Recent developments in nanomaterials in care products

Thakur attempted to quantify the environmental impact and energy use of a commercially produced 1kg sunscreen lotion containing Ocrilene, Avobenzone or nano TiO2 as a UV blocker by comparing environmental impact and energy use using the impact assessment tool TRACI.

In addition to providing total energy demand, TRACI estimates also provide standardized scores for seven impact categories: (1) ozone depletion; (2) Climate change; (3) Acidification; (4) eutrophication; (5) Smoke formation; (6) Human health effects; (7) Ecotoxicity. The results showed a big difference in the effectiveness of sunscreen compared to actual sunscreen products. For sunscreen products, nanoscale TiO2 requires more energy (2.1 MJ) than Ocriline (0.3 MJ) and Avobenzone (0.5 MJ).

However, the final production of a sunscreen containing nano TiO2 used less energy (2.5 MJ) than a sunscreen containing Ocrilene and Avobenzone (4.3 MJ). Considering the energy required to manufacture UV-blocking agents and final sunscreen products, nano sunscreen products are considered to be more sustainable due to their lower energy requirements.

Thakur's analysis was limited, however, because he focused on only one of the many commercial titanium dioxide production processes. The new synthetic route proposes greater sustainability, for example: Middlemas et al report that TiO2 production by alkaline roasting of titanium dioxide slag requires less (10%-15%) cumulative energy demand than the two most common commercial TiO2 production methods. Plant-based methods have also been developed that require very little energy and renewable resources. Analyses that focus solely on environmental impact and total energy use lack other key industry indicators such as production, waste generation and solvent use. Mercado et al. proposed 66 environmental indicators, 26 efficiency indicators, 33 economic indicators and 15 energy indicators for study.

A similar situation exists for other nanomaterials in personal care products. Due to the high demand for multipurpose (antibacterial, electrochemical and photocatalytic) properties of silver, the possible synthetic routes of Ag nanoparticles have been extensively documented. Ag nanoparticles prepared by non-toxic polymer coating reduction method have certain advantages in cosmetic applications because of their protective effect. Other methods for preparing Ag nanoparticles include the lactic acid sol-gel method.

In addition, plant extracts are also considered a green alternative to traditional synthetic chemistry. These plant-based processes reportedly produce less waste, require less energy, and make use of existing natural resources. Mashwani et al. reviewed the literature on the synthesis routes of 69 plant-based Ag nanoparticles and reported that the reduction of AgNO3 to produce Ag was optimized under mild conditions (neutral pH, ambient temperature/pressure).

As can be seen from the sustainability factors in Table 6, the practicability of collecting plant material on a large scale for commercial production of Ag nanoparticles must be considered for this plant-based approach. This will require further evaluation of the resources required for commercial plant farms as raw material ZnO production, as well as the comprehensive investigation of commercial and experimental methods of zinc oxide production proposed by Koloodziejczak Radzimska and Teofil Jesionowski.

The French process has been approved by ISO 9298 and is one of the most widely used on an industrial scale. It includes the oxidation of metal zinc, after melting and evaporation above 900 ° C. The purity of zinc oxide produced by this process is 99.5%, and the surface area and shape of the particles can be adjusted by changing the reaction parameters (heating temperature, oxygen content, etc.). The process must be evaluated quantitatively, but this needs to be weighed against the sustainability involved in the specific parameters that ZnO manufacturers use in the supply chain of personal care products - ideally. While quantitative analysis is beyond the scope of this review, the results will allow us to determine what the most sustainable synthetic route is for ZnO nanoparticles compared to other cosmetic nanomaterials with similar properties.

This will therefore allow us to predict which nanomaterials are more likely to impact consumers as part of a final personal care product. By identifying the most beneficial nanomaterials, subsequent exposure and toxicity analyses can then strategically target these sources to assess their safety risks to consumers.

Naidu et al. propose an alternative approach to sustainability analysis through the U.S. Environmental Protection Agency's Waste Reduction Algorithm, an environmental impact tool similar to TRACI, but with key process metrics such as yield, unit cost, material procurement, waste generation, and nanomaterials recycling. Three preparation processes of silica nanoparticles were sorted by Naidu decision analysis algorithm.

In the context of nanoscale personal care products, NAIADE analysis can be used repeatedly, first to assess the sustainability of the nanomaterial manufacturing process, and then also for the analysis of final consumer products containing nanomaterials. This approach may be limited by manufacturers' reluctance to disclose proprietary formulation data. Windsor et al. recently reviewed a variety of other criteria decision analysis methods.