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People advised to keep using sunscreen, even though it may be absorbed through skin

Wednesday 22 January 2020

"Sunscreens leach up to 360 times more toxic chemicals into the blood than the FDA allows, raising risks for liver and kidney failure," reports the Mail Online.

Researchers from the US Food and Drug Administration (FDA) tested the absorption of 6 ingredients used in 4 different types of chemical-based sunscreen, into the bloodstream of 48 volunteers. Levels of absorption for the ingredients are measured in nanograms (one thousand-millionth of a gram) of chemical per millilitre of blood (per ng/ml)

The sunscreens were applied up to 4 times a day for 4 days.

The test was intended to help the FDA decide if more safety testing is needed on chemical sunscreens. Below the level of 0.5 ng/ml the FDA could waive the demand for further safety testing. However, all the ingredients tested had a higher level than that after a single application.

The researchers stressed that people should not stop using sunscreen, which helps protect against skin cancer. The FDA would like more safety testing done on 12 ingredients in sunscreen, including the 6 tested in this study. Despite the headline, there is currently no information to say that suncreens are harmful to humans in the levels absorbed.

Find out more about sunscreen and staying safe in the sun.

Where did the story come from?

The researchers who carried out the study were from the FDA and Spaulding Clinical Research. The study was funded by the FDA and published in the peer-reviewed Journal of the American Medical Association.

The report in the Mail Online is unnecessarily alarming and had a misleading headline. The FDA threshold of 0.5ng/ml does not show if an ingredient is either unsafe or safe. It helps the FDA decide if they need to do more safety testing. If it's below the threshold they might not do any more safety testing. And despite describing the chemicals as "toxic" in the headline, the report goes on to say "The FDA and American Academy of Dermatology stresses the chemicals are safe."

What kind of research was this?

This was a randomised controlled trial. It compared the absorption of the 6 ingredients in 4 different types of sunscreen. Randomised controlled trials are good ways to compare the effects of different treatments or interventions. The trial only looked at the level of absorption of active ingredients, not at whether the ingredients caused any harm.

What did the research involve?

The researchers recruited 48 healthy volunteers who stayed at the research clinic for 7 days. They included equal numbers of men and women, and people from different ethnic groups (48% black or African American, 48% white, 2% Asian, 2% unknown).

The volunteers were randomly assigned to 4 groups to test the 4 different types of sunscreen:

  • lotion – containing the ingredients avobenzone, oxybenzone and octocrylene
  • aerosol spray – containing the ingredients avobenzone, oxybenzone, octocrylene, homosalate and octisalate
  • non-aerosol spray – containing the ingredients avobenzone, octocrylene, homosalate, octisalate and octinoxate
  • pump spray – containing the ingredients avobenzone, homosalate, octisalate and octinoxate

Researchers applied sunscreen to the participants, to ensure the recommended amount was applied. They covered 75% of the volunteers' bodies with 2mg of sunscreen per cm of skin.

Sunscreen was applied:

  • once on day 1
  • 4 times on days 2 to 4, at 2-hour intervals

Volunteers had 34 blood samples taken, over 21 days from day 1. Researchers tested the blood samples for the levels of 6 chemical ingredients:

  • avobenzone
  • oxybenzone
  • octocrylene
  • homosalate
  • octisalate
  • octinoxate

Their main focus was to check the maximum level of the ingredient avobenzone over 21 days.

What were the basic results?

The maximum level of avobenzone was 7.1ng/ml, in the group of volunteers using sunscreen lotion. Concentrations were lower for sprays (3.5ng/ml) and pumps (3.3ng/ml) although all maximum concentrations were higher than the FDA threshold of 0.5ng/ml.

The maximum concentrations were higher than 0.5ng/ml for all the chemical ingredients tested, and this threshold was reached after a single application. The sunscreen lotion resulted in an avobenzone level of 1.6ng/ml after the first application on day 1.

The avobenzone levels peaked around day 4 and dropped below the 0.5ng/ml threshold by day 21 for most participants.

Nobody had a serious reaction to the sunscreen, although 14 people had a rash.

How did the researchers interpret the results?

The researchers said: "all of the 6 tested active ingredients administered in 4 different sunscreen formulations were [absorbed into the body] and had [blood] concentrations that surpassed the FDA threshold for potentially waiving some of the additional safety studies for sunscreens".

They added: "These findings do not indicate that individuals should refrain from the use of sunscreen."

Conclusion

The headline warning of "toxic chemicals" that "leach" into the blood is unnecessarily alarming. The study is useful for scientists setting standards for safety testing of sunscreens. It tells them how much of the ingredients are absorbed by the skin into the body in different types. It does not tell us anything about whether this absorption is harmful.

The study has some limitations. It was conducted indoors, to make the results less variable. So we do not know if these are the concentrations you might have if you wear sunscreen outside in different weather conditions. It was too small to assess the differences between types of sunscreen (such as lotion or spray) or skin type. The differences between lotion and spray found in the study should be treated with caution.

Most importantly, keeping safe in the sun is important. Sunburn is painful and damages the skin. Exposure to ultraviolet light from the sun is the major cause of skin cancer and sunscreen protects bare skin against this.

These tips can help you keep safe when the sun is strong (between March and October in the UK):

  • spend time in the shade between 11am and 3pm
  • make sure you never burn
  • cover up with suitable clothing and sunglasses
  • take extra care with children
  • use at least factor 30 sunscreen

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Sunscreens leach up to 360 times more toxic chemicals into the blood than the FDA allows, raising risks for liver and kidney failure, study finds.

Mail Online, 21 January 2020

Links to the science

Matta MK, Florian J, Zusterzeel R, et al.

Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients A Randomized Clinical Trial

Journal of the American Medical Association. Published online 21 January 2020