Arsenic is a metalloid, with both metal and non-metal properties, and notorious as the almost perfect murder weapon featured in works of fiction including Agatha Christie’s Murder is Easy, and Flaubert’s Madame Bovary. It’s a natural component of bedrock, but certain pesticides used in the past have added arsenic to some areas.
Luckily, humans have evolved to tolerate naturally occurring arsenic by producing proteins that modify the arsenic molecule to a less toxic form. Our bodies can then excrete the modified arsenic through our urine. These proteins, however, can only process a limited amount of arsenic at a time. Once that level of arsenic is surpassed, our bodies cannot clear the arsenic fast enough before irreversible damage has been done, which may lead to cancer and other serious health side effects.
In a similar fashion, rice also has a threshold for arsenic, but how arsenic is removed from the plant is not well understood. Finding the proteins responsible for eliminating arsenic from the plant and how different cells work together to regulate this process are the questions driving the research of Dartmouth PhD candidate Todd Warczak and others in the Toxic Metals Superfund Research Group.
A recent Brain Buzz event, hosted in partnership with the School of Graduate and Advanced Studies at Dartmouth, the Upper Valley Food Coop in White River Junction, and the Vermont Institute for Natural Science, was an opportunity for members of the local community to learn more about arsenic in food and what researchers at Dartmouth are doing to promote public awareness around the issue, as well as how they are trying to find solutions to the problem.
“Rice has a unique arsenic problem because unlike other crops, rice is grown in flooded paddies. Soil under water has less oxygen and a lower pH, which facilitates more free-roaming arsenic,” explained Warczak. “This means instead of staying bound to other compounds in the soil, the arsenic is released and made more available to the plant.” Furthermore, excess arsenic tends to end up in the bran layer that surrounds the grain, which is bad news for brown rice.
Brown rice in particular has been promoted as a healthy whole grain to incorporate into the diet, and rice in general is often a common substitute for those on a gluten free diet. To illustrate the point, Warczak had several rice products on display including a package of organic brown rice crackers. “Some rice crisps and cakes surveyed by the FDA in 2012 showed inorganic arsenic levels around 250 parts per billion, which is the upper limit for all products sampled,” he said. “For reference, the Environmental Protection Agency regulates a maximum of 10 ppb arsenic in public drinking water,” he noted.
There are different theories about how the plant kicks out excess arsenic; looking at a cellular level is an important part of the research process for Warczak. Using Arabidopsis thaliana, Warczak grows batches of the plant for one week, then exposes them to an arsenic solution for 24 hours before harvesting the roots. “Then the race is on to get those roots to the lab at Dartmouth Hitchcock Medical Center where I use a special laser to isolate different cells for analysis,” Warczak explained. “In this way, rather than looking at the whole plant, we can look at snapshots of the toxin response from each layer of cells.” Once the toxin response at the cellular level in the roots is understood, work can be done to introduce changes to the rice genome and develop crops that put arsenic back in the soil instead of absorbing it in their grain.
Many audience members were curious to hear about the regulatory climate around genetically modified food, which ultimately would provide the fastest route to reducing arsenic uptake in rice. “Regulatory costs are prohibitively expensive for many groups,” states Warczak, “and the timeline required to assess new GM crops makes them nearly impossible to develop. Only a few massive agriculture companies can compete in this market.” He recognized that public distrust of those companies often fosters distrust in the science behind GM crops. Which means, for crop researchers, food developed in our labs that prevent disease and erase malnutrition are unfairly stigmatized.
“There is no nutritional danger associated with GM rice,” asserted Warczak. “Something that could be developed to reduce arsenic uptake in rice, and potentially lower the risk of cancer, would likely not be embraced because it is considered a GM process,” he explained. “It doesn’t have to be this way.”
While there is no current rice on the market completely lacking arsenic, there are measures the public can take to inform themselves. The Dartmouth Toxic Metals Superfund Research Program launched a new website with comprehensive information on the health effects of arsenic, where it can be found, what areas are at higher risk, and how to reduce risks. It also contains arsenic data from different rice products and where that rice is grown. You can access all the information, as well as further literature and research here: www.arsenicandyou.org