Study Warns Hair Products May Harm Aquatic Life

A study conducted by Aarhus University has shown that hair products such as shampoo and conditioner have softening ingredients in them, which are harmful to freshwater organisms, especially small aquatic organisms such as daphnia. These softening chemicals known as polyquaterniums are commonly used within the cosmetics industry to make hair softer and easier to handle. But once the chemicals are washed off from the hair and into water bodies, they have been found to have a detrimental effect on aquatic life.

Polyquaterniums are cationic polymers that adhere to the negatively charged human hair, eliminating frizz and imparting shine. They were once thought not to be environmentally toxic since they were large molecules that were unable to penetrate living cells, a normal prerequisite for toxicity determination. This assumption was challenged by the recent research with results that even though they do not penetrate cells, the polymers are capable of inflicting injury through physically adhering on to the exterior surfaces of water organisms.

Two daphnia species, small crustaceans living in aquatic environments and essential to the food chain, were used in the study, which was published in Aquatic Toxicology, to test a variety of softening products. Daphnia eat algae and bacteria, filter water, and are fish food. The study discovered that one of the species was affected by severe mobility problems after the application of the compounds, impairing its mobility and feeding functions. The second species had fewer impacts but showed signs of disturbance.

Softening agents constitute a class of chemicals, not only used in hair care but also in other personal care products, contact lens products, and in wastewater treatment. The polymers adsorb and clean up the impurities in water as it passes through purification. While of very high utility, the research indicates that their potential effect on the environment was ignored and is bound to necessitate new regulatory interventions.

The cosmetics industry employs over 25,000 softeners globally, but few have been studied to find out how they impact the environment. Because of the difficulty involved in testing such chemicals by the research team, as they tend to stick to varying surfaces, rendering laboratory tests challenging, the researchers developed a method that mimics natural stream and lake environments to better observe how things actually turn out in the world.

Even ecolo-gically labeled products such as the Nordic Swan harbor some of these agents, which goes to illustrate the pervasiveness of their use in such products. The study recommends reformulation of the product and re-assessment of their application in water treatment plants. One of the greatest issues raised by the study is the balance between elimination of other impurities with the application of such agents and the harm brought about by the agents themselves.

While industry has started to sponsor research studies in an attempt to gain a better understanding of such effects, more extensive widespread testing needs to be conducted to aid future environmental regulation. Policymakers in the European Union are starting to realize the significance of studying chemicals that are not permeable through cell membranes but nonetheless remain environmentally harmful. Findings at Aarhus University provide the background for more extensive environmental research and possible policy development.

The study brings to light greater awareness and control of chemicals that were once thought safe through old standards. As a keystone of freshwater food webs and biodiversity, their conservation is paramount. The long-term environmental effects of such substances have yet to be fully examined, particularly with the fact that they remain ubiquitous in common consumer goods.

The entire article entitled "Acute and chronic toxicity of cationic polyquaterniums of different charge density and molecular weight to Daphnia magna and Ceriodaphnia dubia" was released in Aquatic Toxicology (2024) and may be accessed at DOI: 10.1016/j.aquatox.2024.107178.

Source: Aarhus University, Phys.org