A new study quantifies the environmental costs of alternative materials following bans on plastic microbeads used in wash-off cosmetics.
Microbeads are added to cosmetic and personal care products such as toothpaste, industrial hand cleaners and body scrubs often to enhance qualities like abrasiveness.
Microbeads are small, artificial plastic pellets, often with a diameter of less than 0.5 mm (or 500 μm). In several products, they are designed to be washed off, thus passing through wastewater treatment plants and ending up in marine ecosystems. They can accumulate underwater, eventually being ingested by marine organisms, causing harm to them.
Therefore, in several regions, such as the United Kingdom, microbeads are banned in wash-off cosmetics. A team of researchers from Imperial College London has now evaluated 29 alternatives to microbeads for their effect on the environment.
They discovered that silica, an abundant mineral that occurs naturally, was the ideal alternative and performs better compared to plastic microbeads over all the categories. The findings of the study were published recently in Nature Sustainability.
Banning microbeads based on evidence of their long-term environmental impacts is a good step, but there may be unforeseen environmental impacts unless substitutes are chosen carefully. Not every apparently ‘natural’ alternative is desirable, so care is needed in selecting new cosmetic formulations.
Nick Voulvoulis, Lead Researcher and Professor, Centre for Environmental Policy, Imperial College London
The researchers assessed 29 alternatives to microbeads, such as different minerals like silica, pumice and salt; various plastic formulations; as well as plant and animal-derived products such as oats, almond shells and pearls. For each alternative, the researchers took the environmental effect of their 'life cycle' into account—from extraction and production to final use and disposal.
For every stage, they assessed various factors that influence environmental and human health, for example, the use of scarce resources, toxicity and ozone depletion.
They identified that two main factors affect the environmental credentials of the materials: the amount of energy-intensive processing they involve (which leads to the production of greenhouse gases) and, in the case of plant-based materials, the amount of land and water they need.
This analysis revealed that almond shells, usually regarded as a preferred 'natural' alternative, need a lot of land and water to grow and represent a poor environmental alternative when they are grown in water-scarce regions. Although citric acid needs considerably less land and water, it involves heavy processing, thus necessitating a lot of energy for production.
Silica was found to be the best-performing alternative as it is naturally occurring, chemically inactive and non-toxic, which makes it easy to source and process and unlikely to result in long-term negative impacts.
Eliminating Plastic Waste
The research team also adds, however, that the 'best' alternative relies on the context. For instance, titanium dioxide used in toothpaste has a comparatively high effect on the environment—yet it is also used in sunscreens where alternatives might not offer the same health benefit of avoiding skin cancers.
The ban on microbeads was largely driven by concern about the long-term impacts on marine ecosystems. We instead looked for the potentially hidden environmental costs of alternatives. This approach could be replicated in other areas looking to eliminate plastic waste and pollution, such as packaging alternatives using plant-derived materials or biodegradable plastics.
Claire Hunt, Study First Author, Centre for Environmental Policy, Imperial College London
Hunt, C. F., et al. (2020) Evaluating alternatives to plastic microbeads in cosmetics. Nature Sustainability. doi.org/10.1038/s41893-020-00651-w.