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Chemical Reaction: The New Toxicology
By: Steve Herman
Posted: September 5, 2008, from the August 2006 issue of GCI Magazine.
page 3 of 4
Fragrance-free is a rallying cry for many products. Fragrance often is considered a problem for safety, and the heart of the problem is size. For an aroma chemical to have odor, it must be small and volatile, with a molecular weight rarely above 300. Small molecules penetrate the skin easily, and thus fragrances have a tendency to cause irritation. Aroma chemicals have been extensively studied on skin for 30 years, and safety guidelines have been issued on many materials by IFRA.
It may seem peculiar, but until recently, no thought was given to the respiratory effects of fragrance. It was felt that respiration was transitory and involved few molecules, while fragrance applied to the skin had a longer and more intimate exposure profile. Suddenly, in the 1990s fragrances were significantly in the air, with candles and plug-ins and aerosols permeating every nook and cranny. Clearly, respiratory studies were needed, but how does one come to grips with testing 3,000 chemicals?
The modern approach is not to attempt to study every material, since neither the time nor the money is available. Smarter methods are needed. So instead of thousands of chemicals, nine were chosen.4
The selection was based on a chemical’s importance in fragranced products, physicochemical properties and known irritation or sensitization potential. The paper that resulted from the respiratory studies, published in 2005, laid the foundation for an entirely new approach to fragrance safety.
How does one test a fragrance for respiratory safety? It is not remotely obvious what delivery systems would be employed or what a reasonable set of exposure conditions might be. RIFM constructed a prototype residential bathroom (a 2.44 m cube) with standardized air circulation. A five second aerosol spray was analyzed at two heights to simulate exposure for an adult and a child. The evaluation of airborne chemistry revealed that concentration was proportional to the chemical’s volatility.