Toxicity of nano zinc to marine life

In response to (admittedly legitimate) comments that I didn’t understand the impact of nanozinc on marine animals, I have spent some time reviewing the scientific literature to try andunderstand the state of the science.I have relied only on peer reviewed scientific journal articles and not media reports and certainly not chat room forum comments. First, I agree that there is evidence that Oxybenzone is damaging to themarine environment and it is possible that ZnO is the lesser of two evils. However,ANO claims their nano zinc oxide is reef safe but provides no studies to back that up.All published studies show the opposite is true, that even low concentrations of nano zinc oxide particles in sunscreens have a harmful effect on phytoplankton, marine worms, crustaceans, algae, fish, mussels, coral and sea urchin embryos. I have tried to summarise some journal articles, but I would encourage anyone with an interest to go direct to the source in case I have incorporated an unconscious bias.

From Spain in 2014

The study shows that thatnanoparticles of titanium dioxide and zinc oxide in sunscreen can react withsunlight to produce hydrogen peroxide which harms phytoplankton. Phytoplankton are the basis of the entire marine food chain.

The authors theninvestigated the concentrations of hydrogen peroxide in the water at differentbathing beaches in the Mediterranean. The scientists concluded that increasedtourism – and hence increased levels of nanoparticles from sunscreen in marineenvironments – could have “important ecologicalconsequences.”

https://pubs.acs.org/doi/full/10.1021/es5020696

From the USA in 2015

Tests of toxicity of nano-ZnOon Urchins showed that nano-ZnO, even at relatively low concentrations, madedeveloping sea urchin embryos more sensitive to other chemicals, blockingtransporters that would otherwise defend them by pumping toxins out of cells. The study concluded that low concentrations of nano-ZnO can make embryos more susceptible to other contaminants, representing a potent amplification of nanomaterial-related developmental toxicity.

"When they wereexposed to these nanomaterials, even in extremely low concentrations that youwouldn't expect to have an effect, we saw all sorts of unusual patterns ofdevelopment," says study co-author Gary Cherr, interim director of theUniversity of California,

https://pubs.acs.org/doi/abs/10.1021/acs.est.5b00345

The Guardian Newspaper in 2017

The article from the mostlytalks about the impacts of Oxybenzone, but Professor Craig Downs said that “consumersshould take extra care not to use sunscreens advertising “nano” zinc oxide ortitanium oxide, saying that below 120 or just 100 nanometers is “significantlytoxic”.

https://www.theguardian.com/environment/2017/apr/28/sunscreen-damage-coral-research-oxybenzone

From Italy in2018:

Conclusion wasthat TiO₂ did not cause visible bleaching but “Uncoated nano zincoxideinduces a severe and fast coral bleaching due to the alteration of symbiosisbetween coral and zooxanthellae. ZnO also directly affects symbioticdinoflagellates”

https://www.researchgate.net/publication/325344137_Impact_of_inorganic_UV_filters_contained_in_sunscreen_products_on_tropical_stony_corals_Acropora_spp

The researchis consistent that nano zinc oxide is damaging to the reef environment butlarger particle size zinc oxide is not. It seems that the message is getting out, check out the review of “The Best Reef-Safe Sunscreens to Protect Your Skin and the Ocean This Summer” April 2019.

https://www.allure.com/gallery/coral-reef-safe-sunscreen-reviews

The focus ison not using Oxybenzone or Nano zinc but instead using non-nano zinc. Based onthe research above, it seems like a sensible approach for protecting marinelife but not one that is favourable for ANO.