Silicon dioxide (E 551) is a common food additive used as an anticaking agent. This means it helps prevent powdered foods from clumping together, ensuring a smoother texture and easier handling. You can find it in a variety of products, even foods intended for infants older than 16 weeks. But what exactly is silicon dioxide, and is it safe for consumption, especially for the most vulnerable populations?
In 2018, the European Food Safety Authority (EFSA) Panel on Food Additives and Nutrient Sources (ANS Panel) conducted a re-evaluation of E 551’s safety as part of a broader review of food additives permitted in the EU before 2009. At that time, they found the available data insufficient to fully assess E 551 and establish a safe Acceptable Daily Intake (ADI). Furthermore, a safety assessment for its use in foods for infants under 16 weeks couldn’t be completed due to ongoing development of specific scientific guidelines for this age group.
EFSA’s Further Investigation into Silicon Dioxide
To address the gaps identified in the 2018 opinion, the European Commission tasked the EFSA Panel on Food Additives and Flavourings (FAF Panel) with a more in-depth investigation. This included a specific risk assessment for infants under 16 weeks of age, a crucial consideration for infant formula and other early-life foods.
To gather comprehensive data, EFSA launched a public call for data, inviting industry stakeholders involved in the production and use of E 551 to submit relevant information. Recognizing that E 551 particles and their aggregates can be in the nanoscale range, the FAF Panel conducted a risk assessment that considered both conventional and nanoscale aspects. For the infant risk assessment, EFSA adhered to its 2017 guidelines for evaluating substances in food for infants under 16 weeks.
Data and Considerations in the Safety Evaluation
The FAF Panel’s current safety evaluation was informed by a range of data sources:
- Industry Data: Information collected directly from manufacturers and users of E 551 in response to EFSA’s public call.
- Literature and Unpublished Studies: Data from scientific literature searches and unpublished studies provided by the industry at EFSA’s request.
- Real-World Exposure: Safety information from widely used medications containing silicon dioxide that are administered to infants under 16 weeks.
- Previous Findings: Conclusions and recommendations from the 2018 scientific opinion were also taken into account.
Understanding the Uncertainties Around Nano-Sized Silicon Dioxide
Despite the extensive data considered, the FAF Panel acknowledged certain uncertainties:
- Nano-particle Characterization in Food: Currently, there is a lack of precise information on the proportion of E 551 particles that exist as isolated nanoparticles, nano-sized aggregates, and larger agglomerates within food products. The extent of E 551 agglomeration in different food matrices also remains unclear.
- Limited Nano-Specific Toxicology: Toxicological studies specifically examining the potential harmful effects of nano-sized particles and aggregates of E 551 are limited. This lack of specific data introduces uncertainty in evaluating the associated health risks, particularly at the nanoscale.
Key Findings on Silicon Dioxide (E 551)
Characterization of E 551:
- Silicon dioxide (E 551) is classified as a synthetic amorphous silica (SAS). This means it is man-made, lacks a crystalline structure, and is used in its unmodified or uncoated form as a food additive.
- SAS is composed of nearly spherical nanoparticles, primarily ranging from 2 to 28 nanometers in size. These nanoparticles tend to clump together, forming complex aggregates.
- Different manufacturing processes result in various types of SAS, including:
- Fumed silica: Produced by heating chlorosilanes like silicon tetrachloride at extremely high temperatures.
- Precipitated silica, silica gel, and hydrous silica: Created using wet methods, typically involving reactions in aqueous solutions.
- It’s important to note that E 551 may contain trace levels of impurities such as lead, mercury, aluminum, and arsenic, depending on the manufacturing process and source materials.
Safety Assessment of E 551:
- The FAF Panel determined that the systemic bioavailability of E 551 in humans is likely very low. However, due to data limitations, they couldn’t precisely quantify the absorption of silicon dioxide into the body after oral consumption.
- Given these data limitations, the panel opted for a Margin of Exposure (MOE) approach for safety assessment instead of establishing a traditional Acceptable Daily Intake (ADI). The MOE approach is used when data is insufficient for a full ADI determination.
- Crucially, the FAF Panel concluded that silicon dioxide (E 551) does not pose a safety concern for any population group, including infants under 16 weeks. This conclusion provides reassurance regarding the use of E 551 in a wide range of foods, even those designed for the most sensitive age group.
Recommendations to Enhance Safety Margins
While EFSA concluded that E 551 is safe, they also provided recommendations to further minimize potential risks related to trace element impurities. Toxic elements like lead, mercury, aluminum, and arsenic can be present in E 551, and while E 551 is not the only dietary source of these elements, reducing exposure from all sources is a public health priority.
To limit the EU population’s exposure to these toxic elements, the FAF Panel recommended amending the existing EU specifications for E 551 by:
- Lowering the maximum permitted levels for lead, mercury, and arsenic in E 551. This would ensure tighter controls on these contaminants in the food additive itself.
- Setting a maximum limit for aluminum in E 551. Currently, there is no specific limit for aluminum, and establishing one would further enhance safety specifications.
By implementing these recommendations, the EU can further strengthen the safety profile of silicon dioxide (E 551) and minimize potential exposure to trace element impurities for all consumers.
Understanding Key Terms
Acceptable Daily Intake (ADI): This is an estimate of the amount of a substance, like a food additive, that a person can consume daily over their lifetime without any significant health risk. ADIs are usually expressed in milligrams per kilogram of body weight.
Margin of Exposure (MOE): The MOE is a tool used in risk assessment to evaluate potential safety concerns from substances in food or animal feed. It’s calculated as the ratio between a reference point (the dose at which a minimal adverse effect is observed) and the level of exposure to the substance in a population. A higher MOE generally indicates a lower level of concern.
Wet Method (in Silica Production): This refers to a chemical manufacturing technique used to produce different forms of silica, such as precipitated silica, silica gel, and hydrous silica. It typically involves mixing aqueous alkali metal silicates with diluted acids in a controlled environment. The resulting silica compounds are hydrated or contain water adsorbed on their surfaces.
