The Relationship between Occupational Exposure to Lead and Hearing Loss in a Cross-Sectional Survey of Iranian Workers

Abstract

ObjectivesOtotoxic effect of exposure to lead has been reported by many researchers. This study was undertaken with a view to investigate the relationship between blood lead level (BLL) and hearing loss in workers in a lead-acid battery manufacturing plant in Tehran, Iran.MethodsIn a cross-sectional study, 609 male workers were recruited from different locations in the factory. Association between BLL and hearing loss in different frequencies were measured. Relationships were analyzed by logistic regressions. Statistical significance was defined as p-value <0.05.ResultsSix hundred nine male workers with mean age 40 ± 7 years and mean noise exposure level of 80 (75–85) dB were evaluated. BLLs were categorized into four quartiles, and hearing loss in each quartile was compared to the first one. In our regression models, BLL was associated significantly with high frequency hearing loss, adjusted odds ratios for the comparison of the fourth, third, and second quartiles to the first one are respectively: 3.98 (95% CI: 1.63–9.71, p < 0.00), 3.05 (95% CI: 1.28–7.26, p < 0.01), and 2.89 (95% CI: 1.11–7.51, p < 0.03).ConclusionThis study showed a dose–response relationship between BLL and hearing loss, after adjusting for potential confounders (age, body mass index, work duration, smoking, and occupational noise exposure) in logistic regressions. It is concluded that periodic hearing assessment by pure tone audiometry in workers exposed to lead should be recommended. However, additional studies are required to clarify the mechanisms of lead ototoxicity.

Chronic lead exposure induces cochlear oxidative stress and potentiates noise-induced hearing loss

“…The link between environmental or occupational exposure to lead and hearing impairment has been well documented (Choi et al, 2012; Forst et al, 1997; Ghiasvand et al, 2016; Pawlas et al, 2015). Though lead induces oxidative damage to mediate its adverse health effects (Bhatti et al, 2009; Dobrakowski et al, 2017) and the inner ear is highly susceptible to oxidative damage (Henderson et al, 2006; Poirrier et al, 2010) the potential role of cochlear oxidative stress in lead-induced auditory dysfunction is yet to be clarified.…”

Environmental Exposures and Hearing Loss

“…Upon absorption they accumulate in soft tissues and bones and alter cellular homeostasis [8,9]. Long term exposure to heavy metals, such as lead, cadmium, cobalt, arsenic, and mercury, can cause auditory dysfunction [10][11][12][13][14]. Particularly, exposure to cadmium and lead damages the sensory receptor cells in the cochlea [15,16] and induces oxidative stress in several other organs [17][18][19].…”

Association of hearing loss and lead exposure in a North Indian tertiary hospital: a pilot study

“…These findings are in agreement with the observations of Ghiasvand et al who in a population of occupational lead exposure found a significant association between level of lead exposure and pure tone audiometry results. 32 Kang et al in a recent study based on Korean National Health and Nutritional Examination Survey results also found that even exposure to low-level lead is a risk factor for highfrequency hearing loss. 33 The findings of present study thus show that lead exposure could be a possible reason for hearing loss in young patients having no other plausible cause.…”