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Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation

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Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation

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Polypropylene-based products are commonly used for food preparation and storage, but their capacity to release microplastics is poorly understood. We investigated the potential exposure of infants to microplastics from consuming formula prepared in polypropylene (PP) infant feeding bottles (IFBs). Here, we show that PP IFBs release microplastics with values as high as 16,200,000 particles per litre. Scenario studies showed that PP IFB sterilization and exposure to high-temperature water significantly increase microplastic release. A 21-d test of PP IFBs showed periodic fluctuations in microplastic release. To estimate the potential global exposure to infants up to 12 months old, we surveyed 48 regions, finding values ranging from 14,600– 4,550,000 particles per capita per day, depending on the region. We demonstrate that infant exposure to microplastics is higher than was previously recognized due to the prevalence of PP-based products used in formula preparation and highlight an urgent need to assess whether exposure to microplastics at these levels poses a risk to infant health.
IFB sample preparation and establishment and validation of the MP analysis protocol a, Schematic of IFB sample preparation. b–e, Identification and mapping of PP MPs. b, Optical microscope image of particles released from IFBs using a 100× microscope objective. c, Raman mapping of the same region obtained using the PP Raman bands at 2,830–2,870 cm⁻¹. The colour scale bar indicates the intensity of the integrated spectral band in arbitrary units. d, AFM image of the same region to determine the morphology of released MPs. The colour scale bar indicates the height of MPs. e, Three-dimensional (3D) AFM topographic image. f, MPs per litre as determined by the third party versus our laboratory. IFB product 1 was used in this test (n = 5 independent bottles for each laboratory test; P = 0.66). g, MPs released from PP IFBs using tap water versus deionized water. For the control samples, no PP MPs were found when using tap water (n = 5 independent bottles of products 1 and 2 (P1 and P2, respectively) in both the tap water and deionized water tests). The P values obtained using products 1 and 2 were 0.13 and 0.18, respectively. h, Raman spectra of PP MPs, formula particles and the filter background. i, MPs released from PP IFBs using formula versus deionized water. For the control samples, the PP IFBs were replaced by a glass beaker and the same procedure was followed for formula and deionized water sample preparation. For the control samples, no PP MPs were found when using formula while only very small amounts of MPs were found in the deionized water, which was probably due to the plastic tubing used in the deionized water-making process (n = 5 independent bottles of products 1 and 2 were used in the formula and deionized water tests). The P values obtained using products 1 and 2 were 0.89 and 0.96, respectively. In f–i, statistical significance was determined by two-sided t-test with a confidence interval of 95% (for details, see Methods). The black horizontal lines and x marks in the box plots represent the median and mean values, respectively, the boxes represent the 25th to 75th percentile, and the whiskers represent the range of data. Source data
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Articles
https://doi.org/10.1038/s43016-020-00171-y
1AMBER Research Centre and Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin, Ireland.
2Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Dublin, Ireland. 3TrinityHaus, Trinity College Dublin, Dublin, Ireland.
4School of Chemistry, Trinity College Dublin, Dublin, Ireland. 5BiOrbic Bioeconomy SFI Research Centre, University College Dublin, Dublin, Ireland.
6These authors contributed equally: Dunzhu Li, Yunhong Shi. e-mail: jjwang@tcd.ie; jboland@tcd.ie; liwen.xiao@tcd.ie
Microplastics (MPs) are a global concern15 due to their
potential risk to human health69. The estimated MP con-
sumption via food chain and inhalation pathways ranges
from 74,000–211,000 particles annually in the United States10 and
MPs have been detected in human stools11. Exposure to MPs can
induce gut microbiota dysbiosis and lipid metabolism disorder in
mice12,13 and sub-micrometre MPs can penetrate the fish blood–
brain barrier, inducing brain damage and behavioural disorders14.
Research on MPs has focused on major food and water sources
(for example, fish) and the potential transfer of MPs from the ocean
to humans through the food chain10, but little is known about the
direct release of MPs from plastic products. Two specific products
with plastic containers (polyethylene terephthalate (PET) water bot-
tles and PET/nylon teabags1518) were found to release high levels of
MPs under daily use conditions. Polypropylene (PP) MPs accounted
for 62.8% of all MPs detected in adult stools, but the origin of these
MPs is unknown11. The annual production of PP accounts for about
20% of all non-fibre plastic production19 and PP is considered to be
a safe plastic that is suitable for many applications20, such that it is
the most widely used plastic in food preparation21.
PP infant feeding bottles (IFBs) are widely used for the preparation
of infant formula. IFBs are routinely exposed to high-temperature
water and endure shaking during formula preparation procedures.
Since mechanical friction force can break down PP into MPs2225,
there is the potential for MP release from PP IFBs. To assess the
prevalence of PP IFBs, we mined IFB sales data from local leading
e-commerce sites (data from each Amazon site were mined using
the Jungle Scout platform while data from non-Amazon sites were
directly collected via the site’s web page) from 48 regions, covering
77.6% of the global population (Fig. 1). We identified that PP IFBs
in the form of PP bottles, PP accessories or both (Fig. 1a) account
for 82.5% of the global IFB market, with regional differences in
the preference for PP IFBs, accessories and non-PP products. The
balance of the market share is dominated by glass IFBs. Next, we
estimated infant MP exposure by developing a protocol to quan-
tify and characterize the PP MPs release from PP IFBs using ten
representative PP IFB products, accounting for 68.8% of the global
market (Fig. 1b). The effects of water temperature, sterilization and
repeated use over a 21-d period on the levels of MP release were
assessed. Combining the MP release data from PP IFBs with local
non-breastfeeding rates and milk intake volumes, we estimated the
exposure of 12-month-old infants to MPs in 48 regions.
Results
Sample preparation and measurement protocol. We tested
the quantity of MPs released from PP IFBs during standard for-
mula preparation steps involving World Health Organization
(WHO)-recommended26 cleaning, sterilizing and mixing tech-
niques (Fig. 2a). After thoroughly cleaning each of the brand-new
PP IFBs (products 1–10), we soaked them in 95 °C deionized water
for 5 min (cleaning and sterilizing). After air drying, we poured
70 °C deionized water (the recommended temperature for infant
formula preparation26) into the IFBs, which were then mechanically
shaken for 60 s to simulate the formula mixing process (180 r.p.m. in
a reciprocating shaker). After cooling, we filtered the water samples
from the PP IFBs using a gold-coated filter with a pore size of 0.8 µm.
The quantity and topography of the released PP MPs were deter-
mined by Raman spectroscopy and atomic force microscopy (AFM)
(see Fig. 2c,d; details in Supplementary Figs. 2 and 3 and Notes 2,
3 and 6). To confirm the reliability of this protocol (Supplementary
Figs. 4–6 and Supplementary Note 4), we first conducted a recov-
ery test employing standard polystyrene microplastic samples
Microplastic release from the degradation of
polypropylene feeding bottles during infant
formula preparation
Dunzhu Li1,2,6, Yunhong Shi2,6, Luming Yang1,2, Liwen Xiao 2,3 ✉ , Daniel K. Kehoe1, Yurii K. Gun’ko4,5,
John J. Boland 1,4 ✉ and Jing Jing Wang 1 ✉
Polypropylene-based products are commonly used for food preparation and storage, but their capacity to release microplastics
is poorly understood. We investigated the potential exposure of infants to microplastics from consuming formula prepared
in polypropylene (PP) infant feeding bottles (IFBs). Here, we show that PP IFBs release microplastics with values as high as
16,200,000 particles per litre. Scenario studies showed that PP IFB sterilization and exposure to high-temperature water sig-
nificantly increase microplastic release. A 21-d test of PP IFBs showed periodic fluctuations in microplastic release. To estimate
the potential global exposure to infants up to 12 months old, we surveyed 48 regions, finding values ranging from 14,600–
4,550,000 particles per capita per day, depending on the region. We demonstrate that infant exposure to microplastics is
higher than was previously recognized due to the prevalence of PP-based products used in formula preparation and highlight an
urgent need to assess whether exposure to microplastics at these levels poses a risk to infant health.
NATURE FOOD | VOL 1 | NOVEMBER 2020 | 746–754 | www.nature.com/natfood
746
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... The guts of aquatic organisms constitute another natural aqueous system with organic molecules that can function as solubilizers when plastic materials (micro or macro) and water encounter loci of energetic mixing (Benson, Agboola et al., 2022). Foods and drinks in plastic containers that require vigorous shaking, including baby formula in plastic bottles, often provide the necessary conditions for creation of sM&NP (Li, Shi et al., 2020). Human digestive systems may also be capable of converting the microplastics that are ingested or inhaled to sM&NP by this mechanism (Lu, Luo et al., 2019). ...
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