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Exposure estimation

Why is it so important to define an exposure assessment methodology?

In 2016, different types of professional exposures to nanoparticles concern some 2 millions of people worldwide. The compliance to the precautionary principle and the labor regulation related to dangerous products forces the employer to maintain the personnel exposure at as low a level as possible. But how can we express exposure threshold values? What are current exposure recommendation proposals?

Exposure recommendations

Tableau

Number of particles changes with density and size for the same mass concentration.

In 2011, the NIOSH proposed an exposure limit of 2,4 mg.m-3 and 0,3 mg.m-3 for the fine and ultrafine TiO2 particles (weighted values for an 10 hour period per day and 40 hours a week).

In 2008, the workgroup of the OECD on manufactured nanoparticles shows that this mass-concentration of 0.1 mg.m-3 corresponds to very different numbers of particles according to the density of the particle and its size.

The BGIA proposes more reasonably Exposure Limit Values (ELV) in number on the interval 0 - 100 nm. They recommend limit values, bases on mass concentration of 0.1 mg.m-3, for two classes of particles more or less dense and for fibers:

  • if d < 6 g.cm-3 (TiO2, ZnO, C60), ELV = 4x104 part.cm-3,
  • if d > 6 g.cm-3 (CeO2, Fe, Ag, Au), ELV = 2x104 part.cm-3,
  • carbone nanotubes, ELV = 104 part.cm-3.