S. Loranger et J. Zayed, ENVIRONMENTAL CONTAMINATION AND HUMAN EXPOSURE TO AIRBORNE TOTAL AND RESPIRABLE MANGANESE IN MONTREAL, Journal of the Air & Waste Management Association [1995], 47(9), 1997, pp. 983-989
Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organometalli
c compound used as an octane improver in unleaded gasoline. The combus
tion of MMT leads to the formation of manganese (Mn) oxides, mainly Mn
3O4. The objective of this study is to assess the variations over time
and space of respirable (Mn-R) and total (Mn-T) Mn in the urban atmos
phere and to evaluate human exposure by inhalation. Two sampling sites
were selected on the island of Montreal based on their local traffic
density (municipal botanical garden, C- = 10,000-15,000 vehicles d(-1)
; Montreal Waterworks, C+ = 100,000-130,000 vehicles d(-1)). Air sampl
ings were made during the day at stations located 10 m from the road u
sing portable pumps, some of which were equipped with a cyclone. Mn-R
and Mn-T and other metals were measured on Teflon filters by neutron a
ctivation. Mn exposure doses by inhalation were calculated using Monte
-Carlo simulations. Mn-R and Mn-T average concentrations were signific
antly higher at site C+ (Mn-R = 0.024 mu g m(-3); Mn-T = 0.050 mu g m(
-3)) than at site C- (Mn-R = 0.015 mu g m(-3); Mn-T = 0.027 mu g m(-3)
). Temporal profiles at sites C+ and site C- were similar, with a coef
ficient of correlation of 0.24 for Mn-R and 0.26 for Mn-T. Trend analy
ses (ARIMA) also showed that the period of the week (work days vs. off
days) was significantly related to Mn-R and Mn-T variations at both s
ites. The average exposure dose by inhalation to Mn-R and Mn-T ranged
from 0.001 to 0.030 mu g kg(-1) day(-1) and 0.001 to 0.05 mu g kg(-1)
day(-1). Mn-R and Mn-T concentrations reflected a positive relationshi
p with traffic density. However, it remains difficult to attribute the
se results directly to the combustion of MMT in unleaded gasoline. On
average, the Mn-R and Mn-T inhalation doses were 2 to 15 times lower t
han the reference dose (RfC) proposed by the U.S. Environmental Protec
tion Agency (EPA) for the general population.