In support of the U.S. Food and Drug Administration’s (FDA’s) Closer to Zero initiative to reduce the consumption of toxic heavy metals through food, researchers from Michigan State University have conducted a risk assessment that estimates the U.S. population’s dietary exposure to cadmium. The study found children aged 6–24 months and 24–60 months to be the populations most highly exposed to cadmium, with concerning levels of exposure when compared to guidelines set by regulatory agencies.

Chronic exposure to cadmium has been associated with damage to the kidneys, nervous system, renal damage, cardiovascular disease, cancer risk, and liver disease. Due to cadmium’s negative effects on human health, The U.S. Agency for Toxic Substances and Disease Registry (ATSDR) has set a chronic oral minimal risk level (MRL) for the metal of 0.1 micrograms per kilogram of bodyweight per day (μg/kg bw/day). MRLs indicate a dose considered safe for humans to consume regularly without increasing disease risk over a lifetime.

The formation of action levels for cadmium by FDA is ongoing. Action levels are one regulatory tool that FDA uses to help lower levels of chemical contaminants in foods when a certain level of a contaminant is unavoidable. FDA considers action levels, in addition to other factors, when considering whether to bring enforcement action against a firm producing food that is possibly unsafe.

Infants and young children may be more susceptible to adverse effects of cadmium exposure due to higher intakes of food and drink relative to their bodyweight, and greater potential of metals to affect developing bodies. However, few studies have investigated dietary cadmium exposure in young children, and none have investigated exposure in infants 0–6 months of age from commonly consumed foods that are susceptible to high cadmium accumulation.

Therefore, the present study aimed to fill the knowledge gap of dietary cadmium exposure in the U.S. population by assessing exposure to the metal from two major food items—rice and spinach—in various age groups, including infants and young children. The study also evaluated which age groups are more vulnerable to higher cadmium exposure, and whether cadmium exposure for each of age group exceed established guidelines for tolerable intake. Additionally, the researchers determined the cumulative cadmium exposure from six food items commonly used in manufacturing commercial baby food: rice, spinach, oats, barley, potatoes, and wheat.

The study’s findings suggest that, although a 2021 U.S. Congressional report on toxic heavy metals in infant food focused on children aged 6–24 months, it may be equally if not more important to focus on the foods that young children aged 24–60 months (2–5 years of age) consume in high amounts—because predicted cadmium exposure is highest for this age group in the U.S.

Overall, the study confirms the challenge of setting appropriate standards for cadmium in individual food items, due to the possibility of exposure to the metal from multiple foods. At the mean food intake and mean cadmium levels, the cumulative exposure from six food items commonly used in commercial baby food manufacturing exceeded ATSDR's chronic oral MRL values for the 6–24 and 24–60 month age groups, and the group estimated to have highest dietary cadmium exposure was Americans aged 24–60 months. However, exposures to the metal from individual foods such as rice and spinach were found to be generally low at mean levels of food intake for the total US population—below all tolerable intakes set by regulatory agencies.

In addition to setting action levels for individual foodstuffs, the researchers posit that it may make sense for policymakers to set cadmium standards for finished food products like pureed infant foods of mixed ingredients, as exposure to the metal may come from multiple different ingredients with highly diverse cadmium levels.

Rice and spinach were chosen as the focus of the study because they are commonly consumed foods that readily take up cadmium and other heavy metals from soil, and rice is a common ingredient used in commercial infant food.

The researchers conducted a literature search to find studies reporting cadmium levels in rice and spinach, as well as for the six food items commonly used to manufacture baby foods, and used the data collected to calculate daily exposures to cadmium for the total population and for each age group.

The median/mean cadmium values in rice samples ranged from 6.5–18.19 μg/kg, while the maximum cadmium values in samples ranged from 23–71 μg/kg. Mean cadmium levels in spinach were much higher than that of rice, ranging between 117 and 222 μg/kg.

The study found that, for the total population, the average daily dose (ADD) from both rice and spinach were below ATSDR's chronic oral MRL. However, for the sub-population of people who consume the foods on a regular basis, the ADD of spinach for 0–6 months, 6–24 months, and 24–60 months age groups were higher than ATSDR's chronic oral MRL. None of the ADD values exceeded the European Food Safety Authority’s (EFSA's) provisional tolerable daily intake (TDI) level of 0.36 μg/kg bw/day, with the highest ADD value being 0.31 μg/kg bw/day from spinach in the sub-population of regular consumers.

Notably, the researchers highlight that, although the U.S. population consumes far more rice than spinach daily by weight, cadmium exposure is much higher from spinach than from rice.

Regarding the cumulative ADD from the six significant food items—spinach, rice, oats, barley, potatoes, and wheat—ATSDR's chronic oral MRL was exceeded among the total population, with values of 0.15, 0.17, 0.10, and 0.10 μg/kg bw/day for 6–24 months, 24–60 months, 5–18 years, and 18 and above age groups, respectively. For the sub-population of people who consume the foods regularly, the cumulative ADD values exceeded the ATSDR level for all age groups with values of 0.20, 0.29, 0.35, 0.19, and 0.18 μg/kg bw/day for 0–6 months, 6–24 months, 24–60 months, 5–18 years, and 18 and above years age groups, respectively.

Additionally, FDA Total Diet Study (TDS) data revealed that cadmium levels in spinach are higher than those in leafy vegetables in the EU and New Zealand, suggesting that, if FDA sets cadmium action levels similar to those in the EU and New Zealand, there may be a future challenge for some U.S. spinach producers to achieve the action levels without intervention.