Assessing the Safety of Indirect Food Additives

When you buy packaged food, have you ever considered what might transfer from the container into your meal? While we often focus on what’s intentionally added to food, substances from packaging materials can migrate into what we eat. These are called indirect food additives, and regulatory agencies around the world have developed sophisticated systems to ensure they remain safe for consumers.

What makes an additive “indirect” 🔗

Indirect food additives are substances that become part of food unintentionally through contact with packaging, processing equipment, or storage materials. Unlike direct additives that manufacturers deliberately add to food for specific purposes, indirect additives migrate from materials used in manufacturing, packing, or holding food. Common examples include components from plastic containers, adhesives in multilayer packaging, coatings on paperboard, and polymers in food storage bags.

The U.S. Food and Drug Administration defines a food additive as any substance whose intended use results in it becoming a component of food, whether directly or indirectly. This means that even substances migrating at tiny levels from packaging fall under regulatory oversight if they exceed certain thresholds.

The threshold that determines regulation 🔗

Not every substance that could potentially migrate requires extensive safety testing. The FDA established a practical approach called the threshold of regulation to handle substances that migrate at negligible levels. This threshold exempts substances migrating at concentrations below 0.5 parts per billion from detailed safety evaluations, provided they are not known carcinogens.

This 0.5 ppb threshold applies to dietary concentration, not just migration levels. Regulators calculate dietary concentration by applying consumption factors to measured migration values. The threshold applies to what actually ends up in the diet, accounting for how much of different food types people typically consume.

How estimated daily intake works 🔗

Safety assessments rely on calculating how much of a substance consumers might ingest over time. Scientists use two key metrics: estimated daily intake for individual substances and cumulative estimated daily intake when evaluating multiple related compounds. These calculations consider the concentration of the substance in packaging, how much migrates under realistic conditions, the types of foods that contact the material, and typical consumption patterns across different population groups.

For substances already approved as direct food additives, regulators allow their use in packaging if the dietary intake from food contact use does not exceed 1 percent of the established Acceptable Daily Intake. This approach recognizes that some exposure may already occur from approved uses.

Testing requirements based on exposure levels 🔗

When substances migrate above the threshold level, manufacturers must provide toxicological data to demonstrate safety. The extent of testing depends on how much of the substance might enter food. For dietary intakes up to 50 ppb, regulators require in vitro genotoxicity assays such as Ames tests and mouse lymphoma or chromosome aberration studies. These tests evaluate whether substances can damage genetic material.

Higher exposure levels demand more comprehensive evaluation. When dietary exposure exceeds 50 ppb, safety assessments typically include subchronic oral toxicity studies in rats and potentially dogs. These studies must demonstrate a clear no-observed adverse effect level that exceeds the calculated dietary exposure by at least a 1,000-fold safety margin.

Genetic toxicity screening 🔗

Genetic toxicity testing serves as a critical early screening tool. Before substances can be approved for use in food contact materials, they must not show mutagenic or carcinogenic potential. The battery of tests includes bacterial reverse mutation assays, mammalian cell gene mutation tests, and chromosomal aberration studies. These evaluations help identify substances that could pose long-term health risks even at low exposure levels.

Using food simulants for practical testing 🔗

Testing migration directly into every possible food type would be impractical, so scientists use standardized food simulants that mimic different food categories. Common simulants include aqueous simulants for water-based foods, acidic solutions for foods like pickles and sauces, alcohol solutions for alcoholic beverages, and oil-based simulants for fatty foods.

The European Union’s regulations specify simulants including 10% ethanol for aqueous foods, 3% acetic acid for acidic foods, and vegetable oil for fatty products. These simulants extract substances under standardized conditions that represent worst-case scenarios for real-world use, including specific temperatures and contact times based on how the packaging will actually be used.

Migration testing conditions 🔗

Migration studies must reflect intended use conditions. Testing protocols specify contact duration, temperature, and the ratio of packaging surface area to food volume. For materials intended for high-temperature applications like oven-safe containers, testing occurs at maximum cooking temperatures for the longest intended cooking time. Room-temperature applications use different protocols that reflect typical storage conditions.

Specific and overall migration limits 🔗

Regulatory frameworks use two types of migration limits to control substance transfer from packaging. Specific migration limits apply to individual substances or groups of related compounds. These limits are based on the toxicological hazard of each substance, and manufacturers must demonstrate through analysis or calculations that migration does not exceed the respective SML.

Overall migration limits address the total amount of all non-volatile substances that can migrate from packaging. European regulations set the overall migration limit at 60 mg/kg of food or 10 mg/dm² of packaging material. This limit ensures that the cumulative transfer of all substances remains within safe bounds, even if individual components are not specifically regulated.

Why both limits matter 🔗

The dual approach of specific and overall migration limits provides comprehensive protection. Specific limits address substances with known toxicological concerns, ensuring exposure stays well below levels that could cause harm. Overall limits catch substances that may not be individually regulated but contribute to total migration. Together, these standards ensure that packaging materials meet safety requirements from multiple angles.

Real-world application of safety standards 🔗

Food packaging manufacturers must navigate complex regulatory requirements across different markets. In the United States, substances can be authorized through food additive regulations, food contact notifications, or threshold of regulation exemptions. Each pathway has specific data requirements and review timelines.

The European Union maintains a positive list of authorized substances for plastic materials, with detailed specifications for each approved component. This approach requires manufacturers to use only pre-approved substances under specified conditions. Compliance documentation must flow through the supply chain, ensuring that everyone from raw material suppliers to final package manufacturers understands and meets regulatory requirements.

Ensuring ongoing compliance 🔗

Safety assessment does not end once a substance receives approval. Manufacturers must maintain quality systems that ensure consistent production within approved parameters. Changes to formulations, processing conditions, or intended uses may require new safety evaluations. Regulatory agencies also monitor scientific literature for emerging safety concerns that might warrant re-evaluation of previously approved substances.

The balance between innovation and safety 🔗

Modern food packaging continues to evolve, incorporating new materials and technologies that extend shelf life, improve convenience, and reduce environmental impact. Active packaging releases beneficial substances like antimicrobials, while intelligent packaging monitors food freshness. Smart labels change color when products reach unsafe temperatures. Each innovation requires safety assessment to ensure that new functions do not compromise food safety.

Regulators must balance enabling beneficial innovations while maintaining rigorous safety standards. The threshold of regulation allows low-risk substances to enter the market more quickly, while comprehensive toxicological testing protects consumers from substances with higher exposure potential. Migration limits ensure that even approved substances remain at safe levels in actual use.

What do you think? How confident are you in the current systems for evaluating food packaging safety? As packaging technologies become more sophisticated with active and intelligent materials, what additional safeguards might be important to consider?

References

1. https://www.fda.gov/food/food-ingredients-packaging/food-packaging-other-substances-come-contact-food-information-consumers
2. https://www.fda.gov/food/food-additives-and-gras-ingredients-information-consumers/understanding-how-fda-regulates-food-additives-and-gras-ingredients
3. https://www.packaginglaw.com/special-focus/fathoming-food-packaging-regulation-revisited
4. https://www.khlaw.com/insights/fda-regulation-adhesives-food-packaging
5. https://www.khlaw.com/insights/regulation-food-packaging
6. https://www.smithers.com/resources/2024/january/migration-testing-simulants
7. https://food.ec.europa.eu/food-safety/chemical-safety/food-contact-materials/legislation_en
8. https://www.intertek.com/packaging/testing/migration-for-food-contact-materials/
9. https://measurlabs.com/methods/overall-migration-test-oml/