SUBJECTS AND METHODS
This present study is a retrospective occupational injury record study of 5-year duration involving the workers of a chemical industry. Along with this record study, to collect the personal details of the workers, an interview was also conducted with the workers who have worked in the factory in the study
period of 5 years
Prior informed consent was taken from the participants and necessary ethical clearance from the institutional ethical committee was also obtained for this study. Thus, data in relation to age, sex, job, level of education, experience, habits of smoking and alcohol, etc. were collected. A total of 307 permanent and 419 temporary workers were interviewed. Nine permanent and 29 temporary workers, who have worked during the study period could not be interviewed due to nonavailability. But, accident-related data were collected in relation to all 316 permanent and
448 temporary workers. Chi-square test was done on the data regarding the personal characteristics of the workers in order to examine the comparability between temporary and permanent workers.
Occupational injury registers, pay rolls, productivity registers were examined for the study period of 5 years to collect data in relation to number of accidents, number of employees, amount of lost man-days and amount of working man-hours. Frequency rate and severity rate were calculated as per the standard statistical procedure.[12] Ninety-five percent confidence intervals were calculated for each calculation of frequency rate and severity rate for comparison between the two kinds of workers. [13] Frequency rate was calculated as number of accidents per million working man-hours and severity rate was calculated as number of lost man-days per thousand working man-hours.
Mean number of occupational injuries/person was calculated for both permanent and temporary workers. This calculation was done
for all workers, workers with one or more
accidents and workers with two or more accidents.
In this study, only reportable injuries (time loss occupational injuries) have been taken into consideration to take care of the factor of nonreporting. Such an occupational injury is compulsorily reported by the concerned worker
because of the fact that reporting ensures his
worker is given by P (χ) = e- χ/χ for = 0,
Table 1: Personal characteristics of the workers
percentage of migrant workers) in the same
RESULTS
Habit of tobacco use
for highly skilled technical persons). This industry manufacturing fertilizer was an
35.3 years for permanent workers and
35.9 years for temporary workers. One
Others 184 (59.9) 248 (59.2)
industry of semi seasonal nature. Work demand being much more for 7–8 months in a year the temporary workers were employed mostly in that time. The temporary workers also (getting opportunity of regular employment for 7–8 months every year) were working in the same factory for years. No system of shifting from temporary to permanent status was existent in this factory.
Statistical analysis
Comparison was made between permanent and temporary workers by using the Mann– Whitney U-test (normality assumption being violated). Proportion of workers (permanent and temporary both) involved in one or more and two or more occupational injuries were
calculated and comparison of permanent and
hundred and sixty-nine (55.1%) permanent workers and 222 (53.0%) temporary workers were in the age group of less than 35 years. Fifty-three (17.3%) permanent workers were
illiterate, while 32 (10.4%) were higher secondary or above level educated. The numbers were 80 (19.1%) and 33 (7.8%), respectively, in case of temporary workers. Two hundred and fifty (81.4%) permanent workers and 330 (78.7%) temporary workers had experience of 5 years or more in the same factory. Two hundred an d nine (68.1%) permanent workers and 293 (69.9%) temporary workers were tobacco users (either smoking or chewing). Majority of both kinds of workers were involved in production division [One hundred twenty-three (40.1%) permanent
and 171 (40.8%) temporary workers]. Others
temporary workers was found to be 277 (95% CI = 258–297). For permanent workers it was
41 (95% CI = 34–48). Severity rate for temporary workers for the same period was
5.33 (95% CI = 5.24–5.41). For permanent workers it was 0.72 (95% CI = 0.69–0.75). Relative risk calculated on the basis of frequency rate was 6.7 (95% CI = 5.6–8.0) and on the basis of severity rate was 7.43 (95% CI = 7.12–7.75) [Table 2]. Mean number of injuries/person was significantly higher (P < 0.001) in temporary workers in comparison of permanent workers when compared in relation to all workers, workers with one or more occupational injuries and workers with two or more occupational injuries. One or more occupational injuries were found
with 238 (53.1%) of temporary workers and
113 (35.8%) of permanent workers
(P < 0.001), whereas two or more occupational
injuries were met with by 213 (47.5%) temporary workers and 25 (7.9%) permanent workers (P < 0.001) [Table 3].
Repetitive occupational injury occurrence was found in a section of temporary workers. One hundred and eighty (40.18%) temporary workers met with three or more injuries, 107 (23.88%) met with four or more and 26 (5.80%) contacted five or more injuries in the period of
5 years. Comparison of observed and expected (Poisson’s probability distribution) injury occurrences showed that though the injury occurrences in case of permanent
temporary workers in this respect was made by using the chi-square test. A theoretical model of Poisson’s distribution was fitted to the occupational injury occurrence data of permanent and temporary workers to calculate the expected occurrences and a comparison between the expected and actual occurrence was made by using the chi-square test of goodness of fit. Poisson ‘s probability of committing ‘’ number of ‘accidents’ by a
were engaged in different other sections (maintenance, packing, loading, etc.) [Table 1]. All the employees of this factory were males. No female worker was employed in this factory. Application of chi-square test showed that there was no significant difference in the personal characteristics of the two worker groups.
Frequency rate (for a period of 5 years) for temporary workers was found to be 277 (95% CI = 258–297). For permanent workers it was
41 (95% CI = 34–48). Severity rate for temporary workers for the same period was
5.33 (95% CI = 5.24–5.41). For permanent workers it was 0.72 (95% CI = 0.69–0.75). Relative risk calculated on the basis of frequency rate was 6.7 (95% CI = 5.6–8.0) and on the basis of severity rate was 7.43 (95% CI = 7.12–7.75) [Table 2]. Mean number of injuries/person was significantly higher (P < 0.001) in temporary workers in comparison of permanent workers when compared in relation to all workers, workers with one or more occupational injuries and workers with two or more occupational injuries. One or more occupational injuries were found
with 238 (53.1%) of temporary workers and
113 (35.8%) of permanent workers
(P < 0.001), whereas two or more occupational
injuries were met with by 213 (47.5%) temporary workers and 25 (7.9%) permanent workers (P < 0.001) [Table 3].
Repetitive occupational injury occurrence was found in a section of temporary workers. One hundred and eighty (40.18%) temporary workers met with three or more injuries, 107 (23.88%) met with four or more and 26 (5.80%) contacted five or more injuries in the period of
5 years. Comparison of observed and expected (Poisson’s probability distribution) injury occurrences showed that though the injury occurrences in case of permanent