Studies outline toxic metals found in rice and spinach, researchers call for further investigation
The important takeaway is not that rice or spinach are inherently unsafe, but that contaminant levels depend heavily on where and how they are grown. The new findings fit a broader pattern in food safety research: soil chemistry, water management and crop type can shift the balance of metals absorbed by plants. That makes broad rules difficult, because a strategy that lowers one contaminant may raise another.
This is where the evidence needs careful reading. The study is useful because it links growing conditions to measurable changes in grain contamination, but it does not prove a single irrigation method will work across regions or soil types. The relationship between flooding, arsenic and cadmium is biologically plausible, yet the practical answer is likely site-specific rather than universal. That limits how far the findings can be generalized to every farm or every serving of rice.
For families, the main implication is risk management rather than avoidance. Infants and young children are the most sensitive group in this discussion, which is why regulatory monitoring matters. But consumer actions also have trade-offs: washing or acid treatments may reduce some metals in spinach, while other contaminants remain harder to remove. Food choices should therefore be viewed in the context of a varied diet, not as a single-food alarm.
Overall, this research adds to the case for upstream prevention. The biggest gains may come from farm-level practices, targeted testing and clearer standards that reflect how contaminants move through different crops and soils. That approach is more realistic than expecting one kitchen-level fix to solve a problem rooted in agriculture and environment.
Flooding rice fields
Crops such as corn, soybeans and wheat are grown in soils that are not very wet. Angelia Seyfferth, a UD soil biogeochemist and professor in the Department of Plant and Soil Sciences, harvests rice in the University of Delaware Rice Facility.In contrast, rice is often grown in very wet, flooded soils. The oxygen that would normally reside in tiny pores in the soil gets lost very quickly and is replaced by water. The limited oxygen shifts the microorganisms in the soil, and those microorganisms start breathing with iron oxide minerals that give the soil a rusty orange color. โArsenic likes to stick really tightly onto those iron oxides,โ says Angelia Seyfferth, a UD soil biogeochemist and professor in the Department of Plant and Soil Sciences and a co-author of the research. โWhen the iron oxides are used by these organisms to breathe, they go from a solid mineral to a solution phase. You essentially dissolve them, and when you dissolve them, the arsenic thatโs stuck onto them goes into the water.โ Seyfferth affirms that once the arsenic is in the water, it can easily be absorbed by the rice roots and transported into the grain. Seyfferth and research associate Matt Limmer grew rice in 18 small fields on the UD Newark Farm, exposing the rice paddies to different flooded and wet conditions. โWe were hoping to find an optimal irrigation management that minimized both arsenic and cadmium simultaneously,โ Limmer says, โbut we didnโt find one in this soil.โ Once they harvested the grain and analyzed the amount of arsenic and cadmium in it, the researchers instead found that the more flooded the field, the more arsenic and less cadmium accumulated in the rice. By contrast, the drier the field, the more cadmium and less arsenic accumulated. โBut, even under those drier conditions when there was more cadmium, the concentrations of cadmium in the grain were not of concern for human health,โ Seyfferth notes. Through a US Department of Agriculture National Institute of Food and Agriculture research grant, the researchers are studying arsenic in rice through some field work in Arkansas. They will work directly with farmers to develop tools to help them manage water flooding their rice paddies. Meanwhile, the FDA could release new regulations for arsenic and cadmium in infant food by the end of this year, as part of its aforementioned Closer to Zero Action Plan. The agency has researched the effects of arsenic and cadmium and two other toxins, mercury and lead, on child development and has also been evaluating new technologies or interventions that could stymie exposure to these toxins. โOur work could hopefully help shape policy,โ Seyfferth explains.Involving farmers
Seyfferth said one solution to help decrease the levels of toxic metals and metalloids in foods is offering subsidies to farmers to do certain strategies to reduce those levels on their own. Cadmium, which can build up in spinach leaves, could be reduced by making soils less acidic and washing spinach leaves after harvest. Lead is harder to remove, but washing spinach leaves with lemon juice extract could remove up to 26% of the lead in the leaves, the researchers say. โThe solutions are not a blanket solution,โ Seyfferth comments. โTheyโre not for all soils. They would have to be really site-specific.โ Limmer and Seyfferth believe more research is needed to find โan optimal irrigation strategy that lowers levels of both arsenic and cadmium in rice.โ โSimilar experiments need to be done in a variety of soils,โ Limmer notes, โideally under different field conditions.โ As the US waits for the FDAโs draft regulations on the allowable threshold of arsenic, cadmium and mercury in baby food, Seyfferth says she would like to see the federal government review a study last done in the 1980s. The FDA, US Department of Agriculture and the US Environmental Protection Agency analyzed paired soils and plants in agricultural fields across the US to get an idea of the concentration of metals and metalloids in those plants and soils. โSince then, thereโs a lot more spinach being grown now and being grown in areas where it wasnโt grown before,โ Seyfferth assers. โSome of those soils are much higher in cadmium.โEnjoyed this article? Sign up for our newsletter to receive regular insights and stay connected.