Biomarkers of Renal Effects in Children and Adults with Low Environmental Exposure to Heavy Metals

Abstract

The health effects of chronic exposure to heavy metals such as lead, cadmium, and mercury are widely documented, yet few data exist about the renal impact of low environmental exposure to these metals, particularly in children. The aim of this study was to assess renal parameters in children and adults living in an environment known for its past heavy metal contamination around two nonferrous smelters in northern France (Noyelles-Godault and Auby) and to compare their results with age and gender-matched controls living in neighboring municipalities with unpolluted soil (total: 400 children, 600 adults, sex ratio = 1). The integrity of renal function was assessed by measuring the urinary excretion levels of total protein, albumin, transferrin, beta(2)-microglobulin, retinol-binding protein, brush border antigen, and the enzyme N-acetyl-beta-D-glucosaminidase (NAG). The mean blood concentrations of lead (Pb-B, children </=42.2 micro/L, adults </=71.3. micro/L) and of cadmium (Cd-B, children </=0.52 microg/L, adults 0.86 microg/L) were all relatively low, indicating a low uptake of these heavy metals from the environment despite relatively high levels in soil (between 100 and 1700 ppm for lead and 0.7 to 233 ppm for cadmium). Pb-B levels were, however, significantly increased in boys, girls, and women--but not men--living in the polluted area. Boys, men, and women living in the polluted area had also on average higher Cd-B levels. The concentrations of mercury in urine (Hg-U) were by contrast similar in control and exposed groups. None of the renal parameters studied showed a significant difference between control and exposed groups. The influence of heavy metals on renal parameters was further assessed by stepwise multiple regression, testing Pb-B, Cd-B, Hg-U, age, gender, body mass index (BMI), urinary creatinine levels, and area of residence as predictors in both children and adults, including first-order metal interaction terms, smoking habits, and alcohol consumption in adults. The only positive correlation was found between the urinary excretion of NAG activity (standardized for BMI and urinary creatinine) and Cd-B levels when taking the whole children population, indicating that even low cadmium burdens may produce subtle effects on the proximal tubule in children, although deleterious consequences are unlikely should exposure not increase. However, in the absence of other positive findings even after studying the smaller subgroups with higher levels of heavy metals, these results are clearly indicative of the minimal renal impact of living around nonferrous smelters that are currently complying with pollution regulations, even when soil contamination is still high.

Internal exposure to pollutants measured in blood and urine of Flemish adolescents in function of area of residence

“…Smoking increased the internal exposure to cadmium and PAHs. The influence of breast feeding, gender and smoking were in agreement with other studies (Staessen et al, 2001;De Burbure et al, 2003;Strö mberg et al, 2003;Wilhelm et al, 2003;Wilhelm et al, 2006). Exposure to traffic, having exercised in the last three days and having a stove at home were associated with higher internal exposure to PAHs.…”

Blood lead, cadmium and mercury among children from urban, industrial and rural areas of Fez Boulemane Region (Morocco): Relevant factors and early renal effects

“…In this study, none of the renal parameters studied showed any statistically significant differences between the 3 areas, either in girls or in boys (Tables 1 and 2) and no correlation was found between BCLs and the studied renal markers concentrations. This finding is in agreement with the results reported by de Burbure et al, conducted in French and Czech 8-12-yearolds with low BCLs (0.48 and 0.23 μg/l, respectively) [32,52], and it is also in agreement with the findings in Egyptian children with a relatively high cadmium level (1.34 μg/l) with no effects of this level on α-1-microglobulinuria, suggesting a subclinical renal effect after several years of cumulative exposure in children [59]. Moreover, Cikrt et al did not find any relationships between Cd-B and Alb-U or RBP-U in adults even with BCLs above 1 μg/l [74].…”

“…In order to further analyze possible renal effects of lead exposure in children, we checked for any correlations between renal markers and BLLs within the smaller subgroups of children with high BLLs (above 50 μg/l, 70 μg/l and 100 μg/1), but no correlation was detected in these subgroups. This finding was in accordance with other studies describing renal biomarker anomalies in children at a low level of environmental exposure to lead [32,15]. Nevertheless, when we further analyzed the outcomes concerning BLLs effects on physical development of children, the only results found significant concerned girls from the urban area (N = 25) that had the highest BLLs mean in our population (89.451 μg/l) ( Table 1), and for whom BLLs were negatively correlated with height (r = -0.425, p = 0.034) and even negatively correlated with weight, but without clear significance (r = -0.369, p = 0.069).…”

“…The BCLs means were lower than those reported in 103 primary school children (6-12 years old) in Cairo city (1.34 μg/l) [59] and proved to be lower also in comparison with the means in French, Canadian an Chinese children living in urban areas (0.48 μg/l, 0.35 μg/l and 0.69 μg/l, respectively) [32,53,60], but they are somehow elevated in comparison with the BCLs means in children from many urban areas in Central Europe cities [28,[61][62][63][64].…”

“…The mean of BLLs in the urban area (82.361 μg/l) is much higher than the means reported in French children (8-12 years old) exposed to non-ferrous smelters pollution and in children (8-11 years old) inhabiting French industrial areas (39.5 and 34.8, respectively) [32,33]. It is also much higher than the BLLs means in urban areas in Canada (children aged 6-11 years, 10.2 μg/l) and in Brazil (children aged 6-8 years, 24 μg/l) [30,34].…”