» A Major Global Programme

Silicone products increase the quality, comfort and security of daily life in thousands of applications that depend on them for performance. For all substances, however, society needs to understand, as fully as possible, effects in terms of health, safety and environmental impact. Silicone producers are committed to this approach and undertake continuous health, safety, and environmental research on silicone products. An example is the Siloxane Research Programme (SRP), which is directed at issues on health.

Siloxanes are building blocks for many silicone products. Initiated in late 1993 and scheduled to run for ten years, the SRP provides understanding of the safety profile of a carefully selected group of six major siloxanes through advanced studies. The studies aim to see if there are any possible hazards associated with these materials and whether or not there would be concerns potential human health effects under real life conditions.

Costing $30 million, silicone producers fund the SRP but independent institutions such as leading universities play a major role in the research. Findings are set out in scientific publications and communicated to national and international regulators, customers and any other interested stakeholders.

» Comprehensive Research

The chemical names of the six siloxanes studied are:

• Octamethyl cyclotetrasiloxane (D4).
• Decamethyl cyclopentasiloxane (D5).
• Dodecamethyl cyclohexasiloxane (D6).
• Hexamethyl disiloxane (HMDS).
• Two polymeric siloxanes (Polydimethyl siloxanes, PDMS) with different viscosities.

Conceptually, the programme comprises:

• Descriptive studies - experiments to show any effects on animals (rodents).
• Fundamental studies - to explain how siloxanes interact with cells and tissues.
• Clinical studies - to evaluate similarities and differences to rodents when humans are exposed.
• Exposure profile - a numerical assessment of the amount, frequency and length of time that humans come into contact with siloxanes.

The results obtained not only form the basis for risk assessments of the specific siloxanes but also for scientific extrapolation to other related compounds.

» A Good Picture of Safety

The results to date show a good overall picture of safety based on a high volume of detailed data. Industry submits findings from the programme to regulatory authorities globally and for peer review and publication in scientific journals. We present only the main points here. Please consult the attached bibliography if you wish to have further details.

Main Results to Date

The toxicological studies on the two types of PDMS showed no hazard even at high doses.

The studies to date confirm the safety profile of D5. The results indicate clearly that no concerns would be expected for D6 either, as this is even less likely to be taken up by the body.

Research on D4 to date, has shown some minor effects on the organs and reproductive capacity of laboratory animals. These, however, occurred at high exposure concentrations to which people would not be exposed in real life from products that contain D4. In terms of human health, the studies showed a very high level of safety.

Studies on HMDS are under way.

Relevance to people

The potential risk from substances depends on two factors - the hazard of the product itself and the quantities that people could come into contact with in real life. The results obtained from the SRP on exposure demonstrate that workers using siloxane-based products come into contact with quantities well below industry's own voluntary worker exposure guidelines - which are already set to ensure a high level of safety. People using products containing siloxanes are exposed to even lower levels. These products can clearly be regarded as safe when used as intended.

» Conclusion

The SRP has shown and continues to show that siloxanes are safe in consumer products. There are no reasons to believe that they present real dangers to human health based on the results of the experiments and exposure under all realistic conditions.

Details of the scientific reports conducted within the SRP are available on the site of our sister organisation, the Silicones Environmental Health and Safety Council of North America. Please click here to go directly to the data.