Cadmium

Background

Over the last few years there has been increased focus surrounding heavy metals in the food supply. This is, in part, due to the growing concern among consumers about the presence of heavy metals in food products and the potential public health impact that consumption of these products could have.

FDA has published an action plan, Closer to Zero, which identifies the approach the Agency plans to take to reduce exposure to toxic elements in foods commonly eaten by babies and young children—to the lowest possible levels. Some of the activities outlined in Closer to Zero include research and evaluation of changes in dietary exposures to toxic elements such as Cadmium, setting action levels, encouraging adoption of best practices by industry, and monitoring progress.

What is cadmium?

Cadmium is a naturally occurring element found in the environment. Cadmium can be released into the environment through mining and smelting and its use in various industrial processes and can enter the food chain from uptake by plants from contaminated soil or water. Most cadmium used in the United States is extracted as a byproduct during the production of other metals such as zinc, lead, or copper. Cadmium is primarily used in nickel-cadmium rechargeable batteries, alloys, solar cells, and pigments.

The most common way of cadmium exposure into the food supply is through consuming cadmium contaminated foods. These foods are exposed to Cd through the environment where some phosphate fertilizers are used and where industrial processes such as smelting, mining and burning of fossil fuels occur.

Why is cadmium a concern in the food supply?

The presence of cadmium in food comes from the environment where food is grown, raised or processed. The amount of cadmium present in the environment varies and depends on the natural geographical makeup of soil and the proximity to current or former industrial sites that produce products made with cadmium.

How does cadmium get into food?

Once in the environment, cadmium moves easily through the soil and can be taken up by agriculture crops or ingested by animals. Foods mostly likely to contain cadmium include leafy greens (e.g., spinach), root vegetables, grains, rice and nuts. Cadmium concentration in food depends on a number of factors, including the commodity, growing environment and production practices. In a 2021 FDA sampling survey of ready-to-eat baby foods, the medium concentration of cadmium in tested products was 1.81 ppb. Foods containing leafy greens, were the most likely to contain cadmium.

What are the health effects?

The health effects resulting from consuming food contaminated with cadmium depends on several factors, including the level of cadmium in food, age of consumer, and exposure amount (i.e, time and frequency). Babies and young children are particularly susceptible to adverse health effects due to their size and rapid brain development. Studies have shown that exposure to cadmium in foods may lead to bone demineralization, kidney and reproductive dysfunction, cardiovascular disease, and diabetes.

What role does bioavailability have on the risk to human health?

Understanding bioavailability is important for assessing dietary exposure and the potential risk to human health. Not all toxic elements present in the soil, plant or body are completely absorbed. Simply put, there is not a direct correlation between the mere presence of cadmium and human health risk. The fraction of a nutrient or element that is absorbed and utilized is known as bioavailability. The uptake and concentration of cadmium in crops is dependent on the amount of cadmium available in the soil. The bioavailability of cadmium is affected by factors such as soil characteristics, crop genetics, soil cadmium concentration, fertilizer management and irrigation water. As an example, in the soil, when the pH of the soil is lower the bioavailability of Cd in soil increases. Use of irrigation water with higher chloride concentration increases bioavailability.

Within the body, cadmium bioavailability and the amount of cadmium absorbed is influenced by the nutritional status of the individual. Studies have shown that when there is an efficient amount of nutrients in the body (i.e. iron, zinc, calcium, etc.), cadmium bioavailability decreases, thus reducing absorption of cadmium.

What are the current regulatory requirements?

Authorized Uses and Established Limits

There are no FDA regulations authorizing cadmium in food, though FDA seeks to limit the amount of cadmium in food in situations where it is not possible to avoid cadmium entirely. When there are no established limits, FDA can use its authority to take action on a case-by-case basis when the level of metals in FDA regulated products is determined to be unsafe. Under the Closer to Zero initiative, FDA has stated their intention to issue industry guidance on action levels for cadmium in food intended for babies and young children. FDA issues guidance on action levels to communicate to industry the level of contaminants in foods at which the Agency may take enforcement action.

FDA and EPA have established an action level of 5 ppb for cadmium in bottled and drinking water, respectively. The EU has set action levels of cadmium in food, though the limits vary depending on the commodity.

Import Alerts

FDA has issued import alerts for certain food and products and certain manufacturers that may be unsafe due to the presence of elevated cadmium.

Requirements under the Current Good Manufacturing Practice, Hazard Analysis, and Risk-Based Preventive Controls for Human Food Rule

Food manufacturers and processors have the responsibility to consider risks from chemical hazards, including heavy metals such as cadmium, and implement controls to significantly minimize or prevent any of the identified chemical hazards. For example, some manufacturers may conduct verification activities like testing the final product.

FDA provides guidance on chemical hazards, such as heavy metals, in their Draft Guidance for Industry: Hazard Analysis and Risk-Based Preventive Controls for Human Food. The Guidance specially addresses chemical hazards in Chapter 3 (Section 3.4.1.3) and supply chain controls for heavy metals in Chapter 4 (Section 4.6.3).

What can be done to reduce cadmium exposure from the food supply?

While cadmium is impossible to completely avoid in the food supply, there are many mitigation measures that allow for safe produce to be grown. It is important to note that mitigation strategies are not applicable to every commodity. What is used for leafy greens may result in the opposite effect in a commodity such as in rice. Therefore, mitigation strategies must be sustainable and applied on a case-by-case basis.

Two key measures to mitigate cadmium uptake in plants and absorption in the body, include: 1) Modifying the soil environment the plants are grown in and 2) Nutrient efficiency within the body. While these mitigation measures can be applied, more research is still needed to determine the adverse effects of the soil mitigation measures.

What mitigation measures are available to reduce dietary exposure to cadmium?

Because zinc and cadmium bind in a similar manner and have similar chemical properties, they compete in the uptake and absorption by plants. Therefore, zinc has been used to minimize cadmium uptake into plants by increasing zinc concentrations in the soil. Another approach to decreasing the bioavailability of cadmium in the soil is by increasing the pH using lime. In irrigation water, high chloride content of the water can result in an increase in cadmium solubility. As a result, routine testing and monitoring chloride content of irrigation water and understanding soil salinity is important to minimize cadmium uptake in plants.

Although mitigation measures have been identified and are available, it is worth noting that there is not a one-size fits all approach and therefore mitigation measures must be appropriate for the crop, production operation, and environment, taking into consideration potential unintentional consequences that may result from mitigation measures.

What can consumers do to reduce dietary exposure to cadmium?

Many of the foods susceptible to cadmium contain nutrients that contribute to a healthy diet. Rather than avoiding these foods consumers should seek to consume a variety of nutrient dense foods across all of the food groups (i.e., vegetables, fruits, grains, dairy, and protein foods). The nutritional status of an individual is important in determining the cadmium absorption. Studies suggest that absorption and retention of cadmium is reduced when the presence of micronutrients (i.e. zinc, calcium, and iron) of an individual is high. Therefore, adequate intake of nutrients by eating a healthy diet and consuming a variety of foods are important in managing the risk associated with dietary exposure to cadmium.