A synthetic chemical prevents a plant native to Japan from absorbing harmful radioactive elements, according to a study published today in Scientific Reports. The findings raise the possibility that it could be used to decontaminate farmland in Japan — a country still reeling from the Fukushima nuclear disaster of 2011.
"Agricultural products from Fukushima used to be very popular for their quality and taste, and [they] were loved by consumers all over Japan," Ryoung Shin, unit leader at the RIKEN Center for Sustainable Resource Science and co-author of the study, said in an email. Although agricultural products are closely screened before entering the market, Shin says farming has yet to restart in areas with high concentrations of radioactive cesium, and regional agriculture as a whole still suffers from the stigma associated with the nuclear meltdown. "This negative image of Fukushima products can be long-lasting, and I think this is the most serious concern for them."
A promising finding for Fukushima's farmers
To address this issue, Shin and her team searched for a chemical that might decontaminate the plant Arabidopsis thaliana, a mustard weed that is commonly used in scientific studies. Five chemicals were identified among a set of 10,000 synthetic compounds because they were capable of increasing the plant’s tolerance for radioactive forms of the element cesium, which has been shown to inhibit plant growth. But one compound, CsTolen A, stood out. When applied to plants grown in cesium-contaminated soil, CsTolen A significantly reduced the amount of cesium the plants absorbed, resulting in greater growth and healthier leaves. And the chemical's impact appears to be cesium-specific. It wasn't able to reverse growth problems in plants that suffered from a potassium deficiency.
Adams et al., 2015
Record amounts of the isotopes cesium-137 and cesium-134 have been detected in groundwater following the Fukushima disaster, and they take years to decay. Because exposure to high amounts can increase cancer risks in humans, previous studies have explored decontamination techniques based on fertilizers or soil treatments. But as the study authors note, chemical treatments could offer a more efficient and targeted way of reducing cesium around Fukushima, where farming is still suffering nearly four years after a tsunami dispersed tons of radioactive material into the environment.
"Simpler and greener is usually easier to sell."
The soil-based findings are encouraging, the study authors say. But others strike a more cautionary note. "I have mixed feelings about it," says Stephen Ebbs, a professor of plant ecophysiology at Southern Illinois University who was not involved in the study. "There's long been a need for cesium, strontium, and radium contamination issues to be handled in such a way that it protects the environment and food supplies." But Ebbs, who co-authored a study on cesium uptake in plants in 2003, says more tests are needed to determine the long-term impact of CsTolen A on the environment. Little is known about the effects it could have if it enters the food chain, he says. "This is a first step, but... I think it’s very premature to move forward with any kind of field testing."
Shin acknowledges that more work needs to be done before applying CsTolen A to agricultural fields, though she says the chemical "can probably be used efficiently for any kind of crop plants." Convincing regulators and especially the general public, however, may prove more challenging.
"When you add chemicals to the environment, it tends to generate a negative public response," Ebbs says. "Simpler and greener is usually easier to sell to people and convince government agencies."