A team of UK researchers have used an in vitro model to show that nanoparticles may be able to cross into the placenta. The research team, led by Margaret Saunders at St Michael’s Hospital in Bristol, UK, investigated a range of iron oxide and silica nanoparticles and concluded that they could transfer “extensively” across the placental barrier model. The results are consistent with previous animal studies that have shown placental transfer and foetal uptake of gold, radiolabelled carbon, silver, silica, titanium dioxide nanoparticles and quantum dots.

The placenta plays a key role during pregnancy by transporting nutrients to the foetus that are needed to support growth and development. Any interference with its normal function may have an adverse effect on foetal development. The authors have warned that the enhanced sensitivity of the foetus may mean that even low doses of nanoparticles may cause adverse effects.

Despite nanomaterials being widely used in consumer products there have still been very few studies looking at the interaction of nanomaterials with the placenta and the risks to foetal growth and development.

The finding that nanoparticles can cross the placenta are even more concerning when one considers a recent study which found that exposure to silver nanoparticles caused zebra fish embryos to develop with head abnormalities and no eyes. Zebra fish have been widely used as a model organism for the study of embryological development in other vertebrates including humans.

The researchers found that the silver nanoparticles stayed inside the embryos throughout their development and that embryos in earlier developmental stages were much more sensitive to the effects of the nanoparticles than later stage embryos. The results suggest that nanoparticles may disrupt important developmental processes such cell signaling and gene transcription, creating downstream effects upon embryonic development.

Other studies have shown that silver nanoparticles that are ingested or inhaled are absorbed and distributed to organs such as the liver, lungs, skin, brain, kidneys and testes. However, it is unclear in what form the silver is transmitted through and accumulated within the body i.e. whether it is present as particles, ions or complexes.

The authors of the zebra fish study concluded that silver nanoparticles behave unlike any conventional chemicals or ions. This is the same conclusion the UK Royal Society reached in 2004 – when it called for a moratorium on the use of nanomaterials in consumer products until their safety could be properly assessed. However, nearly 10 years on, our regulators have still to regulate the use of nanomaterials such as nano-silver in consumer products. Furthermore, nano-silver is being sold as a supplement, meaning that nano-silver is being directly ingested into the body.

There is clearly an urgent need for our regulators to address the risks nanomaterials pose to pregnant women.