EXPOSURE OF TAXI DRIVERS AND OFFICE WORKERS TO TOTAL AND RESPIRABLE MANGANESE IN AN URBAN-ENVIRONMENT

This research measured the exposure of two groups of workers to respir able and total manganese (Mn) and characterized the Mn particles emitt ed from an automobile tailpipe. The exposure of 20 office workers and 9 taxi drivers in Toronto to total airborne Mn and respirable Mn was m easured over a 7-day period, 24 hours per day. Subjects were asked to wear two pumps (one included a size-selective cyclone that collected t he respirable particles), and two battery chargers were supplied to ea ch person so that the pump batteries could be recharged overnight whil e sampling continued. All filters were analyzed by neutron activation. In addition, Mn particles emitted from a car were collected directly at the exhaust. Particles were observed using secondary electron image s in a scanning electron microscope (SEM), and their elemental composi tion was determined by energy dispersive x-ray spectrometry. The Mn co ncentrations obtained for the group of office workers ranged from 0.00 1 to 0.034 mu g/m(3) for respirable Mn and from 0.002 to 0.044 mu g/m( 3) for total Mn. For the taxi drivers the Mn concentrations ranged fro m 0.007 to 0.032 mu g/m(3) for respirable Mn and from 0.008 to 0.073 m u g/m(3) for total Mn. There was a significant difference (p<0.05) bet ween the two groups for both respirable and total Mn. SEM analysis sho wed that the particles were mostly heterogeneous agglomerates varying from 1 to 100 microns. Even if the specific exposure to Mn from automo biles has not been directly established, these results suggest that th e related increase of exposure may be limited.