Table 3.
Methodological features of twenty-four epidemiological Pb ototoxicity studies
| # | Type | First Author (Year) | N | Sex (F/M) | Mean Age | Pb Exposure Setting | Place | Hearing Test | Pb Measure | Noise | Metals |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Cross-sectional | Baloh, R. (1979) | 69 (64 aud.); 35 (31 aud.) controls | 43 (Spivey et al. 1979) (sd=11) | Secondary Pb smelter – refining, and recasting Pb from auto batteries; controls from aluminum processing facility(Spivey et al. 1979) | US – southern CA | Pure-tone conduction; impedance studies; speech recog. | Current BLL 61 (13) μg/100mL; Longitudinal BLL 60 (14) μg/100mL | No | As | |
| 2 | Prospective | Spivey, G. (1980) | 69 (64 aud.); 35 (31 aud.) controls | - | - | Secondary Pb smelter; controls from aluminum processing facility | US – southern CA | Pure tone conduction; impedance studies; speech recog. | Follow-up BLL 66 (13) μg/dL; | No | No |
| 3 | Cross-sectional | Holdstein, Y. (1986) | 57; Older: 16 exposed and 20 controls | Older exposed 10 F/6 M | Young (8-17); Older (18-56) | Ingestion of Pb-contaminated food source for 1-2 years, study was conducted one year later | Pure-tone thresholds and BAER | Prior BLL were averaged with new levels. Means of older: 31.2 μg/dL, prior 43.4 μg/dL | No | No | |
| 4 | Cross-sectional | Lille, F. (1988) | 13 Pb workers; 20 controls | 3 F/10 M | 37 (sd=10) | Occupationally exposed to inorganic Pb compounds | - | BAEP | Mean BLL 100 μg/dL (range 27-240) | No | No |
| 5 | Cross-sectional | Araki, S. (1992) | 22 workers; 14 controls | 22 M | Median48 (range 32-58) | Gun metal foundry workers | - | Auditory event-related potential | Median BLL 30 μg/dL (range 12-59) (UPb values not reported) | No | Zn, Cu |
| 6 | Cross-sectional | Discalzi, G.L. (1992) | 49 workers; 49 controls (ASM) | 12 F/ 37 M | 34 (sd=11) | 31 from Pb battery factories; 7 from the ceramic industry; 4 Pb contaminated wine; 7 misc. occupational exposures | Europe | BAEP | Mean BLL 55 (16) μg/dL; mean 3-year BLL average 54 (16) μg/dL | No | No |
| 7 | Cross-sectional | Discalzi, G. (1993) | 22 workers; 22 controls | 5 F/17 M | 35 (sd=12) | Pb storage battery factory workers | Italy | BAER | BLL 48 (sd = 11) μg/dL | No | No |
| 8 | Cross-sectional | Hirata, M. (1993) | 41 Pb workers/39 controls | All M | 19 to 58 | Pb-exposed workers from 4 factories and controls from nylon factory. | Japan | ABR | Current BLL and TWA from the past 5 years. | No | No |
| 9 | Cross-sectional | Murata, K. (1993) | 22 workers; 22 controls | 22 M | Range 32-59 | Gun metal foundry worker | - | BAEP | Mean BLL 39 μg/dL (range 16-64 μg/dL) | No | No |
| 10 | Cross-sectional | Murata, K. (1995) | 36 Pb workers/15 textile controls | All F | 21 to 35 | Glass workers (7.8 average years in factory) | China | BAEP | Mean BLL 56 μg/dL (range 26-79); Air concentrations 0.4-1.2 mg/m3 | No | No |
| 11 | Cross-sectional | Farahat T. M. (1997) | 45 workers/45 controls | -- | 20 to 40 | Printing facility and controls from textile factory | Egypt | Pure-tone thresholds | BLL (worker mean 37 μg/dL; control mean 12 μg/dL) | 40-50 dB | No |
| 12 | Cross-sectional | Forst, L. S. (1997) | 183 workers | 12 F/ 171 M | 19 to 65 | Private business. 70% white, 22% African American, 8% Hispanic | US | Pure-tone thresholds | BLL 1-8 μg/dL (5 μg/dL 50th percentile) | No | No |
| 13 | Cross-sectional | Fujimura, Y. (1998) | 2 workers/42 controls | 2 M | 50 & 57 | Pb smelting | - | BAEP | Mean BLL 104 & 79 μg/dL (followed for 12 and 15 months) | No | No |
| 14 | Cross-sectional | Buchanan, L. (1999) | 5 adults | 1 F/ 4 M | Range: (17-51) | Ceramic production and Pb glazing from Pb-acid batteries | Village of LaVictoria in Ecuador | DPOAE, ABR, & Pure-tone threshold | Mean BLL 41 μg/dL (range 19-56) | No | No |
| 15 | Cross-sectional | Wu, T. (2000) | 220 workers | 102 F/ 118 M | 37 (sd=10) | Workers at two Pb-battery factories | Taiwan | Pure-tone thresholds | BLL as short-term and long-tenn value calculated from ambient Pb concentrations and years working at plant | LEQ for each indiv. | No |
| 16 | Cross-sectional | Counter, S. A. (2002) | 30 | 15 F/ 15 M | median age =35 (17-55) | Pb glazing workers | Ecuador | Pure-tone thresholds. BAERs on 12 participants | BLL 45 (20=sd) μg/dL. Range of 11-80 μg/dL. | Reported in survey | No |
| 17 | Cross-sectional | Yokoyama, K. (2002) | 29 | all F | 27 (22-29) | Pb glass factory workers (employed for 3-17 years, mean 8) | Beijing, China | BAEP | Mean BLL 56 μg/dL (range: 26-79) | No | No |
| 18 | Cross-sectional | Bleecker M. L. (2003) | 359 | all M | 41 (sd=9) | Pb smelting workers. French and English speaking. | - | BAER | BLL, TWA from past 5 years, and integrated blood Pb measure - overtime working at plant. | No | No |
| 19 | Case-Control | Chuang, H.-Y. (2007) | 121 HL/173 controls | all M | Cases 44 (sd=9)/Controls 40 (sd=9) | Outpatients and occupational health examination workers with HL. Controls patients with no HL | Taiwan | Pure-tone thresholds | BLL geometric mean (11 μg/dL - cases / 4 μg/dL - controls) | Reported yes/no, if yes years of duration | Blood Mn, As, Se |
| 20 | Cross-sectional | Hwang, Y.-H. (2009) | 412 total, 395 factory/17 admin. | I F / 411 M | 36 (7=sd) | Steel workers | Taiwan | Pure-tone thresholds | BLL Grouped under 4 μg/dL, 4-7 μg/dL, and over 7 μg/dL | Groups <80, 80-85, and >85 dB | Mn, Cu, Zn, As, Cd |
| 21 | Cohort | Park, S. K. (2010) | 448 | all M | 65 (7=sd) | Normative aging study-veterans | Eastern MA | Pure-tone thresholds | Bone (tibia and patella) Pb | Job title | No |
| 22 | Cohort | Choi, Y-H. (2012) | 3698 | 1969 F/1729 M | 42 (0.3=se) | NHANES-representative civilian US population | US | Pure-tone thresholds | BLL Geometric mean 1.54 (95 % CI: 1.49, 1.60) μg/dL | Fireanns, recreational, and job title | Cd |
| 23 | Cross-sectional | Saunders, J. E. (2013) | 59 | 10 F/ 49 M | 9 to 78 | Artisanal gold miners | Nicaragua | Pure-tone thresholds, DPOAE | Finger nail (some toe) clippings. Median = 3.93 μg/g | Reported Low/ High | Hg, As, Mn, Al |
| 24 | Cross-sectional | Huh, D-A, (2016) | 7596 | 4843 F/4115 M* | Range: 10-87 | 2010-2013 National Health Survey | Korea | Pure-tone thresholds | BLL – weighted geometric mean 2.08 μg/dL 95 % CI (2.05, 2.11) | Survey: Loud, occ., firearms | No |
Table Abbreviations: ABR – auditory brainstem response (very similar to BAER); admin. – administration workers; ASM – age and sex matched; BAEP – brainstem auditory evoked potentials; BAER – brainstem auditory evoked response; BLL – blood lead levels; dB – decibels; DPOAE – distortion product otoacoustic emissions; F – female; Hz – hertz; indiv. – individual; LEQ – Equivalent Continuous Sound Level (measured in dB); Loud – loud noise group; M – male; MA – Massachusetts; μg/dL - micrograms Pb per deciliter blood; Occ. – occupational; Pb – lead; sd – standard deviation; se – standard error; TWA – time weighted average.
*
Obtained from downloading available datafile.