Kerketta Sunamani, Gartia Rajendra, Bagh Somanath
Ministry of Environment and Forests, ERO, Bhubaneswar, 751023 Odisha, India.
Malays J Med Sci. 2012 Oct;19(4):63-71.
The aims of the study were to describe the noise levels at an open cast chromite mine in Odisha, India, and the hearing threshold of its workers and to associate their hearing loss with their age, work station and length of employment at the mine.
We performed a cross-sectional study of the hearing threshold of chromite mine workers. Audiometric data from 500 subjects was collected at the mines' hospital in the Sukinda Valley of Jajpur, Odisha, India. The latest audiometry data available for the period 2002 to 2008 was used in the analysis. Audiometric screening was performed using an audiometer (TRIVENI TAM-25 6025A) in a quiet environment by qualified technicians, audiologists or physicians. Tests were conducted on the subjects after they had completely rested for 16 hours or more after their day shift.
A maximum of 262 subjects (52.4%) were employed in the work zone area and a minimum of 2 subjects (0.4%) had less than 5 years working experience. The age of the subjects ranged from 29 to 59 years and their working experience ranged from 4 to 37 years. The subjects' average mean hearing thresholds at 4, 6 and 8 kHz were 21.53 dBA, 23.40 dBA and 21.90 dBA, respectively. The maximum Leq and L90 levels exceeded the prescribed limits for commercial, residential and silence zones. The maximum Leq levels exceeded 95 dBA for large and medium heavy earth moving machineries (HEMMs), both outside and at the operator's position. Hearing loss due to the subjects' work experience was found to be greater than that attributable to age and workstation.
In our study population, the maximum noise levels for large and medium HEMMs and inside the cabins of HEMMs were found to be more than 95 dBA. This indicates that operators in this particular chromite mine at Odisha, India were exposed to noise levels exceeding 95 dBA for more than 10% of the monitoring time. The subjects' hearing loss was also found to increase for every 10-year age interval and that for every 5 years of work experience at high fence. The subjects' age and experience are significantly associated with hearing loss at all levels for frequencies of 4.0, 6.0, and 8.0 kHz, with older and more experienced workers having a higher incidence of hearing loss.
本研究旨在描述印度奥里萨邦一座露天铬铁矿的噪声水平及其工人的听力阈值，并将他们的听力损失与其年龄、工作岗位以及在该矿山的工作年限联系起来。
我们对铬铁矿工人的听力阈值进行了一项横断面研究。在印度奥里萨邦贾朱尔苏金达山谷的矿山医院收集了500名受试者的听力测定数据。分析中使用了2002年至2008年期间可获得的最新听力测定数据。听力筛查由合格的技术人员、听力学家或医生在安静环境中使用听力计（TRIVENI TAM - 25 6025A）进行。在受试者白班后完全休息16小时或更长时间后对其进行测试。
最多有262名受试者（52.4%）受雇于工作区，最少有2名受试者（0.4%）工作经验少于5年。受试者年龄在29岁至59岁之间，工作经验在4年至37年之间。受试者在4kHz、6kHz和8kHz的平均听力阈值分别为21.53 dBA、23.40 dBA和21.90 dBA。最大等效连续A声级（Leq）和L90水平超过了商业、住宅和安静区域规定的限值。大型和中型重型土方机械（HEMMs）在外部及操作员位置处的最大Leq水平均超过95 dBA。发现受试者因工作经验导致的听力损失大于因年龄和工作岗位导致的听力损失。
在我们的研究人群中，发现大型和中型HEMMs以及HEMMs驾驶室内的最大噪声水平超过95 dBA。这表明在印度奥里萨邦这座特定的铬铁矿中，操作员在超过10%的监测时间内暴露于超过95 dBA的噪声水平。还发现受试者的听力损失在每10年年龄间隔以及在高围栏处每工作5年都会增加。在4.0、6.0和8.0 kHz频率的所有水平上，受试者的年龄和经验与听力损失显著相关，年龄较大和经验较丰富的工人听力损失发生率更高。
