**4. Discussion**

In recent years, a number of scientific studies on the concentrations of metals in humans—for occupationally and non-occupationally exposed populations—have been published [26]. Recently, Dudek-Adamska et al. [27] analyzed the concentrations of Cr in samples of blood and internal organs collected at autopsy from 21 female and 39 male non-occupationally exposed subjects in Southern Poland. Reference ranges of Cr in brain, liver, kidney and lung were 4.7–136, 11–506, 2.9–298 and 13–798 ng/g, respectively. The concentrations corresponding to individuals living near the HWI of Constantí would be within that range, but in the upper side for liver, kidney and lung. In turn, the mean levels of Cr in brain for the population of the current study was 2-fold higher than for the Polish residents. In Sweden, Akerstrom et al. [28] studied the relationship between Hg in kidney, blood, and urine in environmentally exposed individuals, and its implications for biomonitoring. The mean concentration of Hg in kidney from 152 healthy kidney donors (65 men and 87 women) was reported to be 0.33 μg/g, a value 4-times higher than that observed in the autopsied subjects who had been living near the HWI here assessed.

The analysis of trace elements in autopsy tissues is part of a large surveillance program on the HWI. In 2017, the concentrations of the same elements in samples of human hair from schoolchildren and of blood from an adult population, all of them living near the facility, were determined [18,19]. The temporal decrease of Pb in autopsy tissues was also observed in the other biomonitors. In 2017, the mean concentration of Pb in human hair from schoolchildren was 1.44 μg/g, being significantly lower than the value found in the baseline survey (5.81 μg/g). In blood, the mean Pb level in 2017 was 12.98 μg/kg, with a significant (*p* < 0.05) reduction with respect to the previous (2012) study but non-significant (*p* > 0.05) compared to the baseline survey. In addition, the notable increase of Cr observed in some autopsy tissues was also detected in blood [19], where values increased from undetected levels to 6.29 μg/kg. In contrast, Cr levels in human hair did not increase through time [18]. Since the biological concentrations of environmental contaminants in the human body are highly dependent on the dietary intake, food levels of the same pollutants are also periodically monitored. In our last study, corresponding to data on foodstu ffs samples collected in 2013 [29], the estimated dietary intake of Cr and Hg was found to progressively and significantly increase with respect to the baseline study.

Some toxic habits, such as smoking or alcohol consumption, have been pointed out as potential sources of toxic elements (i.e., Cd, Pb) [20], whose exposure is related to adverse health e ffects, including the probability to develop cancer [30]. In the present study, a correlation between smoking and the burdens of the toxic elements analyzed in the five human tissues was not found. However, the reduced number of samples (n = 5 smokers out of 20 subjects) makes di fficult to establish any conclusion in this sense.
