The safety evaluation of direct food additives and color additives used in food will be evaluated in this blog post based on recommendations for the minimal toxicity tests to be undertaken.
The details in this FDA guidance document can be used as broad guidelines for figuring out concern levels, the scope, and the types of toxicity testing for added food ingredients and food colorants.
Safety evaluation for a direct food additive background
Using the information on the additive’s predicted toxicological potential from its chemical structure (i.e., low (A), intermediate (B), or high (C)) and an estimation of cumulative human exposure, one can assign the additive to a Concern Level (i.e., low (I), intermediate (II), or high (III). When allocating additives to a Concern Level, exposure information carries more weight than structure alert information. Final safety decisions are made on a case-by-case basis. They may consider additional information when determining the concern level for a food or color additive.
To learn more about the suggested minimum toxicity tests for assessing the safety of indirect food additives, also known as food contact chemicals, now referred to as food contact substances, see Guidance for Industry: Preparation of Food Contact Notifications for Food Contact Substances: Toxicology Recommendations.
Diagram Descriptions
This diagram from the FDA shows the lowest Concern Level that would be given to a direct food additive or food color additive based on the substance’s estimated human exposure from the proposed use and potential toxicity based on structural similarity to known toxicants without toxicological information about an additive. The additive will be classified into one of three broad groups based on the knowledge of its structural characteristics: Category A for minimal toxicological potential, Category B for intermediate potential, and Category C for high toxicological potential. The initial Concern Level to which the additive is given will depend on the expected human exposure within each of the three categories of structures (A, B, and C).
This figure shows recommended breakpoints of exposure that indicate the amount of worry for each structure. The Concern Level equates to the minimum suggested toxicology tests required to assess the toxicological safety of the additive’s new or increased use. I apply concern Level (CL) to Category A structures with cumulative human exposure between 0 and 50 ppb, CL II between 50 ppb and 1000 ppb, and CL III over 1000 ppb. Category B buildings with incremental human exposure levels of 0 to 25 ppb come under CL I, 25 ppb to 500 ppb under CL II, and 500 ppb and higher under CL III. CL I, CL II, and CL III apply to Category C structures with cumulative human exposure between 0 and 12 ppb fall into CL I, CL II from 12 to 250 ppb, and CL III from 250 ppb and above.
The Office of Food Additive Safety, Centre for Food Safety and Applied Nutrition (CFSAN), at the U.S. Food and Drug Administration, has developed this guide with assistance from the Division of Petition Review.
Studies normally indicate that a Concern Level III additive, independent of its chemical structure and exposure, may constitute the minimum toxicological testing to support the safety of a novel additive. To establish the safety of these components, toxicological testing may also be required for metabolites, degradation products, and potential additive contaminants. See below the FDA table on the concern level of various tests that you may need to conduct.
FAQs
What is the purpose of FDA’s toxicological testing guidance for food additives in clinical trials?
This guidance provides recommendations for minimum toxicity tests needed to evaluate the safety of direct food additives and color additives, especially when they are used in foods or in clinical contexts. It helps classify additives into concern levels (low, intermediate, high) based on predicted toxicological potential (from chemical structure) and estimated human exposure. From there, it suggests which specific toxicity tests (e.g. genetic toxicity, subchronic, carcinogenicity) should be performed.
How are Concern Levels determined for a food additive?
Concern Levels (I = low, II = intermediate, III = high) are assigned using two main factors:
Predicted toxicological potential (based on chemical structure, often categories A/B/C)
Estimated human exposure (cumulative exposure through diet or use)
Exposure often carries more weight than structure alerts in deciding the level. Final assignments may also consider additional data or context on a case-by-case basis.
Which toxicity tests are recommended for each Concern Level?
The guidance outlines a “minimum testing” matrix based on the Concern Level:
Level I (low): Genetic toxicity tests, possibly short-term rodent tests
Level II (intermediate): Genetic tests, short-term toxicity, subchronic toxicity in rodents and non-rodents, reproduction and developmental tests
Level III (high): All of the above plus chronic toxicity/carcinogenicity studies, long-term tests, reproductive/developmental, and other studies as needed.
This ensures that higher-risk additives undergo more rigorous testing.
Can the recommended tests be modified or reduced?
Yes — the guidance is not legally binding. Petitioners or researchers may propose alternative or reduced test protocols if scientifically justified. However, the burden is on them to support those modifications with sound rationale and to consult with the FDA in advance.
Why is human exposure estimation so important in the guidance?
Because the same additive’s risk profile can differ drastically depending on how much people are exposed to. Even a compound predicted to have some toxic potential might be acceptable if human exposure is extremely low. Conversely, a seemingly “benign” structure with high exposure may trigger stricter testing. Thus, exposure estimates can shift an additive from one Concern Level to another.
