In recent years, the official regulation of chemicals and chemical products has been intensified. Explicitly for spray products enhanced requirements to assess the consumers'/professionals' exposure to such product type have been introduced. In this regard the Aerosol-Dispensers-Directive (75/324/EEC) with obligation for marketing aerosol dispensers, and the Cosmetic-Products-Regulation (1223/2009/EC) which obliges the insurance of a safety assessment, have to be mentioned. Both enactments, similar to the REACH regulation (1907/2006/EC), require a robust chemical safety assessment. From such assessment, appropriate risk management measures may be identified to adequately control the risk of these chemicals/products to human health and the environment when used. Currently, the above-mentioned regulations lack the guidance on which data are needed for preparing a proper hazard analysis and safety assessment of spray products. Mandatory in the process of inhalation risk and safety assessment is the determination and quantification of the actual exposure to the spray product and more specifically, its ingredients. In this respect the current article, prepared by the European Aerosol Federation (FEA, Brussels) task force "Inhalation Toxicology", intends to introduce toxicological principles and the state of the art in currently available exposure models adapted for typical application scenarios. This review on current methodologies is intended to guide safety assessors to better estimate inhalation exposure by using the most relevant data.

Consumer exposure to cosmetic (personal care) products is mostly by dermal contact, however additional considerations with regards to potential inhalation exposure from some cosmetics, such as sprays and powders, may be needed for a robust and reliable safety assessment. To get a deeper understanding of the exposure to airborne particles and droplets during product application, a team of international experts was founded under the umbrella of the European Association of the Cosmetic Industry "Cosmetics Europe" (CE) in Brussels. This expert team has worked out a pragmatic strategy how small and medium sized enterprises (SMEs), but also relevant authorities, could handle the safety evaluation of cosmetic powder products. Sufficient information on the aerodynamic diameter of sprayed droplets and here specifically of airborne particles is essential in addition to knowing the exposure after typical product application. The current article is focused on the determination of inhalation exposure to solids, and the derivation of safe exposure levels for cosmetic powder products found in the market. The principles described herein are very similar to spray products as published earlier and should be applied in a similar way (Steiling et al., 2014). Prediction models for the best estimate of inhalation exposure, developed with data from computer simulation programs, individual real-time measurements or finally by experience from the market were introduced and applied. Safety assessment approaches for exposure from powder spray products were developed and have been already considered in regulatory guidelines like the EC Cosmetics Regulation.

Up to today, product safety evaluation in the EU is predominantly based on data/information on their individual ingredients. Consequently, the quality and reliability of individual ingredient data is of vital interest. In this context, the knowledge about skin sensitization potential is an explicit need for both hazard and risk assessment. Proper skin sensitization data of the individual chemicals is essential, especially when dermal contact is intended, like for cosmetics. In some cases, e.g., in the presence of irritating chemicals, the combination of individual ingredients may also need to be evaluated to cover possible mixture effects. Today, it seems unlikely or even impossible that skin sensitization in humans can be adequately described by a single test result or even by a simple combination of a few data points (in vivo or in vitro). It is becoming evident that a set of data (including human data and market data) and knowledge about the ingredient’s specific sensitizing potency needs to be taken into account to enable a reliable assessment of skin sensitization. A more in-depth understanding on mechanistic details of the Adverse-Outcome-Pathway of skin sensitization could contribute key data for a robust conclusion on skin sensitization.

An in vitro technique for the prediction of percutaneous penetration/dermal absorption is recommended by the European SCCNFP (The Scientific Committee on Cosmetic Products and Non-Food Products intended for consumers) for the safety evaluation of particular ingredients. In 2002, this in vitro method became officially accepted at the OECD level and will be published as OECD Guideline 428. Examples are given for its routine application, demonstrating the bioavailability of cationic azo hair dyes out of an aqueous solution compared to data from a realistic standard hair dye formulation. Data from two direct hair dyes, BASIC BROWN 17 and BASIC YELLOW 57, demonstrate the results of applying this new in vitro technique without radiolabelled material. Direct hair dyes are frequently used in semi-permanent cosmetic hair colourations without the additional need for hydrogen peroxide. In the light of the in-house experience over about 5 years in using excised pig skin for measurements of the percutaneous penetration and dermal absorption of hair dyes, the technique was found to be successful and appropriate for reducing the number of test animals normally used for toxicological assessments.

Consumer products such as cosmetic spray products must be safe. Strict rules to ensure this for cosmetic spray products are established by the EU Cosmetic Products Regulation, as well as by scientific advisory panels. In this article several default values are proposed from the literature to improve the consistency and accuracy of inhalation exposure assessments performed for cosmetic spray products. The use of these default values is given for the most relevant spray product types currently on the EU market. The use of well-known exposure calculation models (e.g. one-box and two-box models) are discussed for their applicability to estimate consumer inhalation exposure to certain spray product types. The availability of measured data from experimental studies is limited due to the complication caused by parameters such as technical product information relating to droplet/particle sizing of the airborne product. In some cases, there is reliance on conservative, worst-case input values (e.g., spray time and the amount released from the product container) for exposure assessment of individual product uses. Where the authors have identified data gaps for certain parameters for specific product types during the literature review, recommendations are provided for additional consolidated default values to promote the safety assessment.