ABSTRACT
BACKGROUND: Underground coal-mine workers suffer noise-induced hearing loss and continue working in the industry while having varying degrees of deafness. Few studies have researched the risk to safety arising from the loss of hearing. AIMS: This study is designed to investigate the possible association between hearing loss and accidents in the New South Wales underground coal-mining industry. METHODS: A study was conducted, gathering data over a 10-year period from 1994 to 2003, which identified 97 cases that have had accidents and 983 controls that have had no accidents. Hearing loss levels were noted and compared in the cases and controls. Multiple logistic regression was used to determine whether the variables were significant risk factors in the occurrence of accidents. RESULTS: Hearing loss levels in the total cohort varied from 0 to 54%. The proportion of cases with hearing loss appeared to be significantly higher in the young age group of <29 years than in the controls, but was not significantly different in the older age groups. CONCLUSIONS: This study indicates that workers who have lost up to 54% binaural high tone hearing and are older than 29 years do not appear to have an increased risk to safety when compared with workers who do not have hearing loss. However, workers in the young age group of <29 years who have high tone hearing loss may be at an increased risk of accident.
Subject(s)
Accidents, Occupational/statistics & numerical data , Coal Mining , Hearing Loss, Noise-Induced/epidemiology , Occupational Diseases/epidemiology , Occupational Health/statistics & numerical data , Adult , Age Factors , Case-Control Studies , Confidence Intervals , Female , Follow-Up Studies , Hearing Loss, Noise-Induced/diagnosis , Humans , Incidence , Middle Aged , New South Wales/epidemiology , Occupational Diseases/diagnosis , Odds Ratio , Probability , Reference Values , Retrospective Studies , Risk Assessment , Severity of Illness IndexABSTRACT
Following the reporting of a cluster of cases of brain tumour in the workforce of an underground coal mine (Mine A) in the Newcastle coalfield, a study was carried out to determine whether this phenomenon was due to chance alone or whether an environmental cause could be postulated. The study design was a historical cohort study over 15 years comparing the incidence of brain tumour (ICD9 191 and 192) in the index mine with that in two control mines (Mines B and C) in the same area and with that in the general Australian population. We compared environmental exposures (ionising and nonionizing radiation and chemical exposure) in the three mines. With Australian brain tumour incidence rates as reference, the standardised incidence ratio for brain tumour in Mine A was 5.3 (95 per cent confidence interval (CI) 1.08 to 14.04) and in Mines B and C combined was 1.23 (CI 0.02 to 3.80). On most environmental assessments the three mines were similar but Mine A used larger volumes of solvents than the other mines. This study poses two questions: was the increase in cases of brain tumour in Mine A 'real' and if so, was it related to the use of solvents? Data, from an investigation of a cluster such as this, are unlikely to be conclusive. Nevertheless, such answers are demanded not only by those at risk but also by the mine management, which is responsible for a safe working environment. Some of the difficulties involved with this judgment are discussed.
