PREPRINTS OF THE 1996 ANNUAL SCIENTIFIC MEETING 283 conducted at eight wastewater treatment plants representative of those found in North America showed that dimethicones partition into sewage sludge with concentrations from 290 to 5155 mg/kg. These levels varied depending on influent concentration, contributions from industrial plants, and sludge processing methods. Concentrations less than 6 mg/kg were also found in sediments near the outfalls of these wastewater treatment plants. Sludge from these plants is either disposed of by landfill or inciner- ation, or is used as an agricultural soil amendment. Concentrations of dimethicone found in amended soils ranged from 0.4 to 10 mg/kg, which was lower than expected based on theoretical calculations. Dimethylsiloxanediols were also detected, suggesting degradation in the soil (4). Laboratory work with •4C labeled dimethicone has shown that these polymers hydrolyze to low-molecular-weight silanol-terminated oligomers and ultimately to dimethyl- silanediol in soil. Dimethylsiloxanediols were detected in soils where dimethicone load- ing was greatest and environmental conditions were most favorable for degradation. This provides additional evidence of dimethicone degradation in soil (5). Results indicate that degradation rates were dependent on soil moisture conditions. Very dry conditions result in a rapid decline in dimethicone found in the soil, while very wet soil shows only minimal decline. Additional work is in progress to reconcile the laboratory observations to what may happen in the field. The small amount of dimethicone that may be present in wastewater treatment effluent will be sorbed onto sludge solids and be deposited into bottom sediments near the outfall. Sediment-bound dimethicone will also undergo hydrolysis to dimethylsilanediol at rates similar to those observed in moist soil. Preliminary results indicate that deg- radation rates may be faster in some sediments (6). Laboratory work has demonstrated that •4C Dimethylsilanediol is biodegraded at a measurable rate (0.2 to 2% per month) on all of the soils tested, as indicated by the production of •4CO2. The rate of biodegradation was found to be essentially indepen- dent of the source of dimethylsilanediol. A fungus and a bacterium have been isolated, and both organisms were able to biodegrade dimethylsilanediol in liquid culture when another carbon source was available (7). Tests with Daphnia, midge, and a freshwater and marine amphipod (aquatic inverte- brates) exposed to 1 to 20 times the maximum concentration of dimethicone found in natural sediments found no effect on survival, growth, and/or reproduction (8). Labo- ratory tests of earthworms and springtails exposed to concentration ranges from 250 to 4000 mg/kg (8 to 130 times the maximum concentration found in amended soils) showed no effects on earthworms and a statistically significant reduction in the number of offspring produced by the springtails at concentrations above 500 mg/kg (15-20x actually found in the soil) (9). No evidence of bioaccumulation was observed in either the midge or earthworm. CONCLUSIONS Silicones enter the environment through a variety of personal care product consumer uses. Laboratory and field studies indicate that cyclomethicones degrade in the atmo- sphere and have no effect on air quality and that a complex mechanism involving chemical and biological degradation of dimethicone is occurring in soil and sediments.

284 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Effects testing on sediment- and soil-dwelling organisms indicate no adverse effects at concentrations actually found in these environmental compartments. REFERENCES (1) Silicones Environmental Health and Safety Council (SEHSC), unpublished report, Environmental Entry Volumes and Fate Predictions for Organosilicon Compounds, April 7, 1995. (2) EPA RM1 Administrative Record, Final RM1 Aquatic Risk Characterization for Octamethylcyclotetra- siloxane (OMCTS), September 1994. (3) 59FR 50639, October 5, 1994. (4) Fendinger et al., Environmental Occurrence of Polydimethylsiloxnes (PDMS), Society of Environmental Toxicology and Chemistry (SETAC) presentation, November 1996. (5) Xu et al., The Degradation of a Polydimethylsiloxane Catalyzed by Different Clay Materials, SETAC presentation, November 1996. (6) SEHSC, unpublished report, Hydrolysis of PDMS on Sediment, July 1996. (7) Sabourn et al., Investigation of the Biodegradation of Dimethylsilanediol on Soils, SETAC presentation, November 1996. (8) Putt et al., Effects of Sediment-Bound Polydimethylsiloxane (PDMS ) to Aquatic Invertebrates, SETAC pre- sentation, November 1996. (9) Garvey et al., Effects of Polydimethylsiloxane (PDMS) to Soil-Dwelling Organisms, SETAC presentation, November 1996. Vapor pressure of a fragrance in a system of laureth-4 and water STIG E. FRIBERG, TIAN HUANG, LIN FEI, and SAMUAL A. VONA, Clarkson University, Potsdam, NY •3699, and PATRICIA AIKENS, ICI Surfactants, Wilmington, DE 19850. INTRODUCTION The behavior of a fragrance in the presence of a colloidal solution is of particular interest in view of the fact that many alcohol-based products are being replaced with aqueous miceliar systems. The vapor pressure of a volatile material is an estimation of its chemical potential in that environment: P• = p•o + RTlnp/pø = p•o + RTlna where • is the chemical potential with vapor pressure p and •o is the chemical potential in the standard state giving a vapor pressure equal to pO. The investigations of fragrance vapor pressure presented here include the entire system of water, nonionic surfactant, and fragrance. The vapor pressure of the fragrance in the different association structures provides information about the molecular interactions with water and surfactant and enables the evaluation of the fragrance vapor pressure as a function of time during the