Tiny particles used in sunscreens and other consumer products may harm marine creatures by disabling the defense mechanisms that protect their embryos, according to a new study.

Small amounts of microscopic metals in some sunscreens, toothpastes, cosmetics, and boat paints can alter the cells of sea life in ways that make the animals more vulnerable to damage inflicted by other toxic pollutants, according to the study published in the journal Environmental Science and Toxicology.

The findings add to growing evidence that nanomaterials—which are 100,000 times smaller than a human hair—sometimes affect plants and animals in unexpected ways. Previous research has shown that nano-zinc, nano-copper, and other metal nanoparticles widely used in consumer products can harm tiny marine worms, crustaceans, algae, fish,