Preliminary assessment of atmospheric methylcyclopentadienyl manganese tricarbonyl and particulate manganese in selected urban sites

Methylcyclopentadienyl manganese tricarbonyl (MMT: C(9)H(7)MnO(3)) is an organometallic additive that has been used since 1976 as an octane enhancer in Canadian unleaded gasoline. Very few studies have determined its atmospheric concentrations and only one study offers recent data on its ambient level, This preliminary study aims to assess atmospheric concentrations of MMT and respirable and total Mn (Mn(R) and Mn(T)) in selected sites, at two underground car parks and one gasoline station, related to high levels of automobile traffic. It is also an investigation of the applicability of the current analytical method. In total, 34 air samples were collected using a Gil-Air portable pump during 4 consecutive days and then were analyzed by neutron activation analysis. The concentrations vary between 40 and 104 ng/m(3) for Mn(R), 146 and 204 ng/m(3) for Mn(T), and 6 and 128 ng/m(3) for MMT (including ultrafine particulates, Mn(UF)). Of the 12 Mn(R) results, 7 showed concentrations greater than the U.S. EPA reference concentration (RfC = 50 ng/m(3)). The ratios of Mn(R) to Mn(T) varied from 0.20 to 0.65 with a mean of 0.38. The results for MMT and Mn(UF) raise serious doubts about the specificity of the sampling and chemical analysis methodology proposed by the Occupational Safety and Health Administration (OSHA) for MMT in air.