Neurotoxicity induced by lead levels: an electrophysiological study

A diketopyrrolopyrrole-based fluorescence turn-on probe for the detection of Pb2+in aqueous solution and living cells

A diketopyrrolopyrrole-based fluorescent probeDPP-HBTbearing a benzothiazole hydrazone motif exhibited an obvious fluorescent turn-on response toward Pb²⁺ions with a low detection limit of 2.3 × 10⁻¹⁰M in aqueous solution.

Salicylaldehyde phenylhydrazone: a new highly selective fluorescent lead (II) probe

The fluorescence intensity of salicylaldehyde phenylhydrazone (L), in 1:1 (v/v) CH3OH:H2O was enhanced by ca. 100 times with a blue shift in emission maximum, on interaction with Pb(2+) ion. No enhancement in fluorescent intensity of L was observed on interaction with metal ions - Na(+), K(+), Ca(2+), Cu(2+), Ni(2+), Zn(2+), Cd(2+) and Hg(2+). This signal transduction was found to occur via photoinduced electron transfer (PET) mechanism. A 1:1 complexation between Pb(2+) and L with log β = 7.86 has been proved from fluorescent and UV/Visible spectroscopic data. The detection limit of Pb(2+) was calculated to be 6.3 × 10(-7) M.

Early effects of long-term neurotoxic lead exposure in copper works employees

The situation of exposure in a copper works facility in Germany enabled early lead-induced neurotoxic effects to be investigated in the workers. The aim of the investigation was to study the long-term effects of small doses of lead on psychometric/psychophysiological performance of workers. The study involved 70 male lead exposed workers and 27 male controls with no neurotoxic exposure. All test persons were subjected to the method of investigation involving performance data, physiological strain data, and the subjective state. It was found that of the psychometric performance parameters, only the mainly motor performance parameters had a potential for being neurotoxic early indicators. Preferably centrally influenced performance parameters were found to be less suitable early indicators. The lead-exposed subjects exhibited a slowed poststrain resetting behaviour of the vegetative nervous system, which correlated with the individual blood lead level. This was attributed to vagus depression, which had already started in the prevailing situation of exposure and was reflected by diminished cardiac phase duration variability. Our results indicate that it is necessary to more critically choose the lead level standards in the air on the working area. Heart rate variability may be affected even at small lead concentration.

Relationship of blood lead levels to incident nonspine fractures and falls in older women: the study of osteoporotic fractures

Lead is stored in the skeleton and can serve as an endogenous source for many years. Lead may influence the risk of fracture, through direct effects on bone strength or indirectly by disturbing neuromuscular function and increasing the risk of falls. The objective of this analysis is to test the hypothesis that women with higher blood lead levels experience higher rates of falls and fracture. This was a prospective cohort study of 533 women 65-87 yr of age enrolled in the Study of Osteoporotic Fractures at two U.S. research centers (Baltimore, MD; Monongahela Valley, PA) from 1986 to 1988. Blood lead levels (in microg/dl) were measured in 1990-1991 by atomic absorption spectrophotometry and classified as "low" (<or=3; lower 15th percentile, referent); "medium" (4-7); or "high" (>or=8; upper 15th percentile). Total hip BMD was measured by DXA twice, 3.55 yr apart. Information on falls was collected every 4 mo for 4 yr. Incident nonspine fractures were identified and confirmed over 10 yr. Cox proportional hazards models were used to estimate the hazard ratio (HR) and 95% CI of fracture. Generalized estimating equations were used to calculate the incident rate ratio of falls (95% CI). The mean blood lead level was 5.3 +/- 2.3 (SD) microg/dl (range, 1-21 microg/dl). Baseline BMD was 7% lower in total hip and 5% lower in femoral neck in the highest compared with lowest blood lead group (p < 0.02). Hip bone loss tended to be greater in the high lead group, but differences were not significant. In multivariable adjusted models, women with high blood lead levels had an increased risk of nonspine fracture (HR = 2.50; 95% CI = 1.25, 5.03; p trend = 0.016) and higher risk of falls (incident rate ratio = 1.62; 95% CI = 1.07, 2.45; p trend = 0.014) compared with women with lowest lead level. Blood lead levels are associated with an increased risk of falls and fractures, extending the negative health consequences of lead to include osteoporotic fractures.

Occupational exposure to chemicals and sensory organs: a neglected research field

The effect of industrial chemicals on the sensory perception of exposed workers has received scant attention from the medical community to date, and the scientific literature is mainly limited to some case-reports or isolated studies. Possible explanations for this include the complexity of sensory perception, and the lack of agreement among researchers on methods for testing large groups of subjects. Nevertheless, some published studies showed that vision, hearing and olfactory function can be affected by various industrial metals and solvents, and some data exist also for touch and taste. This review discusses the main industrial chemicals involved. The pathogenesis of the toxicity of chemicals to sensory perception may be related to an action on receptors, nerve fibers, and/or the brain; probably, different pathogenetic mechanisms are involved. One of the main problems in this research field is that most of the studies to date evaluated the effect of a single industrial chemical on a single sense: as an example, we know that styrene exposure can impair smell and also hearing and vision but we have little idea whether different senses are impaired in the same worker, or whether each impairment is independent. In addition, workers are frequently exposed to different chemicals: co-exposure may have no effect, or result in both an increase or a decrease of the effect, as was observed for hearing loss, but studies on this aspect are largely insufficient. Research shows that both occupational and environmental exposure to industrial chemicals can affect sense organs, and suggests that the decline of perception with age may be, at least partly, related to this exposure. Nevertheless, available evidence is incomplete, and is largely inadequate for an estimation of a "safe" threshold of exposure. Good quality further research in this field is needed. This is certainly complex and demands adequate resources, but is justified by the ultimate result: the possibility to prevent an avoidable part of the decline in sensory function with age.

Subclinical neurophysiological effects of lead: A review on peripheral, central, and autonomic nervous system effects in lead workers

BACKGROUND

The peripheral nerve conduction velocity (NCV), distribution of nerve conduction velocities (DCV), somatosensory, visual, and brainstem auditory evoked potentials (SEP, VEP, and BAEP, respectively), event-related potential (P300), computerized static posturography with spectral analysis (postural balance), and electrocardiographic R-R interval variability (CV(RR)) with spectral analysis appear to be promising techniques for assessing subclinical effects of lead on the peripheral, central and autonomic nervous systems. This article presents an overview of research addressing subclinical neurophysiological effects of lead in workers exposed to lead.

METHODS

We reviewed 102 articles to examine the effects and dose-effects relationships of lead on peripheral, central, and autonomic nervous system function together with reversibility of the effects, interaction between lead and other metals, and relative sensitivity and specificity of each technique. Background and methodology were also reviewed.

RESULTS AND CONCLUSION

Available data suggest that, on a group basis, the reduction in the NCV, together with the effects on the P300 latency, postural balance, and CV(RR), occurs at a mean blood lead concentration (BPb) as low as 30-40 microg/dL; the effects on the latencies of the short-latency SEP, VEP, and BAEP, as well as the DCV, start at a BPb as low as 40-50 microg/dL. Further cross-sectional and preferably prospective studies by using each of those methods are needed to establish more precise dose-effects (and response) relationships of lead.

Effects of low level exposure to lead on neurophysiological functions among lead battery workers

OBJECTIVES

Assessment of neurophysiological functions in workers with low level exposure to lead and evaluation of the efficacy of bone lead measurements in the prediction of effects of lead.

METHODS

Exposure to lead of 60 workers from a lead battery battery factory was estimated from historical blood lead measurements and analysis of lead in the tibial and calcaneal bones with x ray fluorescence. Peripheral and central nervous system functions were assessed by measuring conduction velocities, sensory distal latencies, sensory amplitudes, and vibration thresholds as well as by quantitative measurement of the absolute and relative powers and mean frequencies of different electroencephalograph (EEG) channels.

RESULTS

Sensory amplitudes, and to a smaller degree sensory or motor conduction velocities, showed a negative correlation with long term exposure to lead, most clearly with integrated blood lead concentration and exposure time. Vibration thresholds measured in the arm were related to recent exposure to lead, those measured in the leg to long term exposure. The alpha and beta activities of the EEG were more abundant in subjects with higher long term exposure to lead. Calcaneal lead content reflected short term exposure, tibial lead content reflected long term exposure. Blood lead history showed a closer relation with effects of lead than the tibial or calcaneal lead concentrations.

CONCLUSIONS

Vibratory thresholds, quantitative EEG, and to a smaller extent the sensory amplitude, provide sensitive measures of effects of lead in occupationally exposed adults. Most accurate estimates of health risks induced by lead can be obtained from a good history of blood lead measurements. If such a history of blood lead concentrations is not available, analysis of bone lead may be used for the assessment of health risks.