Removing heavy metals

This post was initially released on Undark.

Many American babies start out their diets with rice cereal, and it’s often the first solid item they try. However, in recent years, it has also become one of several child diets that have been causing concern among lawmakers and parents.

The majority of the world’s rice is farmed in South and Southeast Asia, while it is also planted in the United States and many other countries. Despite the fact that these flooded fields provide a cool, fruitful environment for a healthy crop, they are also susceptible to pollution by heavy metals such as arsenic, cadmium, lead, and mercury.

Some heavy metals appear to impair brain development and cognition, and they have also been linked to health problems like lung disease, renal illness, skin rashes, and cancer. Because infants have a higher food intake in relation to their body weight and a less varied diet than adults, they are more vulnerable to the effects of heavy metal exposure. Because their bodies are still maturing, infants are also acutely aware of the perilous effects of heavy metals.

Heavy metals were found in infant food made by several of the country’s largest manufacturers, according to a study released in February 2021 by the U.S. House Oversight and Reform Subcommittee on Economic and Consumer Policy. The 59-page dossier concluded with an urgent request for FDA action. Two months later, the FDA unveiled the Closer to Zero initiative, an iterative strategy to reduce children and young people’s exposure to heavy metals. In January 2023, the FDA released a draught of its guidance on lead in kid meals, and in April 2022, it addressed lead levels in produce and fruit juice. The deadline for the completion of arsenic, cadmium, and mercury action plans has been pushed back to 2024.

While colony management practises, nano-sized fertilisers, and genetic manipulation are all being explored, botanists, soil chemists, and plant geneticists who have worked for years to reduce heavy metals in the food supply continue to look for other potential solutions. It will be difficult to completely eliminate heavy metals even when all of these advances become widely available.

However, there are many in the field who are optimistic about the prospects. Crop biotechnology professor at UMass Amherst Om Parkash Dhankher has said, “there is no single magic bullet that can resolve this issue,” but “there are great deals of innovations and practises that farmers can utilise.”

Water travelling through subsurface rock formations can dissolve heavy metals that are naturally present in the Earth’s crust and make their way into aquifers and rivers. The groundwater in the United States, China, and India, for example, has dangerously high amounts of arsenic. Heavy metal pollution has been exacerbated by agricultural practises. Soil, paddy water, and rice grains still exhibit discernible amounts of the pollutants, even though the United States led the world in utilising arsenic for farming and commerce before its use was banned in the 1980s.

The rice plant’s roots absorb these toxins through the cell wall proteins that provide nutrients to the plant. Parkash claims that arsenic essentially “pirates” these routes. Arsenic is taken up by the plant from the soil and makes its way up via the stem, leaves, and grains.

Scientists like Parkash are investigating ways to prevent arsenic from reaching the plants in the first place. Adding additional sulphur to paddy soils is one approach since it can bond to toxic metals, making them less absorbable by plants.

Babies are more vulnerable to the effects of heavy metal exposure than adults because they have a higher food intake in relation to their body weight and a less varied diet.

Parkash and Jason White, director of the Connecticut Agricultural Experiment Station, have been doing microscale studies of this method recently. Parkash and White have really investigated how nanotechnology, which entails managing items at the size of billionths of a metre, may be used for dirt remediation because of the way sulphur binds to dangerous metals. A recent article found that when the more deadly form of arsenic, inorganic arsenic, was combined with nanosulfur in the treatment of rice plants, the amount of arsenic accumulated in the plants’ roots was reduced by almost a third.

Alterations to the playing field might also help. Researchers have looked into intercropping rice paddies with wild plants like water spinach and water celery to help remove pollutants. These water vegetables are cultivated alongside rice to reduce overall arsenic concentrations in the soil, which the wild plants then use to their advantage. It has been revealed that certain varieties of bacteria can survive in environments with high concentrations of arsenic, lead, mercury, and cadmium, and that other bacteria can even mitigate the toxic effects of these metals on plants. Other microorganisms can reduce crop arsenic levels. Scientists have also engineered bacteria to create a protein that boosts their capacity to degrade arsenic.

Some of these methods have not been used to large-scale initiatives outside of research settings. Soil and ecological chemistry researcher at Kansas State University Ganga Hettiarachchi said, “Scientists do not even consider extension,” in reference to the United States Department of Agriculture’s (USDA) and land-grant universities’ century-long partnership. Hettiarachchi emphasises that farmers may not understand how to use the most recent findings on soil and land management. She has an upbeat outlook, saying, “I do see that it’s altering.”

Some findings from the heavy metals in rice study are not yet applicable in practise. Shannon Pinson, a plant geneticist with the USDA’s Agricultural Research Service, told Undark that attempts to genetically modify rice to make the plant more resistant to heavy metals had failed. While genetically modified rice has been a useful research tool for understanding how plants metabolise heavy metals, it is not yet grown commercially in the United States, as Pinson pointed out. Her findings suggest a network of genes with additive effects regulates arsenic accumulation, rather than a single master regulator.

However, not all rice fields are created equal; some require more arsenic and metals than others. In a brief study published in 2015, Pinson’s team evaluated the levels of natural and inorganic arsenic in 1,763 rice cultivars from across the world at different times during their growth. Pinson claims that U.S. cultivars already contain the genes responsible for limiting absorption of both forms of arsenic. According to her findings, this indicates that plants are already doing everything they can to reduce arsenic, and that it “will not be simple to discover extra genes that would even more minimise arsenic in U.S. rice ranges through conventional breeding.”

Blocking arsenic may affect how a plant utilises up other nutrients, which adds another layer of complexity to experimenting with soil chemistry and plant DNA. The necessary nutrients and these toxic components exist in a dynamic equilibrium, Parkash explained. As one person put it, “It’s a really complicated system.”

Beyond the paddy field, there is a wider ramification of the tradeoff between nutrients and heavy metals, and direct exposure to harmful chemicals is not the only element to consider when establishing rules surrounding food.

The FDA recognises that strict limits may not be feasible for manufacturers when providing current support for arsenic in baby rice cereal and for lead in infant food more generally. Pinson told Undark that it’s possible to cultivate rice with relatively low levels of arsenic, but that it’s difficult to achieve low levels in rice-based infant foods due to supply chain realities. This is because retailers often combine grains from multiple truckloads from different farms into single bins, making low-arsenic rice hard to trace.

Concentrations in retail-ready infant and toddler fare can also rise throughout manufacture. According to a study from the Economic and Consumer Policy Subcommittee published in February 2021, inorganic arsenic levels in the finished products were 28-93% higher than in the components in testing of at least one company’s products. The research attributes the increase both before and after production to the high arsenic content of certain of the substances used.

Undark spoke with FDA spokeswoman Elisabeth Davis, who warned of unanticipated costs to consumers if the food industry failed to meet limits on heavy metals in their products. For example, “restricting access to foods that have considerable dietary advantages by making them not available or unaffordable for many households, or inadvertently increasing the existence of one ecological impurity when foods are reformulated to lower the existence of another,” she explained.

The FDA initiated a risk assessment in March 2016 to analyse the cost implications and lifetime cancer risk of various doses of arsenic support. Parts per billion (ppb), which is not a system of mass but rather a description of a ratio, was used in the risk assessment to evaluate the outcome of different limits. The salt concentration in an Olympic-sized swimming pool would be 1 parts per billion if half a teaspoon were added. The FDA estimated that a reduction from 100 ppb to 75 ppb would result in a loss of rice in the food supply of between 4 and 93 percent.

The FDA’s risk assessment estimated the average lifetime risk of cancer from eating baby rice with varying amounts of inorganic arsenic. Limits of 75 and 50 ppb were calculated to reduce the risk of cancer by 41 and 79 percent, respectively, for white rice baby cereal, while a limit of 100 ppb would reduce the risk by about 19 percent.

Experts told Undark that it is difficult to determine the health risks associated with heavy metal exposure using the risk models used in the paper. White, from the Connecticut Agricultural Experiment Station, said, “There isn’t a formula today that might be used to actually compute something like that.” Determining direct exposure from water is very easy, but White said this about food: “There isn’t a formula today that might be used to actually compute something like that.”

The FDA’s preliminary guidance on inorganic arsenic limits was suggested in April 2016 and will be finalised in August 2020, at a concentration of 100 parts per billion. The Baby Food Safety Act recommended a limit of 10 ppb, making this more lenient. However, this bill has been stuck in Congress since March 2021. Although the 100 ppb threshold in food is listed below the voluntary criteria set by the major worldwide food regulations organisation, the Codex Alimentarius, the act would align the limits on inorganic arsenic in food with the U.S. Environmental Protection Agency’s requirement for drinking water.

Baby rice cereal with no more than 100 parts per billion arsenic is only a recommendation, not a mandate, according to the FDA’s rules on food limits. There is some evidence to suggest that the adjustment is working. Since it first announced the draught guidance, the FDA has noticed a little declining trend in the average quantities of arsenic in infant rice cereal.

Four out of seven baby rice cereals tested above the FDA’s restriction of 100 ppb of arsenic, according to recent analyses by Consumer Reports and the advocacy organisation Healthy Babies Bright Futures. Two reports, one in September 2021 and one in February 2021, showed that many companies had arsenic limits that were stricter than the FDA recommended. Some companies also found that the arsenic levels in their infant cereal were far higher than allowed.

“The people who make baby food have a special place in people’s hearts. Their clientele believe that they would not sell potentially harmful products. Customers share the opinion that “the federal government would not knowingly permit the sale of hazardous child food,” according to the research. Makers of infant foods and the federal government agencies overseeing them had “broken the faith.”

There was no FDA-mandated recall despite evidence of arsenic levels exceeding 100 ppb in infant rice cereal. Instead, several companies voluntarily removed stock from shelves. In June of 2021, Beech-Nut announced that it will no longer be producing rice cereal.

Heavy metal exposure is possible from a wide variety of non-Closer to Zero sources. Beyond the action level for arsenic in baby rice cereal and two draught assistance levels for lead in juice and kid meals more generally, the FDA has no restrictions for heavy metals in foods. Even while it is possible to routinely test manufactured foods for heavy metals, Hettiarachchi’s research shows that even private and community gardens can be poisoned, meaning that the risk of direct exposure remains even with handmade food.

Hettiarachchi said, “it’s great, and I completely support getting closer to no,” in regards to the FDA’s efforts to date to minimise heavy metal direct exposure. “But simultaneously, I think we need to do far better,” he said.

Nutrition picture

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