Silicone environmental impact: from its origin to its fate
Podium 76
Presented by: Kathleen Plotzke
Introduction
Silicones are a broad chemical family that take numerous forms. Silicones have a long-standing history of safe use in personal care, health care and other consumer product applications because they make existing materials work better, more efficiently, longer and more reliably.
However, unclear and confusing information around the impact of silicones on the planet and on human safety have caused consumer concern. With data, we want to bridge the gap and lead a transparent science-based dialogue.
Methods
Silicones are one of the most extensively studied class of materials. Because of their unique properties, these types of substances are all resistant to biodegradation using standard OECD testing protocols such that they are typically considered not readily or inherently biodegradable by these international definitions. However, abiotic degradation mechanisms are important in the fate of silicones in the environment and often are overlooked as to their role in removing these substances from the environment. It is important to first understand the distribution and fate during their use to identify the most relevant environmental compartments where they may be found followed by characterization of relevant degradation processes that may be involved in their overall environmental removal.
Results
Most silicones used in personal care applications are not expected to reach the water environment to a significant degree, as, after application, they will have either evaporated (volatile siloxanes) from skin or hair, or when they are washed off through water and go down the drain, where they will be partitioned out of the wastewater by binding to suspended particulate matter. In wastewater treatment plants, they will end in the sludge by sedimentation. The sludge is either handled as waste or spread on land for agricultural purposes. Once in the soil, silicones are degraded by the clay, via abiotic degradation process with ultimate conversion to silica, silicic acid, and carbon dioxide most likely via both chemical and biological degradation processes, leading to the removal of silicones from the environment.
Discussion
Silica, or silicon dioxide (SiO2) is the required building block to make silicones. Silicon is the second most abundant element on the planet after oxygen. Therefore, silica, the building block of silicones, is made out of two most abundant elements on earth. Silica is found as quartz and in certain plant husks in nature and is the major constituent of sand.
Most silicone polymers can be considered of partial mineral origin given silicon, the second most abundant element in the Earth's crust
The transformation of silicon dioxide (SiO2) into silicon metal is an energy-intensive process but can be produced in a highly sustainable way. For example, in Brazil, Dow has a silicon metal facility that uses hydroelectric power with a minimal impact on the environment. At the site, Dow owns 45,000 hectares of land – about 80% of which is preserved native Amazon rainforest and about 20% of which is an eucalyptus plantation. Charcoal used in silicon metal production is made from eucalyptus that is sustainably cultivated and harvested from the plantation per Forest Stewardship Council (FSC) guidelines. Dow recently initiated Project Ybá, which will map the biodiversity of the forestland for bioactive ingredients and help develop a local cooperative that will harvest and sell them. With the launch of this project, Dow is playing an active role in contributing to the social development of the Brazilian Breu Branco community, as more than 150 families in the region are expected to benefit through employment in a sustainable industry. Through the identification and sale of bio-active products for the cosmetics industry, this initiative can increase the income for families, while contributing to the conservation of part of the Amazon rainforest.
Silicone polymers used in personal care products are non-GMO, chemically inert and non-reactive bio compatible ingredients that are stable substances under usual environmental conditions. Non-functional silicones are colorless and odorless. None of their components are derived from animals, meaning silicones are vegan-friendly and cruelty-free by default. Their unique chemistry resists oxidation and they typically do not cause skin irritation or have any allergen or drying effects. The above combined with their ultimate removal from the environment help support the sustainability of silicones.
Conclusion
This paper provides an overview on some of the various sustainability aspects of silicones.
Silicones are a broad chemical family that take numerous forms. Silicones have a long-standing history of safe use in personal care, health care and other consumer product applications because they make existing materials work better, more efficiently, longer and more reliably.
However, unclear and confusing information around the impact of silicones on the planet and on human safety have caused consumer concern. With data, we want to bridge the gap and lead a transparent science-based dialogue.
Methods
Silicones are one of the most extensively studied class of materials. Because of their unique properties, these types of substances are all resistant to biodegradation using standard OECD testing protocols such that they are typically considered not readily or inherently biodegradable by these international definitions. However, abiotic degradation mechanisms are important in the fate of silicones in the environment and often are overlooked as to their role in removing these substances from the environment. It is important to first understand the distribution and fate during their use to identify the most relevant environmental compartments where they may be found followed by characterization of relevant degradation processes that may be involved in their overall environmental removal.
Results
Most silicones used in personal care applications are not expected to reach the water environment to a significant degree, as, after application, they will have either evaporated (volatile siloxanes) from skin or hair, or when they are washed off through water and go down the drain, where they will be partitioned out of the wastewater by binding to suspended particulate matter. In wastewater treatment plants, they will end in the sludge by sedimentation. The sludge is either handled as waste or spread on land for agricultural purposes. Once in the soil, silicones are degraded by the clay, via abiotic degradation process with ultimate conversion to silica, silicic acid, and carbon dioxide most likely via both chemical and biological degradation processes, leading to the removal of silicones from the environment.
Discussion
Silica, or silicon dioxide (SiO2) is the required building block to make silicones. Silicon is the second most abundant element on the planet after oxygen. Therefore, silica, the building block of silicones, is made out of two most abundant elements on earth. Silica is found as quartz and in certain plant husks in nature and is the major constituent of sand.
Most silicone polymers can be considered of partial mineral origin given silicon, the second most abundant element in the Earth's crust
The transformation of silicon dioxide (SiO2) into silicon metal is an energy-intensive process but can be produced in a highly sustainable way. For example, in Brazil, Dow has a silicon metal facility that uses hydroelectric power with a minimal impact on the environment. At the site, Dow owns 45,000 hectares of land – about 80% of which is preserved native Amazon rainforest and about 20% of which is an eucalyptus plantation. Charcoal used in silicon metal production is made from eucalyptus that is sustainably cultivated and harvested from the plantation per Forest Stewardship Council (FSC) guidelines. Dow recently initiated Project Ybá, which will map the biodiversity of the forestland for bioactive ingredients and help develop a local cooperative that will harvest and sell them. With the launch of this project, Dow is playing an active role in contributing to the social development of the Brazilian Breu Branco community, as more than 150 families in the region are expected to benefit through employment in a sustainable industry. Through the identification and sale of bio-active products for the cosmetics industry, this initiative can increase the income for families, while contributing to the conservation of part of the Amazon rainforest.
Silicone polymers used in personal care products are non-GMO, chemically inert and non-reactive bio compatible ingredients that are stable substances under usual environmental conditions. Non-functional silicones are colorless and odorless. None of their components are derived from animals, meaning silicones are vegan-friendly and cruelty-free by default. Their unique chemistry resists oxidation and they typically do not cause skin irritation or have any allergen or drying effects. The above combined with their ultimate removal from the environment help support the sustainability of silicones.
Conclusion
This paper provides an overview on some of the various sustainability aspects of silicones.