Assessment of auditory brainstem function in lead-exposed children using stapedius muscle reflexes.

The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125-4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2-18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n=117) ranged from 4.0 to 83.7 µg/dL with a mean PbB level of 33.5 µg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n=91) of the children had PbB levels greater than the CDC action line of 10 µg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤90 dB HL) and contralateral (mean: ≤97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of stapedius muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.

Preservation of brainstem neurophysiological function in hydranencephaly.

The preservation of central neurophysiological function was assessed in a 32-year-old woman with hydranencephaly using brainstem auditory evoked responses (BAER), auditory middle latency responses (MLR), cortical auditory evoked responses (CER), strobe electroretinograms (ERG), strobe-flash visual evoked responses (VER) and median and tibial nerve somatosensory evoked responses (SER). The BAER to the right ear stimulation revealed wave peaks I through VII with normal thresholds, morphology and latencies, while the BAER in the left ear was abnormal. The auditory MLR and CER were absent. Grossly normal strobe ERGs were acquired bilaterally with peak waves at 20 and 50 ms. Strobe VERs were poorly defined and abnormal bilaterally. Left and right median nerve SER revealed significant conduction defects in the large fiber sensory system caudal to the thalamus, above the lower pontine level. Bilateral tibial nerve stimulation revealed normal knee popliteal fossa potentials, but distinct conduction defects in the large fiber sensory system rostral to the lower spinal cord. Brainstem electrophysiological measures revealed functional auditory afferent tracts and nuclei, in the absence of cortical influence, suggesting intact unilateral auditory function, which would support clinical observations of behavioral auditory responses in hydranencephaly.

Protection and treatment of sensorineural hearing disorders caused by exogenous factors: experimental findings and potential clinical application.

During the last decade, there have been numerous interesting findings regarding the roles of neurotrophins, nitric oxide, reactive oxygen species, glutamate receptors, and shock protein in the auditory system. These findings have provided a scientific basis for the development of techniques to protect the auditory system against trauma as well as for the treatment of peripheral hearing disorders. This review focuses on recent advances in experimental prevention and treatment of hearing impairment which are expected to be of clinical value in the near future. Viral vector and non-viral vector gene therapy and transplantation of stem cells are discussed as potential treatments of irreversible sensorineural inner ear damage.

Gender differences in blood lead and hemoglobin levels in Andean adults with chronic lead exposure.

A field study of the prevalence of lead (Pb) intoxication was conducted in 158 adults (67 men and 91 women) living at 2,500-2,800 meters in Ecuadorian Andean villages with high Pb contamination from local small-scale Pb-glazing cottage industries. Venous blood samples showed mean blood lead (PbB) levels of 34.5 microg/dL (SD 22.2) for men and 27.0 microg/dL (SD 18.4) for women; this difference was significant (t-test, p = 0.022; Mann-Whitney U, p = 0.044). An ANOVA showed no significant main effect for gender (F = 0.118, p = 0.782) or age (F = 2.479, p = 0.117), and no significant gender-by-age interaction (F = 0.273, p = 0.602). In the Pb-glazing study group, 39% of the men had PbB levels > or = 40 microg/dL, while 41% of the women had PbB levels > or = 30 microg/dL (the WHO health-based biological limits). A reference group of 39 adults (24 men and 15 women) had a mean PbB level of 5.9 microg/dL (SD 2.8; range: 1.8-16.8), significantly different from that of the 158 subjects in the study group (t-test, p < 0.0001). The difference in mean PbB levels of men (6.8 microg/dL) and women (4.7 microg/dL) in the reference group was significant (t-test, p = 0.026; Mann-Whitney U, p = 0.019). The mean altitude-corrected hemoglobin levels in the study group were lower than normal, 11.3 g/dL for men and 10.9 g/dL for women.

Analysis of magnetic resonance imaging acoustic noise generated by a 4.7 T experimental system.

High intensity acoustic noise is an undesirable side-effect in magnetic resonance imaging (MRI) that can cause discomfort and hearing loss in patients and may be an impediment in functional MRI (fMRI) studies of the auditory system. Experimental MRI systems with high magnetic field strengths may generate acoustic noise of higher sound pressure levels (SPLs) than conventional 1.0 and 1.5 T clinical systems. We measured the SPL and spectral content of the acoustic noise generated by the Bruker Biospect 47/40 4.7 T experimental MRI system during scanning sequences commonly used in animal testing. Each sequence generated acoustic noise of high SPL, rapid pulse rates, amplitude-modulated pulse envelopes and multi-peaked spectra. The rapid acquisition with enhancement sequence with a 0.25 mm slice thickness generated SPLs of up to 129 dB peak SPL and 130 dB (A). Fourier analysis of the spectral content of the acoustic noise generated by each MRI sequence showed a wide band of acoustic energy with spectral peaks from 0.2-5 kHz. The intense MRI acoustic impulse noise generated by the 4.7 T system may cause masking of stimuli used in fMRI of the auditory cortex, reduce the hearing acuity of experimental animals and present a risk for unprotected human ears.

Environmental lead contamination and pediatric lead intoxication in an Andean Ecuadorian village.

Environmental lead (Pb) contamination was measured in samples of soil and locally grown food produce in a remote Ecuadorian village where Pb glazing of ceramics is the local cottage industry. The Pb concentration levels of local soil samples collected at varying distances from a cluster of backyard Pb baking kilns were 29,213 ppm (microg/g) at 0.001 km, 172 ppm at 0.005 km, 81 ppm at 0.01 km, 55 ppm at 1 km, 19 ppm at 2 km, and 1.4 ppm at 6 km, significantly higher than levels in control soil samples from non-Pb-glazing reference areas. Samples of locally grown food produce were also found to be Pb contaminated. Venous blood samples from 166 schoolchildren (ages 4 months to 15 years) in the study area and 56 children in the reference area showed mean blood lead levels of 40.0 microg/dl (SD: 24.5; range: 6.2. - 119.1 microg/dL) and 6.6 microg/dL (SD: 3.4; range: 1.9 - 18.1 microg/dL), respectively, which were significantly different (p = 0.0001). The Pb levels in milk from breastfeeding mothers ranged from 1.44 to 39 ng/g. Lead isotope ratios of the children's blood and of samples of village soil revealed a common Pb source or "fingerprint."

Blood lead and hemoglobin levels in Andean children with chronic lead intoxication.

This study investigated blood lead (PbB) and hemoglobin (HbB) levels in 88 children (42 females and 46 males; ages: 2-15 years; mean age: 7.2) with chronic Pb exposure, living in a highly Pb-contaminated Andean village at above 2800 meters. The mean PbB level for 88 venous blood samples was 43.2 microg/dl (SD: 25.1; range: 6.2 - 128.2 microg/dl) measured by ICP-MS, and 42.0 microg/dl (SD: 26.0; range: 5.0 - 130.0 microg/dl) by GFAAS analysis. The mean PbB level for the 42 females was 41.0 microg/dl and for 46 males, 45.0 microg/dl. Multiple regression analysis showed a significant gender by age interaction (R2 = 0.099; F = 4.173, p = 0.044), indicating a relationship between age and PbB level for males, but not for females. Simple regression analysis showed a statistically significant positive correlation between PbB levels and age for males (r = 0.416, p = 0.004), but not for females (r = -0.042, p = .793). The measured mean HbB level for the 88 children was 12.6 g/dl (12.5 g/dl for females and 12.8 g/dl for males) and lower than expected for children living in the Ecuadorian Andes. The mean altitude-corrected HbB level was 10.9 g/dl (10.8 g/dl for females and 11.1 g/dl for males). A significant inverse correlation between PbB and HbB levels was observed for the group of 88 children (r = -0.292, p = 0.006). Multiple regression analyses indicated no significant age and gender interaction (R2 = 0.014; F = 0.025, p = 0.876) for HbB levels. In conclusion, the results of this investigation indicate that the children in this Pb-contaminated, high altitude study area had chronic elevated PbB levels, which increased with age for males, and probable Pb-induced anemia.

Magnetic resonance imaging of the membranous labyrinth during in vivo gadolinium (Gd-DTPA-BMA) uptake in the normal and lesioned cochlea.

MRI with a T1 contrast agent was used to investigate the normal and noise-damaged cochlea. The time course and distribution of the in vivo uptake of the gadodiamide chelate bound paramagnetic Gd ion (GdDTPA-BMA) throughout the membranous labyrinth of normal and impulse noise-damaged guinea pig cochleae were measured by MRI at 4.7T. Simultaneous signal enhancement of the basal, medial and apical scala tympani (ST) and scala vestibuli (SV) was observed within 10 min following i.v. injection, reaching maximum levels at around 100 min. ANOVA and post hoc paired t-tests showed statistically significant differences in the levels and rates of Gd uptake-enhancement between the scalae. The ST revealed the most rapid and extensive enhancement throughout the period of active Gd uptake, while the SV showed comparatively slower and less enhancement, and the intact scala media (SM) indicated insignificant enhancement. The in vivo Gd penetration and enhancement of the membranous SM increased significantly in the noise-damaged cochlea, suggesting lesioning of the cochlear membranes.

Distortion product oto-acoustic emissions in Andean children and adults with chronic lead intoxication.

Neuroauditory disorders and sensory-neural hearing loss have been suggested as possible etiologic factors in the neurodevelopmental learning disabilities attributed to lead (Pb) intoxication. However, studies relating hearing loss to Pb poisoning have presented disparate results, suggesting that auditory sensitivity may not be a reliable marker of Pb intoxication. Oto-acoustic emissions, sounds that can be recorded non-invasively from the ear canal and are preneural responses of the outer hair cells of the inner ear, have been found to be diminished in ears exposed to some toxic agents. In the current study, distortion product oto-acoustic emissions (DPOAEs) were obtained from 28 ears of 14 children and 10 ears of 5 adults living in a highly Pb-contaminated environment in remote villages in the Andes Mountains of Ecuador. Blood lead (PbB) levels for the children (ages: 5-14 years) ranged from 33.4 to 118.2 microg/dl (mean: 51.5; SD: 22.9 microg/dl), or 3-12 times higher than the U.S. Centers for Disease Control and Prevention's toxic level of 10 microg/dl. The PbB levels for the adults ranged from 19.2 to 55.7 microg/dl. Despite the high PbB levels, the children had normal hearing thresholds, and DPOAEs were present for the children at the following f2 frequencies: 1187, 1500, 1906, 2406, 3031, 3812, 4812 and 6031 Hz. Although there was a tendency for the children to have diminished DPOAEs, no consistent correlation of DPOAEs with PbB level was found. The adults had diminished DPOAEs that were consistent with their observed, probably noise-related hearing loss. Contrary to some reports in the literature, the current results show no unequivocal clinical or subclinical evidence that high PbB levels have a toxic effect on the cochlea.

Magnetic resonance imaging of the cochlea, spiral ganglia and eighth nerve of the guinea pig.

The membranous labyrinth of the guinea pig cochlea and retrocochlear neural structures were investigated by magnetic resonance imaging (MRI) using an experimental system with a field strength of 4.7T and a single turn surface coil 25 mm in diameter, or standard resonators of 34 or 70 mm in diameter and gradient field strengths of 950 mTm and 200 mTm. High-resolution 2-D and 3-D images of 0.3-1.0 mm slice thickness were acquired by a rapid acquisition with relaxation enhancement (RARE) sequence and a standard multi-echo technique. Structural and dimensional aspects of the cochlea were resolved in vitro and in vivo down to <50 microm, showing the scala vestibule, scala media, scala tympani, spiral ganglia and the cochlear (eighth) nerve. In vivo perfusions with the gadodiamide (GdDTPA-BMA) chelate-bound paramagnetic gadolinium ion resulted in dynamic temporal enhancement of the scala vestibule and scala tympani, but did not penetrate the scala media.

Lead in plasma and whole blood from lead-exposed children.

In 31 children exposed to lead and 13 considerably less exposed children ("unexposed"), the plasma (Pb-P) concentrations ranged from 0.46 to 18.4 (median, 2.4) and from 0.14 to 0.38 (median, 0.21) microg/L, respectively. Corresponding whole-blood concentrations (Pb-B) were 99-920 (median, 370) and 39-120 (median, 66) microg/L, respectively. The relation between Pb-B and Pb-P was nonlinear; when Pb-P rose, the Pb-B increased relatively less. There was a close association between Pb-B and log Pb-P (r=0.95; P=0.0001). When these data were compared to previous data on adults, there was no major difference between children and adults in the Pb-B/Pb-P relation. Free erythrocyte protoporphyrins in blood were associated with Pb-P (r=0.75; P=0.0001) and Pb-B (r=0.90; P=0.0001). Also, there was an association between blood-hemoglobin concentration and Pb-P in both exposed (r=-0.67; P=0.0001) and unexposed (r=-0.67; P=0.01) children; the corresponding figures for Pb-B were r=-0.42; P=0.02, and r=-0.80; P=0.001, respectively. Thus, at least with regard to toxicity on hematopoiesis at high lead levels, Pb-P may be a more relevant indicator of exposure and risk than Pb-B. Because the curved Pb-B/Pb-P relation indicates a saturation of binding sites for lead in red cells, exposure and risk at high lead levels may easily be underestimated from Pb-B data.

Field screening of blood lead levels in remote Andean villages.

Blood lead (PbB) levels were investigated in chronically lead (Pb) exposed Andean children and adults living in a highly Pb contaminated area of Ecuador where Pb glazing of ceramics is prevalent. A comparative study was made of the PbB levels of Pb-glazing and non-Pb-glazing families living in close proximity, using three PbB analysis techniques. Fifty-one, 50-microl blood samples from children and adults were analyzed in the field by a finger-stick capillary screening technique using the portable ESA LeadCare Blood Lead Testing System (LCS). Venous blood samples of 2-4 ml were collected from the same 51 participants and analyzed in the laboratory by inductively coupled plasma mass spectrometry (ICP-MS) and by graphite furnace atomic absorption spectrometry (AAS). The median PbB levels for the Pb-glazing group as determined by the ICP-MS, AAS and LCS techniques were 37.2 microg/dl (range 11.6-101.0), 32.0 microg/dl (range 8.0-70.0 microg/dl) and 44.0 microg/dl (range 19.0-105.0), respectively. The median PbB levels for the non-Pb-glazing group were 9.2 microg/dl (range 5.0-21.7) with ICP-MS, 9.0 microg/dl (range 4.3-32.0) with AAS, and 11.3 microg/dl (range 7.3-21.1) with LCS. The differences in PbB levels between the Pb glazing and non-Pb glazing groups were statistically significant (p = < .0001) for each PbB analysis method. Correlations between paired samples were: LCS and ICP-MS: r = 0.913, LCS and AAS: r = 0.829, and ICP-MS and AAS: r = 0.905. The results suggest that neighboring Pb glazing and non-Pb glazing families have significantly different PbB levels, and that the portable LCS field technique may be useful for screening and periodic monitoring of relatively low and high PbB levels of persons in remote high altitude Andean areas.

Neurocognitive effects of chronic lead intoxication in Andean children.

Lead (Pb) intoxication in children has been associated with neurodevelopmental disabilities which may result in motor and cognitive impairment. We conducted blood lead (PbB) measurements, neurological examinations and cognitive tests on children living in Ecuadorian villages where Pb is used extensively in the glazing of ceramics. Group I consisted of 55 children with a mean PbB level of 48.0 microg/dl (SD: 26.4, range: 9.2-119.1 microg/dl) who received PbB tests and complete neurological examinations. An appreciable number of the children with elevated PbB levels were normal on specific components of the neurological examination. Among the children who showed neurological deficits, higher PbB levels were associated with abnormal tendon reflexes, finger tapping, visual pursuit, size discrimination, draw-a-person, and math calculation skills. Group II consisted of 41 children with a mean PbB level of 47.4 microg/dl (SD: 22.0, range: 6.6-84.7 microg/dl) who were administered Raven's Coloured Progressive Matrices (RCPM) non-verbal reasoning test. Performance on RCPM was abnormal in 22 (53.7%) of 41 children. Children with abnormal RCPM scores had higher PbB levels (t-test: P=0.030). There was a significant inverse correlation between RCPM scores and PbB levels for children ages 9 years and older (r=-0.618, P=0.011). Males had higher mean PbB levels as a function of age than females (t-test: P=0.037), and more males showed neurocognitive deficits. The results demonstrate a range of neurological responses in children with chronically elevated PbB levels from apparent exceptional neuro-physiological tolerance of PbB intoxication, to some fine motor and cognitive deficits.

Blood mercury and auditory neuro-sensory responses in children and adults in the Nambija gold mining area of Ecuador.

This study investigated blood mercury (B-Hg) levels and the auditory neuro-sensory status of children and adults in the remote Andean settlement of Nambija, Ecuador where Hg is used in the extensive gold mining operations. The mean B-Hg level in 75 Nambija (Study Area) inhabitants (36 children and 39 adults) was 17.5 micrograms/L (SD = 11.0) vs 3.0 micrograms/L (SD = 1.6) in a second group of 34 subjects (15 children and 19 adults) in a non-gold mining area (Reference Area), the difference being statistically significant (p < 0.0001). Neuro-otological examinations revealed 34 subjects (45%) with complaints of headaches and/or memory loss, 3 cases of severe neurological impairment and 4 cases of middle ear pathology. Audiological tests on 40 persons in the Study Area (21 children and 19 adults) showed hearing thresholds ranging from normal to mildly abnormal at 2, 3, 4, 6 and 8 kHz for children, and normal to severely abnormal for adults. Correlation coefficients showed a significant relationship between B-Hg level and hearing level in children at 3 kHz in the right ear, and at no frequency for adults. Auditory brainstem evoked responses (ABR) on subjects in the Study Area showed a significant correlation between B-Hg and the I-III interpeak latency on the right side. The results indicated that the study population of the Nambija gold mining area had abnormally elevated B-Hg levels, and may be at neurological risk from exposure to methylmercury (MeHg) from the consumption of contaminated food and possibly from elemental Hg vapors inhaled during amalgam burning in the gold extraction process.

Normal auditory brainstem and cochlear function in extreme pediatric plumbism.

Lead (Pb) intoxication in children has been associated with encephalopathy, sensory and cognitive impairments. We investigated the prevalence and neuro-sensory effects of Pb exposure in children living in Andean villages of Ecuador with high Pb contamination from discarded automobile batteries used in the local ceramics glazing industry. Venous blood samples were collected from 107 children in the Pb glazing area and from 39 children living in a geographically distant area with no known Pb contamination and measured for blood lead (PbB) levels. Auditory brainstem responses (ABR) and audiological/otological tests were conducted on children in the Pb-Glazing Group. The median PbB level for children in the Pb-Glazing Group was 40.0 microg per dl (range: 6.2-128.2 microg per dl) and for the non Pb-Glazing Group 6.0 microg per dl (1.9-18.0 microg per dl). The differences in PbB levels for children in the study and control areas were statistically significant (t-test, P<0.0001). ABR tests on the Pb-Glazing Group indicated normal wave latencies and neural transmission times, and no statistical correlation between PbB level and interpeak latencies. Audiological tests showed normal cochlear function and no statistical relation between auditory thresholds and PbB level. Contrary to prevailing assumptions, elevated PbB levels in children do not invariably impair auditory brainstem neural transmission or sensory-neural cochlear function, both of which have been implicated as significant contributors to the neurodevelopmental disabilities associated with childhood plumbism.

MRI acoustic noise: sound pressure and frequency analysis.

The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

High lead exposure and auditory sensory-neural function in Andean children.

We investigated blood lead (B-Pb) and mercury (B-Hg) levels and auditory sensory-neural function in 62 Andean school children living in a Pb-contaminated area of Ecuador and 14 children in a neighboring gold mining area with no known Pb exposure. The median B-Pb level for 62 children in the Pb-exposed group was 52.6 micrograms/dl (range 9.9-110.0 micrograms/dl) compared with 6.4 micrograms/dl (range 3.9-12.0 micrograms/dl) for the children in the non-Pb exposed group; the differences were statistically significant (p < 0.001). Auditory thresholds for the Pb-exposed group were normal at the pure tone frequencies of 0.25-8 kHz over the entire range of B-Pb levels, Auditory brain stem response tests in seven children with high B-Pb levels showed normal absolute peak and interpeak latencies. The median B-Hg levels were 0.16 micrograms/dl (range 0.04-0.58 micrograms/dl) for children in the Pb-exposed group and 0.22 micrograms/dl (range 0.1-0.44 micrograms/dl) for children in the non-Pb exposed gold mining area, and showed no significant relationship to auditory function.

Pattern of synaptophysin immunoreactivity in the efferent nerve terminals of the guinea pig cochlea.

The goal of the present study was to analyze the distribution of efferent 8th nerve synaptic endings in a surface preparation of the guinea pig cochlea using synaptophysin antibodies. Employing light and confocal microscopy synaptophysin immunoreactivity was found exclusively at the base of the outer hair cells (OHCs) and the inner hair cells (IHCs) axosomatic efferent synapses. Qualitative and quantitative differences were found between the OHCs and the IHCs immunoreactivity. Efferent nerve endings innervating IHCs were comparatively smaller, more numerous and densely packed. Efferent terminals demonstrated a longitudinal gradient for the IHCs and a longitudinal and radial gradient for the OHCs. Quantitative analysis of synaptophysin immunofluorescence demonstrated a higher percentage of efferent terminals innervating the IHCs and the OHCs in the mid and basal segments of the cochlea than in the apical regions. In addition, a radial gradient from the 1st to 3rd row of OHCs was evident. The results from the present study show that the analysis of synaptophysin immunoreactivity on cochlear surface preparations allows the efferent innervation to be determined throughout the entire cochlea. This technique allows for a rapid assessment of the normal cochlea as well as after cochlear insult.

Extensive lead exposure in children living in an area with production of lead-glazed tiles in the Ecuadorian Andes.

We have determined the concentrations of lead (Pb), cadmium (Cd), and mercury (Hg) in the blood of children living in two Andean villages in Ecuador with many family-owned cottage-type industries using Pb from discarded car batteries and occasionally, utility batteries containing Cd and Hg for the production of glazed tiles. The battery metals are ground together with water to a suspension, which is applied manually onto the tiles and then fused at about 1,200 degrees C in sawdust-fired kilns. Children aged 4-15 years were recruited from the schools with the assistance of the school-teachers. Children from homes with and without tile-glazing activities were to be included. Blood metal concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS). The children had extremely high blood lead concentrations (B-Pb), which ranged between 100 and 1,100 micrograms/l (median 510 micrograms/l, n = 82). Children from families engaged in tile-glazing production had significantly higher B-Pb (median 600 micrograms/l) than those living in homes with no such activity (median 210 micrograms/l), although the B-Pb of the latter were nonetheless clearly elevated. B-Cd and B-Hg were low (medians 0.25 microgram Cd/l and 1.6 micrograms Hg/l, respectively), indicating that the exposure from utility batteries containing Cd and Hg was low. The blood hemoglobin concentrations decreased significantly with rising B-Pb, indicating an effect on the heme synthesis. This was supported by a marked increase in the blood concentration of protoporphyrins with increasing B-Pb. It can be concluded that children from families with cottage industries producing glazed tiles are at risk for severe health effects due to high lead exposure.

Electromagnetic stimulation of the auditory system of deaf patients.

Electromagnetically induced auditory perception was investigated in 18 deaf patients who were candidates for cochlear implants. In the extracranial magnetic stimulation (EMS) procedure, patients were stimulated with time-varying magnetic field brief pulses from a coil positioned at the i) auricle, ii) the mastoid, and iii) the temporal lobe area. EMS elicited auditory sensations in 26 ears (of 14 patients/subjects). The lowest threshold of auditory sensation (TAS) was found to be at the 20% EMS level, with a range of 20-50% of the maximum level (2.0 Tesla), and approximately equal sensitivity in each coil position. Eleven of the subjects hearing EMS-induced sound perceived changes in pitch while 6 heard "clicks" or clicks and tones. Spearman Rho correlation analysis showed a mild negative correlation between the EMS/TAS and the pre-implant FFA, best tone threshold (BTT), and direct promontorial electrical stimulation (ES) thresholds at 250 Hz and 500 Hz. No correlation was found between EMS or ES and performance on the pre-implant or post-implant psychacoustic tests (MAC VIII or 3-Digit speech tests) or the measurements of the thickness of cutaneous and osseous tissue from the stimulation sites at the mastoid and ear canal to the cochlear and 8th nerve. A fair positive correlation was found between the EMS/TAS and the post-implant (6 months) ES threshold when the electrodes allocated the 500 Hz frequency range were stimulated. A mild positive correlation between the pre-cochlear-implant promontorial electrical stimulation (ES) at 250 Hz and the four frequency tone average (FFA: 0.5, 1, 2, 4 kHz) was also found.(ABSTRACT TRUNCATED AT 250 WORDS)