Probabilistic modelling of nanobiomaterial release from medical applications into the environment

Nanobiomaterials (NBMs) are currently being tested in numerous biomedical applications, and their use is expected to grow rapidly in the near future. Many different types of nanomaterials are employed for a wide variety of different applications. Silver nanoparticles (nano-Ag) have been investigated for their antibacterial, antifungal, and osteoinductive properties to be used in catheters, wound healing, dental applications, and bone healing. Polymeric nanoparticles such as poly(lactic-co-glycolic acid) (PLGA) are mainly studied for their ability to deliver cancer drugs as the body metabolizes them into simple compounds. However, most of these applications are still in the development stage and unavailable on the market, meaning that information on possible consumption, material flows, and concentrations in the environment is lacking. We thus modeled a realistic scenario involving several nano-Ag and PLGA applications which are already in use or likely to reach the market soon. We assumed their full market penetration in Europe in order to explore the prospective flows of NBMs and their environmental concentrations. The potential flows of three application-specific composite materials were also examined for one precise application each: Fe₃O₄PEG-PLGA used in drug delivery, MgHA-collagen used for bone tissue engineering, and PLLA-Ag applied in wound healing. Mean annual consumption in Europe, considering all realistic and probable applications of the respective NBMs, was estimated to be 5,650 kg of nano-Ag and 48,000 kg of PLGA. Mean annual consumption of the three application-specific materials under the full market penetration scenario was estimated to be 4,000 kg of Fe₃O₄PEG-PLGA, 58 kg of MgHA-collagen, and 24,300 kg of PLLA-Ag. A probabilistic material-flow model was used to quantify flows of the NBMs studied from production, through use, and on to end-of-life in the environment. The highest possible worst-case predicted environmental concentration (wc-PEC) were found to occur in sewage sludge, with 0.2 µg/kg of nano-Ag, 400 µg/kg of PLGA, 33 µg/kg of Fe₃O₄PEG-PLGA, 0.007 µg/kg of MgHA-collagen, and 2.9 µg/kg of PLLA-Ag. PLGA exhibited the highest concentration in all environmental compartments except natural and urban soil, where nano-Ag showed the highest concentration. The results showed that the distribution of NBMs into different environmental and technical compartments is strongly dependent on their type of application.