**3. Results**

Data regarding the concentrations of trace elements in samples of autopsy tissues collected in 2019 are summarized in Table 1. The levels of As, Be, Tl and V were below their respective detection limits (<0.10, <0.10, <0.025 and <0.50 μg/g, respectively) in all tissues. Mercury could be only detected in one sample of liver and three of kidney, with its levels being under the detection limit in the remaining 96 samples. Cadmium showed the highest levels in kidney, with a mean concentration of 11.10 μg/g, while in other organs the concentrations were much lower (range: 0.02–0.76 μg/g). The average Cr concentration in the five analyzed tissues was very similar, with values ranging from 0.29 to 1.02 μg/g. In turn, Mn could be quantified in all tissues, with relatively higher levels in liver and kidney (1.16 and 0.82 μg/g, respectively). Lead showed higher values in bone (mean: 1.00 μg/g; range: <0.025–5.39 μg/g) than in the other evaluated tissues. Finally, Sn was also detected in the five tissues, with similar levels in all (range: 0.78–1.94 μg/g).


**Table 1.** Concentration (in μg/g) of trace elements in samples of autopsy tissues collected in 2019 from subjects who had been living near the HWI of Constantí.


**Table 1.** *Cont*.

Table 2 shows the concentrations of the metals analyzed in autopsy samples (brain, bone, kidney, liver, and lung) in the 1998 (baseline), 2003, 2007, 2013, and 2019 surveys, as well as the percentage variation in the periods 1998–2019 and 2013–2019. Between 1998 and 2019, a significant decrease in Cd, Hg and Pb concentrations was noticed (20%, 70% and 91%, respectively), while only Cd showed a significant reduction between the campaigns performed in 2013 and 2019 (45%; *p* < 0.001).

In kidney, a significant increase in Cr levels, as well as in those of Hg and Sn, was observed between the baseline (1998) and the current (2019) studies. In contrast, none of the evaluated elements showed a significant change of concentration between 2013 and 2019. In 2019, the mean concentrations of As, Be, Hg, Tl and V in brain were lower than their respective detection limits. Regarding Cr, a non-significant decrease (44%) was observed in the period 2013–2019, while a non-significant increase was noted between 1998 and 2019 (*p* > 0.05). Lead was the only element for which a significant change in concentration was observed in kidney, with a significant reduction (94%; *p* < 0.001) between the baseline (1998) and the current (2019) surveys.

In bone, most elements showed a decrease of their concentrations with respect to those found in the baseline study, with significant reductions in Cd, Pb and Sn (50%, 75% and 74%, respectively). In contrast, Cr showed a significant increase, from 0.51 to 1.02 μg/g, between 1998 and 2019. With respect to the previous survey, conducted in 2013, the levels of Sn significantly increased (*p* < 0.001) and those of Mn significantly decreased (*p* < 0.05).


**Table 2.** Mean concentration (μg/g) of trace elements in autopsy tissues collected between 1998 and 2019. Temporal trends.

\* *p* < 0.05; \*\* *p* < 0.01; \*\*\* *p* < 0.001.

In lung, most trace elements presented a reduction of their concentration over time. However, the di fference between 1998 and 2019 were only significant for Pb (*p* < 0.001). In contrast, Ni levels significantly increased (88%; *p* < 0.01). With respect to our most recent study (2013), none of the trace elements showed an increase of concentration in lung, while significant decreases were noted for Cr and Mn (*p* < 0.05 and *p* < 0.01, respectively).

Some fluctuations in the concentrations of trace elements in the analyzed human tissues were found. However, a general trend was not observed after 20 years of continuous operation of the plant. When considering the whole assessment period (1998–2019), no changes were observed for any metal, excepting Cr and Pb. On one hand, between 1998 and 2019, Cr concentration increased in all tissues excepting lung. However, the increase was only significant in kidney and bone. It must be recalled that Cr is a highly toxic metal, being one of the chemical forms (Cr<sup>6</sup>+) fully recognized as carcinogenic [23,24]. On the other hand, the mean Pb levels in autopsy tissues were significantly lower in 2019 than in 1998, with the only exception of kidney, an organ where Pb could not be detected in the baseline survey. This fact would be closely related to the banning of Pb as a gasoline additive, introduced in the early 2000s [25].

The concentrations of trace elements in five autopsy tissues according to sex are depicted in Figure 1. Unfortunately, a proper statistical study could not be performed, since 19 out of the 20 subjects were men. Therefore, scientifically valid conclusions cannot be extracted from such a poorly representative number of samples. Anyway, the most notable finding is that the only recruited woman had higher levels of Pb than the mean of men in liver (1.80 vs. 0.15 μg/g) and kidney (0.51 vs. 0.13 μg/g), while in the other tissues, Pb concentrations were higher in men. In addition, the levels of Cr were higher in the tissue samples corresponding to men than those from women.

**Figure 1.** Concentrations (in μg/g) of trace elements in samples of autopsy tissues collected in 2019 according to the sex of the subjects (M: male; F: female).

Table 3 presents the mean concentrations of the trace elements analyzed in autopsy tissues according to age. Three age groups were considered: <35 (*n* = 3), 35–65 (*n* = 10), and >65 (*n* = 7). Due to the relatively small number of samples, a statistical comparison among groups could not be conducted. However, the data may be indicative to set age-specific trends. A correlation study of the metal concentrations in the autopsy tissues was also performed, taking into account that each subject provided five di fferent tissues (brain, bone, kidney, liver, and lung). Notwithstanding, none of the individuals showed a general increase in the body burdens of trace elements, as Pearson correlations among tissues were not statistically significant.


**Table 3.** Concentrations (μg/g) of trace elements in samples of autopsy tissues collected in 2019 according to the age of the subjects.
