Microplastics in the Olfactory Bulb of the Human Brain.
Level 4 - case-series / case-control
Post-mortem case series analyzing human tissue specimens
PubMed 39283733 · doi:10.1001/jamanetworkopen.2024.40018
What was done
Researchers conducted a cross-sectional case series analyzing olfactory bulb tissue collected during routine coroner autopsies from 15 adult residents of São Paulo, Brazil (residing there >5 years, without prior neurosurgical intervention). Tissues were evaluated through direct examination and digested tissue filtration using micro-Fourier transform infrared spectroscopy (μ-FTIR) to determine the presence, size, morphology, color, and polymeric composition of microplastics, alongside procedural blanks and negative controls.
What was found
Microplastics were detected in the olfactory bulbs of 8 of the 15 deceased individuals (median age 69.5 years, range 33–100; 12 males, 3 females). Across these tissues, 16 synthetic polymer items were identified (75% particles, 25% fibers). Polypropylene was the most frequent polymer (43.8%). Particle sizes ranged from 5.5 μm to 26.4 μm, and fibers had a mean length of 21.4 μm. Polymeric materials were absent in procedural blanks and negative controls.
Why it matters
This study provides direct physical evidence that microplastics can reach the human olfactory bulb, supporting the olfactory route as a potential pathway for environmental particulate matter to bypass the blood-brain barrier and enter the human brain.
Limits
The study is limited by a small sample size (15 individuals) from a single geographic urban area, with an unbalanced sex distribution (12 males, 3 females). Post-mortem cross-sectional tissue examination cannot determine airborne exposure levels, timeline of accumulation, mechanism of entry, or whether the detected particles caused neurotoxic or clinical effects.
Cited by
- context In early 2024, human brain samples were found to contain on average 0.5% plastic by weight.