Table 1.

Epidemiological studies on the effects of exposure to organophosphorus pesticides (OPs) on human auditory system.

OPs	No. of subject	Country	Type of study	Co-exposure to noise	Methods	Result	Reference
Mixture	16246	Iowa or North Carolina in USA	Cohort study	Not specified	Self-report	Compared with no exposure,the odds ratio for the highest quartile of exposure was 1.17 (1.03 to 1.31) for OPs; and 1.11 (0.99–1.24) for fonofos.	(29)
Mixture (methyl parathion, chlorpyrifos, diethyl succinate)	127	The Pontal do Paranapanema region in Brazilian	The observational, prospective, and cross-sectional study	Not specified	Pure tone audiometry, Vocal audiometry, Immittance testing	Auditory complaint and tinnitus with high pitch, had a higher incidence (p < 0.05) in groups exposed to pesticides in comparison to the control group	(31)
Mixture (insecticides, herbicides, and fungicides)	175 conventional farmers and 176 organic farmers	Three agricultural areas in Thailand	Cross-sectional study	Agricultural noise exposure	Standard pure tone audiometry (PTA); An interview	The highest category of cumulative insecticide exposure (score-years), cumulative OPs exposure (score-years) and cumulative noise exposure (dB(A)-years) were associated with an increased high-frequency band hearing threshold among conventional farmers	(32)
Organophosphorus compound (OPC)	100 patients of OPC poisoning	India	Prospective observational study	Not specified	Distortion Product Oto Acoustic Emission (DPOAE); Brain evoked response audiometry (BERA)	DPOAE was absent in 17 patients with respiratory failure and 51 patients without respiratory failure. BERA showed significant prolongation in wave I, wave III and wave V latencies in both the groups.	(33)
Mixture (organophosphates)	18 rural workers	Teresópolis, RJ in Brazilian	Cohort cross-sectional study	Not specified	Otorhinolaryngological, audiological, and vestibular examination; Questionnaires.	Sixteen workers had irritative peripheral body balance disorder and seven workers had sensorineural hearing loss. Agricultural pesticides cause vestibular alterations through a slow and silent intoxication.	(37)
Organophosphates and pyrethroid insecticides	98 workers exposed to insecticides and 54 non-exposed workers	Brazil	Cohort study	Not specified	An interview; Frequency patterns and duration patterns testing	Relative risk for hearing dysfunction was 7.58 for the exposure group (95% CI 2.9–19.8) in comparison with the non-exposed group.	(38)
Mixture (DDT and BHC organophosphates)	98	Brazil	Cross-sectional prevalence studies	Noise	Tonal audiometric test	The intensity of hearing loss in the group exposed to insecticides and noise was higher than in the group exposed to insecticides. The mean values of hearing loss intensity were increasing from 2 to 6 kHz, and decreasing by 8 kHz in relation to 6 kHz.	(39)
Malathion	120	Not mentioned	Retrospective study	With noise	Audiological interview; threshold tonal audiometry; Immittance measures	The group with concurrent exposure to noise and pesticide presented a higher incidence of hearing loss than group exposed to noise alone.	(40)
Mixture (organophosphates and pyrethroids)	56	Brazil	Cross-sectional cohort study	With noise	Pure-tone audiometry; acoustic immittance measurement; Brainstem auditory evoked potentials (BAEP); Dichotic digits test (DDT) assessment; Transient evoked otoacoustic emissions (TEOAE)	Compared with control group, the absolute latency of wave III and wave V was delayed, while the latency between peaks I—III and I—V increased at 2–4 kHz in the group exposed to Insecticides.	(41)
Mixture (chlorpyrifos, diazionon, fonofos, malathion, parathion-ethyl, parathion-methyl, profenofos, terbufos)	116 infants	China	Cohort study	Not specified	ABR	Exposure to multiple pesticides prenatally caused longer central conduction time and wave V latencies	(44)
Organophosphate insecticide	359 healthy women and 237 of their infants	China	Cohort study	Not specified	ABR	Many infants missed ABR wave I and III data at 18 months (n = 132); Methamidophos exposure was significantly different among infants with and without 18-month ABR data	(45)