Exposure of communities (block groups)
Population exposure to pollutants emitted by MSWIs was
estimated only as a function of the geographic zone of res-idence. The immission estimate assigned to each of the
2270 communities was the median of all receptor esti-mates located in each block group (the mean block group
surface was 9.45 km2, corresponding on average to 231
receptors). When a community was under the plume of
several MSWIs, the exposure index was defined as the sum
of the estimated indexes of each. We calculated two differ-ent exposure indexes for each community, according to
different hypotheses about the mode of exposure: (1) the
immission estimate alone represented exposure from
inhalation only (expressed in ng/m3); (2) this score was
transformed to account for the number of years the plant