While concerns have been raised about the safety of nano-zinc, current government advice is that there is insufficient evidence for it to be considered dangerous.

Now a new study reported on the ABC has suggested that when nano-zinc is mixed with surfactants — a common class of chemical found in detergents, shampoos, and pharmaceutical products — the combined effect can be more toxic than nano-zinc alone.

Louise Sales, nano-campaigner at environment group Friends of the Earth said the study sounds a warning. “Many studies looking at the toxicity of nanomaterials such as nano zinc oxide look at these substances in isolation and don’t reflect real life conditions,” she said. “Although the study is largely theoretical it highlights the importance of looking at the ways nanomaterials interact with other substances when assessing their toxicity.”