Ask a RIFM Scientist

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How are Natural Complex Substances (NCS) evaluated?

Danielle Botelho, PhD

NCS stands for Natural Complex Substances and refers to ingredients extracted from plants and used in fragrance mixtures for various consumer products. An NCS contains several individual fragrance materials with different physical-chemical properties. Assessing NCS materials differs from that of individual materials in that that you’re assessing many materials rather than just one. Big picture, the practice is similar, using the stepwise process we use to evaluate discrete materials and covering the same areas of human health and the environment. (See How is fragrance safety evaluated?)

The process begins by evaluating the typical composition of the NCS. What individual materials does the NCS contain, and in what percentages? These can vary for different reasons (for instance, the part of the plant used and the processing method), although toxicologically speaking, the differences having an impact on safe use tend to be minimal.

Our human health and environmental scientists then follow a stepwise decision tree for each area, or “endpoint” (e.g., genotoxicity, repeated dose toxicity, skin sensitization). The process is designed to ensure safe use while avoiding animal testing.

The first step is to determine if sufficient data exists on the NCS to evaluate its safe use for that endpoint. If not, they must determine if one’s exposure to the NCS falls below the threshold of toxicological concern, or TTC. Most fragrance ingredients, including NCS materials, are used in minimal amounts. That’s because it doesn’t take much of an individual fragrance material for it to register as a smell.

Then the endpoint scientists must evaluate each of the materials in the NCS, referred to as “components,” individually. Assessing each component makes the process more complex. However, RIFM has peer-reviewed and published safety assessments for most of the components found in NCS materials, which saves a lot of time and effort—in addition to avoiding the need for animal testing.

The process is outlined in the recently peer-reviewed and published NCS Criteria Document. In addition, for those not used to reading scientific documents, science journal publisher Elsevier hosted a webinar featuring Dr. Api and me and several RIFM endpoint scientists walking through their process of evaluating NCS materials. (Register here to view a recording of the webinar.)

Danielle Botelho, PhD, is Safety Assessment Manager for the Research Institute for Fragrance Materials (RIFM).