[Intelligence and neurocognitive tests among students living in a industrialized region of Sardinia with relatively low blood levels of lead]. / Quoziente intellettivo e test neuro-cognitivi in studenti di un'area industrializzata della Sardegna con relativamente bassi livelli attuali di piombo ematico.

In several recent epidemiological studies blood lead levels (BLLs) even below the current CDC intervention level of 10 microg/dl have been associated with reduced neurocognitive capacities of children, with no clear evidence of a "safe" threshold. We analyzed the relationship between the BLLs and the neurocognitive capacities of 205 Sardinian students aged 11 to 15 years, using 2 tests of the Swedish Performance Evaluating System (SPES) and the full-scale Intelligence Quotient (IQ) derived from the Wechsler Intelligence Scale for Children (WISC). The studied population included 104 children (61 males and 43 females) living in Portoscuso, a town 2 Km far from a lead smelter (mean BLLs: 5.98 +/- 2.2; max 11.5 microg/dl), and 101 age-matched students (55 males and 46 females) living in Sant'Antioco, a town about 20 Km far from the same smelter (mean BLLs: 2.08 +/- 0.8; max 4.5 microg/dl). Subjects with BLLs above 4 microg/dl performed worse in the SPES tests and scored about 5.0 points less on the full-scale IQ compared to the students with lower BLLs. The adjusted regression coefficients derived from the multivariate analysis showed that higher BLLs were significantly associated with worse performances in the SPES tests and with reduced IQ (0.94 points for each microg/dl of BLL). This study confirms the potential neurotoxicity of low-levels of lead suggesting the need of lowering the actual CDC "limit of concern" for children to values lower than 4 microg/dl, improving at the same time the environmental primary prevention for limiting the lead exposure of subjects living near the lead smelter.

Application of a latent variable model for a multicenter study on early effects due to mercury exposure.

A latent variable model was applied to the results of an Italian multicenter nation-wide cross-sectional study to assess the earliest health effects due to mercury (Hg) exposure caused by occupation, dental amalgams (DENTAM) and fish eating (FISH). The studied population included subjects recruited from four different geographical areas. A total number of 122 workers from chloroalkali plants and production of thermometers and neon lamps formed the occupationally exposed group, whereas 196 subjects, recruited from the same areas and not occupationally exposed to mercury, formed the control group. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine function was examined with the measurement of prolactin (PRL) level. Parameters of immunological and renal function were also measured. The target population was characterized by the number and surface of dental amalgams and consumption of fish. In the exposed workers the average urinary mercury (U-Hg) was 10.4+/-6.9 (geometric mean 8.3, range 0.2-35.2) microg/g creatinine, whereas in the control group it was 1.9+/-2.8 (geometric mean 1.2, range 0.1-33.2) microg/g creatinine. The preliminary results indicated that finger tapping (FT) and the Branches alternate movement task (BAMT) coordination test were associated with the occupational exposure (OCCEXP). PRL was significantly decreased among the exposed workers, and inversely related to U-Hg. Among the immunological and renal parameters, cytokine serum interleuchin-8 (sIL8) and beta(2) micro globulin (beta(2)MG) were lower in the exposed group and negatively correlated to U-Hg. Small-size fish consumption was associated to a beneficial effect on symptoms reporting. No effects were observed concerning dental amalgams. After first evaluating the relationship between mercury exposure and each indicator of effect, further assessment was performed to identify the earliest effects related to mercury exposure among those who resulted in being associated in the preliminary elaboration. Two latent variables "exposure" and "effect" were identified, integrating respectively the different forms of exposure (occupational, due to dental amalgams and fish consumption) and the indicators of effects (FT, BAMT, PRL, sIL8, beta(2)MG). Confounding factors (age, alcohol, body mass index (BMI)) were considered in the same model. This further analysis showed that an inverse association of occupational exposure to mercury with PRL and BAMT, with Hg-U mediating the effect on PRL, was predominant with respect to the other form of mercury exposure, the other indicators of effect and the confounders. In conclusion, this study supports the finding of alterations of neuroendocrine secretion and motor coordination at very low occupational exposure levels of inorganic mercury, below the current ACGIH Biological Exposure Index. These changes occur at lower levels than other subtle effects on the renal function and the immunitary system. On the contrary, dental amalgams and small-size fish consumption do not seem to be associated to any adverse health effect at these exposure levels.

Sub-clinical neurobehavioral abnormalities associated with low level of mercury exposure through fish consumption.

In order to assess early neurotoxic effects associated with relatively low levels of mercury absorbed through fish eating, two groups of 22 adult male subjects, habitual consumers of tuna fish, and 22 controls were examined using a cross-sectional field study. The assessment included neurobehavioral tests of vigilance and psychomotor function, hand tremor measurements and serum prolactin assessment. Mercury in urine (U-Hg) and serum prolactin (sPRL) were measured in all exposed subjects and controls, whereas measurements of the organic component of mercury in blood (O-Hg) were available for only 10 exposed and six controls. U-Hg was significant higher among exposed subjects (median 6.5 microg/g of creatinine, range 1.8-21.5) than controls (median 1.5 microg/g of creatinine, range 0.5-5.3). The median values of O-Hg were 41.5 microg/l among the tuna fish eaters and 2.6 microg/l in the control group. Both U-Hg and O-Hg were significantly correlated with the quantity of fish consumed per week. Significant differences in sPRL were found between exposed (12.6 ng/ml) and controls (9.1 ng/ml). Individual sPRL were significantly correlated with both U-Hg and O-Hg levels. The neurobehavioral performance of subjects who consumed tuna fish regularly was significantly worse on color word reaction time, digit symbol reaction time and finger tapping speed (FT). After considering the education level and other covariates, the multiple stepwise regression analysis indicated that O-Hg concentration was most significantly associated with individual performance on these tests, accounting for about 65% of the variance in test scores.

Biomonitoring of primary aluminium industry workers: detection of micronuclei and repairable DNA lesions by alkaline SCGE.

The genetic effects of occupational exposure to low polycyclic aromatic hydrocarbon (PAH) concentrations were investigated in primary aluminium industry workers. The study subjects were employed in a plant that uses pre-baked anode cells, and has relatively low PAH contamination. Forty-two male workers belonging to different job categories (anode fabrication, baking, rodding, electrolysis, maintenance), together with 16 male local residents with no occupational exposure to PAHs were selected for the analysis of micronuclei and DNA lesions in peripheral lymphocytes. The incidence of micronuclei determined in 1000 cytokinesis-blocked cells in each subject was not significantly different between workers and controls (8.5+/-5.4 per thousand versus 9.7+/-4.9 per thousand, respectively), nor between smokers and non-smokers (8.3+/-5.8 per thousand versus 9.2+/-5.1 per thousand), but was significantly (P<0.05) related to the subjects' age. Also the analysis of DNA damage in unstimulated and mitogen-stimulated lymphocytes by single cell gel electrophoresis (SCGE) did not show significant differences between the studied groups (average tail moment values were 0.53+/-0.53 and 0.49+/-0.45 microm in exposed subjects and controls, respectively). However, when lymphocytes were cultured in the presence of cytosine arabinoside (Ara-C, 1 microg/ml for 16h) the SCGE analysis revealed a significant (P=0.018) difference in tail moment values between aluminium workers and controls (1.73+/-1.05 microm versus 0.93+/-0.88 microm, respectively). This difference may highlight an excess of relatively stable DNA lesions, that do not affect strand integrity, and are expressed as intermediates of excision repair in stimulated cells, when gap refilling is inhibited by cytosine arabinoside (Ara-C).