Lotion in the Ocean

The benefits of applying sunscreen during a well-deserved beach holiday are widely acknowledged, but the environmental impact of these products is less well known. In addition to UV filters, commercial sunscreens contain a great variety of further ingredients, making sunscreen a complex matrix that is difficult to manage both analytically and environmentally. Now, researchers have developed a kinetic model capable of determining the behavior, variability, and contribution of metals and inorganic nutrients from sunscreens to seawater composition. We spoke to Araceli Rodríguez-Romero, one of the project leads, to find out more.

What inspired the work?

The quality of our oceans – home to rich biodiversity and invaluable natural resources – can be affected by excessive human pressures. We are well aware of many pollution contributors – plastic, microbeads, and chemical toxins to name just a few. In recent years, attention has turned towards sunscreens. Organic (oxybenzone, octinoxate) and inorganic (titanium dioxide, zinc oxide) UV filters – as well as other innumerable compounds that are incorporated into sunscreen formulations – are emerging as contaminants of aquatic ecosystems.

Policy makers need to be well informed if they are to implement strategies that protect marine environments, and drive Good Environmental Status. Hence, we wanted to develop a tool capable of modeling the release of metals and inorganic nutrients from sunscreens into marine ecosystems; understanding these risks will be critical for governments concerned with sustainable growth and development in coastal regions.

What analytical techniques did you employ?

Using inductively coupled plasma (ICP)-MS after chemical digestion, we determined the metal (aluminum, cadmium, copper, manganese, molybdenum, nickel, lead, cobalt, and titanium) and total phosphorus and silicon content of sunscreens. To determine the quantity of metals released from the sunscreen to the seawater after the experimental exposure, we pre-concentrated seawater samples using a liquid-organic extraction method before analysis – again using ICP-MS. The concentrations of inorganic nutrients in sunscreen and seawater samples were determined using colorimetric techniques in parallel.

We then modeled the data obtained from our laboratory experiments using Aspen Custom Modeler Software.

What did you uncover?

We’ve been able to explore numerous key variables describing the effects of dissolved trace metals and inorganic nutrients from sunscreen products on marine coastal waters. Release rates (from sunscreen into seawater) were greater under higher UV light conditions for all compounds, with the exception of lead. Notably, titanium and phosphorus were the most readily affected by changes in UV light. As algal blooms in oligotrophic waters such as the Mediterranean Sea are, in part, influenced by an increase of phosphorous, it is clearly of importance to understand the risks associated with sunscreens released into marine coastal ecosystems. We hope that our elemental release model might form the basis of future models that incorporate further chemical and environmental variables.

What are your next steps?

We plan to test our model using other commercial sunscreens – including those labeled as “ecofriendly.” We also want to sample coastal waters throughout the day to verify the results obtained in the lab; this will allow us to evaluate the true impact of sunscreens on marine ecosystems. At the same time, we are also working to create and promote a new network dedicated to fostering scientific collaboration between researchers working in the field, the cosmetics industry, and the public and private sectors.

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