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A recently held study with farmers exposed to organophosphates for five years concluded that such exposure increases the risk of the person developing hearing loss. Other authors have also shown central auditory dysfunction in workers using these types of insecticides in campaigns to fight vectors in endemies.
A study carried out with workers exposed to noi-se and pyrethroids and organophosphates insecticides found that chronic exposure to these insecticides affect the peripheral and central auditory system, regardless of a concurrent exposure to noise.
Another study analyzed audiometries from “insect busters” who worked regularly with pesticides in 2001/02, and in this latest year the company studied had 600 of these insect fighters. The study reported that 33 of these audiometric exams had NIHL-related alterations. Nonetheless, the authors argue that the study involved 37% of the workers; therefore, this figure can be three times greater. The study also challenged the hypothesis that these agents may have a synergic effect. An evaluation of the peripheral auditory alteration in a group of workers exposed to organophosphates and pyrethroid insecticides, used in control campaigns, showed that of the workers exposed to the insecticides, 63.8% had hearing loss. For the group with concurrent exposure to insecticides and noise, the hearing loss was of 66.7%. The average time taken to develop hearing alterations in the high mean frequencies, for combined exposures to insecticides and noise was 3.4 years, and for exposure to insecticides alone was 7.3 years. Hearing loss arising from concurrent exposure to both factors was higher in these frequencies than when the person was exposed to insecticides only.
The investigation of the rural work process in nine towns in Minas Gerais showed that about 50% of the workers interviewed were at least moderately affected by organophosphates and carbamates. This study shows the need for better controlling the exposure to these chemical agents. In a study held with farmers from Rio Grande do Sul, among the chemicals they were being exposed to there were pyrethroids and organophosphates, the authors found hearing loss in 60% of the individuals exposed to pesticides and noise, on the other hand, only 7% of the control group (without exposure to noxious elements) presented altered thresholds.