Arsenic exposure and rice consumption- The most toxic grain of them all

Arsenic is a naturally occurring element that is found in water, air, food, and soil. It is also used in pesticides, different chemicals, tobacco, wood preservatives, in metal mining.

Most exposure comes from water. The water becomes contaminated underground by rocks that release arsenic. It can be found in groundwater, drinking water, lakes or reservoirs, and wells.

Some countries are more affected than others and some areas are more affected than others. Arsenic in drinking water is a really big problem in many countries around the world. China has a big problem with arsenic water pollution. India, Bangladesh, Chile, Vietnam, Taiwan, and the United States. (Naujokas et al., 2013) In some parts of the world the water supply is so polluted that WHO estimates are that for example in a highly affected area of Bangladesh, more than 21.4% of all deaths were attributed to high arsenic levels in drinking water (Argos et al., 2010). The problem with this toxin is that it does not have an odor, taste, or color.

Arsenic may also be found in foods, including rice and some fish. It can also enter the body by breathing dust containing arsenic, or through the skin, though this is not a major route of exposure.

Although top predatory fish is a significant source of exposure, from all known food sources rice absorbs the highest concentration among all commonly eaten foods. It contains between 10 to 20 times more arsenic for example than other cereal crops.

Because rice grows in flooded conditions arsenic in the soil is released and more readily available. That released arsenic will be absorbed by the rice plant, and some of it will end up in rice grains. Because arsenic is already naturally found in the soil, it will be absorbed regardless of farming practices. If there is pollution of water even if the rice is grown organically the concentrations will be high.

High exposure of people is reported in different areas of the world, especially in parts of Asia and South America. China and Bangladesh have a problem with arsenic leaching into drinking water and are countries that traditionally eat a rice-dominated diet. In some parts of China and Bangladesh drinking water is thoroughly contaminated with high levels of arsenic. From 2004, in the EU a stricter precautionary standard for maximum total arsenic of 10 µg/l in drinking water came into effect but to be fair EU never had a problem like China so for the EU it is easy to adopt strict standards where there are no problems in the first place.

Like any other poison, children are more exposed because they will typically consume more per unit of body weight as well as have more particular eating patterns and limited dietary choices. For instance, rice is used in many first foods. If we calculate dietary arsenic exposure in children per kilogram of body weight, it is estimated to be about on average 2- to 3-fold that of adults. High levels are found in most rice-based foods and drinks widely used for infants and young children. Low levels of arsenic impact fetuses or children on different levels like growth development, and immune development, and they impact IQ development as well. In 2004 one study was done in Bangladesh that showed that children that were exposed to arsenic in drinking water had much-lowered scores on standardized tests. In 2013 one study showed that pregnant women who were exposed to even tiny amounts of arsenic in drinking water had children that had significantly more chance of developing respiratory problems. In Sweden, their National Food Agency (SNFA) has an official recommendation that children under the age of six do not consume rice in any form, especially rice cakes. Rice cakes have more arsenic than any other rice product, and a recommendation for an adult is also to cut down on the consumption of rice cakes if they eat rice on regular basis. Children should have a balanced diet based on different grains as a source of carbohydrates and infants, and young children should avoid eating rice at all especially rice cakes and rice drinks. Prolonged exposure to arsenic in adults is associated with an increase in heart disease as well as lung, skin, and bladder cancers.

There are steps to take if we want to eat rice to lower the arsenic content, but it will vary depending on the type of rice, the way it was processed, the condition and place where it was grown, and the way it was cooked.

The highest concentration is in the bran. Rice bran should not be eaten at all so any product that was made out of it, for example, commercial rice milk would have higher concentrations.

There are methods of cooking to lower the level of finished rice.

The first method is to soak. When you soak the rice it will absorb water but also that will open up the grains structure, so some of the arsenic that is water-soluble will leach out from the rice to the liquid. When you soak the rice or beans throw away the water. Do not use it.

Also when the rice is cooked some of the arsenic will leach out to the water as well. So again do not let the water evaporate because the arsenic will be still in there. This is the traditional way of cooking. Cook the rice in the proper amount of water and then throw it away.

To recap, soak, drain, rinse with fresh water, cook with fresh water, and rinse again.

Basmati rice tends to contain less arsenic than other types, and brown rice tends to contain more because a big chunk of the arsenic is in the husk.

With just regular cooking of rice in a rice cooker or cooking to dryness without soaking 84% of arsenic will remain.

When one part of rice with five parts water is used, only 43% of the arsenic initially detected in the rice will remain.

The best method is to soak then rinse then do 5 to 1 cooking. That method will eliminate more than 80% of arsenic. And because arsenic occurs naturally, buying organic doesn’t generally help. Organic produce consumption does not necessarily impact the levels of metals or POPs. If there is arsenic in the soil, it is still “organic” produce.

References:

1. Naujokas, M. F., Anderson, B., Ahsan, H., Aposhian, H. V., Graziano, J. H., Thompson, C., & Suk, W. A. (2013). The broad scope of health effects from chronic arsenic exposure: update on a worldwide public health problem. Environmental health perspectives, 121(3), 295–302. https://doi.org/10.1289/ehp.1205875
2. Argos, M., Kalra, T., Rathouz, P. J., Chen, Y., Pierce, B., Parvez, F., Islam, T., Ahmed, A., Rakibuz-Zaman, M., Hasan, R., Sarwar, G., Slavkovich, V., van Geen, A., Graziano, J., & Ahsan, H. (2010). Arsenic exposure from drinking water, and all-cause and chronic-disease mortalities in Bangladesh (HEALS): a prospective cohort study. Lancet (London, England), 376(9737), 252–258. https://doi.org/10.1016/S0140-6736(10)60481-3