The general public trust food for human consumption to be safe and their assumption is that these expectations are delivered by the authorities via regulations related to food contact materials and articles (FCM&As), by producers of these items following guidelines, and by beverages and foodstuffs manufacturers themselves. However, inaccurate negative media reports of the impact of food, as well as food contact materials on health and well-being, can cause concerns and undermine consumers’ confidence on its actual safety.

This fact sheet presents the current state of knowledge related to oral exposure to nickel via stainless steel FCM&As, its potential impacts and the protection offered to consumers by regulations and other means.

There are many different regulations across the globe that govern FCM&As. Table 1 provides an overview of the regulations governing FCM&As in China^(1),(2),(3), the European Union⁽⁴⁾ and the United States⁽⁵⁾. It also highlights the differences in their individual approaches. Regulations can be horizontal and/or covering specific types of materials (e.g., metals, plastics, paper and board, ceramics, glass). However, they share the same common objectives of consumer and food safety [i.e., “under normal or foreseeable conditions of use FCM&As should not transfer their constituents to food in quantities which could: endanger human health; or bring about an unacceptable change in the composition of the food; or bring about a deterioration in the organoleptic characteristics”⁽⁴⁾].

In addition to regulations governing FCM&As, there are globally a large number of voluntary standards. The following are some examples:

• NSF/ANSI 51 Food Equipment Materials⁽⁶⁾—applies to all commercial equipment for producing and distributing foodstuffs (food service);
• NSF/ANSI 2 Food Equipment⁽⁷⁾—sets minimum food protection and sanitation for the materials, design, fabrication, construction, and performance of food handling process equipment;
• NSF/ANSI 36 Dinnerware⁽⁸⁾—intended for use in food establishments; and
• NSF/ANSI/3-A 14159-1⁽⁹⁾—hygiene requirements for designing meat and poultry processing equipment.

Although these standards are voluntary, they are important as they are used as reference for State and Federal regulatory authorities in the United States.

At the European level, there is the Council of Europe (CoE) Technical Guide⁽¹⁰⁾ on Metals and Alloys used in FCM&As, which was developed by the European Directorate for the Quality of Medicines and HealthCare (EDQM). Though not legally binding, the Technical Guide is very influential as it serves as a reference for manufacturers and regulators, in the absence of specific European Union (EU) harmonized legislation for food contact metals and alloys. This is particularly relevant for those European countries that do not have specific national rules for metal and alloy FCM&As. The Technical Guide provides safety reviews and recommendations for metals, alloys, metal contaminants, and impurities of concern found in FCM&As, which form the basis for specific release limits (SRLs).

Chapter 3 of the Technical Guide⁽¹⁰⁾ describes analytical methods for release testing of metallic food contact materials and articles, the outcome of which can then be compared with the SRLs in Chapter 2.

Stainless steels are selected because of their cleanability, durability, hygienic properties, attractive appearance, and their excellent mechanical and physical properties

In addition to general safety requirements and release limits, test protocols play a very important role in ensuring the safety of food and FCM&As. They offer a means of estimating the release (migration) of substances into foodstuffs or food simulants under controlled conditions. Whether documented in regulations or guidelines, they represent a means of ensuring the key objectives for FCM&As are fulfilled and that they are in compliance with specified release/migration limits. Test protocols share a number of common features:

1. measurement of maximum overall (for all substances combined) and specific metal release/migration limits in terms of mg/kg (ppm) food or food simulant;
2. the use of different food simulants where contact with a diversity of foodstuffs is envisaged;
3. overall and specific metal release/migration limits are usually expressed in terms of mg/kg (ppm) food or food simulant, but can also be expressed as mg/dm² of the FCM or article;
4. unless otherwise specified, 1 kg of food or food simulant is deemed to be in contact with an area of 6 dm²;
5. test conditions are selected to reflect both the actual conditions of use and a reasonable worst-case for foreseeable conditions of use; and
6. test conditions should not result in changes in the physical properties of the test samples that would not occur under normal use conditions or lead to precipitation, turbidity, and other changes in the food simulants.

However, there are also differences between FCM&A test protocols, as described in Table 2.

European Food Safety Authority (EFSA), in its 2015 Scientific Opinion⁽¹⁹⁾ on nickel in food and drinking water, concluded that exposure via the diet is likely to represent the most important contribution to the overall exposure in the general population. The highest concentrations of nickel have been measured in wild growing edible mushrooms, cocoa or cocoa-based products, beans, seeds, nuts, and grains^{(19),(20),(21)}.

Stainless steel kitchenware utensils are used in commercial and high-end kitchens

Various studies of the dietary intake indicate that 90 to 361 μg/day of nickel are consumed⁽²²⁾. The quantity of nickel absorbed from food depends on its form (i.e., soluble nickel is more readily absorbed than Ni²⁺ in organic complexes⁽²²⁾ in a food matrix). Soluble nickel is found in beverages, drinking water, soup, etc. Ni combined with organic molecules can be found in beef, poultry, pork, fish, eggs, dairy products, soy foods, nuts, seeds, many whole grains, vegetables, and legumes⁽²²⁾.

Orally absorbed nickel is distributed to the kidneys, followed by the liver, brain, lung, fat, and heart⁽¹⁹⁾. The toxicity of nickel varies depending on the chemical form of nickel and the bioavailability of the Ni²⁺ ion at target sites in humans⁽²³⁾. Nickel absorbed via the gastrointestinal tract is excreted predominantly in urine and unabsorbed nickel is eliminated with the feces.

Toxicity data is used to determine the tolerable daily intake (TDI) of substances. The TDI is an estimate of the amount of a substance in food or drinking water which is not added deliberately (naturally occurring) and which can be consumed over a lifetime without presenting an appreciable risk to health. TDIs are taken into consideration during the establishment and revision of specific migration limits (SMLs) and SRLs for substances in FCM&As.

EFSA has recently revisited its 2015 Opinion on nickel in food and drinking water⁽¹⁹⁾ taking into account newly available scientific information. The latest EFSA Scientific Opinion⁽²⁴⁾ proposes a TDI of 13 μg/kg body weight to protect from chronic effects observed in animal studies and, as a small subset of the hypersensitive nickel-allergic population also react to oral nickel exposure, EFSA recommends a lower reference value to protect this subpopulation from the for acute effects of nickel in the diet.

Nickel-containing stainless steels are one of the most widely used food contact materials; applications range from domestic utensils and kitchen equipment, through commercial catering equipment to mass food production equipment and facilities. Stainless steels are selected for these applications because of their cleanability, durability, hygienic properties, inertness, and their excellent mechanical/physical properties.

In these food contact uses, stainless steels fulfill the key regulatory requirements that constituents are not transferred to food in quantities sufficient to bring about unacceptable changes in its composition, color, odor, taste, or texture. They satisfy too the explicit requirement that substances in FCM&As should not be released in quantities that endanger human health, which is the basis of SRLs of FCM&A constituents. Indeed, experience has shown this to be the case.

Of the numerous studies that have assessed the amount of metals that are released (or migrate) into foodstuffs during the use of stainless steel FCM&As, Table 3 provides a summary of four studies measuring nickel release under conditions mimicking stainless steel use as FCM&As. These studies were selected to illustrate the influence of the study design (e.g., choice of food or food simulant, the form of test samples and test conditions) on the metal release outcome.

The EFSA Scientific Opinion on nickel in food and drinking water⁽²⁴⁾ indicates that the concentrations of nickel following migration (release) are in the same order of magnitude as concentrations reported to occur in food. The studies by Flint and Packirisamy⁽²⁵⁾ and Hedberg et al.⁽²⁶⁾ in Table 3 support this statement. With the exception of nickel release values reported by Guarneri et al.⁽²⁷⁾ and Kamerud et al.⁽²⁸⁾, the SRLs of 0.14 mg/kg for Ni and 0.25 mg/kg for Cr were not exceeded. These outcomes illustrate the importance of testing FCM&As in accordance with accepted national or international protocols and in an appropriate form [e.g., relevant pots and pans versus non-relevant granules as in Kamerud et al.⁽²⁸⁾].

In times past, copper/nickel/chromium-plated food serving utensils (e.g., carving forks, serving spoons, spatulas, etc.) and nickel-plated kettle elements were common. However, over time, electroplated utensils tended to rust as the underlying steel substrate was exposed by abrasion and wear. Furthermore, nickel release from nickel-plated kettle elements, and to a lesser extent electroplated kitchen utensils, could be very high and was a cause for concern. Hence, electroplated items (particularly kettle elements) have now largely been replaced by stainless steel. In addition, electroless nickel is used for certain components in coffee making machines.

The Council of Europe has, in principle, accepted that provided the SRL for nickel is not exceeded, nickel-plated, nickel/chromium-plated, and electroless nickel plating can be used in contact with food. However, manufacturers are urged to consider carefully whether suitable alternative FCMs might be preferable to nickel plated materials.

• Regulations and technical guidelines governing FCM&As share the same common objectives of consumer and food safety.
• Test protocols, whether in regulations or guidelines, represent a means of ensuring the key objectives for FCM&As are fulfilled and that they are in compliance with specified release/migration limits.
• Nickel-containing stainless steels are one of the most widely used food contact materials due to its durability, ease of cleaning and inert nature (corrosion resistance and low nickel ion release).
• Various studies of the dietary intake indicate that 90–361 μg/day of nickel are consumed.
• Well-constructed and well-executed studies on commonly used stainless steel FCM&As indicate that the amount of nickel and other metals transferred into food is small in comparison to the naturally occurring levels in food and within the release limits set for FCM&As.
• Stainless steels used for food contact fulfill the key regulatory requirements: they do not transfer their constituents to food in quantities that cause toxicity or bring about unacceptable changes in its composition, color, odor, taste, or texture.

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