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Smelling good without stinking up the environment

Environmental Health News
December 1st, 2011

Chemists developing compounds used to create fragrances can weed out chemicals that don't meet toxicity and environmental standards early in the design process, finds a study that predicted the toxicity and persistence of a variety of musk chemicals using a sophisticated computer program.

The program developed by the U.S. Environmental Protection Agency uses molecular structure and other chemical attributes to predict if a compound will easily break down in the environment. The results are published in the journal Green Chemistry.

While the tools are not perfect, they help for early screening. One important use would be to compare the environmental effects of chemical classes or individual molecules to determine whether to proceed or block a chemical's development. Further analysis and testing on the musks given the go ahead would still be needed to avoid producing a harmful molecule that might not be tagged as dangerous at this stage of development, because the computer modeling did not consider many potential mechanisms of toxicity, for example, whether or not the molecule is a potential endocrine disruptor.

The findings show that chemists can avoid making certain types of musks that may be harmful. Musks add scent to consumer products and can harm the environment. Predicting a compound's later performance at a very early stage even before the molecules are made would make design and development of safer fragrance musks much cheaper.

Fragrances are used in a wide variety of products from the obvious perfumes to soaps, detergents, shampoos and toothpastes. The natural and synthetic musk compounds produce the rich and deep smells that form the base of some fragrances. The long-lived musks are chemically heavy and evaporate slowly. Their scents surface well after their use at least 30 minutes and may linger for a day. They also help hold lighter smells for a longer period of time.

These same longevity properties mean the compounds tend to end up in municipal wastewater and its solid sludge, which is often reused as fertilizer. Through these routes, musk compounds are released into the environment. They can accumulate in soils, wildlife and people. Several synthetic musks are toxic to fish, algae and aquatic invertebrates.

Chemists still design new synthetic musks. They use tools to predict the compounds' future performances as a fragrance. A similar tool to predict their toxicity, their accumulation in the environment and their persistence in the environment is needed. A compound persists in the environment if it does not biodegrade.

The new research from the U.S. EPA looked at 106 synthetic and natural musk chemicals. The predictions on the environmental impact of these musks were compared to experimental data.

The study found and identified specific types of musks that were less problematic than others. It also verified that existing tools and knowledge could be used to screen new molecules for their potential to be toxic, not break down and accumulate.

According to the author, the research shows "that it can be convenient and useful to include environmental properties in that screening prior to any testing or manufacture of a chemical." The tools and knowledge exist, and it is time to apply them to chemical production for "economic as well as environmental sense."