis. Several parameters were optimised, such as sonication time, amplitude, immersion depth of the probe into the solution, extraction temperature, etc. Quantitative extraction for total arsenic (>95%) and 90% extraction for the sum of the arsenic species without species transformation were obtained by applying an enzymatic treatment using an aqueous mixture of protease XIV and α-amylase in only 3 min. A disruption of the cell membranes due to the focused sonication energy, which alleviates enzyme attack, seems to be the responsible of such extraction enhancement.The method was applied to a rice sample used in an inter-comparison exercise (SEAS G6RD-CT2001-00473) and to two commercial rice samples. The method was validated for total arsenic extraction by analysing a certified reference material from NIST (SRM 1568a).
Article
Two approaches were undertaken to characterize the arsenic (As) content of Chinese rice. First, a national market basket survey (n = 240) was conducted in provincial capitals, sourcing grain from China's premier rice production areas. Second, to reflect rural diets, paddy rice (n = 195) directly from farmers fields were collected from three regions in Hunan, a key rice producing province located in southern China. Two of the sites were within mining and smeltery districts, and the third was devoid of large-scale metal processing industries. Arsenic levels were determined in all the samples while a subset (n = 33) were characterized for As species, using a new simple and rapid extraction method suitable for use with Hamilton PRP-X100 anion exchange columns and HPLC-ICP-MS. The vast majority (85%) of the market rice grains possessed total As levels < 150 ng g(-1). The rice collected from mine-impacted regions, however, were found to be highly enriched in As, reaching concentrations of up to 624 ng g(-1). Inorganic As (As(i)) was the predominant species detected in all of the speciated grain, with As(i) levels in some samples exceeding 300 ng g(-1). The As(i) concentration in polished and unpolished Chinese rice was successfully predicted from total As levels. The mean baseline concentrations for As(i) in Chinese market rice based on this survey were estimated to be 96 ng g(-1) while levels in mine-impacted areas were higher with ca. 50% of the rice in one region predicted to fail the national standard.
Article
In Bangladesh, rice is boiled with an excessive amount of water, and the water remaining after cooking will be discarded. We did an on-site experiment to assess the effect of this cooking method on the amount of arsenic retained in cooked rice. The concentration of arsenic in cooked rice was higher than that in raw rice and absorbed water combined, suggesting a chelating effect by rice grains, or concentration of arsenic because of water evaporation during cooking, or both. The method of cooking and water used can affect the amount of arsenic in cooked rice, which will have implications for the assessment of the health risks of arsenic.
Article
Arsenic contaminated groundwater is used extensively in Bangladesh to irrigate the staple food of the region, paddy rice (Oryza sativa L.). To determine if this irrigation has led to a buildup of arsenic levels in paddy fields, and the consequences for arsenic exposure through rice ingestion, a survey of arsenic levels in paddy soils and rice grain was undertaken. Survey of paddy soils throughout Bangladesh showed that arsenic levels were elevated in zones where arsenic in groundwater used for irrigation was high, and where these tube-wells have been in operation for the longest period of time. Regression of soil arsenic levels with tube-well age was significant. Arsenic levels reached 46 microg g(-1) dry weight in the most affected zone, compared to levels below l0 microg g(-1) in areas with low levels of arsenic in the groundwater. Arsenic levels in rice grain from an area of Bangladesh with low levels of arsenic in groundwaters and in paddy soils showed that levels were typical of other regions of the world. Modeling determined, even these typical grain arsenic levels contributed considerably to arsenic ingestion when drinking water contained the elevated quantity of 0.1 mg L(-1). Arsenic levels in rice can be further elevated in rice growing on arsenic contaminated soils, potentially greatly increasing arsenic exposure of the Bangladesh population. Rice grain grown in the regions where arsenic is building up in the soil had high arsenic concentrations, with three rice grain samples having levels above 1.7 microg g(-1).