Arsenic’s reputation as a potent poison has been known since ancient Greeks and Romans used it to dispatch rivals. But scientists are just beginning to get a handle on the risks that come from chronic exposure to low doses of arsenic, which has complicated efforts to regulate the most common route of exposure: through diet.
Arsenic has been detected in a variety of foods, including fruits, juices, flour, rice and other grains, yet there are no safety standards in place to protect consumers, said Keeve Nachman, an environmental scientist at Johns Hopkins Bloomberg School of Public Health in Baltimore, at the annual meeting of the American Association for the Advancement of Science in Boston last Friday.
“Our focus on arsenic exposure in the United States has been through drinking water,” Nachman explained. That’s largely because most epidemiology studies have concentrated on risks associated with exposures that occur when arsenic in geological deposits leaches into groundwater.
Most public water supplies fall below the level of concern set by safety standards, which means that consumers are more likely to be exposed to arsenic through food. And even though epidemiologists have increasingly focused on risks of arsenic exposures through the diet, Nachman said, “there’s been relatively little regulatory focus around arsenic in food.”
Multiple studies have shown that grains, especially rice, can have high levels of arsenic. In some agricultural regions, arsenic is natural component of the soil. It can also increase when contaminated groundwater is used for irrigation. Fields can contain high arsenic levels leftover from the days when it was used as a pesticide. Rice is especially likely to absorb high levels of arsenic from the soil when water in flooded fields turns the toxic element into a form the plant mistakes for an essential nutrient.
Rice in cereal and snacks is a common staple for many babies and toddlers, who ingest two to three times more arsenic than adults by weight. Babies can also be exposed while still in the womb. Research led by Dartmouth epidemiologist Margaret Karagas, who also spoke at the meeting, shows that women’s consumption of rice during pregnancy was associated with levels detected in their baby’s toenails. Arsenic in food is also a concern for people with celiac disease, who can’t digest wheat gluten and tend to eat more rice instead.
A wealth of evidence links chronic arsenic exposure to cancer, heart disease, diabetes, respiratory disorders and skin lesions. Children exposed during early life face higher risks of lung and bladder cancer, as well as immune and neurodevelopmental disorders.
Despite the mounting evidence of harm from chronic low-dose exposures, regulatory efforts have stalled partly because no one knows how much arsenic you can eat before you start seeing adverse health consequences, Nachman said.
It may be years before policymakers overcome the technical and political hurdles to regulating arsenic in food, Nachman says. Until then, he recommends what he calls “prudent avoidance”: avoid eating foods likely to contain high levels of arsenic, like rice.
Because parents often give infants rice cereal as a first food, the American Academy of Pediatrics recommends trying cereals made from other grains, or vegetable purees, instead.
Nachman followed the AAP’s advice. His two young children were born while he started working on issues relating to arsenic in food. “Knowing that rice can contain elevated levels of arsenic, my family chose to pursue other types of infant cereals,” he said.