This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New international best practice guidance, co-written at ANSTO, sets out how to measure where nanoparticles like titanium dioxide end up in the body and how long they remain. The guidance has been shared by the Organization for Economic Co-operation and Development (OECD), a forum and knowledge hub for data, analysis and best practices in public policy.
Scientists have well-established ways to measure how a dissolved chemical is absorbed, distributed and cleared by the body. The OECD test guideline for those studies was first adopted in 2010. It was written for chemicals that dissolve and states that it is not intended for nanomaterials.
Poorly soluble nanoparticles are harder to follow. Once they reach the bloodstream, many are rapidly taken up by immune cells that clear foreign material, so very little ever shows up in a blood sample. The nanoparticles collect in a few organs, mainly the liver, spleen, lungs and lymph nodes, and can stay there for months or longer.
The OECD has now published guidance on how to test the safety of nanoparticles that enter our bodies. Its Guidance Document on Toxicokinetics to accommodate Testing of (Nano)particles sets out how researchers should design, conduct and report studies of nanoparticles that are swallowed or inhaled. Paul Callaghan was part of the core expert group that wrote it and the only member from the Southern Hemisphere.
Titanium dioxide, a white pigment used in food for decades, is a good example of why guidance was needed. When it is used as a food additive, we absorb very little of what we swallow, probably no more than 0.5%, according to the European Food Safety Authority (EFSA). Even so, the nanoparticles have been detected in human liver and spleen, and working out how quickly they leave the body has proved difficult.
Any assessment of whether a nanoparticle like this is safe depends on knowing where it goes in the body, how much builds up and how long it stays. Animal studies of three kinds of nanoparticles humans are commonly exposed to—containing titanium, cerium and silica—show how variable clearance can be. Two studies injected the same 21-nanometer particles and came up with very different half-times, the time it takes for the amount in the liver to fall by half.
Extract — continue reading at the source.
