The use of tree barks and human fingernails for monitoring metal levels in urban areas of different population densities of Porto Alegre, Brazil

Abstract

The aim of this study was to evaluate the use of tree barks as a bioindicator of atmospheric pollution in areas of contrasting population densities and to associate the levels of elements found in this bioindicator with those obtained in fingernail samples collected from students living in the same study areas. Tree bark samples were collected from urban areas near highways in regions with high (Area A), intermediate (Area B), and low (Area C) population densities of Porto Alegre, Brazil, and evaluated for chemical elements concentration. Since these areas also differed in traffic density, NO was measured by passive sampling. For a comparative purpose, the elements were also determined in fingernail samples collected from students living in the same areas. Accumulated elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) and principal component analysis (PCA) was used as a tool in exploratory data analysis to identify possible sources. We found that Ba, Cd, Co, Cu, Mg, Mn, Ni, Pb, Sb, Sr, V, and Zn were at higher concentrations in tree barks in Area A, while Cd, Co, Cu, Mg, Mn, Ni, and Sr were at higher levels in students' fingernails of Area A as well. Furthermore, concentrations of elements found in barks were associated with those identified in fingernails collected from students living in the same areas. PCA demonstrated that vehicular traffic explained 66.4 % of the variance in tree bark and 50.8 % of the variance in fingernails. NO levels were significantly different among the areas, what is consistent with their respective vehicular flow and population density. In conclusion, we found conformance of elements levels accumulated in barks and fingernails at three monitoring areas with different profiles. The amount of traffic-related elements accumulated appears to be associated with the degree of urbanization and vehicular flow. Overall, data suggests a relationship between fingernails and tree bark as bioindicators of exposure to metals from air pollution.

Biomonitoring of Metals in Children Living in an Urban Area and Close to Waste Incinerators

“…Several studies measured the concentration of V in nails [40,47,48,81,94,95], reporting an LOD of 0.001 µg/g [81], an inverse relation with age [47,94,95], and values generally lower than 1 µg/g [40]. This was also the case of toenail V concentration measured in the exposed children from our study (0.19 µg/g).…”

“…This explains about half (50.8%) of the variance in metal concentration. In the cited study, the average Mn nail concentration measured in subjects living in the area with the highest population density was 1.3 µg/g, a value about 3.3 times lower than the mean Mn concentration detected in our series of exposed children [48]. This difference could be due, at least in part, to the coexisting exposure in our series of exposed children to vehicular traffic and industrial pollution.…”

“…Toenail concentration of Mn has been frequently studied both in children [47][48][49][50] and in adults [40], with an LOD ranging from 0.001 [81] to 0.33 µg/g [66] and values usually below 10 µg/g [40]. The highest Mn toenail concentrations have been found in subjects living near a highly industrialized city in Pakistan (average value 52.1 µg/g) [82] and in highly polluted areas in Cambodia (average concentration 43.9 µg/g) [66].…”

“…Toenails were selected for sampling as preferential to fingernails due to a minor risk of external contamination [58]. The procedures for toenail collection, sample preparation, and analysis have been extensively employed in previous studies [47,48,[59][60][61][62][63][64][65][66][67].…”

“…In fact, human biomonitoring has been proposed as more useful to assess possible health effects than environmental monitoring [44,45]. In this respect, human nails have been frequently employed for the assessment of metal exposure of various origin [46], have been used in pediatric age [47][48][49][50][51], and have been indicated as suitable indicators of long-term exposures [52,53].…”