Polyethylene microplastics shows no “significant toxicity” in aquatic life, yet researchers flag environmental persistence

10 Oct 2023 --- A new study compares the ecotoxicity of microplastic polyethylene (PE) and naturally sourced microcrystalline cellulose microbeads, both extracted from cosmetic products. The research investigates the influence of the two types of particles on aquatic plants, including common duckweed and planktonic crustacean, alongside the bioadhesion of the particles to common duckweed.

Microbeads made from plastics are added to cosmetic products to add an abrasive texture to scrub the skin. These beads, after application, are washed down the drain, allowing microplastics to leak into the world’s waterways. 

However, there is a shift in the industry due to this micro-plastic pollution. Many companies have replaced microplastics with natural particles, such as microcrystalline cellulose. Although natural particles are considered more environmentally friendly, their ecotoxicological profile is unknown. 

No significant damage
The results revealed no significant effects of either particle on common duckweed’s specific growth rate, root length and chlorophyll content. The bioadhesion of both types of particles to the plant biomass was comparable.

Microplastic beads are commonly found in face scrubs.No significant effects were observed on planktonic crustaceans’ mobility and body length. Thus, the investigated PE and cellulose microbeads showed no significant toxic effects on the tested organisms.

Despite the lack of evidence to suggest that microplastics harm the investigated organisms, the scientists indicate that due to the persistence of PE in the environment, the use of PE microbeads in cosmetics and personal care products should be avoided.

These particles have been used as cleansing or exfoliating agents in shower gels, toothpaste and nail polishes. They are made from various polymers, most commonly from PE, polypropylene, polyethylene terephthalate, polymethyl methacrylate, nylons and polyurethanes.

Microplastic hesitation
After use, microbeads are released into the sewage system through wastewater and enter a wastewater treatment plant (WWTP). The removal efficiency depends on the type and design of a WWTP, but even with a high removal efficiency, many microbeads can still enter the environment.

The scientists assert that the personal care and cosmetic industry uses various polymers as essential ingredients. They can be divided into synthetic, semi-synthetic and natural polymers.

Due to the ubiquitous presence of microplastics in the environment, manufacturers have begun to replace synthetic polymers with semi-synthetic ones, such as microcrystalline cellulose.

“This replacement is desirable according to eco-friendliness. On the other hand, they can still achieve the same cleaning efficiency as particles made from synthetic polymers,” says the report. 

The researchers continue that the cellulose beads are readily degradable, whereas PE is persistent, and its degradation lasts for decades.

PE also has several direct and indirect adverse effects on the environment. For example, PE in the soil increases the mobility of organic contaminants, alters soil properties such as aggregation and pore size, subsequently increasing water evaporation, fosters microbial growth in lakes and affects microbial activity in sediment.

Therefore, the scientists conclude that the personal care industry should minimize the release of PE into the natural environment.

By Sabine Waldeck