Tonalide®

Chemistry

Tonalide is a member of the tetralins. Among the classes of synthetic musks, it belongs to the hydronaphthalenes. Its IUPAC name is 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone. Two different CAS numbers exist for it, because one company reported an erroneous molecular structure and a second company the correct one. Tonalide is moderately volatile and slightly soluble in water. It is stable under recommended storage conditions.

Production volume

AHTN was identified as a high production volume chemical by the OECD in 2004. It is the second highest volume polycyclic musk in global production, after galaxolide, with 247 tonnes used in Europe in 2004. Circa 62% of the production volume was exported outside Europe.

Occurrence and fate in the environment

Wastewater treatment plant effluent is a major source of synthetic musk fragrances to the environment. In such effluent, HHCB and AHTN are normally found in the highest concentrations, typically on the order of 1000 ng/L to 5000 ng/L. Synthetic musk concentrations in effluent leaving a treatment plant are typically less than 30% of those in the influent. The removal of HHCB and AHTN from wastewater is primarily to sludge. There is little evidence that synthetic musk fragrances are degraded during wastewater treatment. In surface waters of the Ruhr megalopolis, about 10 ng/L AHTN was found as a typical riverine concentration in the part of the river where drinking water is extracted. The sewage treatment plants were the dominant source of these pollutants there. In sludge-amended soils, the concentration of HHCB dropped below measurable levels in one year. AHTN was lost more slowly and was still above detection limits after one year. Synthetic musks are lipophilic compounds and tend to deposit and persist in fat tissues. An environmental assessment found tonalide persistent and toxic to the environment, but not bioaccumulative. Its measured bioconcentration factors in fish are below 2000 L/kg. On a weight of evidence, AHTN is not endocrine disrupting. Germany has nevertheless scheduled it for re-evaluation in the Rolling Action Plan, as a potential endocrine disruptor and because of its high aggregated tonnage. The environmental risk assessment for AHTN and HHCB found sufficient data to assess the environmental risks. Risk ratios are generally below 1, but for sediment organisms living in areas contaminated with a high effluent load they may be above 1.

Human exposure and safety

In a survey of consumer products, AHTN ranged from under 5 ng/g to 451 μg/g. The highest concentrations were found in perfumes, body creams and lotions, and deodorants. Tonalide has been detected in human breast milk, adipose tissue and blood. Reported concentrations in whole milk ranged between 0.59-53 μg/kg, and in adipose tissue between 1-72 μg/kg fat. The oral LD50 values for AHTN ranged from 570-1377 mg/kg bw, and the dermal LD50 values are above 5000 mg/kg bw. AHTN is not a skin or eye irritant. No sensitisation reactions were seen in three separate human repeated insult patch test studies at concentrations between 2-10 % in a total of 188 human subjects. AHTN is a non-genotoxic substance.

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