Nanopolystyrene translocation and fetal deposition after acute lung exposure during late-stage pregnancy

Abstract

Background: Plastic is everywhere. It is used in food packaging, storage containers, electronics, furniture, clothing, and common single-use disposable items. Microplastic and nanoplastic particulates are formed from bulk fragmentation and disintegration of plastic pollution. Plastic particulates have recently been detected in indoor air and remote atmospheric fallout. Due to their small size, microplastic and nanoplastic particulate in the atmosphere can be inhaled and may pose a risk for human health, specifically in susceptible populations. When inhaled, nanosized particles have been shown to translocate across pulmonary cell barriers to secondary organs, including the placenta. However, the potential for maternal-to-fetal translocation of nanosized-plastic particles and the impact of nanoplastic deposition or accumulation on fetal health remain unknown. In this study we investigated whether nanopolystyrene particles can cross the placental barrier and deposit in fetal tissues after maternal pulmonary exposure.

Results: Pregnant Sprague Dawley rats were exposed to 20 nm rhodamine-labeled nanopolystyrene beads (2.64 × 10¹⁴ particles) via intratracheal instillation on gestational day (GD) 19. Twenty-four hours later on GD 20, maternal and fetal tissues were evaluated using fluorescent optical imaging. Fetal tissues were fixed for particle visualization with hyperspectral microscopy. Using isolated placental perfusion, a known concentration of nanopolystyrene was injected into the uterine artery. Maternal and fetal effluents were collected for 180 min and assessed for polystyrene particle concentration. Twenty-four hours after maternal exposure, fetal and placental weights were significantly lower (7 and 8%, respectively) compared with controls. Nanopolystyrene particles were detected in the maternal lung, heart, and spleen. Polystyrene nanoparticles were also observed in the placenta, fetal liver, lungs, heart, kidney, and brain suggesting maternal lung-to-fetal tissue nanoparticle translocation in late stage pregnancy.

Conclusion: These studies confirm that maternal pulmonary exposure to nanopolystyrene results in the translocation of plastic particles to placental and fetal tissues and renders the fetoplacental unit vulnerable to adverse effects. These data are vital to the understanding of plastic particulate toxicology and the developmental origins of health and disease.

Keywords: Fetal; Maternal; Nanoplastics; Perfusion; Polystyrene; Pregnancy; Translocation.

Fig. 1

Schematic of nanoplastic exposure and dosimetry. a We utilized a 1 mm² microparticle as a representative microplastic (blue). The extrapolation of this microplastic microparticle to a nanoparticle is 1 × 10⁶. Our representative nanopolystyrene nanobeads are spherical and 21 nm in diameter (red). Therefore, there would be 2.39 × 10¹⁴ nanopolystyrene beads in a single plastic microparticle. b Cox et al. identified that women inhale an average of 132 microplastics. The upper bound of this measurement (279 microplastics), is more representative of exposure for pregnant women. The calculated dosage is 6.67 × 10¹⁶ nanopolystyrene beads. c The surface area of the Sprague Dawley rat lung is significantly smaller (0.409 m²) compared with the human lung (62.7 m²). The calculated dose for a laboratory rat is 4.34 × 10¹⁴. The exposure dose used in these studies was 2.64 × 10¹⁴ nanopolystyrene beads

Fig. 2

Optical images of maternal and fetal tissues. Graphical representation of the optical intensities between a maternal and b fetal control and exposed tissues. n = 6–8 pregnant rats. Values are shown as mean ± SEM. Statistics were analyzed with a Student’s t-test. (*p ≤ 0.05; T ≤ 0.10)

Fig. 3

Identification and visualization of nanopolystyrene particle deposition within the fetal tissues placenta after material pulmonary exposure using enhanced hyperspectral microscopy (CytoViva, Inc.). These tissues include fetal a liver, b lung, c kidney, d heart, and e brain. n = 3 fetuses from 3 different pregnant rats. Polystyrene nanoparticles are identified as white specs within the images

Fig. 4

Identification of rhodamine-labeled nanopolystyrene bead translocation based on increased fluorescence through the a distal uterine effluent and b umbilical vein effluent over time. n = 9–24. c Time-course of fluid flow through the umbilical vein between saline (black) and nanopolystyrene (red) infused placenta. n = 6–8. Values are shown as mean ± SEM and presented as percent above baseline. Statistics were analyzed with Student’s t-test (*p ≤ 0.05; T ≤ 0.10)