Sunscreens containing zinc oxide lose their effectiveness after 2 hours and are toxic

According to a new collaborative study between the University of Leeds, the University of Oregon, and Oregon State University, a chemical reaction involving a main ingredient, zinc oxide, means that many sunscreens will fail after two hours of sun exposure
.

Researchers are now calling for consideration of using innovative new ingredients as ultraviolet (UV) filters to help provide effective protection
.

Richard Blackburn, a professor of sustainable materials at the Leeds School of Design, led part of the research in Leeds and worked with two academic teams in Oregon, USA
.

He said that the current testing methods need to be changed
.

"Zinc oxide itself is an effective and harmless UV blocker," said Professor Blackburn
.

"Once exposed to the sun for two hours, zinc oxide destroys the UVA protection provided by other ingredients
.

There are two main types of ultraviolet light: UVA and UVB, both of which are electromagnetic radiation that can cause skin cancer
.

UVB is usually associated with direct, short-term effects, such as sunburn, while UVA can cause longer-term damage to DNA, such as wrinkles and skin aging
.

Many sunscreens include zinc oxide, which is proven to help block UV rays
.

Professor James Hutchison and University of Oregon colleague Dr.
Aurora Ginzberg co-led the research
.

“In the test, we found that zinc oxide can cause the degradation of other UV absorbers, and the protection provided by sunscreens is significantly reduced in a relatively short period of time, especially in the UVA area
.

The research team from the University of Oregon and the University of Leeds found that in sunscreens containing zinc oxide particles, the UVA protection factor was reduced by 84.
3% to 91.
8%, while the UVA protection factor of sunscreens without zinc oxide particles was two hours after UV exposure.
Only a decrease of 15.
8%
.

Professor Hutchison said: "The degradation of the UV filter will not only reduce the effectiveness of the sunscreen, but also increase the toxicity of the formulation
.

"Therefore, not only is the lack of effective UV protection a problem, but the product itself may cause harm when used in the sun
.

Zinc oxide is classified as a mineral, widely used by many brands as a "chemical-free" ingredient (although it is a chemical ingredient), and is advertised as a "natural" ingredient in many cosmetics, which is more skin-friendly
.

But Dr.
Ginzberger said the study challenges these assertions and calls for consideration of alternatives
.

She explained: "Zinc oxide particles are often combined with UV filters in mixed sunscreens or multi-layer cosmetics
.

"Therefore, in future cosmetic formulation design, the key is to consider the potential of zinc oxide to induce photodegradation of the entire formulation, or to combine products on the skin
.

"In the U.
S.
sunscreen, the loss of UVA protection is particularly problematic because there are too few filters approved for use
.

Professor Blackburn said that this research is a call for action to develop new sunscreen ingredients
.

"As an alternative, there are some very good potential candidates in nature.
They are effective UV filters, but according to current legislation, the process of obtaining regulatory approval is extremely expensive and takes many years
.

"This has proven to be an obstacle to innovation, and innovation can provide a more effective, safer, and more sustainable alternative to existing raw materials
.

For more information about this study, please read "Zinc oxide-induced changes to sunscreen ingredient efficacy and toxicity under UV irradiation" by Aurora L.
Ginzburg, Richard S.
Blackburn, Claudia Santillan, Lisa Truong, Robyn L.
Tanguay and James E.
Hutchison, 14 October 2021, Photochemical & Photobiological Sciences.

DOI: 10.