BACKGROUND AND OBJECTIVES:
A cross-sectional biomonitoring study was carried out to investigate exposure to incinerator emission in relation to the body burden of selected biomarkers in the population living around the plant.
Approximately 500 people, aged 18-69 yrs, living within 4 km from the incinerator were randomly selected form the population register. Exposure was measured through fall-out maps of particulate matter (PM), used as tracer for incinerator emissions. Ten metabolized polycyclic aromatic hydrocarbons (PAHs), from naphthalene to chrysene, 1-hydroxypyrene and twelve metals (Cd, Cr, Cu, Hg, Ni, Pb, Ni, Zn, V, Tl, As, Sn) were measured in spot urine samples. Confounders, such as diet, smoking, traffic, occupation and personal characteristics were assessed by questionnaires and objective measurements, and included into multivariate linear regression models.
Metal concentrations in urine were in line with or higher than Italian reference limits, besides Cr and V with more than twofold concentrations. Metal levels did not show clear association to exposure categories. Most abundant PAHs were naphthalene (median 26.2 ng/L) and phenanthrene (7.4 ng/L). All PAHs, but benz[a]anthracene and 1-hydroxypyrene, were found in more than 52% of samples, and included in regression models. Significant associations between urinary PAHs and exposure were found, strong for fluorene, and weaker for naphthalene, fluoranthene and pyrene. Results were confirmed by sensitivity analyses. Correlation with variables reported in literature were observed.
The study indicates that the emissions were very low and highlights that specific urinary PAHs provided useful information about the internal dose arising from incinerator emission.
2.1 Study population and area
A cross-sectional biomonitoring study was carried out in the winter season 2012/2013 (November to
March) in Modena, Italy, a medium-sized town of 180,000 residents in the Po Valley characterized
by a flat topography and meteorological conditions which favor pollutant accumulation.
A municipal solid waste incinerator has been operating since 1980 in the industrial/rural area of
Modena, north-west of the town center.
2.3 Exposure to SWI pollutants
Exposure assessment was performed at address level, using fall-out maps of PM10 emitted by the
plant. This represents a suitable exposure assessment approach (Ashworth et al., 2013; Cordioli et
al., 2013), because it allows the investigation of pollutants emitted by the plant, taking into account
their diffusion, mainly driven by local meteorological conditions. PM10 was used as the tracer of air
pollution from the incinerator as data on this pollutant are routinely monitored at the stack every 30
minutes, while data on PAHs and metals are collected less regularly.
Figure 1. 2010 Annual median PM10 concentration fall-out map of SWI emissions, stratified by quartiles.
For each study subject the actual exposure level was calculated on a monthly base. Monthly fall-out
PM10 concentration was assigned to each subject for a period of 30 days prior to the sampling date;
this time window was chosen as the study biomarkers reflect a short-time exposure.
3.1 Study population
Overall, 497 subjects agreed to participate in the study, 9 of them were excluded from statistical
analysis due to residence out of the study area, resulting in 488 study subjects. The response rate
was 54% (non-availability rate 19%, refusal rate 27%).
The mean residential PM10 exposure from SWI was 0.25 ± 0.3 ng/m3 (maximum 2.51 ng/m3). Four
SWI exposure levels were obtained based on the quartile distribution: level 1: <0.09 ng/m3; level 2:
0.09 – 0.19 ng/m3; level 3: 0.20 – 0.29 ng/m3; level 4: >0.29 ng/m3.
The residence of study subjects and their distribution according to SWI exposure level is shown in
fig. 2. Incinerator emissions varied during the study period and subjects may have experienced
different exposure even though residing in close area.
Figure 2. Residence of study subjects and their distribution according to SWI exposure levels.
The main characteristics of study subjects, stratified by SWI exposure levels, are shown in Table 1.
No significant differences were found in terms of gender, age and BMI. Some differences were
related to education level and citizenship, with a lower percentage of highly educated subjects in the
highest SWI exposure levels, and higher presence of foreign citizens in the lowest SWI exposure
level. No differences were observed among SWI exposure levels and smoking status neither for
urinary cotinine nor for self-reported smoking status.
3.2 Biological monitoring
The summary statistics of urinary biomarkers are reported in Table 2. Urinary PAHs were detected
at least in 68% of samples, beside BaA, that was detected only in 20% of samples. Nap, Phe, Ant
were detected in all samples. The observed values of most PAHs were lower than the values
obtained in the pilot study (Ranzi et al., 2013). 1OHPYR was quantified only in 52% of subjects, with
levels well below the reference values for the Italian population.
Urinary metals were detected at least in 77% of samples. Levels were in line with or higher than (up
to 40%) the references values proposed for the Italian population, beside for Cr (95th percentile 0.86
vs. 0.35 μg/L) and V (95th percentile 0.81 vs. 0.2 μg/L),
Median urinary cotinine was 0.8 μg/L while the mean value was 312 μg/L; the large difference is due
to the presence of a majority of non-smokers (69%) in the investigated subjects. Dividing subjects
according to actual smoking habit, the median levels were 0.48 and 883 μg/L in non-smokers and
Table 4 shows the results of the adjusted linear regression models. None of the metals showed
clear relationship with SWI exposure; however some indications that exposure level 3 marginally
increased Hg and Tl (ß = 0.232 and ß = 0.211) were found; on the contrary exposure level 4 was
negatively correlated to As (ß = – 0.483).
Female gender resulted in an increased level of Cu, Pb, Cd, Ni, and As, and a decreased level of
Zn. Age positively increased Pb, Cd, As and V (ß = 0.019, ß = 0.008, ß = 0.014, ß = 0.004), and
decreased Cu (ß = – 0.008). Education level was inversely associated with Cu, Pb and V (ß = –
0.334; ß =-0.152; ß = -0.153), and positively associated with Hg (ß = 0.185). Foreign citizenship
showed positive associations with Sn and Tl (ß = 0.325; ß = 0.308). BMI was inversely associated
with Zn (ß = -0.050).
Tobacco smoking, measured as urinary cotinine, increased Pb and Cd.
The present study suggests that the exposure to SWI emission from the municipal SWI of Modena
was very low, with biomarkers ranging within the reference values of general population. However,
some associations between SWI emissions and urinary biomarkers were found, in particular urinary
PAHs emerged as possible biomarkers of internal exposure to pollution from the SWI. Taking into
account also the findings of the previous pilot study (Ranzi et al., 2013); Flu appears to be the best
Funding: The study was funded by the Province of Modena in the frame of the authorization for an
upgrade of the local SWI (resolution n° 74 of 02/02 /2007).
Declaration of interest: The Authors declare no conflict of interest. The funding body had no
involvement in the collection, analysis and interpretation of data; neither in the writing of the article.
Ethics: The study was approved by the Ethics committee of Modena and has been carried out in
accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) for
experiments involving humans.