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Some Food Contamination Starts In The Soil

By Kaine Korzekwa
 
When most people hear “food contamination,” they think of bacteria present on unwashed fruits or vegetables, or undercooked meat. However, there are other ways for harmful contaminants to be present in food products.
 
Angelia Seyfferth, a member of the Soil Science Society of America, investigates food contamination coming from the soil where the plants grow. “It all comes down to the chemistry of the soil,” explains Seyfferth.
 
Most recently, Seyfferth has been studying rice. The elements arsenic and cadmium can be present in the paddies where rice is grown. She presented her research at the virtual 2020 ASA-CSSA-SSSA Annual Meeting.
Rice Investigation
Rice Investigation, Communication and Education (RICE) Facility at the University of Delaware where the Seyfferth Lab conducts rice experiments in outdoor rice paddies.
 
“Contaminants being taken up by crop plants is a route of dietary exposure to contaminants that is understudied,” Seyfferth says. “We can help decrease human exposure to toxins by applying our knowledge of soil chemistry.”
 
Small amounts of arsenic and cadmium are present all over the globe and can be detected in many food products. It’s the concentration in the vegetable or fruit, the chemical form of the element, and how much of it someone eats that determines if an individual experiences a negative health effect.
 
High concentrations of arsenic and cadmium are harmful to the body. Consuming low doses over a long period of time can even cause cancer.  
 
Elements like arsenic and cadmium can be in different chemical forms depending on their environment. Contaminants are taken up by plants when their chemical form in the soil resembles a nutrient the plant needs.
 
Rice plants growing
Rice plants growing hydroponically, meaning in nutrient solution without soil, under different arsenic and silicon levels. 
 
“How food is grown affects not only the concentration of contaminants, but also where the contaminants are stored within the food,” says Seyfferth. “If we understand the chemical forms of contaminants in soil, we can design solutions to decrease plant uptake of them.”
 
In rice, arsenic and cadmium uptake results from opposite conditions. Arsenic can be taken up when the field is flooded. Cadmium is more likely to be taken up when the field is not flooded.
 
Seyfferth’s work has searched for a way to prevent plants from taking up arsenic and cadmium from the soil. This is often done by adding materials to the soil, called amendments.
 
An amendment helps change the soil environment. By changing the soil environment, researchers can help control the chemical forms and plant uptake of contaminants in the soil.
 
In this case, Seyfferth found that adding rice husk residue to rice paddy soils can help lower the amount of arsenic and cadmium taken up by the plants. Rice husk residue is plant material left over after processing rice for human consumption.
 
This solution is simple yet effective. Rice husk residue is high in the element silicon, which is an important nutrient for rice. The chemical form of silicon is similar the form of arsenic taken up by rice plants when fields are flooded. This similarity helps ‘distract’ the plant, which prevents it from taking up as much arsenic. 
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