Pharmaceutical/food grade titanium dioxide particles are absorbed into the bloodstream of human volunteers.
BACKGROUND
Exposure to persistent engineered nano and micro particles via the oral route is well established. Animal studies have demonstrated that, once ingested, a small proportion of such particles translocate from the gastrointestinal tract to other tissues. Exposure to titanium dioxide is widespread via the oral route, but only one study has provided indirect evidence (total titanium analyses) of absorption into the blood stream in humans. We sought to replicate these observations and to provide additional evidence for particulate uptake.


RESULTS
Human volunteers with normal intestinal permeability were orally administered 100 mg pharmaceutical/food grade titanium dioxide. Blood samples were collected from 0.5 to 10 h post ingestion and analysed for the presence of reflectant bodies (particles) by dark field microscopy, and for total titanium by inductively coupled plasma mass spectrometry (ICP-MS). Blood film analyses implied early absorption of particles (2 h) with a peak maximum at 6 h following ingestion. The presence of these reflectant particles in blood roughly mirrored the levels of total titanium by ICP-MS, providing good evidence for the latter being a measure of whole particle (titanium dioxide) absorption.


CONCLUSIONS
This study shows that a fraction of pharmaceutical/food grade titanium dioxide is absorbed systemically by humans following ingestion. It confirms that at least two routes of particle uptake may exist in the human gut- one proximal and one distal. Further work should quantify human exposure and uptake of such persistent particles.
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK.
Laetitia C
LC
Pele
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK.
Vinay
V
Thoree
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK.
Sylvaine F A
SF
Bruggraber
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK.
Dagmar
D
Koller
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK.
Richard P H
RP
Thompson
Department of Gastroenterology, Guys and St Thomas' NHS Foundation Trust, St Thomas' Hospital, London, SE1 7EH, UK.
Miranda C
MC
Lomer
Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK. jonathan.powell@mrc-hnr.cam.ac.uk.
Jonathan J
JJ
Powell
D064368:Healthy Volunteers; D006801:Humans; D007408:Intestinal Absorption; D004364:Pharmaceutical Preparations; D014025:Titanium / Q000097:blood*
D004364:Pharmaceutical Preparations; C009495:titanium dioxide; D014025:Titanium