The authors regret that: (1) the footnote (a) in Tables 4a, 5a, 4b and 5b requires an amendment due to insufficient information on the sources of RfC, and (2) the RfC values of Cd and Hg listed in Table 5a are not consistent with those in Table 4a due to an oversight. (1) The amended footnote (a) in 4a and 5a is given below: aThe inhalation reference concentration (RfC) values of Be and Hg were obtained from US EPA Integrated Risk Information System (IRIS) (www.epa.gov/iris), and that of Cd from the California EPA, the office of Environmental Health Hazard Assessment (OEHHA) (https://oehha.ca.gov). The RfC of Pb was not established by the US EPA. Instead, the US EPA Ambient Air Quality Standard set for Pb (0.15 μg/m3) was considered to be the RfC value by the authors.(2) The amended footnote (a) in 4b and 5b is given as follows: aThe unit risk factor (URF) values of As, Cd, Cr(VI), and Ni were obtained from the US EPA Integrated Risk Information System (IRIS) (www.epa.gov/iris), and those of Be, and Pb from the California EPA, the office of Environmental Health Hazard Assessment (OEHHA) (https://oehha.ca.gov). The correct RfC values (mg/m3) of Cd, and Hg included in Table 5a are 2.0 × 10− 5 (instead of 2.1 × 10− 5), and 3.0 × 10− 4 (instead of 3.2 × 10− 5), respectively as they appear in Table 4a.The authors apologize for any inconvenience caused. © 2017