Ashis Bhattacherjee Apurna Kumar Ghosh Nearkasen Chau

1. 17th International Symposium on Epidemiology in Occupational Health, Melbourne, Australia, 13-16 October 2004 Associations of Safety Environment, Training and Individual Characteristics with Occupational Injuries: A Case-Control Study Ashis Bhattacherjee Apurna Kumar Ghosh Nearkasen Chau Indian Institute of Technology National Institute of Technology (India) and National Institute for Health and Medical Research (France)

2. Outline of Presentation • Introduction • Background • Methodology • Study design • Statistical Analysis • Case Study Application • Conclusions

3. Background • Coal mines safety is a perennial problem as the coal mining industry is associated with high accidents and injuries • To reduce the occurrence of accidents, preventive approaches are necessary • So far studies were mainly concerned with the quantitative analysis of accident/injury data • Classification based analysis • Correlation and Regression • Reliability and Risk • Multivariate analysis • Cost-benefit analysis • Time series analysis

4. Background (Contd.) • There is a need to address the accident prevention problem through epidemiological investigation • The occupational injury prevention and control using epidemiological methods can be considered to be a relatively new field of research in mining • Human error has been identified as the major causative factor in (about 93% of the total accidents) mine accidents in a study conducted by the former United States Bureau of Mines • In this study, an epidemiological investigation is conducted to examine various patterns of possible accident causes in coal mines. Special attention has been paid to personal and impersonal variates responsible for mine accidents

5. Objectives of the Work • Investigation of public health approach, based on scientific methods of epidemiology where the injury can be measured in relation to population at risk • Identification of possible personal and impersonal risk factors responsible for injuries based on extensive literature review, suspicion and the practicality of data collection • Identification of a suitable Study Design based on epidemiological concept • Development of response devices for measuring personal and impersonal variates • Applications of univariate and multivariate statistical tools based on principles of epidemiology • Identification of statistically significant risk factors • Identification of the risk group of workers and quantify how much they are liable to risk in comparison to other group of workers

6. Major Factors Contributing to Accidents

7. METHODOLOGY • Case-Control Study Design • a group that has faced injury in the last 5 years (the cases) and • a group that has not faced injury in their career (the controls) One control with the same job and from the same mine was matched to each case Interview questionnaire: • The Worker’s Response Device (WRD) and Supervisor’s Response Device (SRD) have been used in the present investigation • The WRD is a questionnaire based on following factors: safety environment, risk-taking, emotional instability, job dissatisfaction, and job stress • The supervisor’s response device includes ‘safety performance’ of workers Assessment of relationships of some individual factors, safety environment, and training with occupational injuries

8. METHODOLOGY (Contd.) • Statistical analysis • The scores for the factors were computed by summing the scores on individual items. • logistic regression model The data were analyzed via adjusted odds ratio

9. CASE STUDY • Data were collected from three underground coal mines during the period 1999 - 2001 • The average annual productions for the mines were 0.10, 0.10 and 0.24 million tons; average underground employments (per day) were 860, 722 and 1323 miners respectively. • The subjects of this study consist of 404 workers aged between 20 and 60. Out of them 202 were from non-accident group (NAG) or control and 202 were from accident group (AG) or case group. • The workers were administered response device based on safety environment, risk taking behaviour, emotional instability, job dissatisfaction and job stress • Background of the workers has been taken in terms of age, experience, education, total members in the family etc. • Fifteen supervisors were administered response device to identify the safety performance of the workers

10. Table 1 Injury statistics and distribution of the samples according to their occupation

11. Table 2 Description of the variables on the basis of their categories VARIABLESNO. OFNAME CATEGORIES • AGE 3 AGE0 (<30), AGE1 (30-45), AGE2 (>45) • FAMILY SIZE 2 BIG, SMALL • INCOME 2 HIGH, LOW • EDUCATION 2 HIGH LEVEL, LOW LEVEL • SAFETY TRAINING 2 HIGH LEVEL, LOW LEVEL • SAFETY ENVIRONMENT 2 GOOD, POOR • RISKTAKINGBEHAVIOUR 2 HIGH, LOW • EMOTIONAL INSTABILITY2 HIGH, LOW • JOB DISSATISFACTION 2 HIGH, LOW • JOB STRESS 2 HIGH, LOW • SAFETY PERFORMANCE 2 GOOD, POOR • INJURY 2 INJURY, NO INJURY

12. Table 3 Characteristics of the cases and controls (%) % in cases % in Controls Comparison of (202 subjects) (202 subjects) the two groups Age (yrs) <30 16.3 25.8 30 - 45 49.5 47.5 p<0.05 >45 34.2 26.7 Big family size 51.0 37.1 p<0.01 High income group 57.9 43.1 p<0.01 Low level of education 59.9 47.5 p<0.05 * Lack of training 6.4 8.4 NS Poor safety environment 33.7 10.9 p<0.001 Risk taking behavior 27.2 15.8 p<0.001 Emotional instability 24.8 11.4 p<0.001 Job dissatisfaction 28.7 12.4 p<0.001 Job stress 25.7 10.4 p<0.001 Poor safety performance 28.7 10.4 p<0.001 NS: Not Significant

14. Results of Logistic Regression Analysis Adjusted Odds Ratios Indicated the following: • Compared with the emotional stable workers, the emotional instable workers have an odds ratio (OR) of 1.91 (95% CI 1.01 to 3.61). The OR is 2.52 times higher (95% CI 1.37 to 4.63) for those workers who perceived safety environment as poor compared to those who perceived it as good • Workers whose safety performance was poor are found to be more susceptible to injuries compared to the workers whose safety performance was good (OR 2.71, 95% CI 1.50 to 4.89). Compared to the low family size group, high family size group had OR of 1.85 (95% CI 1.19 to 2.87). High income group had an OR 1.64 times higher (CI 1.01–2.67) compared to the less income group

15. Conclusions • In this study 11 risk factors were suspected at the start of investigation. But the epidemiological analysis suggested that only 5 factors are statistically significant. Those are perception of safety environment, emotional instability, poor safety performance, big family size and high income • In this study not only significant risk factors were identified but also the groups which were exposed to risk were identified. The workers who are emotionally instable (score >23), having poor safety performance (score >39), poor perception of safety environment (score >31), big family size, high income come under the risk group • The risk of injury for emotionally instable, poor safety performance, poor perception of safety environment, big family size and high income group are 1.91, 2.71, 2.52, 1.85 and 1.64 times higher compared to other groups. Thereby, information is obtained regarding how much times the risk group of workers are more susceptible to injury compared to the other group

16. Thank You Thank You