JACC Report 55 – Linear Polydimethylsiloxanes second edition

JACC 055 : Linear Polydimethylsiloxanes CAS No. 63148-62-9 (Second Edition) | December 2011

ISSN-0773-6339-55 print
ISSN-2079-1496-55 online
D-2011-3001-220

EXECUTIVE SUMMARY

This report presents a critical evaluation of the toxicity, physico-chemical properties, and environmental fate and effects of linear polydimethylsiloxanes (PDMSs), a type of non-volatile (odourless), fluid (viscous) "silicones" that are virtually insoluble in water. PDMSs are widely used in industrial, consumer, food and medicinal or pharmaceutical applications. The report has been produced as part of the ECETOC Joint Assessment of Commodity Chemicals (JACC) programme and updates an earlier ECETOC review^[1].

Almost all PDMS discarded "down-the-drain" is expected to be removed during sewage treatment. Any PDMS released into the environment will strongly sorb to particulate matter in water and soil. PDMSs are immobile in soil and sediment, but will break down slowly (abiotic) to dimethylsilanediol, which is soluble in water and can biodegrade to carbon dioxide, water and inorganic silicate, as demonstrated in the laboratory. Due to its molecular size, bioconcentration of PDMS is very unlikely. PDMSs are not detected in surface waters, except at low concentrations downstream from wastewater treatment plants.

PDMS has no effects when tested on aquatic organisms (fish, daphnia, algae), sediment-dwelling organisms (e.g. midge larva) and little or no effect on soil organisms (e.g. earthworm). PDMS is lethal to insects when applied directly, probably due to a physical rather than toxicological action.

Humans may be exposed to PDMS via oral ingestion and dermal contact. In laboratory animals, PDMS had a low potential for absorption via these routes. Swallowed PDMS is rapidly excreted unchanged in the faeces. Aerosolised PDMS may give rise to inhalation exposure, but there is no indication of any adverse effects. PDMS is not a skin irritant or a skin sensitiser and it is only mildly to non-irritating to the eyes.

Acute and repeated dose toxicity studies conducted in laboratory animals on PDMS of different viscosities do not show any significant adverse effects. Long-term chronic/carcinogenicity and reproductive toxicity studies were also without adverse effects. PDMS is not mutagenic in vitro.

In humans, PDMS has no effect on the immune system. PDMS is used in urology, ophthalmology and dermatology (skin correction). Autoimmune disorders (e.g. scleroderma) cannot be linked to PDMS. Several human diseases (connective tissue, atypical connective tissue, rheumatic and autoimmune diseases, and breast cancer) have been reported after injection of PDMS (for cosmetic purposes) or placement of breast implants (made of high viscosity PDMS). These diseases are, however, not associated with PDMS.

Overall, PDMS does not present a risk to the environment or to human health.