» Water

For uses such as shampoos, conditioners and detergents, which naturally enter wastewater, the aquatic compartment is of key importance. However volatile methylsiloxanes (VMS) are rapidly lost into the air, and polydimethylsiloxanes (PDMS) do not dissolve in water. Therefore it is very rare to detect either of them in rivers or lakes.

Nevertheless, studies have been conducted using relatively high concentrations of PDMS. No significant effects on fish or other aquatic life have been seen.

A major positive environmental use was the treatment of otters caught in a large oil spill in Arctic waters. After using detergents to remove the oil, a coating of PDMS gave their fur the necessary protection against the freezing waters until their natural waterproofing system could recover. They would not otherwise have survived.

» Sediments

As sediments are an integral part of the aquatic environment, several studies have focused on the fate and effects of silicones in sediments. During wastewater treatment, in particular non-volatile silicones, bind tightly to particulates. They are thus removed from wastewater during treatment and are processed as part of the sludge.

The sludge is normally either sent to land fill, incinerated or used to improve the quality of soils used for agriculture or other purposes (e.g. for golf courses, landscaping etc).

A minor percentage (less than 5%) of silicones adhere to suspended solids in the water outlet of treatment plants and may become part of river sediments. In laboratory experiments with PDMS on a number of sediment-living organisms, such as worms and insect larvae, no adverse effects were seen even at high concentrations.

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