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The toxicology of musk fragrances

Synthetic musk fragrances are widely used as replacements for natural musks not only in perfumes but also in soaps, toiletries and disinfectants. The worldwide annual production of musk fragrances ranges between 6000 and 8000 metric tons per year, of which nitroand polycyclic musks represent 30 and 70%, respectively. As a result of their inherently low biodegradability, nitroand polycyclic musks as well as their respective metabolites are persistent and have been detected predominantly in the aquatic environment. The presence of ‘not-readily-biodegradable’ compounds in the aquatic environment raised major concerns, primarily in Europe, where the horrendous impact of polychlorinated biphenyls (PCBs), especially on fish-otter (Luttra luttra) populations, is vivid in the memories of scientists, health officials and the public. However, moderate to high lipophilicity, slow biodegradation, and the presence in water, sediments and edible fish tissues does not automatically warrant the comparison of musk fragrances with PCBs. Indeed, only a thorough review of the available toxicological data in conjunction with analytical data from the environment allows appropriate judgement of the ‘real’ risks associated with these synthetic fragrance materials for humans and the ecosystem. This view of the situation, and the need for a robust toxicological assessment of these compounds, led the European Union to include musk xylene and musk ketone on their third priority list under Council Regulation (EEC) No. 793/93, and the inclusion of these compounds in the OSPAR List of Chemicals for Priority Action. These official listings, and pressure from the public, also enticed toxicologists in industry, academia and in research foundations to invest time and capital to assemble already available toxicological data as well as to carry out new experiments. Most of the data that has come from the latter efforts is now assembled in this Special Topics Issue of ‘Toxicology Letters’. Although this special issue does not claim to cover every conceivable aspect of toxicological assessment, it represents most of what we currently know about musk fragrance toxicity determined with state-of-the-art toxicological methodology and risk assessment processes. As indicated above, a clear distinction has been made between the potential effects of musk fragrances in the environment (primarily the aquatic environment) and putative effects in mammals, i.e. humans. In order to maintain this distinction, this special issue was divided into two main sections ‘I. Environmental Impacts and II. Mammalian Toxicology and Risk Assessment’. Both sections include reviews of the current literature, papers on new experimental data, and descriptions of risk assessment processes. The first section dealing with the environmental impacts of musk fragrances is dominated by review articles regarding the presence of nitroand polycyclic musk fragrances in the environment (Rimkus, 1999; Rimkus et al., 1999) and elaborate