National Institute of Occupational Health

Reports of Completed Research Projects



Identification of carcinogen-haemoglobin adduct in benzidine exposed workers

Our earlier findings on the workers exposed to benzidine (BZ) and BZ based dyes revealed that exposure status and excretion pattern of benzidine metabolites were strongly correlated with the level of DNA  benzidine adducts in exfoliated urothelial cell. Further, in an attempt to examine haemoglobin (Hb) adducts, the blood samples were collected from 33 exposed subjects (15 subjects exposed to benzidine and 18 subjects exposed to benzidine based dyes e.g. Direct Black 38) and 15 control subjects matched on age, sex and socio-economic status. These samples were processed and shipped to NCI, NIH,USA on dry ice (-700C) for the analysis of acetylated benzidine-Hb adduct level.

             The haemoglobin content was precipitated from the blood samples by alkaline hydrolysis. After the conventional procedure of extraction and cleanup, the samples were derivatized with heptaflurobutyric anhydride (HFBA). The sample were analyzed by capillary GC equipped with mass detector operating in negative chemical ionization mode with CH4 as reactant gas (ion source 2500C, electron energy 2400C) selected ion monitoring. 
            The mean age of control group (N=15), benzidine dye exposed group (N=18) and benzidine exposed group (N=15) was 26.5 5.1, 23.8 3.7 and 23.3 4.1  years respectively. The findings revealed that the haemoglobin adducts of acetylated benzidine were non-detectable in the control subjects. However, it was present at relatively low level in benzidine dye exposed workers  (1.56 1.06 ngAcBz/100mgHb) and at a very high level among benzidine exposed workers (27.99 13.67 ngAcBz/100mgHb). Comparatively Hb adduct content was about 18 times higher in BZ exposed workers than BZ dye exposed workers. Thus, the findings indicate the usefulness of this technique in screening of subjects from high risk population groups exposed to benzidine and other related aryl amines used in industrial settings.   



Assessment of Work Environment and Health Status of Employees of Southern Iron and Steel Company Limited, Mecheri, Tamil Nadu (Siscol)

The objectives of the study were to assess the dust concentrations of working environment of the Plant and to correlate them with health status of the workers. Hence, a detailed environmental-cum-medical surveillance study was carried out.

Dust sampling was carried out with a dust monitoring equipment. Ambient air temperature was measured with dry bulb thermometers. Sound pressure levels were measured with a sound level meter. Clinical examination was carried out through a standardised questionnaire. Hearing acuity was assessed with an audiometer.


It was observed that the RPM values were 1.78mg/m 3 in Blast Furnace Section (BF), 1.46 mg/m3 in Energy Optimisation furnace (EOF), 1.27 mg/m3 in Ore yard, 0.69 mg/m3 in Continuous Casting Machine (CCM), 0.52 mg/m3 in Sintering Plant and 0.32 mg/m3 in Administration section. This shows that the Blast Furnace Section was the dustiest among all the sections. The average concentration of silica dust  (7.68mg/m3) in Sintering Plant well exceeded the TLV of 4.09g/m3 .


The ambient air temperature was measured to be as high as 30.05-36.2C during tapping operation and 26.5-30.7C without tapping operation against the recommended limit of exposure of 25.9C. The noise level also exceeded the recommended limit of 90 dBA in turbo-blower (96.9 dBA), turbogenerator (92.3 dBA), and compressor area (92.3 dBA) of the power plant.


High blood lead levels were observed in 26.6% workers (160-428mg/dl) of the EOF Section, and in 20% workers (100-358mg/dl) in Blast Furnace Section against the permissible level of 300mg/dl (Biological Exposure Index). Interestingly, 42.85% of control subjects were also observed to have Pb-B levels above the permissible level because of the fact that the administrative section is located opposite to the Petrol Filling Station inside the factory premises and also the high frequency of vehicles passing through the road in front of the administrative section.

The common morbidity pattern observed were: refractive errors (2.2-19.4%), joint pain (2.3-12.5%), pterygium (2.9-4.6%) and chronic bronchitis (1.4-2.9%).The prevalence of hearing impairment was observed in 10 out of 29 subjects (34.5%) in maintenance and mechanical section, 14 out of 44 subjects (31.0%) in CCM, 22 out of  75 subjects (29.0%)  in BF and 3 out of 11 subjects (27.3%) in Sintering Plant. It is suggested that audiometry should be carried out periodically as an intervention programme



Health Surveillance of Workers Exposed to Chromium in a Chemical Industry

                                Chromium occurs in environment in different forms. The respiratory tract in human beings is a major target organ of inhalation exposure to chromium compounds. Workers exposed to Cr (VI) compounds may develop asthma, nasal perforation and other signs of respiratory distress. Therefore, a study was undertaken on environmental and biological monitoring of chromium to assess the health consequences among the workers exposed to chromium in a chemical industry. 

A complete health check up of 176 exposed and 30 control subjects was conducted. Blood and urine samples were collected for estimation of chromium levels as well as relevant biochemical parameters. Sixty-one semen samples were collected from exposed subjects to find out the effect of chromium on human sperm.  

Environmental monitoring of chromium at different places in industrial premises revealed that the level of chromium was highest at filtration unit (27.9-82.3 mg/m3) followed by storage (5.7-76.6 mg/m3) and furnace area (10.5-49.3 mg/m3). The lowest level of chromium (3.6-4.9 mg/m3) was found at office premises. The above result shows that chromium level in the industry was lower than the prescribed TLV of 500 mg/m3

The mean blood Cr level  in exposed workers (6.41 mg/100 ml) was considerably high as compared to the control subjects (2.96 mg/100 ml). A total of 22 cases (16 in furnace staff, 4 in supervisory staff and 2 in maintenance staff) with nasal perforation  were observed with no such cases in control subjects. Biochemical parameters, like glucose, cholesterol, serum protein, creatinine, SGPT showed insignificant alterations in the exposed group compared to control subjects. 

The data of semen analysis of Cr. exposed workers revealed that sperm concentration was below 20 million/ml (lower than normal value) in semen of the ten (16.3%) out of the 61 subjects studied. The sperm motility and sperm viability were below 50% in three and six subjects respectively out of the 59 subjects studied. The data of the seminal pH indicated  that 58.8% subjects were in the normal range ( 7.2-8.0; reported by WHO). However a considerable number of cases i.e. 39.2% showed the higher pH value than the normal range. Recently, Harraway et al. (Am. J. Obstetrics & Gynecol. 182, 1045, 2000) also reported a consistently higher pH value in normal semen as well as in abnormal characteristic semen as compared to reported normal range by WHO. Further the detailed analysis of the parameters is in progress. 





Interaction Effects of Noise, Illumination and Time of Day on Human Work Performance

The ubiquitous presence of noise in industry may be potential enough to cause adverse health consequences. Furthermore, illumination levels lower than those needed could reduce productivity and enhance risk to health and safety of workers. Human activity is also guided by the "Time of Day". In the shop floor all these three stresses could influence work performance. The objective of this study was, therefore, to examine whether the combined effects of noise, illumination and " time of day" had greater effects in human functions than the independent effects of either of these factors. A part of the experiment carried out under quiet condition was reported in 2001. The findings of the experiment, now concluded, are presented here.

 A group of 64 young healthy male human subjects, unexposed to occupational noise, with normal hearing and vision, was administered a battery of six psychological tests viz. DORN, memory, letter cancellation, hand precision, card sorting and digit symbol. These tests were identified following ILO recommendations related to behavioural effects due to physical hazards. The subjects were allocated to two equal groups (Group A and Group B) of 32 each. Subjects of group A worked under quiet condition (60 dB), while those of Group B worked under noise condition (100 dB). The subjects of Group A was further divided into 4 equal sized groups.  Group 1 worked under low illumination level (350 lx) during forenoon (1000-1200h) followed by afternoon (1500-1700h) session, while those of Group 2 worked in the reverse order of afternoon-forenoon sessions. The subjects of Group 3 and Group 4 worked similarly under high illumination level (700 lx). The subjects of Group B worked in the same order as those of Group A.

 The psychological test scores of all the subjects under each illumination level were pulled together for statistical analysis. The test scores were analyzed into three components: speed, accuracy and error. Speed was expressed as either the time taken in performing the task or the total number of attempts. Accuracy was taken to be as the ratio of number of correct attempts to the total number of attempts. While error scores were in terms of proportion of the total number of errors to the total number of attempts. However, the error score in `card sorting` was taken to be the number of cards wrongly sorted out as the speed score was in terms of time taken. The accuracy scores and error scores were transformed into arcsine square root for the best fit of the data to normality. A three way lay out (2x2x2) analysis of variance (ANOVA), with repeated measure, was employed to determine the main and interaction effects of noise.

 The ANOVA showed that the interaction effects of noise and illumination were statistically appreciable reflecting that with the rise in illumination level (700 lx) the speed of performance in DORN test increased under noise condition than in quiet condition. However, the accuracy scores deteriorated under noise condition at 100 dB than that under quiet condition at 60 dB. The times of day effect was not significant on memory (forward) but was appreciable on memory (backward), suggesting superior performance (Mean 6.57) during afternoon than in the forenoon (Mean 4.26). In card sorting test (by face value), noise or illumination did not have any considerable influence on the speed of performance or error scores although the interaction of noise in combination with the illumination reached statistical significance on the latter. This illustrates the fact that the error rates were significantly increased with the noise at high illumination level. In card sorting test (design configuration), the interaction effects of noise x illumination x time of day, did reflect statistical significance, although the independent effects were absent, nor were the interaction effects of any of these two factors significant. The error scores increased significantly under noise condition during forenoon, which however decreased with the rise in illumination level in the afternoon . In the letter cancellation test significant slowing of response rate occurred in noise condition (Figure 3a), while progressive improvement in performance was reflected under increased illumination level. The significant combined effect of noise x illumination x time of day, shows decrements in accuracy of performance during forenoon under noise condition, which was found to improve with the rise in illumination level during afternoon. In the hand precision test the significant interaction effects of these three factors indicate that the rate of decline in accuracy scores under high illumination level was more pronounced under high noise condition during afternoon compared to that in quiet condition. In the digit symbol test the significant interaction effect indicate degradation in accuracy score at high illumination level both under noise and quiet condition in the afternoon with the deterioration being greater under noise condition.

 Thus it may be suggested that the interaction effects of the noise, illumination and time of day were demonstrable on the speed, accuracy and error scores in some of the psychological tests employed in this investigation.