The report, commissioned by Friends of the Earth (FoE), said seven off-the-shelf baby formula products were tested and that two — Nestle's NAN HA 1 Gold and Nature's Way Kids Smart 1 — contained "needle-shaped hydroxyapatite nanoparticles".
"It should certainly not be in infant formula," FoE's Jeremy Tager told the Sydney Morning Herald. "Babies are particularly vulnerable to food safety risks since their immune systems are still developing and often infant formula is the only food an infant receives."
FoE is calling on regulator Food Standards Australia and New Zealand (FSANZ) to recall the products and undertake further tests to ensure consumer safety.
But FSANZ has insisted the products are safe, while leading scientists have criticised FoE for creating unnecessary concern.
"FSANZ has reviewed the available information and concluded it does not contain any new evidence to suggest these products pose a risk to infant health and safety," stated the regulator.
"Carers of infants should not be alarmed by this report or concerned about the safety of these products."
FSANZ noted that hydroxyapatite is soluble in acidic environments such as the stomach, so small amounts in food are likely to dissolve to release calcium and phosphate.
"These are essential minerals that are required to be in infant formula product," it added.
Dr Ian Musgrave, a senior lecturer in the Faculty of Medicine at the University of Adelaide, said the FoE report failed to put nanoparticles in their natural biological context, or provide any significant support that particles detected in milk are engineered nanomaterials.
"Nanoparticles have become the latest boogeyman, despite nanoparticles occurring naturally," he said. "Infant formula is based on milk, which naturally contains calcium and phosphorus (as phosphates). The calcium and phosphates are in a complex balance between soluble and protein-bound forms.
No health implications
"One of the forms of calcium phosphate in milk is hydroxyapatite. So it is unsurprising that hydroxyapatite is found in dried infant formula which is predominantly dried milk powder. Experiments with drying milk have found that nanometre-sized particles of calcium phosphate form naturally.
"The health effects of hydroxyapatite nanoparticles have been studied in animals with no toxicity at levels well above those present in milk. There are no significant public health implications for the finding small crystals of naturally occurring calcium phosphates in milk-based products."
Adjunct Professor Andrew Bartholomaeus, a consultant toxicologist with appointments at the University of Canberra and the University of Queensland, said the report was "unexciting and facile".
Bartholomaeus, who was previously been the chief toxicologist for the Therapeutic Goods Administration and the general manager of the Risk Assessment Branch of FSANZ, added: "One would hope that Friends of the Earth have sufficient moral compass to not seek to exploit the natural concern of mothers for the health of their children to further their corporate objectives by scaremongering analytical findings of no special significance."