« Humans may absorb trillion particles per day- Titanium dioxide particles, in food and pharmaceutical products, can cross from the gut into the bloodstream, according to a UK Medical Research Council (MRC) study, using human volunteers.
Titanium dioxide, valued for its gleaming whiteness, is commonly added to a wide range of food products, pharmaceuticals, toothpaste and chewing gum. Although some animal studies have shown that a small proportion of persistent particles migrate from the gut into the blood system, human evidence has been lacking.
For the study, eight healthy volunteers ingested capsules containing 100 mg of titanium dioxide. A team from the MRC’s Elsie Widdowson Laboratory in Cambridge, working with St Thomas’ hospital, London, then used dark field microscopy to identify titanium dioxide particles in the blood, thanks to their reflective properties.
The researchers began to spot particles in the blood two hours after ingestion, with a peak at six hours. The results confirm that persistent particles can be taken up in humans, they write in Particle and Fibre Toxicology.
Examination of surgical and post-mortem specimens has shown that engineered particles are retained for long periods in the intestines, especially in lymphoid follicles called Peyer’s patches. These patches are lined with special microfold cells that “avidly” capture small particles. The effect is similar to tattoos, where ink is held in fixed macrophages in the skin.
The researchers suggest that their recent results can be explained by early titanium dioxide absorption in the duodenum and then later Peyer’s patch uptake further along the small intestine, in the ileum.
The team estimates that adult humans may absorb a staggering one trillion titanium dioxide particles per person, per day. Lead author Jonathan Powell suspects that chance dictates whether particles end up trapped in the gut or in the blood stream.
“It’s rather like emptying a bag of table tennis balls into the Thames from Westminster Bridge,” he says.
The Cambridge work does not focus on particle size. However, a recent study commissioned by Friends of the Earth found nano-sized titanium dioxide particles in 14 popular food products.
This follows a US study, which also identified nanosized materials in food grade titanium dioxide samples. The researchers, led by Yu Yang from Arizona State University, are calling for environmental and human fate and toxicity studies to examine food grade titanium dioxide and to compare it with industrial products.
Efsa’s Scientific Panel on Food Additives and Nutrient Sources (ANS) is currently “re-evaluating” a range of food additives, including titanium dioxide.
Dr Powell and his colleagues are preparing a position paper on titanium dioxide in humans.
Following where the particles end up is “really difficult work in humans”, says Dr Powell. “Unfortunately, much of the animal work that has been reported to date is of insufficient quality to get clear signals and cannot be relied on.”
Article of Emma Davies
Journal article : http://particleandfibretoxicology.biomedcentral.com/articles/10.1186/s12989-015-0101-9
Friends of the Earth report : http://emergingtech.foe.org.au/wp-content/uploads/2015/09/FoE-Aus-Report-Final-web.pdf
Food grade titanium dioxide study (abstract) : http://pubs.acs.org/doi/abs/10.1021/es500436x
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