Environmental Engineering Reference
In-Depth Information
exposure area we assigned in the present investigation according to residence at the
beginning of pregnancy and 10 (21.7%) immigrated after that date into the municipal-
ity (8 towards the low-exposure area and 2 in the high-exposure area), thus suggesting
a limited mobility of the study population across the different exposure areas.
Exposure misclassifi cation might have also occurred due to additional sources
of dioxins and of heavy metals in the study area, apart from the incineration plant,
through different pathways of intake (inhalation, ingestion, and dermal contact). How-
ever, concerning the fi rst category of contaminants, in the study municipality no major
industrial sources of dioxins were located such as electric arc furnaces, cement kilns,
and copper, and aluminum smelters, while the contribution of vehicle fuel combustion
and of domestic wood burning to emissions is expected to be substantially lower that
waste incineration and more evenly distributed [26, 27], thus suggesting that waste in-
cineration was by far the major source of environmental contamination with dioxins in
the study area, in line with other observations [28, 29]. Concerning exposure to heavy
metals, fi ndings from studies examining the specifi c burden of exposure attributable
to waste incineration through measurement of biomarkers of exposure in nearby resi-
dents or occupationally-exposed workers are confl icting [30-32], and therefore the risk
of exposure misclassifi cation in our study area cannot be entirely ruled out.
Estimating if (and to which extent) exposure to the contaminants emitted by the
incinerator actually changed during the study period as a consequence of the interrup-
tion in the activity of the incinerator is not easy. Few studies examined the kinetics of
dioxins in humans, and half-life of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was
around 3 years in a Seveso population with a mean age of 24 years [33] and 7-9 years
in other selected groups of adults [34]. However, it is unclear if these indications may
be extended to dioxins and related compounds other than TCDD, “low-level” expo-
sures might be much less effi cient in the TCDD transfer to the foetus [35], and these
kinetics appear also to be markedly infl uenced by the lipid status of the individuals
[34], further complicating this issue. Overall, we estimate that the short-term interrup-
tion of waste incineration occurred in our study setting had limited effects on expo-
sure status of the local population, also considering the prolonged half-life of dioxins
in soils and in locally grown produces, and therefore we emphasize risk estimates
based on the overall follow-up period for dioxin exposure. A separate analysis for each
operation period might be more meaningful for heavy metals and for their potential
teratogenic effects, since it seems likely that interruption of plant activity markedly
decreased exposure to elements such as arsenic, lead and mercury having short half-
lives in human blood, in the order of 3-40 days [10, 36, 37].
Results of the present study must be extended with caution to other contexts and
particularly to older incinerators, to the relevant differences in amounts and types of
contaminants which may be released into the environment by these plants, owing to
the type of wastes combusted and the air pollution control technologies, as well as to
potential differences in susceptibility of the exposed individuals. Moreover, we did not
examine other reproductive issues apart from congenital anomaly risk such as altered
male-to-female birth ratio, low birth weight or twinning, and therefore our investiga-
tion cannot be considered a comprehensive assessment of reproductive health in the
exposed population.
Search WWH ::
Custom Search