Guidelines recently published by the World Health Organization offer several recommendations for protecting workers from the potential risks of manufactured nanomaterials (MNMs). The guidelines address assessment of MNM health hazards and exposure, controls, health surveillance, and training of workers. One of the 11 recommendations presented in the guidelines is to assign hazard classes to MNMs on safety data sheets according to the Globally Harmonized System of Classification and Labelling of Chemicals. This recommendation is based on the work of WHO researchers who used MNM-specific dossiers developed by the Organization for Economic Cooperation and Development to determine hazard classes for several types of nanomaterials, including fullerenes, single-walled carbon nanotubes, multi-walled carbon nanotubes, silver nanoparticles, silicon dioxide, and others. The researchers published their work on the in 2017.  The guidelines state that the “benefits of having MNMs properly classified and labelled according to their hazards . . . clearly outweigh the possible harm that the classification might be overly cautious given the lack of information about the hazards of MNMs in general.” The guidelines also caution that, in some cases, assigning GHS hazard categories to nanomaterials “could also result in underestimation of the hazard.” The guidelines also recommend a specific approach to the assessment of inhalation exposure to MNMs and note that insufficient evidence exists to develop a specific approach for dermal exposure. is available as a . A summary of WHO’s recommendations appears on the .