Silicon quantum dots (SiQDs) have gained significant attention due to their unique optical and electronic properties, making them promising candidates for applications in optoelectronics, photovoltaics, and quantum computing. However, their commercialization necessitates rigorous evaluation of regulatory and safety aspects to ensure safe handling, usage, and disposal. This article examines the toxicity profiles of SiQDs, occupational exposure limits, disposal guidelines, and global regulatory frameworks, alongside encapsulation strategies and industry standards for risk mitigation.

Toxicity assessments of SiQDs have been conducted to evaluate their potential hazards. Studies indicate that the toxicity of SiQDs is influenced by factors such as size, surface chemistry, and dosage. Smaller SiQDs, typically below 10 nm, exhibit higher reactivity due to their increased surface area-to-volume ratio, potentially leading to greater biological interactions. Surface modifications, such as carboxylation or PEGylation, can reduce cytotoxicity by minimizing unintended interactions with biological systems. In vitro studies on human cell lines suggest that unmodified SiQDs may induce oxidative stress and inflammatory responses at high concentrations, while encapsulated or functionalized SiQDs show reduced adverse effects. In vivo studies on animal models report low acute toxicity for properly passivated SiQDs, with no significant accumulation in major organs over short-term exposure. However, long-term biodistribution and chronic toxicity data remain limited, necessitating further research.

Occupational exposure limits for SiQDs are not yet explicitly defined in most regulatory frameworks due to their emerging nature. However, guidelines for engineered nanomaterials provide a provisional basis for risk assessment. The National Institute for Occupational Safety and Health (NIOSH) recommends a recommended exposure limit (REL) of 1 μg/m³ for ultrafine titanium dioxide as a conservative benchmark for nanoscale particles, which may be adapted for SiQDs until substance-specific limits are established. The Occupational Safety and Health Administration (OSHA) does not currently enforce nanomaterial-specific permissible exposure limits (PELs), but general dust regulations under 29 CFR 1910.1000 may apply. The European Chemicals Agency (ECHA) under REACH requires manufacturers to conduct chemical safety assessments for nanomaterials, including SiQDs, if annual production exceeds one ton. Control measures such as local exhaust ventilation, personal protective equipment (PPE), and closed handling systems are advised to minimize airborne exposure.

Disposal guidelines for SiQDs are similarly evolving, with recommendations based on existing hazardous waste protocols. The U.S. Environmental Protection Agency (EPA) classifies SiQDs as solid waste under the Resource Conservation and Recovery Act (RCRA), with disposal methods dependent on surface functionalization. Unmodified SiQDs may require treatment as hazardous waste if they exhibit ignitability or reactivity, while inert, encapsulated SiQDs can often be disposed of as non-hazardous waste. The European Union’s Waste Framework Directive mandates careful consideration of nanoparticle release during waste treatment, favoring incineration with advanced filtration for SiQD-containing materials to prevent environmental release. Landfill disposal is discouraged unless leachate testing confirms no nanoparticle mobilization.

Global regulatory frameworks for SiQDs vary in stringency and scope. In the U.S., the EPA regulates SiQDs under the Toxic Substances Control Act (TSCA), requiring pre-manufacture notices (PMNs) for new nanomaterials. The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) may apply if SiQDs are used in pesticidal formulations. Under the EU’s REACH regulation, SiQDs are subject to registration, evaluation, and authorization processes, with additional nano-specific requirements for environmental and health risk assessments. Japan’s Ministry of Health, Labour and Welfare (MHLW) enforces mandatory safety data sheets (SDS) for nanomaterials, including SiQDs, under the Industrial Safety and Health Law. China’s National Standard GB/T 33850-2017 outlines general safety guidelines for nanomaterials but lacks SiQD-specific provisions. These divergent approaches highlight the need for harmonized international standards to facilitate global trade and compliance.

Encapsulation strategies are critical for mitigating risks associated with SiQDs. Silica shell coating is a widely used method, providing chemical stability and reducing leaching of silicon cores. Polymer encapsulation with materials like poly(lactic-co-glycolic acid) (PLGA) or polyethylenimine (PEI) enhances biocompatibility and prevents aggregation. Inorganic coatings, such as aluminum oxide or titanium dioxide, offer additional barriers against degradation under harsh conditions. Core-shell architectures with graded interfaces further improve stability by minimizing lattice mismatch stresses. These encapsulation techniques not only reduce toxicity but also enhance the performance of SiQDs in applications such as light-emitting diodes (LEDs) and solar cells by passivating surface defects.

Industry standards for the commercialization of SiQDs are still under development, but several organizations are actively working toward consensus. The International Organization for Standardization (ISO) has published ISO/TS 12901-2:2014 for nanomaterial risk evaluation, which can be adapted for SiQDs. The American National Standards Institute (ANSI) is collaborating with the Nanotechnology Industries Association (NIA) to develop labeling and handling protocols. The European Committee for Standardization (CEN) has released CEN/TS 17010:2016 for workplace exposure monitoring, applicable to SiQD manufacturing facilities. These standards emphasize the importance of lifecycle assessment, from synthesis to end-of-life, to ensure comprehensive risk management.

In conclusion, the regulatory and safety landscape for SiQDs is complex and evolving, with ongoing research needed to fill data gaps in long-term toxicity and environmental persistence. Current frameworks rely on adaptive guidelines from broader nanomaterial regulations, underscoring the necessity for SiQD-specific standards. Encapsulation technologies play a pivotal role in minimizing hazards, while industry-led standardization efforts aim to streamline safe commercialization. Stakeholders must remain proactive in aligning with global regulations to ensure the responsible development of SiQD-based technologies.