October 23, 2018

expert reaction to conference abstract that reports finding microplastics in human stools

A conference abstract being presented at United European Gastroenterology (UEG) Week reports finding microplastics in human stools.

Prof Alistair Boxall, Professor in Environmental Science, University of York, said:

“I had seen this presented as a poster at the EmCon2018 meeting in Oslo earlier this year. It is a very interesting study and highlights that humans are being exposed to microplastics in our day to day lives. There are other studies that have looked for microplastics in humans.

“I’m not at all surprised or particularly worried by these findings. Microplastics have been found in tap water, bottled water, fish and mussel tissue and even in beer. We will also be exposed to particles from house dust, food packaging materials and the use of plastic bottles. It’s therefore inevitable that at least some of these things will get into our lungs and digestive systems.

“There are some data from laboratory studies on uptake and effects on non-human animals but quite often these studies are done at very high concentrations it is therefore really hard to conclude whether there is a risk to human health or not. I think much more needs to be done with realistic exposures – this was one of the recommendations from our paper that came out last week on environmental risks of microplastics.

“This is very much a preliminary study. From my reading of the abstract, I don’t think we should jump to the conclusion that this is down to true environmental exposure (i.e. from what gets into soil, river waters and marine waters). We don’t have exact evidence from where this is coming from – it could be that most of these materials may be coming from house dust and the use of plastic containers and packaging or, for example, nylon fibres from our tumble dryer – and this could potentially outweigh the environmental routes of exposure. To truly understand the sources of exposure we need much more thorough studies where we monitor closely people’s day-to-day activities and the media they are exposed to (food, water, air). Only then will we be able to be confident on where these materials originate and, if they are found to be of concern to health, where to focus interventions.”

Dr Peter Jenkinson, Consultant Toxicologist, said:

“I suppose it is possible that the researchers have generated more data since the abstract was written but the number of plastics included in the screening is not correct (abstract says 11, press release says 10) and this should not have changed. The abstract says that only 5 samples have been analysed so far and that only 2 plastics (PS and PU) have been identified in 2 of 5 samples, but the press release says PP and PET and that microplastics have been identified in all samples. There is too little information on the methods and results to make a meaningful comment on the limitations of the study, except to say that it is very limited!

“I do not find their results surprising (assuming that they have actually detected microplastics in human stools) because we know that microplastics are endemic in the environment, in consumer products we all use, and in many different species of animals that we consume directly or indirectly, so it would be more surprising if they had NOT detected microplastics in human stools. The bigger question is whether there is an effect on health, and this paper provides no information on this point.”

Dr Stephanie Wright, Research Fellow, King’s College London, said:

“From this abstract, there isn’t evidence of microplastics in the body, but that they have been in the body and travelled through, and as such this does not show any evidence of accumulation. There are several limitations with this study, including; small sample size, whether the stool sample digestions effected/degraded microplastics and the analytical technique’s size cut-off. This research is not surprising as several studies now have documented microplastics in bottled water, in some cases up to 10521 microplastics/L.

“In reference to particular comments in the press release:

‘…every single stool sample tested positive…up to nine different plastic types were identified…six (out of 8) of them consumed sea fish.’ suggests this isn’t just a marine exposure pathway i.e. via seafood, as non-seafood consumers also tested positive. The fact that so many different polymers were measured suggests a wide range of contamination sources, although the usual culprits polypropylene (PP) and polyethylene terephthalate (PET) were most common, and these are the plastics which often comprise plastic bottles/lid counterparts, among other items.

‘…sized between 50 and 500 micrometres…’ starch particles up to 130 micrometres (um) have been documented to cross the human gut wall via a phenomenon known as persorption, however the rate of this occurring is very low i.e. rare, and whether this is true for plastics in humans is unknown. What is of concern is whether this size range reflects our true exposure, or if a smaller size fraction (<50 um) is being retained/is able to cross over the gut wall. Unfortunately, the analytical method used here is only capable of chemically identifying particles down to 20 um in size, which may explain the lower size limit reported.

‘On average, the researchers found 20 microplastic particles per 10g of stool.’  This concentration is low. It is unclear whether this is an artifact of the analytical technique missing out smaller microplastics (<20 um). What is unknown is whether the concentration going in (i.e. being ingested) is higher than that coming out due to particles crossing the gut wall.”

“’There is no published evidence to indicate what the health effects might be. It is likely that the larger particles i.e. 130-500 um are just passing through. Smaller particles could potentially cross the gut wall and redistribute to target tissues, however, for the size range reported, the rate of this happening is likely to be low. What may be of greater concern for these large microplastics, is whether any associated chemical contaminants leach off during gut passage and accumulate in tissues.”

 ‘Assessment of microplastic concentrations in human stool – Preliminary results of a prospective study’ by Schwab P et al. This is a conference talk that will be discussed at the United European Gastroenterology (UEG) Week in Vienna.

Declared interests

Prof Alastair Boxall: Prof Boxall’s latest study was funded by the Personal Care Products Council

None others received.