Evaluation of inhalation exposure to essential oils

Sébastien Grégoire PhD 1, Manon Fournier2, Agathe Deniau Pharm D. 2, Adeline Nalin Pharm D. 2

1. Sébastien Grégoire Consulting, Thorigny sur Marne, France

2. Aroma Zone, 1366 Route de Gordes, Cabrières d’Avignon, France

Essential oils (EOs) are widely used in aromatherapy, cosmetics, perfumes, and air fresheners. They contain numerous volatile compounds, which can lead to inhalation exposure. Exposure levels depend on chemical properties, product formulation, physiological factors, and the specific exposure scenario. When direct analytical measurements are not available, simple mathematical models can provide exposure estimates.

Two scenarios have been considered. The first involves topical application, such as a roll-on on the forearms. The SCCS equation provides a rough estimation by dividing the exposure period into two phases: a “close-range” phase, with chemical diffusion near the nose, followed by a “room-scale” phase, accounting for broader diffusion. Key variables include the respirable and airborne fractions of the product.

The second scenario models emission from a single source in a room, such as a diffuser. A differential equation describes chemical emission and removal via inhalation and ventilation. The model assumes instantaneous homogenization and no chemical stratification, meaning that exposure is independent of distance from the source.

These models enable practical estimation of inhalation exposure without complex measurements. Equations are provided, along with calculation examples using real products, illustrating their application for both topical and diffusion EO exposures.

This communication is in memory of Maxime Nibart for his so precious input. RIP.

1. SCCS. The SCCS notes of Guidance for the Testing of Cosmetic Ingredients and their Safety Evaluation 12th revision. 2023. No.: SCCS/1647/22.

2. RIVM (2017). ConsExpo Web: Consumer Exposure Models – Model Documentation. RIVM Report 2017-0197.

Key words: in silico models, risk assessment, inhalation exposure, essential oils