Particles smaller than 100 nanometers are marginally more toxic to colon cells than conventional-sized zinc oxide particles, the report in the ACS’ Chemical Research in Toxicology states, documenting a study conducted at the University of Utah.
“Manufactured nanoparticles are being marketed as having unique properties due to their size, shape, surface area, and composition as compared to bulk material, but there remains concerns regarding toxicities associated with these novel materials,” the report states.
The team of six researchers led by Philip Moos also found that solid zinc oxide was more toxic than equivalent amounts of soluble zinc and that direct particle-to-cell contact was required to cause cell death.
Eating nano sunscreen endangers colon cells
Direct contact with colon cells is likely to be triggered even if a small amount of zinc oxide nanoparticle containing sunscreen is inadvertently consumed orally.
The scientists said their report particularly flags up the dangers of children eating sunscreen containing zinc oxide nanoparticles, particularly as smaller infants often experiment by orally testing all kinds of substances as part of their development process.
“Unintended exposure to nano-sized zinc oxide from children accidentally eating sunscreen products is a typical public concern, motivating the study of the effects of nanomaterials in the colon,” the report states.
The scientist’s experiments compared the effect of conventional zinc oxide powder on a culture of colon cells compared to the effect from a zinc oxide nanoparticle formulation.
Nano formula had twice the toxicity
This procedure found that the nanoparticle formulation was twice as toxic to the colon cells as that of the formulation with the larger cells.
Likewise, the experiments also concluded that the concentration of nanoparticles that were toxic to the colon cells was the equivalent of eating 2 grams of sunscreen, an amount that would normally provide enough sun protection for the face.
The scientists say that the next stage of the research will be to take the experiments beyond cell cultures to discover the effects of zinc nanoparticle toxicity on both laboratory animals and humans.