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Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment a
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B.L. Batista , V.C. De Oliveira Souza , F.G. Da Silva & F. Barbosa, Jr
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Departamento de Análises Clínicas , Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto – FCFRP – USP – Avenida do Café , s/n, Monte Alegre, 14040-903, Ribeirão Preto, SP, Brazil Published online: 25 Nov 2010.
To cite this article: B.L. Batista , V.C. De Oliveira Souza , F.G. Da Silva & F. Barbosa, Jr (2010) Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment, Food Additives & Contaminants: Part B: Surveillance, 3:4, 253-262, DOI: 10.1080/19393210.2010.516024 To link to this article: http://dx.doi.org/10.1080/19393210.2010.516024
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Food Additives and Contaminants: Part B Vol. 3, No. 4, December 2010, 253–262
VIEW DATASET Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment B.L. Batista, V.C. De Oliveira Souza, F.G. Da Silva and F. Barbosa, Jr* Departamento de Ana´lises Clı´nicas, Toxicolo´gicas e Bromatolo´gicas, Faculdade de Cieˆncias Farmaceˆuticas de Ribeira˜o Preto – FCFRP – USP – Avenida do Cafe´, s/n, Monte Alegre, 14040-903, Ribeira˜o Preto, SP, Brazil
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(Received 25 June 2010; final version received 12 August 2010) Twenty-seven rice samples from Brazil, four parboiled brown, seventeen white and six parboiled white were analysed by ICP-MS for trace element determination. Concentrations of arsenic varied from 58.8 to 216.9 ng g1, for cadmium from 6.0 to 20.2 ng g1, for antimony from 0.12 to 1.28 ng g1, and for uranium from 0.025 to 1.28 ng g1. The estimated daily intake through rice consumption was 9.5 mg for As, 2.4 mg for Cd, 0.029 mg for Sb, 0.013 mg for U, 3.1 mg for Co, 0.2 mg for Cu, 85.6 mg for Mg, 1.9 mg for Mn, 333 mg for P, 3.0 mg for Se, 1.6 mg for Zn, 0.9 mg for Rb, and 0.3 mg for V. Found values represent a considerable percentage of the dietary reference intakes and provisional tolerable daily intake for essential and toxic elements, respectively. Keywords: rice; cereals; trace elements (nutritional); trace elements (toxic)
Introduction Rice (Oryza sativa L.), the second most widely produced cereal in the world, is an important component of the world population’s basic diet. Rice cultivation is the principal activity and source of income for millions of households around the globe, and several countries in Asia and Africa are highly dependent on rice as a source of foreign exchange earnings and government revenue. At the beginning of the 1990s, annual production was around 350 106 tons and by the end of the century it had reached 410 106 tons. Brazil is the most important non-Asian producer, followed by the United States. Brazil’s rice consumption is 74–76 kg/inhabitant/year (rice with chaff). Unfortunately, populations of many of the main rice-consuming countries suffer from nutrient deficiency-related diseases, with an insufficient intake of important essential elements. In some cases, diet is also an important source of toxic elements (Barbosa et al. 2009; Grotto et al. 2010). Despite this scenario, systematic evaluation of the composition of essential and toxic elements in the most commonly consumed food in developing countries is not a routine practice. Measuring the concentration of toxic and essential elements in rice is thus of enormous importance in Brazil. Moreover, a study of this kind will also assist in estimating the daily intake of both important essential elements and toxic elements through rice consumption. To determine chemical elements in food samples, distinct atomic spectroscopy techniques have been *Corresponding author. Email: [email protected] ISSN 1939–3210 print/ISSN 1939–3229 online ß 2010 Taylor & Francis DOI: 10.1080/19393210.2010.516024 http://www.informaworld.com
proposed (Saracoglu et al. 2007; Tuzen 2003; Tuzen et al. 2007). However, inductively coupled plasma mass spectrometry (ICP-MS) offers distinct advantages, including simultaneous multi-element measurement capability coupled with very low detection limits (Ammann 2007; Parsons and Barbosa 2007; Rodrigues et al. 2008). Moreover, it offers a wide linear dynamic range which makes it possible to determine major and trace elements in the same sample injection (Ammann 2007; Parsons and Barbosa 2007). Therefore, the aims of this study were: (1) to investigate the mineral composition (essential and toxic elements) of three different types of Brazilian rice samples (white, parboiled white and parboiled brown) by using inductively coupled plasma mass spectrometry (ICP-MS); and (2) to estimate the population’s daily intake through rice consumption of a number of toxic and essential elements.
Materials and methods Rice sampling and treatment Twenty-seven raw rice samples, four parboiled brown (PB), seventeen white (W) and six parboiled white (PW) were randomly purchased at supermarkets in different Brazilian cities. Before digestion, samples (15 g) were separated by quartering as described by the Codex Alimentarius
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Commission (CAC) (2004) and divided into three plastic tubes. The contents of each tube were ground for 3 min in a ball mill (Tecnal TE 350, Piracicaba, Brazil) and sifted in a 106 mm sieve (Bertel, Caieiras, Brazil). Then, samples were digested in closed vessels using a microwave oven decomposition system (Ethos D, Milestone, Sorisole, Italy) according to the validated method proposed by Nardi et al. (2009). Briefly, rice samples (250 mg) were accurately weighed in a PFA digestion vessel and then 5 ml of nitric acid 20% v/v þ 2 mL of 30% (v/v) H2O2 were added. The vessel was placed inside the microwave oven and decomposition was carried out according to the programme shown in Table 1. After that the solutions were left to cool and the volume was made up to 50 mL with MilliQ water. Rhodium was then added as an internal standard to a final concentration of 10 mg L1.
Apparatus Analyses were carried out with an inductively coupled plasma mass spectrometer equipped with a reaction cell (DRC-ICP-MS ELAN DRCII, PerkinElmer, Sciex, Norwalk, CT, USA) operating with highpurity argon (99.999%, Praxaair, Brazil). The sample introduction system was composed of a quartz cyclonic spray chamber and a MeinhardÕ nebulizer connected by TygonÕ tubes to the ICP-MS’s peristaltic pump (set at 20 rpm). The ICP-MS was operated with platinum sampler and skimmer cones, both purchased from Perkin Elmer. Other instrumental settings and operative conditions are reported in Table 2.
Table 1. Microwave oven-heating programme for the decomposition of food samples. Step 1 2 3 4 5
Temperature ( C)
Power (W)
Time (min)
160 160 230 230 0
1000 0 1000 1000 0
4.5 0.5 5.0 15.0 20.0
Quality control of data and analytical characteristics In order to verify the accuracy and precision of the proposed method, two Standard Reference Materials from the National Institute of Standards and Technology (NIST). RM 8415 Whole Egg Powder and SRM 1568a Rice Flour, were digested and analysed. Results are shown in Table 3. Values found were in good agreement with target values. The method detection limits (LODs) obtained for As, Cd, Co, Cu, Mg, Mn, P, Rb, Sb, Se, Zn, U and V were 5.0, 0.2, 0.5, 16, 60, 5.0, 34, 12, 6.2, 20, 30, 0.1 and 5.0 ng g1, respectively. LODs were determined as 3 standard deviations (SD) of the 20 consecutive measurements of the reagent blanks multiplied by the dilution factor used for sample preparation (250 mg of sample/50 mL). The between- and within-batch precision for most of the elements analysed were lower than 14% and 5%, respectively (n ¼ 10, SRM 1568a Rice Flour).
Daily intake estimation
Reagents High-purity de-ionized water (resistivity 18.2 M V cm1) used in sample and solution preparation was obtained using a Milli-Q water purification system (Millipore RiOs-DITM, Bedford, MA, USA). All reagents used were of analytical-reagent grade, except for nitric acid (HNO3), which had been previously purified in a quartz sub-boiling still (Ku¨rner Analysentechnik) before use. A clean laboratory and laminar-flow hood capable of producing class 100 were used for preparing solutions. Rhodium (1000 mg L1) and multi-element (10 mg L1) solution were obtained from PerkinElmer (Shelton, CT, USA). TritonÕ X-100 was purchased from Sigma-Aldrich (St. Louis, MO, USA). Plastic bottles, vessels and conic tubes (Sarstedt, Germany) were cleaned by soaking in 15% (v/v) HNO3 for 24 h, rinsed five times with Milli-Q water and dried in a class-100 laminar flow hood before use. All operations were performed in a class-1000 clean room.
Daily metal intake depends on both metal concentration in food and daily food consumption. Estimated daily intake was calculated as: EDI ¼Cce Mrdc where EDI is the estimated daily intake of chemical elements (mg/day/person or mg/day/person); Cce is the chemical element concentration in rice (white rice); and Mrdc is the mass of rice consumed daily in Brazil, based on Instituto Brasileiro de Geografia e Estatı´ stica (IBGE) rice consumption statistics which show polished rice consumption in the different Brazilian regions (IBGE 2003). Estimated daily intake was compared with the provisional tolerable daily intake (PTDI) for toxic elements (Joint FAO/WHO Expert Committee on Food Additives (JECFA)/WHO guidelines 2000; World Health Organization (WHO) 2004). PTDI was considered provisional tolerable weekly intake (PTWI) divided by 7; and the dietary reference intakes (DRIs) for essential elements established by the Food and
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Table 2. Instrument settings for q-ICP-MS and DRC-ICP-MS.
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Instrument Nebulizer Spray chamber Torch injector Auto lens RF power (W) Gas flow rates (L min1) Interface Sampler Skimmer q-ICP-MS (standard mode)
Elan DRCII (PerkinElmer SCIEX) MeinhardÕ Cyclonic Quartz for clinical sample (2.0 mm) On 1100 Nebulizer 0.56–0.98; plasma 15; auxiliary 1.2 Platinum cones 1.1 mm 0.9 mm 75 As, 111Cd, 59Co, 123Sb, 82Se, 238U, 51V, 65Cu, 24 Mg, 55Mn, 31P, 85Rb, 66Zn 103 Rh Peak hopping 2000 3 40 1 50 6.0 1.0
Internal standard Scanning mode Integration time (ms) Replicates Sweeps Readings Dwell time (ms) Lens voltage (v) Sample uptake rate (mL min1) Correction equations Zinc ¼ 64Zn – (0.035247 60Ni) Selenium ¼ 82Se – (1.007833 83Kr) Antimony ¼ 0.125884 125Te
Table 3. Analysis of NIST-Certified Reference Material SRM 1568a rice flour and SRM 8415 whole egg powder for the determination of trace elements. SRM 1568a rice flour Target value Analytes (ng g1) As 290 30 Cd 22 2 Co 18 Sb 0.5 Se 380 40 U 0.3 V 7 Analytes (g g1) Cu Mg Mn P Rb Zn
2.4 0.3 560 20 20.0 1.6 1530 80 6.14 0.09 19.4 0.5
SRM 8415 egg powder
Found value
Target value
Found value
317 9 26 2 17 0.2 0.3 0.05 402 20 0.2 0.01 6.3 1.7
10 5 12 5 2 1390 170 – 459 81
14 0.1 4 0.2 17 3 1.73 0.12 1440 150 – 471 27
2.7 0.35 305 27 1.78 0.38 10010 320 – 67.5 7.6
3.1 0.3 290 21 1.74 0.30 9744 430 – 66.2 3.7
2.0 0.1 521 32 19.4 0.3 1480 79 5.9 4.5 19.7 0.2
Note: Values are as mean SD (n ¼ 5).
Nutrition Board of the Institute of Medicine, 1997–2001 (Institute of Medicine 2002).
samples divided among W, PW and PB. Values are shown in Table 4.
Results and discussion
Toxic elements (As, Cd, Sb and U) in rice samples
The levels of As, Cd, Sb and U (toxic elements), Co, Cu, Mn, Mg, P, Se and Zn (essential elements) and Rb and V (other elements) were measured in 27 rice
Arsenic (As) is considered one of the most toxic elements to humans and animals. Exposure to As leads to an accumulation of As in tissues such as skin, hair
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B.L. Batista et al. Table 4. Determination of essential, toxic and other elements in different types of Brazilian rice samples.
Toxic elements As (ng g1) Cd (ng g1) Sb (ng g1) U (ng g1) Essential elements Co (ng g1) Cu (mg g1)
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Mn (mg g1) Mg (mg g1) P (mg g1) Se (ng g1) Zn (mg g1) Other elements Rb (mg g1) V (ng g1)
White (n ¼ 17)
Parboiled white (n ¼ 6)
Parboiled brown (n ¼ 4)
105.3 40.8 (58.85–216.69) 13.0 4.5 (6.9–20.2) 0.3 0.1 (0.12–0.52) 0.059 0.053 (0.025–0.26)
98.4 40.3 (63.82–158.61) 11.1 4.5 (6.04–17.92) 0.5 0.2 (0.22–0.76) 0.12 0.07 (0.057–0.26)
154.0 22.6 (132.03–183.71) 17.5 1.2 (15.97–18.81) 0.5 0.5 (0.16–1.28) 0.8 0.4 (0.32–1.28)
29.3 24.8 (4.53–71.92) 2.4 0.8 (1.19–3.69) 12.1 4.0 (5.36–20.48) 462.3 134.5 (237.5–751.9) 2140.8 422.9 (1532.3–3110.6) 32.1 6.2 (22.79–44.94) 15.3 3.0 (11.35–14.77)
33.4 25.2 (6.1–69.3) 3.7 1.2 (2.13–5.57) 18.2 5.1 (13.23–27.14) 1132.2 517.5 (633.3–2107.3) 4078.5 1603.4 (2673.2–7176.8) 44.9 11.6 (31.25–63.16) 17.8 3.8 (13.43–24.23)
69.1 23.7 (53.8–104.5) 4.2 0.7 (3.38–5.17) 91.0 35.6 (61.61–146.42) 4890 1168 (3857–6474.0) 15618.8 5465.8 (11412–23544) 42.1 13.2 (32.01–60.13) 44.2 12.9 (35.02–62.65)
5.7 2.8 (2.08–13.39) 2.1 2.2 (0.05–9.45)
12.1 7.4 (4.74–26.22) 6.0 4.7 (1.23–13.28)
39.9 7.3 (32.85–50.01) 5.4 5.7 (0.69–13.6)
Note: Values are means of n samples, in triplicate, on a wet basis, expressed as mean standard deviation (SD); the respective lowest and highest values are shown in parentheses.
and nails, resulting in various clinical symptoms such as hyperpigmentation and keratosis. There is also an increased risk of skin, internal organ and lung cancers. Cardiovascular disease and neuropathy have also been linked to As consumption. Based on these toxic effects, JECFA has set the PTWI (PTDI 7) for this heavy metal at 15.0 mg kg1 of body weight (JECFA 2000; WHO 2004). Rice is one of the major contributors to dietary arsenic intake after fish and seafood (Tao and Bolger 1999). In the case of Brazil, this is a major concern since rice is the dominant staple food. Arsenic levels in the Brazilian rice samples varied from 58.8 to 216.9 ng g1. Among the three rice types analysed in this study, PB rice presented the highest arsenic levels (mean ¼ 154 ng g1) followed by W rice (mean ¼ 105.3 ng g1) and PW rice (mean ¼ 98.4 ng g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 5. Cadmium is also a very toxic element. It accumulates in kidneys where it damages filtering mechanisms. This causes the excretion of essential proteins and sugars from the body and further kidney damage.
It takes a very long time before cadmium that has accumulated in kidneys is excreted from a human body. Other health effects that can be caused by cadmium are diarrhoea, stomach pains and severe vomiting, bone fracture, reproductive failure and possibly even infertility, damage to the central nervous system, damage to the immune system, psychological disorders, and possible DNA damage or cancer development. Based on these toxic effects, JECFA has set the PTWI (PTDI 7) for this heavy metal at 7 mg kg1 of body weight (JECFA 2000; WHO 2004). The levels of cadmium in the Brazilian rice samples varied from 6.0 to 20.2 ng g1. PB rice presented the highest mean levels of cadmium (17.5 ng g1) followed by W rice (13.0 ng g1) and PW rice (11.1 ng g1), as shown in Table 4. These values are quite close to those observed for rice samples cultivated in other areas of the world, as shown in Table 5. However, the difference in cadmium levels within each group of rice was significant, as shown in Table 3. The same variations were observed by Jorhem et al. (2008) with rice collected from Swedish markets. Explanation for this could include variation of cadmium levels in the cultivated soil, differences in Cd uptake between plant
W PW PB W PW PB W
105.4 39.3 98.4 38.8 154.0 32.6 12.7 4.5 11.1 4.4 17.5 1.8 29.33 23.55
Present study 120–776 – – 53 – – –
Australian rice (Phuong et al. 1999) 43–199 – – 10–32 – – –
South Korean rice (Jung et al. 2005)
Note: W, white rice; PW, parboiled white rice; and PB, parboiled brown rice.
Co
Cd
As
Analytes (ng g1)
169.4 169.7
34.5 34.5
69.50 34.9
Chinese rice (Fu et al. 2008)
Table 5. Comparison of microelement composition in rice samples cultivated in different regions.
65 93
240 100
Japanese rice (Oshima et al. 2004)
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– – – 1–230 – – –
American rice (Phuong et al. 1999)
32–465 – – 3–48 – – –
Vietnamese rice (Phuong et al. 1999)
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genotypes (Cui et al. 2004) or the soil type used for rice cultivation (Herawati et al. 2000). As observed by Herawati et al. (2000), rice cultivated in fluvisols has more potential for accumulating arsenic. Effects on liver, kidney, endocrine and cancer can be expected after antimony exposure (Gebel 1997). Antimony levels found in the Brazilian rice samples varied from 0.12 to 1.28 ng g1. White rice presented the highest mean levels of cadmium (0.51 ng g1), followed by PB rice (0.49 ng g1) and W rice (0.29 ng g1), as shown in Table 4. Uranium is a primordial radioactive element distributed widely in the Earth’s crust. As all uranium isotopes in nature are radioactive, the harmful effects of the high intake of this element are increased. The hazards of high uranium intake are twofold: chemical toxicity and radiological damage (Berlin and Rudell 1986). Uranium levels in Brazilian rice samples varied from 0.025 to 1.28 ng g1. PB rice presented the highest mean levels (0.78 ng g1) against 0.12 ng g1 in PW rice. The mean values for W rice were considerably lower (0.059 ng g1), as shown in Table 4.
Essential elements (Co, Cu, Mn, Mg, P, Se and Zn) in rice samples Cobalt is an essential trace element and a component of the vitamin B12 complex. Cobalt levels in the Brazilian rice samples varied from 4.5 to 104.4 ng g1. PB rice presented the highest mean levels (69.1 ng g1), followed by PW rice (mean ¼ 33.4 ng g1). The mean value for white rice was almost the same as that found for PW rice (31.1 ng g1), as shown in Table 4. These values are quite close to those observed for rice samples cultivated in other areas of the world (Table 5). Copper is in the structure of various enzymes, especially superoxide dismutase, which also participates in cleaning up free oxygen radicals from the intracellular environment (Terre´s-Martos et al. 1997). Copper levels in Brazilian rice samples varied from 1.2 to 5.6 mg g1. PB rice presented the highest mean levels (4.2 mg g1), while the mean for PW rice was 3.7 mg g1. On the other hand, the mean copper value for W rice samples was considerably lower than that found for parboiled samples (2.3 mg g1), as shown in Table 4. These values are in good agreement with values observed for rice samples cultivated in other areas of the world, as shown in Table 6. Manganese serves as an active constituent of several enzymes, including antioxidants such as mitochondrial superoxide dismutase among others (Prohaska 1987). Manganese levels in Brazilian rice samples varied from 5.4 to 146.4 mg g1. PB rice presented the
highest levels (mean ¼ 91 mg g1) followed by PW rice (mean ¼ 18.2 mg g1). Manganese levels in W rice samples were a little bit lower than those found for PW rice (mean ¼ 12.1 mg g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 6. Magnesium and phosphorus are major essential elements for humans. Phosphorus is a critically important element in every cell of the human body. It is a major component of bone, where it exists as hydroxyapatite. Moreover, plasma membranes require phosphorus as a component. Magnesium deficiency in the organism may lead to serious biochemical and symptomatic changes. This element is involved in more than 300 essential metabolic reactions. The levels of these essential elements vary considerably according to the type of rice analysed. PB rice presented much higher levels of P compared with PW and W rice (means ¼ 4890 mg g1 P versus 1132.2 mg g1 and 462.3 for PB, PW and W rice, respectively). The same was observed for Mg, with a mean levels of 15618.8, 4078.5 and 2140 mg g1 for PB, PW and W rice, respectively. Adequate Se intake is essential for several selenoenzymes involved in protection against oxidative stress, maintenance of redox status, immune and thyroid regulation (Reeves and Hoffmann 2009). The Se content in rice depends on soil Se concentration and bioavailability as well as the ability of plants to accumulate Se from soils (Lemire et al. 2010). Se levels in Brazilian rice samples varied from 22.8 to 63.2 ng g1, with higher levels for PW and PB rice samples compared with W rice samples. Zinc is an important essential element and plays a major role in protein synthesis, with an important gene expression function. Moreover, zinc stabilizes the structures of proteins and nucleic acids and is also involved in immune phenomena (Salgueiro et al. 2000; Camara and Amaro 2003). We found that zinc levels in the Brazilian rice samples varied from 11.4 to 62.6 mg g1. Among the three rice types evaluated in the present study, PB rice presented the highest levels (mean ¼ 44.2 mg g–1) followed by PW rice (mean ¼ 17.8 mg g1). However, the observed zinc levels for W rice were almost the same as those for PW rice (mean ¼ 15.3 mg g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 6. Other elements (Rb and V) in rice samples Rubidium and vanadium are other elements that may be added to the list of essential elements. Rubidium resembles potassium, especially in its pattern of absorption, and may play a role similar to that of potassium (Nielsen 1998; Kosla et al. 2002). Vanadium
W PB W PB W PB W PB W PB
2.4 0.8 4.2 0.8 433.8 193.1 4890 1231 12.1 4.0 91.0 35.6 2140.9 470.3 15618 5283 15.3 3.6 44.2 12.8
Present study 1.8–2.8 – 164–421 – 8.3–17.3 – 789–1440 – 13.8–22.8 –
Australian rice (Phuong et al. 1999)
Note: W, white rice; and PB, parboiled brown rice.
Zn
P
Mn
Mg
Cu
Analytes (mg g1) 1.29–2.53 – – – – – – – 14.8–19.7 –
South Korean rice (Jung et al. 2005)
9.36 3.29
3.32 0.77
Chinese rice (Fu et al. 2008)
Table 6. Comparison of macro-element composition in rice samples cultivated in different regions.
53–12 – 348–1324 – 8–28 – 1158–4750 – 14–55 –
Tanzanian rice (Mohamed and Spyrou 2009)
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1235 352 2894 213 17.0 4.2 24.0 4.3
2.79 0.66 3.43 0.70 377 150 1078 66
Japanese rice (Zhang et al. 1997)
0.5–5.1 – 40–920 – 4.2–39.0 – 480–2300 – 7.2–21.0 –
American rice (Phuong et al. 1999)
1.1–5.8 – 137–887 – 5.9–16.3 – 819–2589 – 14.6–30.1 –
Vietnamese rice (Phuong et al. 1999)
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Table 7. Estimated daily intake of chemical elements and potential health risk due to rice consumption for Brazilians of different regions. Estimated daily intake
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Region
North
Toxic elementsa As (mg/day) 9.78 Cd (mg/day) 2.53 Sb (mg/day) 0.029 U (mg/day) 0.012 Essential elementsa Co (mg/day) 3.11 Cu (mg/day) 0.236 Mg (mg/day) 78.59 Mn (mg/day) 1.76 P (mg/day) 314.69 Se (mg/day) 3.06 Zn (mg/day) 1.63 Other elementsa Rb (mg/day) 0.833 V (mg/day) 0.245
Northeast
Southeast
South
Center–West
Brazil (mean intake) (% of the PTDIb or DRIc)
PTDIb/DRIc
9.46 2.16 0.030 0.016
9.54 2.52 0.028 0.010
7.60 1.81 0.024 0.011
13.29 3.33 0.041 0.017
9.5 (6.3) 2.4 (3.4) 0.029 0.013
150 70 n.e. n.e.
3.18 0.242 105.82 2.20 394.55 3.02 1.73
3.00 0.228 71.29 1.63 290.75 2.98 1.56
2.51 0.191 77.03 1.63 292.78 2.41 1.35
4.29 0.326 117.83 2.58 460.98 4.18 2.27
3.1 0.2 (28.5) 85.6 (26.7 W/20.3 M) 1.9 (105 W/82.6 M) 333 (47.6) 3.0 (5.4) 1.6 (20 W/14.5 M)
n.e. 0.7 320 W/420 M 1.8 W/2.3 M 700 55 8 W/11 M
1.044 0.277
0.770 0.232
0.775 0.212
1.220 0.348
0.9 0.3
n.e. n.e.
Notes: aConsidering a 70-kg body weight person. W, women; and M, men. b PTDI, provisional tolerable daily intake for toxic elements, based on PTWI/7 (WHO guidelines). c Dietary reference intakes (DRI) for essential elements are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine. n.e., Not established (JECFA 2000; WHO 2004; Institute of Medicine 2002).
is probably involved in normal bone growth. Moreover, vanadium may reduce blood sugar levels and improve sensitivity to insulin in people with type-2 diabetes. Vanadium levels in the Brazilian rice samples varied from 0.05 to 13.6 ng g1. PB rice presented the highest levels, with a mean of 6.0 ng g1, followed by PW rice (mean ¼ 5.4 ng g1). However, vanadium levels in W rice samples were considerable lower, with a mean of 2.1 ng g1, as shown in Table 4. Rubidium levels in the Brazilian rice samples varied from 2.1 to 50.0 mg g1. However, PB rice presented much higher levels than PW and W rice, with means of 39.9 mg g1, 12.1 mg g1 and 5.7 mg g1, respectively (Table 4).
Estimation of the daily intake of toxic and essential elements from rice consumption White rice is the predominant type of rice consumed in Brazil. Thus, for the estimation of daily intake of chemical elements through rice consumption, we have used the mean levels of the chemical elements obtained for the white rice samples analysed in this study. Since Brazilian rice consumption is approximately 86 g/day (IBGE 2003), the estimated daily intake through rice consumption is 9.5 mg for As, 2.4 mg for Cd, 0.029 mg for Sb, 0.013 mg for U, 3.1 mg for Co, 0.2 mg for Cu,
85.6 mg for Mg, 1.9 mg for Mn, 333 mg for P, 3.0 mg for Se, 1.6 mg for Zn, 0.9 mg for Rb, and 0.3 mg for V (Table 7). These values represent a considerable percentage of the DRI for many essential elements, as shown in Table 7. On the other hand, rice may be a significant source of toxic elements, mainly cadmium and arsenic. According to Tao and Bolger (1999) of the estimated total arsenic intakes for American infants, 42% comes from seafood and 31% from rice/rice cereals. Of the estimated total arsenic intakes, seafood contributes 76–90% for children for 2–10-year-olds, 79–85% for 14–16-year-olds, and 89–96% for adults (greater than or equal to 25–30-year-olds); rice/rice cereals contribute 4–8% for children, 8% for 14–16-year-olds, and 1–4% for adults (greater than or equal to 25–30-yearolds). In Sweden, rice contributes 1.3% of the PTWI for inorganic arsenic. In a WHO European diet, rice contributes on average 0.8% (range ¼ 0.3–1.3%) to the current PTWI for inorganic arsenic, while in the WHO Far East diet, the corresponding values are considerably higher, with a mean of 24% (range ¼ 8.9–41%) (Jorhem et al. 2008). According to Jorhem et al. (2008) in Sweden rice contributes 0.6% (0–2.2%) of the PTWI for Cd. In an average European diet, rice contributes a mean of 0.4% (range ¼ 0.0–1.3%), while in the Far East, the corresponding values are on average 11% (range ¼ 0.5–41%) of the PTWI.
Food Additives and Contaminants: Part B In this study, we found rice contributing to 6.3% and 3.4% of the PTWI for arsenic and cadmium, respectively.
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Conclusions Rice is an important food commodity and a dominant staple food in Brazil. In general, PB rice samples presented higher levels of elements compared with W or PW rice samples. Moreover, it was observed that rice can contribute significantly to the RDIs of many essential elements for Brazilians. As an example, up to 20%, 26%, 33%, 47.5% and 100% of the RDIs of Zn, Mg, Cu, P and Mn, respectively, are covered by rice consumption. On the other hand, rice is also an important source of toxic elements for Brazilians. Up to 6.3% and 3.4% of the PTDI for As and Cd can be obtained by rice consumption. Moreover, since the toxicity varies according to the form of the arsenic, further studies are underway in our laboratory to speciate arsenic in Brazilian rice samples.
Acknowledgements The authors are grateful to the Fundac¸a˜o de Amparo a` Pesquisa do Estado de Sa˜o Paulo (FAPESP) and the Conselho Nacional de Desenvolvimento Cientı´ fico e Tecnolo´gico (CNPq) for financial support and fellowships.
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Food Additives & Contaminants: Part B: Surveillance Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tfab20
Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment a
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B.L. Batista , V.C. De Oliveira Souza , F.G. Da Silva & F. Barbosa, Jr
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Departamento de Análises Clínicas , Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto – FCFRP – USP – Avenida do Café , s/n, Monte Alegre, 14040-903, Ribeirão Preto, SP, Brazil Published online: 25 Nov 2010.
To cite this article: B.L. Batista , V.C. De Oliveira Souza , F.G. Da Silva & F. Barbosa, Jr (2010) Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment, Food Additives & Contaminants: Part B: Surveillance, 3:4, 253-262, DOI: 10.1080/19393210.2010.516024 To link to this article: http://dx.doi.org/10.1080/19393210.2010.516024
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Food Additives and Contaminants: Part B Vol. 3, No. 4, December 2010, 253–262
VIEW DATASET Survey of 13 trace elements of toxic and nutritional significance in rice from Brazil and exposure assessment B.L. Batista, V.C. De Oliveira Souza, F.G. Da Silva and F. Barbosa, Jr* Departamento de Ana´lises Clı´nicas, Toxicolo´gicas e Bromatolo´gicas, Faculdade de Cieˆncias Farmaceˆuticas de Ribeira˜o Preto – FCFRP – USP – Avenida do Cafe´, s/n, Monte Alegre, 14040-903, Ribeira˜o Preto, SP, Brazil
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(Received 25 June 2010; final version received 12 August 2010) Twenty-seven rice samples from Brazil, four parboiled brown, seventeen white and six parboiled white were analysed by ICP-MS for trace element determination. Concentrations of arsenic varied from 58.8 to 216.9 ng g1, for cadmium from 6.0 to 20.2 ng g1, for antimony from 0.12 to 1.28 ng g1, and for uranium from 0.025 to 1.28 ng g1. The estimated daily intake through rice consumption was 9.5 mg for As, 2.4 mg for Cd, 0.029 mg for Sb, 0.013 mg for U, 3.1 mg for Co, 0.2 mg for Cu, 85.6 mg for Mg, 1.9 mg for Mn, 333 mg for P, 3.0 mg for Se, 1.6 mg for Zn, 0.9 mg for Rb, and 0.3 mg for V. Found values represent a considerable percentage of the dietary reference intakes and provisional tolerable daily intake for essential and toxic elements, respectively. Keywords: rice; cereals; trace elements (nutritional); trace elements (toxic)
Introduction Rice (Oryza sativa L.), the second most widely produced cereal in the world, is an important component of the world population’s basic diet. Rice cultivation is the principal activity and source of income for millions of households around the globe, and several countries in Asia and Africa are highly dependent on rice as a source of foreign exchange earnings and government revenue. At the beginning of the 1990s, annual production was around 350 106 tons and by the end of the century it had reached 410 106 tons. Brazil is the most important non-Asian producer, followed by the United States. Brazil’s rice consumption is 74–76 kg/inhabitant/year (rice with chaff). Unfortunately, populations of many of the main rice-consuming countries suffer from nutrient deficiency-related diseases, with an insufficient intake of important essential elements. In some cases, diet is also an important source of toxic elements (Barbosa et al. 2009; Grotto et al. 2010). Despite this scenario, systematic evaluation of the composition of essential and toxic elements in the most commonly consumed food in developing countries is not a routine practice. Measuring the concentration of toxic and essential elements in rice is thus of enormous importance in Brazil. Moreover, a study of this kind will also assist in estimating the daily intake of both important essential elements and toxic elements through rice consumption. To determine chemical elements in food samples, distinct atomic spectroscopy techniques have been *Corresponding author. Email: [email protected] ISSN 1939–3210 print/ISSN 1939–3229 online ß 2010 Taylor & Francis DOI: 10.1080/19393210.2010.516024 http://www.informaworld.com
proposed (Saracoglu et al. 2007; Tuzen 2003; Tuzen et al. 2007). However, inductively coupled plasma mass spectrometry (ICP-MS) offers distinct advantages, including simultaneous multi-element measurement capability coupled with very low detection limits (Ammann 2007; Parsons and Barbosa 2007; Rodrigues et al. 2008). Moreover, it offers a wide linear dynamic range which makes it possible to determine major and trace elements in the same sample injection (Ammann 2007; Parsons and Barbosa 2007). Therefore, the aims of this study were: (1) to investigate the mineral composition (essential and toxic elements) of three different types of Brazilian rice samples (white, parboiled white and parboiled brown) by using inductively coupled plasma mass spectrometry (ICP-MS); and (2) to estimate the population’s daily intake through rice consumption of a number of toxic and essential elements.
Materials and methods Rice sampling and treatment Twenty-seven raw rice samples, four parboiled brown (PB), seventeen white (W) and six parboiled white (PW) were randomly purchased at supermarkets in different Brazilian cities. Before digestion, samples (15 g) were separated by quartering as described by the Codex Alimentarius
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Commission (CAC) (2004) and divided into three plastic tubes. The contents of each tube were ground for 3 min in a ball mill (Tecnal TE 350, Piracicaba, Brazil) and sifted in a 106 mm sieve (Bertel, Caieiras, Brazil). Then, samples were digested in closed vessels using a microwave oven decomposition system (Ethos D, Milestone, Sorisole, Italy) according to the validated method proposed by Nardi et al. (2009). Briefly, rice samples (250 mg) were accurately weighed in a PFA digestion vessel and then 5 ml of nitric acid 20% v/v þ 2 mL of 30% (v/v) H2O2 were added. The vessel was placed inside the microwave oven and decomposition was carried out according to the programme shown in Table 1. After that the solutions were left to cool and the volume was made up to 50 mL with MilliQ water. Rhodium was then added as an internal standard to a final concentration of 10 mg L1.
Apparatus Analyses were carried out with an inductively coupled plasma mass spectrometer equipped with a reaction cell (DRC-ICP-MS ELAN DRCII, PerkinElmer, Sciex, Norwalk, CT, USA) operating with highpurity argon (99.999%, Praxaair, Brazil). The sample introduction system was composed of a quartz cyclonic spray chamber and a MeinhardÕ nebulizer connected by TygonÕ tubes to the ICP-MS’s peristaltic pump (set at 20 rpm). The ICP-MS was operated with platinum sampler and skimmer cones, both purchased from Perkin Elmer. Other instrumental settings and operative conditions are reported in Table 2.
Table 1. Microwave oven-heating programme for the decomposition of food samples. Step 1 2 3 4 5
Temperature ( C)
Power (W)
Time (min)
160 160 230 230 0
1000 0 1000 1000 0
4.5 0.5 5.0 15.0 20.0
Quality control of data and analytical characteristics In order to verify the accuracy and precision of the proposed method, two Standard Reference Materials from the National Institute of Standards and Technology (NIST). RM 8415 Whole Egg Powder and SRM 1568a Rice Flour, were digested and analysed. Results are shown in Table 3. Values found were in good agreement with target values. The method detection limits (LODs) obtained for As, Cd, Co, Cu, Mg, Mn, P, Rb, Sb, Se, Zn, U and V were 5.0, 0.2, 0.5, 16, 60, 5.0, 34, 12, 6.2, 20, 30, 0.1 and 5.0 ng g1, respectively. LODs were determined as 3 standard deviations (SD) of the 20 consecutive measurements of the reagent blanks multiplied by the dilution factor used for sample preparation (250 mg of sample/50 mL). The between- and within-batch precision for most of the elements analysed were lower than 14% and 5%, respectively (n ¼ 10, SRM 1568a Rice Flour).
Daily intake estimation
Reagents High-purity de-ionized water (resistivity 18.2 M V cm1) used in sample and solution preparation was obtained using a Milli-Q water purification system (Millipore RiOs-DITM, Bedford, MA, USA). All reagents used were of analytical-reagent grade, except for nitric acid (HNO3), which had been previously purified in a quartz sub-boiling still (Ku¨rner Analysentechnik) before use. A clean laboratory and laminar-flow hood capable of producing class 100 were used for preparing solutions. Rhodium (1000 mg L1) and multi-element (10 mg L1) solution were obtained from PerkinElmer (Shelton, CT, USA). TritonÕ X-100 was purchased from Sigma-Aldrich (St. Louis, MO, USA). Plastic bottles, vessels and conic tubes (Sarstedt, Germany) were cleaned by soaking in 15% (v/v) HNO3 for 24 h, rinsed five times with Milli-Q water and dried in a class-100 laminar flow hood before use. All operations were performed in a class-1000 clean room.
Daily metal intake depends on both metal concentration in food and daily food consumption. Estimated daily intake was calculated as: EDI ¼Cce Mrdc where EDI is the estimated daily intake of chemical elements (mg/day/person or mg/day/person); Cce is the chemical element concentration in rice (white rice); and Mrdc is the mass of rice consumed daily in Brazil, based on Instituto Brasileiro de Geografia e Estatı´ stica (IBGE) rice consumption statistics which show polished rice consumption in the different Brazilian regions (IBGE 2003). Estimated daily intake was compared with the provisional tolerable daily intake (PTDI) for toxic elements (Joint FAO/WHO Expert Committee on Food Additives (JECFA)/WHO guidelines 2000; World Health Organization (WHO) 2004). PTDI was considered provisional tolerable weekly intake (PTWI) divided by 7; and the dietary reference intakes (DRIs) for essential elements established by the Food and
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Table 2. Instrument settings for q-ICP-MS and DRC-ICP-MS.
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Instrument Nebulizer Spray chamber Torch injector Auto lens RF power (W) Gas flow rates (L min1) Interface Sampler Skimmer q-ICP-MS (standard mode)
Elan DRCII (PerkinElmer SCIEX) MeinhardÕ Cyclonic Quartz for clinical sample (2.0 mm) On 1100 Nebulizer 0.56–0.98; plasma 15; auxiliary 1.2 Platinum cones 1.1 mm 0.9 mm 75 As, 111Cd, 59Co, 123Sb, 82Se, 238U, 51V, 65Cu, 24 Mg, 55Mn, 31P, 85Rb, 66Zn 103 Rh Peak hopping 2000 3 40 1 50 6.0 1.0
Internal standard Scanning mode Integration time (ms) Replicates Sweeps Readings Dwell time (ms) Lens voltage (v) Sample uptake rate (mL min1) Correction equations Zinc ¼ 64Zn – (0.035247 60Ni) Selenium ¼ 82Se – (1.007833 83Kr) Antimony ¼ 0.125884 125Te
Table 3. Analysis of NIST-Certified Reference Material SRM 1568a rice flour and SRM 8415 whole egg powder for the determination of trace elements. SRM 1568a rice flour Target value Analytes (ng g1) As 290 30 Cd 22 2 Co 18 Sb 0.5 Se 380 40 U 0.3 V 7 Analytes (g g1) Cu Mg Mn P Rb Zn
2.4 0.3 560 20 20.0 1.6 1530 80 6.14 0.09 19.4 0.5
SRM 8415 egg powder
Found value
Target value
Found value
317 9 26 2 17 0.2 0.3 0.05 402 20 0.2 0.01 6.3 1.7
10 5 12 5 2 1390 170 – 459 81
14 0.1 4 0.2 17 3 1.73 0.12 1440 150 – 471 27
2.7 0.35 305 27 1.78 0.38 10010 320 – 67.5 7.6
3.1 0.3 290 21 1.74 0.30 9744 430 – 66.2 3.7
2.0 0.1 521 32 19.4 0.3 1480 79 5.9 4.5 19.7 0.2
Note: Values are as mean SD (n ¼ 5).
Nutrition Board of the Institute of Medicine, 1997–2001 (Institute of Medicine 2002).
samples divided among W, PW and PB. Values are shown in Table 4.
Results and discussion
Toxic elements (As, Cd, Sb and U) in rice samples
The levels of As, Cd, Sb and U (toxic elements), Co, Cu, Mn, Mg, P, Se and Zn (essential elements) and Rb and V (other elements) were measured in 27 rice
Arsenic (As) is considered one of the most toxic elements to humans and animals. Exposure to As leads to an accumulation of As in tissues such as skin, hair
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Toxic elements As (ng g1) Cd (ng g1) Sb (ng g1) U (ng g1) Essential elements Co (ng g1) Cu (mg g1)
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Mn (mg g1) Mg (mg g1) P (mg g1) Se (ng g1) Zn (mg g1) Other elements Rb (mg g1) V (ng g1)
White (n ¼ 17)
Parboiled white (n ¼ 6)
Parboiled brown (n ¼ 4)
105.3 40.8 (58.85–216.69) 13.0 4.5 (6.9–20.2) 0.3 0.1 (0.12–0.52) 0.059 0.053 (0.025–0.26)
98.4 40.3 (63.82–158.61) 11.1 4.5 (6.04–17.92) 0.5 0.2 (0.22–0.76) 0.12 0.07 (0.057–0.26)
154.0 22.6 (132.03–183.71) 17.5 1.2 (15.97–18.81) 0.5 0.5 (0.16–1.28) 0.8 0.4 (0.32–1.28)
29.3 24.8 (4.53–71.92) 2.4 0.8 (1.19–3.69) 12.1 4.0 (5.36–20.48) 462.3 134.5 (237.5–751.9) 2140.8 422.9 (1532.3–3110.6) 32.1 6.2 (22.79–44.94) 15.3 3.0 (11.35–14.77)
33.4 25.2 (6.1–69.3) 3.7 1.2 (2.13–5.57) 18.2 5.1 (13.23–27.14) 1132.2 517.5 (633.3–2107.3) 4078.5 1603.4 (2673.2–7176.8) 44.9 11.6 (31.25–63.16) 17.8 3.8 (13.43–24.23)
69.1 23.7 (53.8–104.5) 4.2 0.7 (3.38–5.17) 91.0 35.6 (61.61–146.42) 4890 1168 (3857–6474.0) 15618.8 5465.8 (11412–23544) 42.1 13.2 (32.01–60.13) 44.2 12.9 (35.02–62.65)
5.7 2.8 (2.08–13.39) 2.1 2.2 (0.05–9.45)
12.1 7.4 (4.74–26.22) 6.0 4.7 (1.23–13.28)
39.9 7.3 (32.85–50.01) 5.4 5.7 (0.69–13.6)
Note: Values are means of n samples, in triplicate, on a wet basis, expressed as mean standard deviation (SD); the respective lowest and highest values are shown in parentheses.
and nails, resulting in various clinical symptoms such as hyperpigmentation and keratosis. There is also an increased risk of skin, internal organ and lung cancers. Cardiovascular disease and neuropathy have also been linked to As consumption. Based on these toxic effects, JECFA has set the PTWI (PTDI 7) for this heavy metal at 15.0 mg kg1 of body weight (JECFA 2000; WHO 2004). Rice is one of the major contributors to dietary arsenic intake after fish and seafood (Tao and Bolger 1999). In the case of Brazil, this is a major concern since rice is the dominant staple food. Arsenic levels in the Brazilian rice samples varied from 58.8 to 216.9 ng g1. Among the three rice types analysed in this study, PB rice presented the highest arsenic levels (mean ¼ 154 ng g1) followed by W rice (mean ¼ 105.3 ng g1) and PW rice (mean ¼ 98.4 ng g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 5. Cadmium is also a very toxic element. It accumulates in kidneys where it damages filtering mechanisms. This causes the excretion of essential proteins and sugars from the body and further kidney damage.
It takes a very long time before cadmium that has accumulated in kidneys is excreted from a human body. Other health effects that can be caused by cadmium are diarrhoea, stomach pains and severe vomiting, bone fracture, reproductive failure and possibly even infertility, damage to the central nervous system, damage to the immune system, psychological disorders, and possible DNA damage or cancer development. Based on these toxic effects, JECFA has set the PTWI (PTDI 7) for this heavy metal at 7 mg kg1 of body weight (JECFA 2000; WHO 2004). The levels of cadmium in the Brazilian rice samples varied from 6.0 to 20.2 ng g1. PB rice presented the highest mean levels of cadmium (17.5 ng g1) followed by W rice (13.0 ng g1) and PW rice (11.1 ng g1), as shown in Table 4. These values are quite close to those observed for rice samples cultivated in other areas of the world, as shown in Table 5. However, the difference in cadmium levels within each group of rice was significant, as shown in Table 3. The same variations were observed by Jorhem et al. (2008) with rice collected from Swedish markets. Explanation for this could include variation of cadmium levels in the cultivated soil, differences in Cd uptake between plant
W PW PB W PW PB W
105.4 39.3 98.4 38.8 154.0 32.6 12.7 4.5 11.1 4.4 17.5 1.8 29.33 23.55
Present study 120–776 – – 53 – – –
Australian rice (Phuong et al. 1999) 43–199 – – 10–32 – – –
South Korean rice (Jung et al. 2005)
Note: W, white rice; PW, parboiled white rice; and PB, parboiled brown rice.
Co
Cd
As
Analytes (ng g1)
169.4 169.7
34.5 34.5
69.50 34.9
Chinese rice (Fu et al. 2008)
Table 5. Comparison of microelement composition in rice samples cultivated in different regions.
65 93
240 100
Japanese rice (Oshima et al. 2004)
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– – – 1–230 – – –
American rice (Phuong et al. 1999)
32–465 – – 3–48 – – –
Vietnamese rice (Phuong et al. 1999)
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genotypes (Cui et al. 2004) or the soil type used for rice cultivation (Herawati et al. 2000). As observed by Herawati et al. (2000), rice cultivated in fluvisols has more potential for accumulating arsenic. Effects on liver, kidney, endocrine and cancer can be expected after antimony exposure (Gebel 1997). Antimony levels found in the Brazilian rice samples varied from 0.12 to 1.28 ng g1. White rice presented the highest mean levels of cadmium (0.51 ng g1), followed by PB rice (0.49 ng g1) and W rice (0.29 ng g1), as shown in Table 4. Uranium is a primordial radioactive element distributed widely in the Earth’s crust. As all uranium isotopes in nature are radioactive, the harmful effects of the high intake of this element are increased. The hazards of high uranium intake are twofold: chemical toxicity and radiological damage (Berlin and Rudell 1986). Uranium levels in Brazilian rice samples varied from 0.025 to 1.28 ng g1. PB rice presented the highest mean levels (0.78 ng g1) against 0.12 ng g1 in PW rice. The mean values for W rice were considerably lower (0.059 ng g1), as shown in Table 4.
Essential elements (Co, Cu, Mn, Mg, P, Se and Zn) in rice samples Cobalt is an essential trace element and a component of the vitamin B12 complex. Cobalt levels in the Brazilian rice samples varied from 4.5 to 104.4 ng g1. PB rice presented the highest mean levels (69.1 ng g1), followed by PW rice (mean ¼ 33.4 ng g1). The mean value for white rice was almost the same as that found for PW rice (31.1 ng g1), as shown in Table 4. These values are quite close to those observed for rice samples cultivated in other areas of the world (Table 5). Copper is in the structure of various enzymes, especially superoxide dismutase, which also participates in cleaning up free oxygen radicals from the intracellular environment (Terre´s-Martos et al. 1997). Copper levels in Brazilian rice samples varied from 1.2 to 5.6 mg g1. PB rice presented the highest mean levels (4.2 mg g1), while the mean for PW rice was 3.7 mg g1. On the other hand, the mean copper value for W rice samples was considerably lower than that found for parboiled samples (2.3 mg g1), as shown in Table 4. These values are in good agreement with values observed for rice samples cultivated in other areas of the world, as shown in Table 6. Manganese serves as an active constituent of several enzymes, including antioxidants such as mitochondrial superoxide dismutase among others (Prohaska 1987). Manganese levels in Brazilian rice samples varied from 5.4 to 146.4 mg g1. PB rice presented the
highest levels (mean ¼ 91 mg g1) followed by PW rice (mean ¼ 18.2 mg g1). Manganese levels in W rice samples were a little bit lower than those found for PW rice (mean ¼ 12.1 mg g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 6. Magnesium and phosphorus are major essential elements for humans. Phosphorus is a critically important element in every cell of the human body. It is a major component of bone, where it exists as hydroxyapatite. Moreover, plasma membranes require phosphorus as a component. Magnesium deficiency in the organism may lead to serious biochemical and symptomatic changes. This element is involved in more than 300 essential metabolic reactions. The levels of these essential elements vary considerably according to the type of rice analysed. PB rice presented much higher levels of P compared with PW and W rice (means ¼ 4890 mg g1 P versus 1132.2 mg g1 and 462.3 for PB, PW and W rice, respectively). The same was observed for Mg, with a mean levels of 15618.8, 4078.5 and 2140 mg g1 for PB, PW and W rice, respectively. Adequate Se intake is essential for several selenoenzymes involved in protection against oxidative stress, maintenance of redox status, immune and thyroid regulation (Reeves and Hoffmann 2009). The Se content in rice depends on soil Se concentration and bioavailability as well as the ability of plants to accumulate Se from soils (Lemire et al. 2010). Se levels in Brazilian rice samples varied from 22.8 to 63.2 ng g1, with higher levels for PW and PB rice samples compared with W rice samples. Zinc is an important essential element and plays a major role in protein synthesis, with an important gene expression function. Moreover, zinc stabilizes the structures of proteins and nucleic acids and is also involved in immune phenomena (Salgueiro et al. 2000; Camara and Amaro 2003). We found that zinc levels in the Brazilian rice samples varied from 11.4 to 62.6 mg g1. Among the three rice types evaluated in the present study, PB rice presented the highest levels (mean ¼ 44.2 mg g–1) followed by PW rice (mean ¼ 17.8 mg g1). However, the observed zinc levels for W rice were almost the same as those for PW rice (mean ¼ 15.3 mg g1), as shown in Table 4. These values are quite close to the values observed for rice samples cultivated in other areas, as shown in Table 6. Other elements (Rb and V) in rice samples Rubidium and vanadium are other elements that may be added to the list of essential elements. Rubidium resembles potassium, especially in its pattern of absorption, and may play a role similar to that of potassium (Nielsen 1998; Kosla et al. 2002). Vanadium
W PB W PB W PB W PB W PB
2.4 0.8 4.2 0.8 433.8 193.1 4890 1231 12.1 4.0 91.0 35.6 2140.9 470.3 15618 5283 15.3 3.6 44.2 12.8
Present study 1.8–2.8 – 164–421 – 8.3–17.3 – 789–1440 – 13.8–22.8 –
Australian rice (Phuong et al. 1999)
Note: W, white rice; and PB, parboiled brown rice.
Zn
P
Mn
Mg
Cu
Analytes (mg g1) 1.29–2.53 – – – – – – – 14.8–19.7 –
South Korean rice (Jung et al. 2005)
9.36 3.29
3.32 0.77
Chinese rice (Fu et al. 2008)
Table 6. Comparison of macro-element composition in rice samples cultivated in different regions.
53–12 – 348–1324 – 8–28 – 1158–4750 – 14–55 –
Tanzanian rice (Mohamed and Spyrou 2009)
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1235 352 2894 213 17.0 4.2 24.0 4.3
2.79 0.66 3.43 0.70 377 150 1078 66
Japanese rice (Zhang et al. 1997)
0.5–5.1 – 40–920 – 4.2–39.0 – 480–2300 – 7.2–21.0 –
American rice (Phuong et al. 1999)
1.1–5.8 – 137–887 – 5.9–16.3 – 819–2589 – 14.6–30.1 –
Vietnamese rice (Phuong et al. 1999)
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Table 7. Estimated daily intake of chemical elements and potential health risk due to rice consumption for Brazilians of different regions. Estimated daily intake
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Region
North
Toxic elementsa As (mg/day) 9.78 Cd (mg/day) 2.53 Sb (mg/day) 0.029 U (mg/day) 0.012 Essential elementsa Co (mg/day) 3.11 Cu (mg/day) 0.236 Mg (mg/day) 78.59 Mn (mg/day) 1.76 P (mg/day) 314.69 Se (mg/day) 3.06 Zn (mg/day) 1.63 Other elementsa Rb (mg/day) 0.833 V (mg/day) 0.245
Northeast
Southeast
South
Center–West
Brazil (mean intake) (% of the PTDIb or DRIc)
PTDIb/DRIc
9.46 2.16 0.030 0.016
9.54 2.52 0.028 0.010
7.60 1.81 0.024 0.011
13.29 3.33 0.041 0.017
9.5 (6.3) 2.4 (3.4) 0.029 0.013
150 70 n.e. n.e.
3.18 0.242 105.82 2.20 394.55 3.02 1.73
3.00 0.228 71.29 1.63 290.75 2.98 1.56
2.51 0.191 77.03 1.63 292.78 2.41 1.35
4.29 0.326 117.83 2.58 460.98 4.18 2.27
3.1 0.2 (28.5) 85.6 (26.7 W/20.3 M) 1.9 (105 W/82.6 M) 333 (47.6) 3.0 (5.4) 1.6 (20 W/14.5 M)
n.e. 0.7 320 W/420 M 1.8 W/2.3 M 700 55 8 W/11 M
1.044 0.277
0.770 0.232
0.775 0.212
1.220 0.348
0.9 0.3
n.e. n.e.
Notes: aConsidering a 70-kg body weight person. W, women; and M, men. b PTDI, provisional tolerable daily intake for toxic elements, based on PTWI/7 (WHO guidelines). c Dietary reference intakes (DRI) for essential elements are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine. n.e., Not established (JECFA 2000; WHO 2004; Institute of Medicine 2002).
is probably involved in normal bone growth. Moreover, vanadium may reduce blood sugar levels and improve sensitivity to insulin in people with type-2 diabetes. Vanadium levels in the Brazilian rice samples varied from 0.05 to 13.6 ng g1. PB rice presented the highest levels, with a mean of 6.0 ng g1, followed by PW rice (mean ¼ 5.4 ng g1). However, vanadium levels in W rice samples were considerable lower, with a mean of 2.1 ng g1, as shown in Table 4. Rubidium levels in the Brazilian rice samples varied from 2.1 to 50.0 mg g1. However, PB rice presented much higher levels than PW and W rice, with means of 39.9 mg g1, 12.1 mg g1 and 5.7 mg g1, respectively (Table 4).
Estimation of the daily intake of toxic and essential elements from rice consumption White rice is the predominant type of rice consumed in Brazil. Thus, for the estimation of daily intake of chemical elements through rice consumption, we have used the mean levels of the chemical elements obtained for the white rice samples analysed in this study. Since Brazilian rice consumption is approximately 86 g/day (IBGE 2003), the estimated daily intake through rice consumption is 9.5 mg for As, 2.4 mg for Cd, 0.029 mg for Sb, 0.013 mg for U, 3.1 mg for Co, 0.2 mg for Cu,
85.6 mg for Mg, 1.9 mg for Mn, 333 mg for P, 3.0 mg for Se, 1.6 mg for Zn, 0.9 mg for Rb, and 0.3 mg for V (Table 7). These values represent a considerable percentage of the DRI for many essential elements, as shown in Table 7. On the other hand, rice may be a significant source of toxic elements, mainly cadmium and arsenic. According to Tao and Bolger (1999) of the estimated total arsenic intakes for American infants, 42% comes from seafood and 31% from rice/rice cereals. Of the estimated total arsenic intakes, seafood contributes 76–90% for children for 2–10-year-olds, 79–85% for 14–16-year-olds, and 89–96% for adults (greater than or equal to 25–30-year-olds); rice/rice cereals contribute 4–8% for children, 8% for 14–16-year-olds, and 1–4% for adults (greater than or equal to 25–30-yearolds). In Sweden, rice contributes 1.3% of the PTWI for inorganic arsenic. In a WHO European diet, rice contributes on average 0.8% (range ¼ 0.3–1.3%) to the current PTWI for inorganic arsenic, while in the WHO Far East diet, the corresponding values are considerably higher, with a mean of 24% (range ¼ 8.9–41%) (Jorhem et al. 2008). According to Jorhem et al. (2008) in Sweden rice contributes 0.6% (0–2.2%) of the PTWI for Cd. In an average European diet, rice contributes a mean of 0.4% (range ¼ 0.0–1.3%), while in the Far East, the corresponding values are on average 11% (range ¼ 0.5–41%) of the PTWI.
Food Additives and Contaminants: Part B In this study, we found rice contributing to 6.3% and 3.4% of the PTWI for arsenic and cadmium, respectively.
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Conclusions Rice is an important food commodity and a dominant staple food in Brazil. In general, PB rice samples presented higher levels of elements compared with W or PW rice samples. Moreover, it was observed that rice can contribute significantly to the RDIs of many essential elements for Brazilians. As an example, up to 20%, 26%, 33%, 47.5% and 100% of the RDIs of Zn, Mg, Cu, P and Mn, respectively, are covered by rice consumption. On the other hand, rice is also an important source of toxic elements for Brazilians. Up to 6.3% and 3.4% of the PTDI for As and Cd can be obtained by rice consumption. Moreover, since the toxicity varies according to the form of the arsenic, further studies are underway in our laboratory to speciate arsenic in Brazilian rice samples.
Acknowledgements The authors are grateful to the Fundac¸a˜o de Amparo a` Pesquisa do Estado de Sa˜o Paulo (FAPESP) and the Conselho Nacional de Desenvolvimento Cientı´ fico e Tecnolo´gico (CNPq) for financial support and fellowships.
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