Under standardized production and proper use, polyanionic cellulose (PAC) is a low-toxic, readily biodegradable, and environmentally compatible industrial chemical, but potential risks must be managed.
From a safety perspective, PAC is modified from natural cellulose and primarily consists of polysaccharides, making it extremely low in toxicity. Its acute oral toxicity (LD₅₀) is typically greater than 5000 mg/kg, placing it at the "practically non-toxic" level. Food-grade versions of the same type can also be used as food additives. It is minimally irritating to the skin and eyes, but dry powder can be easily airborne and inhaled, potentially irritating the respiratory tract. Non-food-grade versions may contain trace amounts of residual byproducts, which can cause mild gastrointestinal discomfort if accidentally ingested. Risks primarily arise during the production process. Raw materials such as chloroacetic acid and sodium hydroxide are corrosive and irritating, requiring protective equipment during handling and attention to dust generation during handling and dissolution.
Environmentally friendly, the PAC molecule's main chain is a cellulose structure, which can be broken down by natural microorganisms into glucose, carbon dioxide, and water. Its biodegradation rate reaches 60%-80% within 28 days, far exceeding that of some synthetic polymers. Although the degradation rate of over-crosslinked PAC decreases, it is still degradable and poses no long-term accumulation risk. Low concentrations of PAC (≤100 mg/L) entering water bodies are harmless to aquatic life, while high concentrations (such as drilling fluid waste) can affect dissolved oxygen in water bodies. PAC can be decomposed in soil and can even improve soil aggregate structure. Different waste scenarios require targeted treatment: drilling fluid waste undergoes solid-liquid separation and regeneration treatment, food and pharmaceutical wastewater can be treated conventionally, and papermaking and textile wastewater can be degraded using activated sludge.
PAC complies with multiple regulatory standards and is not listed as a substance of very high concern under EU REACH. It is designated as a low-risk chemical by the US EPA. China also has strict limits on harmful impurities in food-grade and industrial-grade PAC.
Controls must cover the entire supply chain: Equipment must be sealed throughout the production process, and operators must ensure adequate protective equipment. Ventilation must be maintained during use to prevent dust, and any inhalation or eye contact must be treated promptly. Waste must be biochemically treated to meet standards before discharge, and direct discharge of high-concentration wastewater is strictly prohibited.
In summary, PAC has a strong foundation for safety and environmental protection. Its core risks lie in the protection of production raw materials and the control of high-concentration waste, making it a promising alternative to some highly polluting synthetic polymers.
