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Rice--a nutritious food or a heavy metal source?

Rice is a staple food for over 50% of the world's population. It is highly nutritious, especially when the outer bran is not removed, providing a good source of carbohydrate, vitamins and essential minerals. However, chemical analysis of rice grain samples shows rice may also be a significant source of the heavy metal, arsenic. (1)

Arsenic: inorganic vs organic

Arsenic occurs naturally in the environment as an organic or inorganic substance. The difference between these forms relates to their chemical structure, not to farming practices. When arsenic is bound to a carbon atom it is organic, without the carbon atom it is inorganic. (2)

The inorganic form of arsenic is the most toxic and is classed as a Group 1 human carcinogen. (1)

Long-term exposure to inorganic arsenic can increase the risk of skin, lung and bladder cancer, and may negatively affect foetal and infant development. (3) The effect on children is of particular concern as they have a smaller body mass and are therefore more vulnerable to arsenic exposure. Also, many infants are regularly fed rice-based cereals, milks and foods. (1)

How inorganic arsenic contaminates rice

Inorganic arsenic has been a known factor in some drinking water supplies, but it now appears, from the work of various analytical studies, that rice is the main plant-based food source. (3) This is due to rice being grown in arsenic-polluted soil or being irrigated with arsenic-contaminated water. Unfortunately, many of the rice-exporting countries have arsenic-contaminated soil. (1)

Even Australian soil and rice samples have been found to contain arsenic and other heavy metals. (4,5)

Different types of rice = different levels of arsenic

Consuming particular types of rice may reduce exposure, with one study showing basmati and red rice to have low levels of total arsenic (organic and inorganic). In this same study, rice crackers had undetectable amounts of the inorganic form. (3) However, with so many different varieties of rice and numerous rice producing countries, levels may not be guaranteed.

A recent study showed widespread arsenic levels in rice consumed in Australia, with Australian grown arborio and sushi rice containing the highest mean values of total arsenic. However, all levels were below the Food Standards Australia New Zealand (FSANZ) limit. (6)

Although brown rice contains higher levels of nutrients than polished white rice, the level of arsenic and other heavy metals may be higher too, as they are stored within the outer bran layer. (5)

Reducing exposure and combating toxicity of arsenic in rice

To reduce high intakes of arsenic, the U.S. Food and Drug Administration recommends a well-balanced diet, incorporating a variety of grains and not relying on rice as the main source in infant cereals. (2)

Additionally, how the rice is prepared can make a difference to the arsenic concentration.

Rinsing the rice well before cooking can reduce the arsenic levels by 9% and 16% in parboiled and polished rice, respectively. Cooking rice in excess water (from six to 10 parts water to one part rice), and draining the excess water, can reduce the inorganic arsenic content by 40% to 60%. Unfortunately, these practices also reduce the nutrient content of the rice. (2)

Therefore, the best ways to avoid the toxicity of arsenic include consuming a wide variety of foods, checking the water supply or using appropriate filtration, not relying heavily on rice products, reviewing rice cooking practices and supporting the body's detoxification processes.

REFERENCES

(1.) Shraim AM. Rice is a potential dietary source of not only arsenic but also other toxic elements like lead and chromium. Arabian Journal of Chemistry. 2014. http://dx.doi. org/10.1016/j.arabjc.2014.02.004

(2.) Center for Food Safety and Applied Nutrition. Metals--questions & answers: Arsenic in rice and rice products 2016. Viewed August2016. http://www.fda.gov/Food/ FoodbornelllnessContaminants/Metals/ ucm319948.htm.

(3.) Brandon EFA, Janssen PJCM, de Wit-Bos L. Arsenic: Bioaccessibility from seaweed and rice, dietary exposure calculations and risk assessment. Food Additives & Contaminants Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment. 2014;31(12):1993-2003.

(4.) Food science: findings on food science discussed by investigators at Royal Melbourne Institute of Technology University (arsenic speciation in Australian-grown and imported rice on sale in Australia: Implications for human health risk). Agriculture Week 2014:299

(5.) Rahman MA, Rahman MM, Reichman SM, et at. Heavy metals in Australian grown and imported rice and vegetables on sale in Australia: Health hazard. Ecotoxicology and environmental safety. 2014:100:53-60.

(6.) Fransisca Y, Small DM, Morrison PD, et at. Assessment of arsenic in Australian grown and imported rice varieties on sale in Australia and potential links with irrigation practises and soil geochemistry. Chemosphere. 2015:138:1008-13.

Top toxic chemicals the home

Recently, the Environmental Working Group (EWG) released a list of high-priority chemicals found in homes they think authorities should review and regulate as soon as possible. (1) The following lists the top 10.

1 Asbestos--This is a carcinogen, found in automobile brake pads and clutches, vinyl tiles, and roofing materials. (1) News reports have recently revealed that asbestos is still being used illegally in Australian building materials. (2)

2 PERC (Perchloroethylene or Tetrachlorethylene)--This is a potential carcinogen with links to numerous cancers. It is used in dry-cleaning fluids, water repellents, paint removers, printing inks, glues, sealants, polishes and lubricants. (1,3)

3 Phthalates--Also called plasticisers, this group of chemicals is linked to reproductive harm and early puberty in girls. They are found in PVC, plastic wraps, toys, vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, garden hoses, blood-storage containers, medical tubing, plastic clothes (raincoats), and personal-care products (soaps, shampoos, hair sprays and nail polishes). (1,4)

4 BPA (bisphenol A)--Used in the lining of food cans, plastic food containers, tetra packs, plastic and baby bottles, plastic dinnerware and cash register receipts, BPA is carcinogenic and an endocrine disrupter with links to infertility, developmental risks and diabetes. (1,5)

5 Chlorinated phosphate fire retardants--With links to possible brain and nerve damage, these chemicals are found in upholstered furniture, foam cushions, infant car seats and insulation. (1)

6 TBBPA (Tetrabromobisphenol A)--TBBPA is a flame retardant with potential carcinogen and endocrine disruption properties. It is found in electronic equipment, auto parts and appliances. (1)

7 Brominated phthalate fire retardants--Found in polyurethane foam for furniture and baby products, these chemicals are linked to developmental toxicity. (1)

8 1-Bromopropane (IBP or n-propyl bromide)--This is found in degreasers and cleaners, spray adhesives, aerosol cleaners, spot removers, coin cleaners, paintable mould release, automotive refrigerant flushes and lubricants. It may have adverse developmental and reproductive effects. (1,6)

9 DEHA (Diethylhydroxylamine)--This probable carcinogen is also linked to developmental toxicity and is found in plastic wrap and PVC plastic (1)

10 P-dichlorobenzene--This is mainly used in deodoriser blocks in domestic and public toilet facilities. It is also used as a domestic air freshener, in moth balls, and has some uses in the pharmaceutical industry. It is linked to liver and nerve damage. (1,7)

References

(1.) AmareloM. EWG lists the top 10 toxic chemicals EPA should review now 2016. Viewed August 2016. http://www.ewg.org/reiease/ewg-iists-top-ten-toxicchemicals-epa-should-review-now.

(2.) Shepherd B. Asbestos-tainted Chinese firm's Australian projects 'need investigation' 2016. Viewed August 2016. http://www.abc.net.au/news/2016-07-14/ asbestos-tainted-firm-yuanda-australian-projects-investigation/7630552.

(3.) American Cancer Society. Tetrachlorethylene (perchloroethylene) 2014. Viewed August 2016. http://www.cancer.org/cancer/cancercauses/othercarcinogens/ intheworkplace/tetrachlorethylene-perchloroethylene.

(4.) Centers for Disease Control and Prevention. CDC-NBP-factsheet-phthalates. Viewed August 2016. http://www.cdc.gov/biomonitoring/phthaiates_factsheet. htmi.

(5.) US. National Library of Medicine. Tox town: Bisphenol A (BPA) 2016. Viewed August 2016. https://toxtown.nlm.nih.gov/text_version/chemicals.php?id=69.

(6.) US Environmental Protection Agency. Fact sheet: 1-Bromopropane (1-BP). Viewed August 2016. https://www.epa.gov/assessing-and-managing-chemicaisunder-tsca/fact-sheet-1-bromopropane-1-bp.

(7.) National Industrial Chemicals Notification and Assessments Scheme (NICNAS). Para-dichlorobenzene safety fact sheet 2013. Viewed August 2016. https://www. nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/para-dichlorobenzene- safetyfactsheet.

Melissa Peterson | AdvDipHSc(Nat), GradCertEvBdPrac
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Title Annotation:TOXINS AND YOUR HEALTH
Author:Peterson, Melissa
Publication:Journal of the Australian Traditional-Medicine Society
Date:Dec 1, 2016
Words:1320
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