This summary presents noncancer health effect reference values for inhalation exposures to manganese (Mn) across all durations for both the general public and workers. The physical size of Mn-containing particles has a bearing on the toxicity and some organizations have created different reference values based on size fraction, therefore some definitions of terms regarding particle size are provided below. A detailed description of the reference values compared in this summary and the categories of reference values can be found in Section 1 of the EPA report (U.S. EPA, 2009a). In general, inhalation health effect reference values have been included which have been developed and formally reviewed by an authoritative governing body (government agency or professional association) for use in assessments of risk to support regulatory decision-making. The main exception to this inclusion criteria are the Provisional Advisory Concentration (PAC) and Temporary Emergency Exposure Level (TEEL) values for emergency response, which are the only emergency response values available for manganese compounds. Another exception is the discussion of a proposed reference value developed by Bailey et al. (2009) and reviewed by a panel convened by Toxicology Excellence for Risk Assessment (TERA, 2011); this value was not developed or endorsed by an agency or professional association which typically develops such reference values.