Octamethylcyclotetrasiloxane in aquatic sediments: toxicity and risk assessment.
The toxicity of octamethylcyclotetrasiloxane (OMCTS) to the midge Chironomus tentans was examined in a series of aqueous and sediment exposures. Midge larvae were exposed for 14 days to five concentrations of radiolabeled [14C]OMCTS in each of three sediments (low, medium, and high organic carbon content). Additional tests were conducted with a water-only exposure. Results indicate the lowest 14-day no observed effect concentrations (NOEC) to be 65, 120, and 54 mg/kg for the low, medium, and high organic carbon sediments, respectively. For the water-only exposure, the 14-day NOEC was > 15 micrograms/liter. These results were used in the preparation of a risk assessment for OMCTS which took into consideration the physicochemical and environmental fate properties of the compound, as well as actual field monitoring and worst-case modeling results for assessment of exposure. Available evidence suggests that sediment concentrations of OMCTS do not present a risk to sediment-associated organisms. For 95% of sediment samples, data indicate that the margins of safety would be greater than 400 and potentially over 1000. Worst-case margins of safety were greater than 150.
Kent
D J
DJ
Technology Sciences Group, Incorporated, Washington, District of Columbia 20036.
McNamara
P C
PC
Putt
A E
AE
Hobson
J F
JF
Silberhorn
E M
EM
D000818:Animals; D002250:Carbon Radioisotopes; D002683:Chironomidae / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D017753:Ecosystem; D005618:Fresh Water; D007814:Larva / Q000502:physiology; D018570:Risk Assessment; D012833:Siloxanes / Q000633:toxicity*; D012987:Soil; D013997:Time Factors; D014873:Water Pollutants / Q000633:toxicity*
D002250:Carbon Radioisotopes; D012833:Siloxanes; D012987:Soil; D014873:Water Pollutants; C024064:octamethylcyclotetrasiloxane