The environmental impact and safety assessment of precipitated silica requires comprehensive consideration of its entire lifecycle, including production, use, and disposal.  Generally, precipitated silica itself is non-toxic and classified as a non-hazardous substance. However, its production process generates certain pollution, and dust control is necessary during its use.  Furthermore, new research indicates that it may accelerate the migration of harmful substances in tire wear particles.
I. Environmental Impact of Precipitated Silica
1. Environmental Impact during Production
Wastewater Pollution: The production of precipitated silica generates wastewater containing high concentrations of organic pollutants (such as toluene and phenol) and suspended solids, causing acute and chronic toxicity to aquatic organisms and severely affecting water quality.
Solid Waste: Waste carbon black and filter residues generated during production contain volatile organic compounds and heavy metals. If not properly treated, they will pollute soil and groundwater.
Exhaust Gas Emissions: The exhaust gases emitted during production mainly contain sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and suspended particulate matter. These gases can lead to acid rain, air pollution, and health problems.
Energy Consumption: The preparation of precipitated silica requires high temperatures and high energy consumption, which may lead to the emission of carbon dioxide and other greenhouse gases, having a certain negative impact on climate change.
2. Environmental Impact during Use
Dust Problem: The ultrafine particles of precipitated silica can generate dust, leading to air pollution from suspended particulate matter. These ultrafine particles may cause chronic effects on the human respiratory system, such as airway inflammation and bronchial constriction.
Water and Soil Pollution: Precipitated silica particles may enter water bodies and soil, causing toxic effects on aquatic organisms and soil microorganisms.
Impact of Tire Wear Particles: Recent studies show that the migration rate of 6PPD-based tire antidegradants from precipitated silica-reinforced rubber is significantly higher than that from carbon black-reinforced rubber. The migration rate of precipitated silica tire tread wear particles (TWP) is on average twice that of carbon black tread TWP.21 This migration may lead to the conversion product of 6PPD, 6PPD-q, entering water bodies, affecting aquatic organisms, especially salmon growth. 3. Ecosystem Impacts
Aquatic organism impacts: Studies have shown that fumed silica particles have toxic effects on some aquatic organisms and may have a certain impact on the balance of aquatic ecosystems.
Soil biodiversity: The use of fumed silica may have a certain impact on microbial activity and biodiversity in the soil, and the richness and diversity of microorganisms in the soil are crucial to the ecological function of farmland.3
Lake Taihu sediment study: Studies show that the black carbon (BC) content in Lake Taihu sediments reaches 1.2-4.6 g kg⁻¹ (average 2.7 g kg⁻¹), of which BC char accounts for 85%. The BC char content is significantly negatively correlated with the bacterial Shannon index (r=-0.42) and positively correlated with fungi (r=0.38), indicating that black carbon inhibits bacterial diversity but promotes fungal diversity.

II. Safety Assessment of Fumed Silica
1. Basic Safety
Non-hazardous substance classification: Fumed silica is classified as a non-hazardous substance. According to EU chemical regulations, national hazardous substance laws, and international transport regulations, fumed silica is not a hazardous substance or dangerous good.5
Toxicological characteristics: Fumed silica is amorphous and does not contain the fibrous properties that crystalline silica may have. Long-term inhalation tests have shown that it does not cause silicosis.
Food and pharmaceutical applications: Untreated fumed silica has been approved by the US Food and Drug Administration for use in food, cosmetics, and pharmaceuticals.
2. Human Health Impacts
Respiratory system: Fumed silica dust may cause respiratory problems, and long-term exposure may lead to airway inflammation and bronchoconstriction.2 However, unlike harmful substances such as asbestos, fumed silica is not fibrous and does not cause silicosis.
Skin and eyes: The irritation to the skin is non-irritating to mildly irritating, and may cause dryness, but this can be eliminated by washing and skin care; the irritation to the eyes is non-irritating to very mildly irritating.
Animal experiments: Animal experiments have shown that fumed silica at high concentrations has no significant toxic effects on the respiratory, digestive, and reproductive systems of animals, and long-term exposure has no adverse effects on the survival rate, weight, and reproductive capacity of experimental animals. 3. Safety Precautions
Dust Control: It is recommended that the 8-hour time-weighted average dust exposure for each person does not exceed 10 mg/m³. The workplace should have adequate ventilation, and dust masks should be used.
Fire and Explosion Prevention: Silica dust may cause explosions and fires; strict fire prevention measures must be taken during storage and handling.
Personal Protection: Workers must wear appropriate personal protective equipment to reduce the generation and spread of dust and ensure good ventilation in the workplace.

III. Environmental Management and Mitigation Measures
1. Production Process Optimization
Wastewater Treatment: A combination of physical, chemical, and biological treatment methods, including sedimentation, filtration, adsorption, oxidation, reduction, and neutralization, is used to effectively remove pollutants from wastewater.
Waste Gas Treatment: Methods such as absorption, catalysis, and filtration are used to capture pollutants in waste gas using absorbents and convert harmful gases into harmless substances through catalysts.
Solid Waste Treatment: Waste carbon black can be recycled through methods such as pyrolysis and calcination, and filter residues can be treated through chemical solidification and incineration.
2. Usage Phase Management
Tire Design Optimization: Studies show that using silica instead of carbon black as a reinforcing agent can significantly reduce energy consumption while improving tire performance, thereby reducing the environmental impact of the tire's entire life cycle.
Dust Control Technology:  Technologies such as pulse bag dust collectors, pneumatic conveying, and automated monitoring are used at the production site to reduce dust concentration to below national standards.
Intelligent Management: Establish a meteorological monitoring system, an environmental monitoring network, and disaster emergency plans to continuously monitor the environment surrounding the silica project.
3. Future Development Directions
Environmentally Friendly Production Processes: Develop more environmentally friendly preparation methods, such as the sol-gel method and electrochemical method, to reduce exhaust emissions and resource consumption.
Alternative Research: Explore alternatives such as inorganic nanomaterials and organic fillers to reduce the demand for silica.
Risk Assessment Model: Construct a spatial clustering risk assessment model to achieve a leap from laboratory toxicity testing to watershed-scale early warning.

IV. Comprehensive Assessment and Recommendations
Silica, as an important industrial raw material, has environmental impacts mainly concentrated in pollution emissions during the production process and dust problems during the use process, while its inherent safety is relatively high. The key lies in environmental control during the production process and dust management during the usage process. With the improvement of environmental regulations and advancements in production technology, the environmental impact of precipitated silica is gradually decreasing. Future efforts should focus on:
Strengthening pollution control during the production process, especially the treatment of wastewater and exhaust gases;
Improving production processes to reduce dust emissions; environmental monitoring systems to promptly identify and address potential environmental problems; Conducting in-depth research on the mechanisms by which precipitated silica accelerates the migration of harmful substances in tire wear particles, and developing safer alternatives; Through scientific management and technological innovation, the environmental impact of precipitated silica can be effectively controlled, enabling its sustainable application in fields such as rubber, plastics, and coatings.