Last Friday, the United States Food and Drug Administration announced that it was moving to set official safety standards for infant rice cereal due to persistent problems with arsenic contamination in rice. In a Consumer Update published on its website, the agency also recommended a reduction in rice consumption for both babies and pregnant women, citing a range of potential adverse effects from arsenic exposures, including cognitive deficits in children.

As a result of these concerns, the FDA is proposing a 100 part-per-billion limit on allowable arsenic in baby rice cereal, comparable to levels proposed by the European Union and the World Health Organization. The announcement is only a first step toward setting regulatory guidelines, and the agency will open up a 90-day public comment period before making a final decision.

In the meantime, here are ten questions (and answers) to help make sense of what’s going on.

1. Is rice just naturally poisonous?

Absolutely not. The rice plant — and its seed or grain – do not belong to any of the known risky plant groups (such as, for instance, the deadly nightshade family). Rice is such a diet staple, from Asia to Latin America, that researchers usually focus on enriching it as a way to deliver needed vitamins and minerals to disadvantaged populations.

2. Then why is the FDA so worried about rice?

It turns out that the rice plant is a very efficient vacuum for pulling metallic elements out of the soil. The most troubling of these include three well-known trouble-making elements: mercury, cadmium, and arsenic, which is considered a a metalloid element. Researchers say the plant is at least ten times as effective as other grains at siphoning up arsenic from soil and water. Further, it has a particular affinity for inorganic arsenic (an arsenic compound that lacks the organic element carbon). Inorganic arsenic compounds are known to be far more poisonous to humans than organic, carbon-based arsenic compounds.

3. Where does the arsenic come from?

Arsenic is a naturally occurring element found in both soil and water. Natural arsenic is the primary source for the inorganic arsenic found in rice. There is some suggestion that, in the United States, rice grown in southeastern states is higher in arsenic than that found in other parts of the country because the crop is often grown in old cotton fields where arsenic based pesticides were widely used. But most of the contamination is actually a result of geology. Some excellent maps of arsenic contamination of both ground water and soil in the U.S. are displayed here. Naturally occurring arsenic appears to be concentrated in the United States and parts of South America and Asia. As where rice is grown turns out to be important, some experts are recommending geographic labeling.

4. Does it help if the rice is grown organically?

No. Rice takes up arsenic directly from soil and water, so in terms of arsenic concentrations, there’s typically no real difference between crops grown organically and those grown by conventional methods.

5. What about brown rice?

Brown rice generally contains more arsenic than white rice. That’s because the arsenic concentrates in the husk and the bran, which are mostly polished off during white-rice processing. One study that found high levels of arsenic was specifically focused on organic brown rice products.

6. Why are we worrying about this now?

Inorganic arsenic is most familiar to people as a homicidal poison of a bygone era. It was only in the late 20th century that scientists began to detect arsenic in soil, water and food — not at levels high enough to kill people outright, but at the part-per-billion level. The question was whether even these levels were cause for concern, and in the 1970s and 80s, researchers did begin making links between even tiny levels of arsenic in ground water and a surprising range of illnesses, from cancer to cardiovascular disease. Much of our modern awareness of the issue is tied to studies in Bangladesh, where so many people are exposed to arsenic-contaminated ground water that the World Health Organization describes it as the greatest mass poisoning in human history.

7. When did rice become a concern?

In Bangladesh, further research showed that arsenic’s toxic effects were being increased by rice consumption, because the grain was absorbing arsenic from both soil and water. But interest in the food supply really took off in the last decade. In Europe, the pioneering work was done by Andrew Meharg, of Queen’s University in Belfast, Ireland, who showed that a dismaying number of rice-based foods sold in Great Britain were tainted with arsenic. In the United States, similar research was done by Consumer Reports, which published a wide-ranging investigation in 2012. That same year, the FDA published its own investigation showing that arsenic could be found in various products in the American food supply, and it acknowledged that rice stood out for its ability to concentrate the product.

8. Why did the FDA decide to only regulate infant rice cereal?

The agency calculated that, relative to body weight, infants who are fed a steady diet of rice cereal were consuming three times as much arsenic each day as adults eating rice products. Public health regulators found that worrying because a steady diet of inorganic arsenic, even at the part-per-billion level, is known to affect cognitive development, particularly learning and memory. The agency also recommended that pregnant women reduce their rice-based arsenic exposure, citing the potential for adverse pregnancy outcomes like premature and still births. Research has also found that children’s immune systems can be undermined if their mothers experienced chronic arsenic exposure during pregnancy. The agency decided to move first to protect an obviously vulnerable population.

9. What about toddlers, other children and everyone else?

Consumer groups are already pushing the FDA to expand its protections, pointing out that that arsenic in the food supply represents a much larger problem than just baby cereal. “There is a much broader problem from high levels of arsenic across rice products for children and adults – and none of these have standards,” said Urvashi Rangen, Director of Consumer Safety and Sustainability at Consumer Reports. “Without meaningful standards, consumers of all ages who eat rice and especially those who eat a lot of rice are still at risk. So FDA literally and figuratively took a baby step last week.”

10. Is this worth panicking over?

Absolutely not. These are trace amounts of arsenic and the worst effects reported are related to long-term, chronic exposure. The poison cycles out of the body in a just a few days, so by reducing rice consumption and eating a varied diet with a mix of grains, it’s fairly simple to reduce your risk. More research – and stronger regulation – are needed, but we are at least making a start.

Deborah Blum is a Pulitzer prizewinning science journalist and the publisher of Undark.