Is Zinc Oxide Reef Friendly and Safe? Safety Data Sheets say “NO”: “Very toxic to Marine and Aquatic Life”

Is Coral Isles Really Reef Safe?  

Are Avobenzone and Octocrylene Reef Safe?

Is Zinc Oxide reef friendly?

What is Reef Safe anyway? (PART ONE: ZINC OXIDE)

Great questions.

This post was going to be about the benefits of both zinc oxide and avobenzone/ octocrylene.

However, when I started digging, I was left with more questions than answers myself, and I ended up going a LOT deeper into what Zinc Oxide really is.

Sunscreens typically boast that they have “mineral zinc” in their formulas.

First of all, it is Zinc Oxide, not Zinc, that you are putting on your skin.

Secondly, if it were truly the mineral Zinc Oxide, you would be rubbing this on your skin:

Wikipedia pic zinc oxide(image via Wikipedia)

Which leads us to:

How is Zinc Oxide in sunscreens made?

From my understanding, Zinc Oxide either has to be broken down through chemical means, or created synthetically. Neither of these is very natural.

  • From KenySYS: “About sunscreens labeled natural and the use of Titanium and Zinc Oxide – common alternatives to chemical sunscreens:

Titanium Dioxide & Zinc Oxide can be considered natural…in the sense they are mined from the earth. But crude Ti & Zn ores have to be purified via chemical & physical processes into pure mineral that are used in sunscreens. There is no amount of hammering you can do to make the minerals small enough to put into a cream. As for “chemical free”, there is simply no such thing once you understand that Zinc & Titanium need to be processed…”

  • And, from EWG: “There is good evidence that little if any zinc or titanium particles penetrate the skin to reach living tissues. Thus, mineral sunscreens tend to rate better than chemical sunscreens in the EWG sunscreen database. However, it is important that manufacturers use forms of minerals that are coated with inert chemicals to reduce photoactivity. If they don’t, users could suffer skin damage. To date, no such problems have been reported. The FDA should set guidelines and place restrictions on zinc and titanium in sunscreens to minimize the risks to sunscreen users and maximize these products’ sun protection.”
  • From Badger Balm: “Zinc oxide is the metal zinc that has been oxidized. The chemical formula is ZnO, 1 zinc atom and 1 oxygen atom held together by an ionic bond. Zinc oxide does occur in nature as the mineral zincite, but it is quite rare and commercially unavailable. Badger’s zinc oxide is manufactured using mined zinc which is then purified into pharmaceutical grade zinc oxide.”

Because of this, I wanted to know more about Zinc Oxide and its origins, so I went to Wikipedia and had my MIND BLOWN.

Down at the very bottom of the article I saw this:

“Zinc Oxide is toxic to aquatic life”

Zinc Oxide Wikipedia

WHAT?! The ONE ingredient that companies all over the US are saying is best to help preserve the reefs? I was disturbed. So, I started with the Wikipedia footnote sources and came across these official websites saying the same thing:


“Very toxic to Marine Life with Long-Lasting Effects”

Zinc Oxide 1


“The substance is very toxic to aquatic organisms. The substance may cause long-term effects in the aquatic environment. It is strongly advised not to let the chemical enter into the environment.”

Sinc Oxide 3


“EC Risk Classification: N – Dangerous for the environment: R50, R53”

Zinc Oxide 3Zinc Oxide 3.5



4.1A hazardous to the aquatic environment – acute hazard (Aquatic Acute 1) H400

4.1C hazardous to the aquatic environment – chronic hazard (Aquatic Chronic 1) H410

Precautionary statements – prevention: P273 Avoid release to the environment.

Keep away from drains, surface and ground water. Retain contaminated washing water and dispose of it. Environmental hazards yes (hazardous to the aquatic environment)

Zinc oxide 5Sinc oxide 6


GHS09 Environment

Aquatic Acute 1 H400 Very toxic to aquatic life.

Aquatic Chronic 1 H410 Very toxic to aquatic life with long lasting effects

It goes on and on.

The big thing that Zinc Oxide and Mineral companies like to say over and over is “non-nano”. We have had a conversation recently with a leader in the industry who that noted that yes, nano is bad. And currently, the non-nano coatings that are applied to Zinc Oxide and Titanium DiOxide are not always water-resistant, so they come off in the water, leaving Zinc Oxide exposed. Some even say that they are “uncoated” (not only is this bad for the ocean but remember EWG’s warning above: “it is important that manufacturers use forms of minerals that are coated with inert chemicals to reduce photoactivity. If they don’t, users could suffer skin damage.”). Zinc Oxide is insoluble in water; this means is it incapable of being dissolved. Because of this, it is not biodegradable. But it’s okay, because the zinc oxide will just settle on the seafloor, right? It’s natural, right?

  • From Badger Balms’s website: “It is a powdered mineral that does not dissolve in seawater and instead becomes part of the seafloor sediment… Additionally, zinc oxide can be photo-reactive, meaning that UV exposure can generate reactive oxygen species, or free radicals, which can damage living cells. This too is not a concern with the zinc oxide in our sunscreens because: The rate of reactivity is still very low compared to that of titanium dioxide, nanoparticle zinc oxide, and many other chemical sunscreen actives”

My question is: if the coatings come off in the water, and the zinc stays/ settles there on the seafloor, aren’t we killing the fish and plankton because Zinc Oxide is toxic to marine life? Not to mention, sunscreens with Zinc Oxide are thick and goopy, making your skin white. Imagine that floating around in the water, blanketing the marine life and reefs present…

One of our employees had taken these pictures on vacation in Hawaii:

This seems to be right: according to the several sources above, the sign needed when transporting or using Zinc Oxide is this one, signaling “Environmental Hazard”:

Zinc oxide 4

Zinc Oxide, as long as it is NOT IN POWDERED FORM (please do not buy or use spray zinc oxide/ mineral sunscreens, inhalation is very bad for your lungs), is fine for humans. In fact, according to Wikipedia, some companies even put it in human food. It has been used for years in medicines and ointments. It has broad spectrum sunscreen coverage. But over and over again on multiple chemical fact sheet websites is the warning: “Do Not Expose to the Environment” – Moderate to severe long-term damage noted in fish and marine life.

If Zinc is not to be used near marine life, it at least should provide great coverage, right?

Wrong: even through it is Broad-Spectrum, Consumer Reports has shown year over year that the SPF on the labelling is very often incorrect, resulting in more exposure to UV rays than chemical sunscreens.

“In our tests over the years, so-called natural or mineral sunscreens—those that contain only titanium dioxide, zinc oxide, or both as active ingredients—have tended to perform less well than those that have chemical active ingredients, such as avobenzone. None of the mineral sunscreens in our tests this year did well enough to make our list of recommendations.”

If you’re not protecting the reefs with mineral sunscreen, and you’re not protecting your skin, what are you doing?

I am left wondering several things, like what happens when Zinc Oxide sunscreen is exposed to Seawater? How do the non-nano coatings really hold up in the ocean? Why do some companies brag that their Zinc Oxide is uncoated? Is Zinc Oxide really reef-friendly? Why is Zinc Oxide so toxic and harmful to marine life – is it because of its antifungal properties?

Also, why is it so expensive compared to its chemical counterparts – so much so that daily-use is really just not feasible for most people?

I still have a lot of research to do, but I was shocked at what I uncovered this time around. I have reached out to some mineral sunscreen companies and will let you know their responses.

Dig around for yourself, and please let me know in the comments what you find! Next we will cover Avobenzone and Octocrylene.


More general Zinc Oxide (ZnO) facts from Wikipedia:

  • From Wikipedia: Zinc Oxide reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate.
    • Oleate- Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. The principal use of oleic acid is as a component in many foods, in the form of its triglycerides. It is a component of the normal human diet as a part of animal fats and vegetable oils.
    • Stearate- Stearates are the salts and esters of stearic acid. As its ester, stearic acid is one of the most common saturated fatty acids found in nature following palmitic acid.
  • ZnO forms cement-like products when mixed with a strong aqueous solution of zinc chloride and these are best described as zinc hydroxy chlorides.
  • Ordinary white powdered zinc oxide can be produced in the laboratory by electrolyzing a solution of sodium bicarbonate with a zinc anode. Zinc hydroxide and hydrogen gas are produced. The zinc hydroxide upon heating decomposes to zinc oxide.
  • The applications of zinc oxide powder are numerous. Most applications exploit the reactivity of the oxide as a precursor to other zinc compounds. For material science applications, zinc oxide has high refractive index, high thermal conductivity, binding, antibacterial and UV-protection properties.
  • Reflecting the basic properties of ZnO, fine particles of the oxide have deodorizing and antibacterial properties and for that reason are added into materials including cotton fabric, rubber, oral care products, and food packaging.
  • Zinc oxide is widely used to treat a variety of skin conditions, including dermatitis, itching due to eczema, diaper rash and acne.
  • Zinc oxide can be used in ointments, creams, and lotions to protect against sunburn and other damage to the skin caused by ultraviolet light (see sunscreen). It is the broadest spectrum UVA and UVB absorber[66][67] that is approved for use as a sunscreen by the U.S. Food and Drug Administration (FDA),[68] and is completely photostable.[69] When used as an ingredient in sunscreen, zinc oxide blocks both UVA (320–400 nm) and UVB (280–320 nm) rays of ultraviolet light. Zinc oxide and the other most common physical sunscreen, titanium dioxide, are considered to be nonirritating, nonallergenic, and non-comedogenic.[70] Zinc from zinc oxide is, however, slightly absorbed into the skin.[71]
  • Micronized and nano-scale zinc oxide and titanium dioxide provide strong protection against UVA and UVB ultraviolet radiation, and are used in suntan lotion,[82] and also in UV-blocking sunglasses for use in space and for protection when welding, following research by scientists at Jet Propulsion Laboratory (JPL).[83]
  • Zinc oxide is added to many food products, including breakfast cereals, as a source of zinc,[77] a necessary nutrient.
  • Zinc oxide can react violently with aluminium and magnesium powders, with chlorinated rubber and linseed oil on heating causing fire and explosion hazard.
  • As a food additive, zinc oxide is on the U.S. FDA’s list of generally recognized as safe, or GRAS, substances.[106]
  • Zinc oxide itself is non-toxic; however it is hazardous to inhale zinc oxide fumes, as generated when zinc or zinc alloys are melted and oxidized at high temperature. This problem occurs while melting brass because the melting point of brass is close to the boiling point of zinc.[107] Exposure to zinc oxide in the air, which also occurs while welding galvanized (zinc plated) steel, can result in a nervous malady called metal fume fever. For this reason, typically galvanized steel is not welded, or the zinc is removed first.[108]
  • Zinc Oxide is toxic to aquatic life [109]

This post was written by Emily. She joined Coral Isles in December 2017 and wants to know more about the chemicals involved in sunscreen. She had a reef-themed bedroom growing up, still loves the ocean, and wants to find the best way to help preserve that delicate ecosystem, in addition to being knowledgeable about skin cancer prevention. Please join her on her journey to find out the truth!

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