“Warning to pregnant women, don't use antibacterial soap! Chemicals in the products can make children fat and disrupt their development,” is the alarming, yet entirely unsupported, headline from the Mail Online.
US researchers wanted to see if pregnant mice exposed to the chemical triclocarban (TCC), previously used in a wide range of soaps and lotions due to its antibacterial properties, could be passed to offspring via the placenta or breast milk.
Researchers added TCC to the mother’s daily drinking water and looked at the short and long term development of the offspring.
They found the substance does enter the placenta and, even more so, the breast milk. Exposed offspring had smaller brains and were fatter with female offspring having particularly high fat levels.
The authors of the study say TCC is a common contaminant of wastewater, but humans don’t habitually drink wastewater, or come to that, antibacterial lotions.
Even if humans did drink similar amounts of TCC, we can’t use the findings of this study to say what the impact would be human foetuses and new-borns.
Therefore we cannot conclude from this study that using antiseptic soap while pregnant makes children fat.
Nevertheless TCC, along with a similar chemical triclosan, are already banned in the US and are also being phased out of consumer products in Europe, as we reported earlier this year.
Child obesity can be caused by lots of factors so it seems unlikely that a single chemical would make a child “fat”.
Where did the story come from?
The study was carried out by researchers from Lawrence Livermore National Laboratory, Livermore, Slippery Rock University and a Californian based bio-tech company called Bio-Rad.
The research was funded by the US Department of Energy by Lawrence Livermore National Laboratory, Laboratory Directed Research and Development (LDRD) funding and National Institutes of Health in the US.
While the actual content of the Mail’s story was accurate, ensuring readers knew the research involved mice, the headline – “Warning to pregnant women, don't use antibacterial soap!” – was misleading and arguably guilty of scaremongering.
We don’t know how much or of what substances women would need to match a comparable level of exposure to mice in this study.
What kind of research was this?
This was laboratory research in mice looking at the effects of a substance called triclocarban (TCC) on the offspring of mothers who were exposed to TCC through contaminated drinking water.
TCC is an antibacterial substance often used in products such as soap, as well as in the medical field and is said to be a common contaminant of wastewater. In mouse studies it has been shown to have detrimental effects on the hormone (endocrine) system at certain doses, along with effects on sexual organs and reproduction.
The US Food and Drug Administration (FDA) has banned TCC along with the antiseptic triclosan due to concerns around their safety. Various UK companies are reported to be phasing out their use in antibacterial products.
This type of research is useful to look at the effects that substances can have on animals, including humans, though we aren’t exactly the same as mice. Also in real life humans aren’t likely to be drinking water directly dosed with triclocarban.
What did the research involve?
Researchers wanted to see if giving pregnant mice drinking water contaminated with TCC affected the development of baby mice. This was said to be an environmentally relevant dose similar to that found in the US water supply – but it’s not clear if they’re meaning levels found in the wastewater supply rather than drinking water coming out of the tap.
Researchers looked at placental transfer (where the mother transfers oxygen and nutrients to their baby via blood), and breast milk transfer in the short-term and long-term
Transfer by placenta
To examine exposure in the womb, female mice were given TCC contaminated water from the first day of pregnancy until the 18th day of pregnancy (almost full term). Foetuses and mothers were then assessed for amount of TCC in the system using accelerator mass spectrometry (AMS). AMS is type of imaging scan that can be used to measure very small concentrations of potentially toxic compounds in the body.
Transfer by breast milk in the short-term
Mice mothers were given standard water until the offspring were born and then TCC contaminated water from the day of birth for the first 10 days of lactation.
The mice babies and mothers were then assessed using AMS analysis.
Transfer by the breast milk in the long-term
Mothers were again given contaminated water from birth for the first 10 days of lactation and then reverted to standard water. The long-term effects on mice babies and mothers were assessed, from three weeks after birth up until eight weeks after birth using AMS analysis.
Control groups not exposed to TCC contaminated water were used as a comparison for each group.
What were the basic results?
TCC was found to transfer from mother to offspring both through the placenta and through breastfeeding.
- Foetuses at 18 days gestation had 0.005% of the ingested dose per gram in their bodies. Higher concentrations were detected in the foetal tissue (0.011%) and maternal placental tissue (0.007%).
- Offspring at 10 days after birth had three times higher concentration in their body (0.015% ingested dose per gram) than the foetuses exposed during pregnancy, showing TCC transfers readily through breast milk.
- There was no significant difference in foetal weight of those exposed to TCC (through placenta) compared to controls. Those exposed through breast milk also did not differ from controls in the short-term (10 days).
- However, from day 21 to 56 post birth, those exposed to TCC through breast milk had greater weight than controls (11% higher body weight for females and 8.5% for males). However the brain weight of those in the TCC group was reduced.
- Looking at gene activity also showed that fat metabolism and energy regulation were poorer in female offspring exposed to TCC compared to controls, but not males.
How did the researchers interpret the results?
The researchers conclude that “this study represents the first report to quantify the transfer of an environmentally relevant concentration of TCC from mother to offspring in the mouse model and evaluate bio-distribution after exposure using AMS. Our findings suggest that early-life exposure to TCC may interfere with lipid metabolism and could have implications for human health”.
This experimental study in mice demonstrates the ability of TCC, a substance found in some antibacterial soaps, to transfer from mother to baby across the placenta and through breast milk. Moreover, this had signs of developmental effects on newborn mice, reducing brain size. It also increased body weight, which was associated with poorer fat metabolism in the female mice.
This research adds to the body of research suggesting that triclocarban, like the antiseptic triclosan, has potentially harmful effects and should not be used in consumer products.
However, the study was carried out on mice and they are not biologically identical to people. TCC was also given directly through daily drinking water. The dose given was said to be similar to that found in US water supplies – however, the authors did say it is a common contaminant of waste water. They didn’t say anything about levels in household drinking water supplies. Therefore it’s not completely clear from the study how relevant this dose is. The levels in US water supplies may also not be relevant to the UK setting.
Even if it is similar to our exposure – through water, soap or otherwise – the effects to human foetus and newborn development might not be as severe, if it has any effect at all.
TCC is being phased out of products. If you are pregnant or breastfeeding and are concerned about potential exposure, there are a range of soaps and other products out there that do not contain TCC.
And as we reported at the beginning of June there is evidence that washing your hands with cold water for 30 seconds is just as effective in getting rid of bacteria as antibacterial handwash.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Mail Online, 11 August 2017
Links to the science
PLOS One. Published online August 7 2017