National Institute of Occupational Health

Research Project

Prevention control and treatment of silicosis &
Silico tuberculosis in agate industry
 

       Introduction

       Objectives

       Funding Agency, Subject, STUDY TYPE

       Methodology 

       RESULTS

       CONCLUSIONS

 

 

 

 

 

Introduction

 

Agate industry has been developed primarily as a cottage or household industry mainly located in and around Khambhat (Cambay), Gujarat. The industry gives direct employment to about 15000 employees of both sexes and earns a valuable foreign exchange worth few crores of rupees. 

Agate is semiprecious silica mineral, a variety of chalcedony that occurs in bands of varying colours and transparency having density 2.6 gms/c.c. and hardness of 6.0 to 6.5 on Mohs Scale.  It is essentially quartz and its physical properties are essentially of that mineral.  Grinding and polishing of agate puts it in semi-precious category of ornamental stones.  A variety of articles like necklaces, earrings, cuf-links, key chains, ashtrays, etc., are made from agate.  During grinding of agate large amount of dust containing free crystalline silica is generated in the work environment.  Exposure to this type of dust produces not only silicosis, but also predisposes to the development of tuberculosis.  Recently crystalline silica has been identified as a carcinogen also. 

An epidemiological study carried out by NIOH in 1987 showed that the prevalence of silicosis was 38.2%. The menace of child labour was also observed in this industry.  Environmental Hygiene survey also showed that dust concentration were higher than the prescribed limits.  But the information regarding health status of people living in the vicinity of these units and their exposure to dust containing crystalline silica is not available. 

Amongst various processes, the agate grinding activity, where the agate beads are ground against the rotating emery wheel, generates lots of silica dust. During the preliminary visits, it was observed that this dust not only pervades the work environment but also the indoor and outdoor air of the house where agate grinding is carried out. Consequently, the family members of the house where agate grinding activities are carried out and the community subjects residing in the neighboring houses are also exposed to the air borne silica dust, although they are not engaged in this occupation.

The process of making of agate beads and other decorative articles consist of the following steps. 

1.      Baking of stone

The raw stones are too hard to work out. To make them little brittle, they are subjected to heat treatment in two stages. Initially the stones are left under the sunlight to get rid of its moisture content. This is followed by fire heating. The fire heating of the stone is done in a square pit of about 1-2 in depth. The stones are placed in the earthern pots of about 12 in diameter. The cheap materials, like saw dust, rice husk, cow dung cake etc. are used as fuel. This material burns at a relatively low temperature. After lighting the sawdust, the furnace is covered by a thick iron sheet to prevent the escape of a cracking stone. In a few hours the fuel burns out leaving a cover of hot ash over the stones. The stones are left in ash to bake for about 24-48 hours. After baking, the stones at about 350-450oC, colour of the stones changes to permanent metallic oxide colour because stones contains some metals also. For example, if it contains iron then after heating it is converted into red oxide and the colour of stone changes to red.

2.      Chipping (Breaking) of stone: 

The objective of this process is to break and shape the stone into smaller pieces of approximate size and shape of the final product. Placing the stone on an iron rod, which is about 20 in length, carries out the process. One of its ends is embedded obliquely in the ground at an angle of about 60o. The stones are placed over the upper end of this iron rod which points away from the worker. A hammer, which is made of a cane handle, gently hammers the stone and its barrel shaped head is made up of a cow or buffalo horn. After initial breaking the stone chips are dressed to round, triangular or rectangular pieces. 

3.      Ball milling 

Articles prepared from agate can be classified in two ways

a)      Round (spherical) beads and
b)      All other articles of any shapes 

The grinding machines for above mentioned two types of articles are also different. Necklaces are prepared from spherical beads. For spherical beads, rough rounding is done in a ball mill (rotating drum). After this process grinding is done. For other shapes, this process is not carried out. 

4.      Grinding 

Based upon the shape of the articles, two types of grinding machines are used

 a) Vertical shaft grinding machine (Bankada): Any type of shape can be produced by vertical shaft grinding machine. Emery wheel of 10-12 in diameter and about 3-4 in thickness is electrically rotated. The horse power of the motor is 0.25-0.50 hp (1440 RPM). 

b) Horizontal shaft grinding machine (Patia): This is used for giving spherical shapes to stone for making necklaces. The emery is rotated with an electric motor of 0.5 hp (1440 RPM). The beads are held in the grooved notches of a wooden plank against the movement of emery wheel. 

During the process of grinding, a lot of dust is generated in the work environment. The dust also goes to the surrounding residential areas. 

5.      Drilling 

The drilling of beads is carried out mainly in Nagra and Kharodi villages. To drill a bead, the worker places the bead in a wooden stand. A long spindle studded with diamond on its top does drilling. The rotatory movement of this spindle is produced by a hand-operated bowstring like mechanism. To keep the process cool, water is slowly but steadily dropped over the drilling point. Now a days, machine drilling is also commonly used. 

6.      Polishing 

The agate stone alongwith agate and emery powder with water is placed in an electrically rotated drum. The drum is allowed to rotate for about 48-96 hours. At the end of this process the final product is smooth and glossy.

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Objectives
 

  1. To carry out Environmental and Medical Survey in agate industry and its  vicinity.
  2. To redesign the dust control system on grinding machines so as to make it   effective and acceptable to workers.

3.      To study efficacy of the dust control system.

  1. To organize awareness and educational programmes for agate workers and people living in the vicinity of the industry.

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Funding Agency, Subject, STUDY TYPE

 

Funding Agency Ministry of Health & Family Welfare, Govt. of India.
 
Subject Keys

Silicosis, Silico-tuberculosis, Quartz,
Air Pollution, Serum Angiotensin Convertase
 Enzyme and Copper, Engineering Control
 

Study type EPI, CLN, LAB

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Methodology

 

Methodology and Plan of work

(A) PLAN OF WORK

(1)   Control of dust

There are two types of grinding machines viz. Vertical Grinding Machine (Bankada) and Horizontal Grinding Machine (Patia).  Any shape can be given to the stone by Vertical grinding machine, whereas, Horizontal grinding machine is used only for spherical articles.  Traditional vertical agate machine operates with the motor of 0.25 hp whereas traditional horizontal machine operates with the motor of 0.5 hp.  In 1987-88, NIOH developed a model exhaust system for grinding machines.  Later on, Rural Technology Institute developed both types of machines.  Field trials showed that efficacy of these machines was good but the power consumption was high (1-2 hp). Therefore, it was felt that there is a need for modification in the machine for reducing power consumption to make it economically viable.

(2)   Medical survey 

There is no information available on the exact number of agate grinders, past grinders, the family or community subjects directly or indirectly exposed to the dust generated by the agate grinding machines. Therefore, it was decided to prepare a list of persons by carrying out a door-to-door survey in Khambhat and surrounding villages. Accordingly, a preliminary list of 5080 subjects was prepared from these areas. These were classified as present agate grinders (593), past agate grinders (533), family members (599), community persons (1706) and other workers (1649). The subjects of the category of present grinders were working in the process of agate grinding at the time of study, whereas the past grinders were not working in agate grinding presently but were working at some times in the past. Thus, the subjects of these two categories had occupational history suggesting direct exposure to the silica dust either in the present or in the past. The subjects under the categories community and family had no work history involving silica dust exposure. The family category included those subjects residing in the houses where agate-grinding machines are situated. Similarly, the community subjects resided in the neighboring houses of the houses having agate-grinding machines. The other workers were not engaged in agate grinding in the present or past, but were working in other processes like stone heating, chipping, drilling, polishing, etc. in the agate industry. As these processes are either wet or not generating silica dust, these workers are not exposed to the silica dust during their work but are exposed to the silica dust generated by the agate grinding machines located in the neighboring houses. Therefore, the subjects of community, family and other workers categories are indirectly exposed to the silica dust. Out of the 5080 subjects, a total of 1927 subjects were randomly selected for inclusion in the epidemiological study. In addition, 841 subjects from two villages situated about 20 km from Khambhat were randomly selected as controls. The control subjects had no exposure to the silica dust, as they had never worked in their life in the occupations involving silica dust generation. Thus, the study population included 2768 subjects consisting of 397 present grinders, 341 past grinders, 127 family members, 748 community persons, 314 other workers and 841 control subjects.

(3)   Community monitoring

Air pollution survey will be carried out in the vicinity of agate units.

(4)   Strengthening of industrial hygiene laboratory under Chief Inspectorate of Factories, Gujarat.

Department of Labour, Govt. of Gujarat has started Industrial Hygiene Laboratory under Chief Inspector of Factories. The laboratory is not equipped with instruments like personal samplers, sound level meter and illumination meters. Without these instruments, it is impossible for them to carry out any survey in industry.  Under this project, NIOH decided to equip their laboratory with instruments used in Hygiene Survey in Agate industry so that they can carry out monitoring in future.

(5)   Strengthening of diagnostic and treatment facilities for workers and community.

It was decided to develop special facilities for workers and community having silicosis or silico-tuberculosis at Khambhat.  New X-ray machine for radiographs, and essential medicines will be given to CHC Hospital at Khambhat.

(6)   Awareness and Education Programmes.

Awareness programmes for workers, supervisors, owners and people staying in the vicinity of agate units will be conducted.  Some training programmes for Factory Inspectors and Medical Doctors of Khambhat also will be conducted.

(B) Methodology

(1)   Environmental Hygiene Survey

Total and Respirable dust samples were collected using personal samplers (Envirotech Make Model 801) at a flow rate of 1-6-2.0 liters per minute (LPM).  Duration of each sample was about 5 hours.  Sampling was carried out on traditional machine without exhaust and with exhaust system and efficacy of the system in reducing dust levels was computed after background dust deduction.

(2)   Air Pollution Survey

Four sampling sites were selected in the vicinity of agate units.  Twenty-four hours sampling was carried out continuously for five days using PM-10 high volume samplers (M/s. Netel Chromatographs, India). One sampling site was selected away from the units also and was considered as control site.  There were no units in the vicinity of this site.  Flow rates for PM-10 high volume samples were kept constant at 1100 LPM.  Samples for free crystalline silica (Quartz) analysis were collected separately on 37mm membrane filters at the same sites and the same time for same sampling duration of 24 hrs. every day using vertical elutriators having median cut off at 10 mm, which matches with PM-10 dust.

(3)    Free Crystalline Silica Analysis

Free crystalline silica (Quartz) analysis was carried out by Fourier Transform Infrared (FTIR) Spectroscopy. Air Pollution samples were also analyzed by FTIR (Bomem, Model MB 104), using Standard Reference Materials (SRM) supplied by National Institute of Standards & Technology (NIST), USA. 

a)      Sample Preparation: In this method samples collected on membrane filters (37 mm dia, 0.8 m pore size) are placed in porcelain crucibles, loosely covered, and asked in muffle furnace for 2 hours at 600oC. After ashing, the ash is mixed with 200 mg of potassium bromide (IR grade) dried over night at 110oC. Sample ash and KBr are mixed thoroughly with pestle. The mixture is transferred carefully to a 13-mm evacuable pellet die using glassine paper and camels hair brush. Pellet is then pressed by standard technique. The sample handling equipment is cleaned with ethanol between the samples, so that there is no contamination. Pellets are prepared in an air-conditioned laboratory because sample handling is facilitated by low humidity environment.

b)      Calibration and measurement: Standard pellets are prepared with known quantity of quartz (SRM 1878, NIST, USA). Spectras are taken in the range of 1000 cm-1 to 600 cm-1. Absorbance is measured at 800 cm-1. Calibration curve is prepared using quant method software supplied by the manufacturer (Win-Bomem easy software). The method developed remains in the memory of the computer and can be applied directly on unknown samples.

 (4)    Particle size analysis

Total dust generated by a process of grinding agate stones was collected from work environment for analysis of particle size distribution. The samples were analyzed by the Accusizer 770 Optical Particle Sizer (PSS Particle Sizing Systems, USA). This method of single particle optical sensing (SPOS) enables particles in liquid or gas suspension to be sized individually as they pass through a narrow photo zone of uniform illumination. The system operates with auto dilution resulting in efficient and accurate analysis. A complete analysis and flush cycle can be completed in less than 5 minutes.

 (5)    Designing of the Dust Control System

 Working group consisting of Rural Technology Institute, Gandhinagar, NIOH representatives, a private Pollution Control Consultant and a Mechanical and Environmental Engineer from L.D. Engineering College, Ahmedabad was made under the Chairmanship of Director, NIOH.  The group was assigned the job of designing dust control system. 

(6)    Medical Survey

All the 2768 subjects underwent a detailed medical and occupational history taking followed by a complete medical examination with special reference to the respiratory system. The findings were recorded on standardized questionnaires. Chest x-rays (PA view) were taken in all the subjects on a standard 12 X 15 film at full inspiration on a 300 MA machine. The chest x-rays were evaluated by two experts as per the Guidelines for the Use of International Labour Organization (ILO) International Classification of Radiographs of Pnemoconioses, revised edition, 1980. The pulmonary function tests (PFT) were performed in 1515 subjects with Spirovit SP-10 spirometer.  Three readings of the forced vital capacity (FVC) were recorded. The values of FVC, forced expiratory volume in one second (FEV1.0) and FEV1.0/FVC ratio from the best FVC curve out of the three efforts were considered for analysis. Kamat et al calculated the predicted FVC values using the regression equation. The obstructive abnormality was defined as FEV1.0/FVC ratio less than 75 % of the FVC. The restrictive abnormality was defined as observed FVC value less than 80 % of the predicted FVC value. The mixed or combined abnormality was considered when FEV1.0/FVC ratio was less than 75 % of the FVC and the observed FVC value was less than 80 % of the predicted FVC value. In addition, blood was collected for specialized tests like serum ACE (Angiotensin Convertase Enzyme) and serum copper estimation in 342 randomly selected subjects.  Serum ACE was estimated using diagnostic kits available from Audit diagnostics, UK. The kinetic analysis of ACE was carried out on Smart lab Random Access Batch Analyzer. After appropriate sample preparation, serum copper analysis was done using Atomic Absorption Spectrophotometer (AAS).

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Results
 

(1)                                        Analysis of Free Crystalline Silica (Quartz) in the dust

The permissible level of Exposure in case of dust containing quartz depends upon the percentage of Quartz in the dust and is computed by following formulas:

Permissible Level for Total Dust

=

30

mg/m3

% Quartz + 3

 

Permissible Level for Respirable Dust

=

10

mg/m3

% Quartz + 2

 

Our analysis showed that average quartz content in dust samples was 34.19 14.54.  Based upon this quartz content, Permissible Exposure Level for total dust is 0.81 mg/m3 and for respirable dust is 0.28 mg/m3.

 (2)                                        Environmental Hygiene Survey:

Environmental Hygiene survey at agate grinding units using traditional vertical and horizontal agate grinding machines (Bankada and Patia) showed that dust concentration were much higher than the permissible level of exposure (Tables-I & 2).

 Table-1         Dust Levels (Mean Sd) At Different Traditional Vertical Agate Grinding Machines (Bankda) 

UNIT

A

B

C

D

E

F

G

Total Dust (mg/m3)

9.07 3.55 (7)

25.20 10.87 (4)

8.40 2.72 (7)

58.78 12.83 (5)

39.31 27.38 (9)

11.32 5.22  (4)

39.3 7.42 (4)

Respirable dust (mg/m3)

3.38 0.71 (5)

7.95 4.20  (5)

3.24 0.87 (5)

7.73 2.26  (5)

5.26 2.83  (9)

3.51 1.79 (4)

7.60 1.44 (4)

Figures in the parenthesis indicate number of samples.

 Table-2        Dust Levels (Mean Sd) At Different Traditional horizontal Agate Grinding Machines (Patia)

 

Unit

H

I

J

Total Dust (mg/m3)

8.20 5.62

(5)

15.63 13.63

(4)

18.23 10.52

(5)

Respirable dust (mg/m3)

2.20 0.35

(5)

3.13 2.37

(5)

2.51 0.88

(5)

Figures in the parenthesis indicate number of samples.

 (3)                                        Particle size analysis: Few samples of total dust were analyzed for particle size distribution. A typical set is given in Table-3 

Table-3 : Particle size distribution of total dust 

Diameter (d) (microns)

Number %

Cumm. Number % d

1.12

2.537

0.00

1.32

21.925

2.537

1.64

17.945

24.462

2.03

16.19

42.406

2.52

13.78

58.597

3.13

9.791

72.377

3.89

7.262

82.168

4.82

4.751

89.430

5.99

2.635

94.181

7.43

1.718

96.816

9.22

0.876

98.534

11.44

0.377

98.911

14.19

0.136

99.047

            Median : 2.03 m   Mode : 1.32 m   Mean : 2.55 m

 This table shows that the median particle size is 2.03 m, which means that 50% of the particles are having the size less than 2.03 m. About 96% of the particles are having size less than 10 m. This indicates that the dust produced by grinding of agate stones contains mainly particles in the respirable range (Fig. 1)

(4)                                        Development of Dust Control System and Dust Reduction:

 

(a)                                                          New Vertical Grinding Machine


A new vertical agate-grinding machine was conceived by the working group based upon earlier design of the Rural Technology Institute (Fig.2).  This machine was different from the Conventional Bankada (Fig.3). 

 

Text Box: Fig.3 :      Traditional Vertical Agate Grinding Machine (Bankada)

 

Text Box: Fig.2 :      New Agate Grinding machine

Three persons could sit on this machine at a time.  The machine has 0.75 hp motor and an inbuilt blower, which sucks air through hood placed near the grinding wheel.  Blower and grinding wheel are connected to the same shaft and rotated by same motor.  Exhausted dust laden air goes to Bag Filter.  Dust is collected in the bag filter and dust-free air goes to the environment.

Five units of new agate grinding machine were fabricated and installed at different units.  The efficacy of the system was tested at three units (A, B & C).  The average efficacy for total and respirable dust with respect to traditional machine was 82.41% and 77.40% respectively (Table-4).

Table-4 :       Dust Reduction New Agate Vertical Grinding Machine

 

UNIT

A

B

C

 

Total Dust (mg/m3)

Respir-able dust (mg/m3)

Total dust (mg/m3)

Respir-able Dust (mg/m3)

Total dust (mg/m3)

Respir-able dust (mg/m3)

TRADITIONAL MACHINE

9.07 3.55 (7)

3.38 0.71 (5)

25.20 10.87(4)

7.95 4.20 (5)

8.40 2.72 (7)

3.24 0.87 (5)

NEW MACHINE

1.48 0.31 (4)

0.79 0.58 (4)

9.75 7.00 (9)

4.17 2.30 (10)

1.53 0.55(10)

1.24 0.73 (9)

BACKGROUND DUST

0.49 0.04 (4)

0.30 0.04 (4)

3.72 1.42 (5)

3.23 1.38 (5)

0.49 0.04 (4)

0.30 0.04 (4)

EFFICACY

88.46%

84.09%

71.92%

80.08%

86.85%

68.02%

*  Average efficacy for total dust - 82.41 %        *  Average efficacy for respirable dust 77.4%

*  Figures in the parenthesis indicate number of samples.

Dust reduction n units A, B and C for total and respirable dust using new agate grinding machine is shown in Fig-4. 

The efficacy of the system was good but this machine was not accepted by workers for following reasons.More power consumption, Speed variation could not be given to grinding wheel. Workers were reluctant to change old working habits of sitting on ground while working, and fear of Electric Shock.

(b)   Dust Control System on Traditional Vertical Grinding Machine

Taking into consideration of the views of workers and owners of these units, it was decided to develop dust control system on their traditional Bankadas.  The hood was designed on the Bankada and was connected to Blower with 0.5 hp motor and as in earlier machine dust was collected in the bag filter (Fig.5). 

 

Text Box: Fig. 5 : Traditional Vertical Agate Grinding Machine (Bankada) with Dust Control System.

In this case, grinding wheel and blower are rotated by different motors. This system was installed at one of the units (Unit-E). 

The efficacy of the system was found to be 75.27% and 60.40% for total & respirable dust respectively (Table-5). 

 Table-5           Dust reduction by exhaust system on traditional vertical grinding machine (with old bag filter)

 

Unit

E

 

Total Dust (mg/m3)

Respirable dust (mg/m3)

Traditional Machine

39.31 27.38                       (9)

5.26 2.83     (9)

Traditional Machine With Exhaust

10.51 8.48 (10)

2.59 1.33 (9)

Background Dust

1.05 0.52    (5)

0.84 0.49     (5)

Efficacy

75.27 %

60.40 %

Figures in the parenthesis indicate number of samples.


Reduction in dust concentration for total and respirable dust using dust control system on traditional vertical grinding machine (Bankada) is shown in Fig.6

 

 

Workers were happy to see dust control system on their traditional Bankada but the power consumption remained the same i.e. 0.75 hp. (0.5 hp for blower + 0.25 hp for grinding wheel). 

(c)          Modified Dust Control System for Traditional Vertical Grinding Machine:

Design of the dust control system was modified with the aim of reducing power consumption and better efficacy.  It was decided to drive grinding wheel with the motor of blower having 0.5 hp.  Pulley was attached to the motor of the blower and grinding wheel was rotated with the help of belt.  Thus, the separate motor for grinding wheel (0.25 hp) was excluded.  The total power consumption reduced to 0.5 hp instead of 0.75 hp.  To increase efficacy of the system, design of the bag filter was changed.  Filtration area was increased and dust was collected at the bottom in the water (Fig.7). 

 

Text Box: Fig.7 : Traditional Vertical Grinding Machine (Bankada)
with modified dust Control system


 

G).  Average efficacy of the dust control system was found to be 93.55% and

         93.80% for total and respirable dust respectively (Table-6).

 Table-6 : Dust reduction by modified dust control system on traditional vertical grinding machine 

UNIT

F

G

TOTAL DUST (mg/m3)

RESPIRABLE DUST (mg/m3)

TOTAL DUST (mg/m3)

RESPIRABLE DUST   (mg/m3)

Traditional Machine

11.32 5.22 (4)

3.51 1.79 (4)

39.34 7.42 (4)

7.60 1.44 (4)

Traditional machine with exhaust

1.51 0.06 (4)

0.76 0.37 (4)

2.98 1.68 (4)

0.90 0.45 (4)

Background dust

0.83 0.21 (4)

0.64 0.26 (4)

0.49 0.04 (4)

0.30 0.04 (4)

Efficacy

93.51 %

95.82 %

93.59 %

91.78 %

         Average efficacy for total dust 93.55 %

         Average efficacy for respirable dust 93.80 %

         Figures in the parenthesis indicate number of samples.

 


Dust reduction for total and respirable dust using modified dust control system on traditional Bankada is shown in Fig.8. 

 

Thus, in modified system, not only power consumption reduced but efficacy also increased.  In addition to this, variations in the speed of the grinding wheel can be given simply by changing size of the pulley attached to the motor of blower.

(d)         Dust Control System for Horizontal Grinding machine (Patia)


Dust control system for Horizontal grinding machine (Patia) was same as that of modified dust control system for Vertical grinding machine (Bankada).  The grinding wheel and blower of the dust control system are driven by same motor with 0.5 hp consumption of power.  The hood for the horizontal machine was designed in a different way.  Traditional Patia is shown in Fig.9.  Traditional Patia with hood is shown in Fig.10.

Text Box: Fig.9 :    Traditional Horizontal Grinding Machine (Patia)
Text Box: Fig.10 : Traditional Horizontal Grinding Machine (Patia) with Hood

 

 

 

Traditional Patia with complete dust control system is shown in Fig.11 

Text Box: Fig. 11 :      Traditional Horizontal Machine (Patia) with Dust Control System.


 

This system was installed at the units (Unit-H, I & J).  Efficacy of the system was tested and average efficacy was found to be 93.73% and 90.21% for total and respirable dust respectively (Table-7).   

Table-7 :          Dust Reduction by Dust Control System on Traditional Horizontal Grinding Machine (Patia)

Unit

H

I

J

Total dust (mg/m3)

Respirable Dust (mg/m3)

Total dust (mg/m3)

Respirable Dust (mg/m3)

Total dust (mg/m3

Respirable Dust (mg/m3)

Traditional machine

8.20 5.62 (5)

2.20 0.35 (5)

15.63 13.63 (4)

3.13 2.37 (5)

18.23 10.52 (5)

2.51 0.88 (5)

Traditional machine with exhaust

1.84 0.69 (5)

1.04 0.42 (5)

0.73 0.56 (9)

0.37 0.21 (9)

0.82 0.37 (5)

0.38 0.18 (5)

Background dust

0.83 0.21 (4)

0.64 0.26 (4)

0.35 0.1 (4)

0.33 0.11 (4)

0.35 0.1 (4)

0.33 0.11 (4)

Efficacy

86.30 %

74.36 %

97.41%

98.57%

97.37%

97.71%

Figures in the parenthesis indicate number of samples.

Average efficacy for total dust  = 93.73%

Average efficacy for respirable dust = 90.21%

Reduction in dust levels for total and respirable dust using dust control system on horizontal grinding machine is shown in Fig.12. 


This system was shown to many workers and they really appreciated this system and they are willing to install the system. 

(5)                                        Air Pollution Survey

Four sampling sites (A, B, C, D) in the vicinity of agate units were selected and 24 hrs continuous monitoring was carried out with PM-10 high volume samplers.  Three control sites (E, F and G) were selected away from these units also.  Dust concentrations (mg/m3) are shown in Table-8.   

Table-8           PM 10 Dust Levels (mG/M3) At Various Locations in the Vicinity of Agate Units 

Type of location

Locations

Dust Levels   (Mean Sd)

Quartz%

Quartz Concentration (mg/M3)

In the vicinity

A  (Shakkarpur)

311.80 46.66 (5)

9.03 3.93(5)

28.15

B (Hajju Fajju)

325.21 34.84 (5)

5.66 1.88 (5)

18.41

C (Vadava)

235.18 14.13 (5)

4.00 2.67 (5)

9.40

D (Bhoiwadi)

204.78 27.22 (5)

3.45 1.30 (5)

7.06

          Average

272.46 57.83 (20)

5.61 3.31 (20)

15.28

Range

204.78 325.21

3.45 9.03

7.06 28.15

Control site

E                                 (Nareshwar)

154.84 36.56 (5)

1.89 0.35 (4)

2.92

F (Rohini)

95.80 10.78 (5)

1.91 1.19 (5)

1.83

G (Pandad)

236.18 40.12 (5)

1.82 1.58 (5)

4.30

Average

162.27 66.50 (15)

1.87 1.11 (14)

3.03

Range

95.80 236.18

1.82 1.91

1.83 4.30

Figures in the parenthesis indicate number of samples.

Quartz content and quartz concentration at different localities is shown in the Table-8.

The average dust concentration (for sites A, B, C & D) is 272.46 mg/m3 where as the dust concentration at control sites (E, F & G) was 162.27 66.50 mg/m3.

The average quartz content in the vicinity of agate units (Sites A, B, C & D) was found to be 5.61% whereas the average quartz content at control sites (E, F & G) was only 1.87%.  The average quartz concentration for sites A, B, C and D (in the vicinity) was found to be 15.28 mg/m3, whereas the quartz concentration for control sites was 3.03 mg/m3.   The average quartz concentration in the vicinity of Agate units are 5.04 times higher than the same for control sites.   Hence, it can be concluded that agate units do contribute to the deterioration of community environment.

(6)   Medical Survey 

Table 9 shows the category and sex wise distribution of the study subjects. The study population included 2768 subjects consisting of 397 present grinders, 341 past grinders, 127 family members, 748 community persons, 314 subjects from the Other workers group and 841 control subjects. Out of these, 1456 subjects were men and 1312 were women.

Table 9: Category and sex - wise distribution of the study subjects 

Category

Men

Women

Total

Control

412 (28.3)

429 (32.7)

841 (30.4)

Community

294 (20.2)

454 (34.6)

748 (27.0)

Family

53 (3.6)

74 (5.6)

127 (4.6)

Other workers

216 (14.8)

98 (7.5)

314 (11.3)

Present grinders

296 (20.3)

101 (7.7)

397 (14.3)

Past grinders

185 (12.7)

156 (11.9)

341 (12.3)

Total

1456 (52.6)

1312 (47.4)

2768 (100.0)

 Figures in parenthesis indicate percentages

Table 10 shows the age and category wise distribution of the study subjects. The mean age of all the categories except the past grinders (41.7 years) is comparable. It is noted that except the past grinders, the majority subjects in all the groups were below the age of 40 years and therefore in the working age group.

Table 10: Age and category - wise distribution of the subjects 

 

 

Category of the subjects

Control

Family

Commu-nity

Other workers

Past grinders

Present grinders

Total

< 20

179 (21.3)

38 (29.9)

161 (21.5)

59

(18.8)

7

(2.1)

46

(11.6)

490 (17.7)

20-29

175 (20.8)

19 (15.0)

143 (19.1)

74

(23.6)

41

(12.0)

129

(32.5)

581 (21.0)

30-39

182 (21.6)

32 (25.2)

140 (18.7)

100 (31.8)

103 (30.2)

115

(29.0)

672 (24.3)

40-49

132 (15.7)

15 (11.8)

124 (16.6)

52

(16.6)

93

(27.3)

77

(19.4)

493 (17.8)

> 49

173 (20.6)

23 (18.1)

180 (24.1)

29

(9.2)

97

(28.4)

30

(7.6)

532 (19.2)

Mean

34.3

31.6

35.4

31.6

41.7

31.9

34.7

SD

15.9

15.5

16.9

12.2

12.5

11.3

15.1

Total

841

127

748

314

341

397

2768

 

Figures in parenthesis indicate percentages X2 (20) = 183.5***, p <0.001

Table 11 shows the prevalence of different respiratory symptoms as reported by the study subjects. It is seen that apart form nocturnal dyspnoea among the family members and other workers, the prevalence of all the respiratory symptoms was significantly higher in all the categories as compared to the controls. It is noted that the family members and other workers had relatively lower prevalence than the remaining categories. Similarly, the past grinders had higher prevalence of respiratory symptoms than the present grinders. 

Table 11: Prevalence of respiratory symptoms among the study subjects according to the categories

Category

Respiratory symptoms

Cough

Chronic bronchitis

Hemoptysis

Dyspnoea

Nocturnal dyspnoea

Chest pain

Control

(N = 841)

81

(9.6)

17

(2.0)

3

(0.4)

21

(2.5)

17

(2.0)

39

(4.6)

Community

(N = 748)

310

(41.4) ***

77

(10.3) ***

22

(2.9) ***

175

(23.4) ***

34

(4.5) ***

143

(19.1) ***

Other workers

(N = 314)

106

(33.8) ***

17

(5.4) ***

15

(4.8) ***

70

(22.3) ***

3

(1.0)

35

(11.1) ***

Family

(N = 127)

32

(25.2) ***

6

(4.7) ***

1

(0.8) ***

25

(19.7) ***

2

(1.6)

18

(14.2) ***

Present grinders

(N = 397)

168

(42.3) ***

41

(10.3) ***

23

(5.8) ***

127

(32.0) ***

11

(2.8) ***

85

(21.4) ***

Past grinders

(N = 341)

215

(63.0) ***

56

(16.4) ***

56

(16.4) ***

180

(52.8) ***

27

(7.9) ***

130

(38.1) ***

 N = Total number of subjects in the category

Figures in parenthesis indicate percentages

*** = p < 0.001

The comparative analysis of grades of dyspnoea among the study subjects is presented in Table 12. It is seen that a significantly lower proportion of the past grinders (47.2 %) followed by present grinders (68.0 %) and others as compared to 97.5 % of the control subjects had no dyspnoea (grade zero). Considering the severe grades (grades 4 and 5) of dyspnoea, the past grinders (22.6 %) followed by present grinders (10.5 %) had higher prevalence than the remaining categories. 

Table 12:         Distribution of the study subjects according to the category and grade of dyspnoea

Category

Grade of dyspnoea

0

1

2

3

4

5

Control

(N = 841)

820

(97.5)

2

(0.2)

2

(0.2)

8

(1.0)

4

(0.5)

5

(0.6)

Community

(N = 748)

573

(76.6)

5

(0.7)

47

(6.3)

49

(6.6)

30

(4.0)

44

(5.9)

Other workers

(N = 314)

244

(77.7)

3

(1.0)

27

(8.6)

21

(6.7)

12

(3.8)

7

(2.2)

Family

(N = 127)

102

(80.3)

3

(2.4)

5

(3.9)

8

(6.3)

3

(2.4)

6

(4.7)

Present grinders

(N = 397)

270

(68.0)

5

(1.3)

32

(8.1)

48

(12.1)

26

(6.5)

16

(4.0)

Past grinders

(N = 341)

161

(47.2)

5

(1.5)

42

(12.3)

56

(16.4)

41

(12.0)

36

(10.6)

Note: For analysis purpose, grades 1 and 2 and grades 4 and 5 were pooled separately.

N = Total number of subjects in the category   

Figures in parenthesis indicate percentages   

X2 (15) = 420.3 *** (p < 0.001) 

Table 13 shows the prevalence of different non respiratory symptoms as reported by the study subjects. It is seen that the constitutional symptoms like weight loss, anorexia and low-grade fever and work related joint pains were significantly higher among the exposed subjects as compared to the controls. It is also noted except joint pains, the grinders had higher prevalence of these symptoms than the remaining categories.

Table 13: Prevalence of non respiratory symptoms among the study subjects according to the categories 

Category

Weight loss

Fever

Anorexia

Joint pains

Control

(N = 841)

13

(1.5)

7

(0.8)

21

(2.5)

4

(0.5)

Community

(N = 748)

96

(12.8) ***

104

(13.9) ***

107

(14.3) ***

89

(11.9) ***

Other workers

(N = 314)

30

(9.6) ***

30

(9.6) ***

37

(11.8) ***

11

(3.5) ***

Family

(N = 127)

10

(7.9) ***

13

(10.2) ***

13

(10.2) ***

3

(2.4) ***

Present grinders

(N = 397)

73

(18.4) ***

69

(17.4) ***

71

(17.9) ***

17

(4.3) ***

Past grinders

(N = 341)

94

(27.6) ***

96

(28.2) ***

82

(24.0) ***

35

(10.3) ***

N = Total number of subjects in the category    

Figures in parenthesis indicate percentages

*** = p < 0.001

The respiratory system abnormalities were higher among the grinders as compared to other three categories and controls had the lowest prevalence as seen from table 14.

Table 14: Prevalence of respiratory abnormalities among the study subjects according to the categories

Category

Respiratory system abnormalities

Tracheal shift

Abnormal breath sounds

Rales

Persistent

rales

Rhonchii

Control

(N = 841)

11

(1.3)

0

(0.0)

0

(0.0)

0

(0.0)

6

(0.7)

Community

(N = 748)

6

(0.8)

26

(3.5) ***

30

(4.0) ***

13

(1.7) ***

15

(2.0) ***

Other workers

(N = 314)

9

(2.9) ***

17

(5.4) ***

31

(9.9) ***

6

(1.9) ***

9

(2.9) ***

Family

(N = 127)

6

(4.7) ***

6

(4.7) ***

11

(8.7) ***

3

(2.4) ***

5

(3.9) ***

Present grinders

(N = 397)

38

(9.6) ***

65

(16.4) ***

71

(17.9) ***

22

(5.5) ***

16

(4.0) ***

Past grinders

(N = 341)

21

(6.2) ***

38

(11.1) ***

48

(14.1) ***

17

(5.0) ***

26

(7.6) ***

N = Total number of subjects in the category  

Figures in parenthesis indicate percentages

*** = p < 0.001 

The prevalence of silicosis, tuberculosis and silico-tuberculosis among different categories of the study subjects is shown in Table 15. The prevalence of tuberculosis in the control subjects was 3.7 % and is comparable with the national prevalence of tuberculosis. As compared to this, the prevalence of tuberculosis in other categories was significantly higher (18.8 53.7 %). The odds ratio was calculated for each category keeping the prevalence of the control category as reference. The odds ratio ranged from 6.1 6.6 in the categories of community, other workers and family and was significantly higher than the controls but among themselves they were comparable. In the present grinders the prevalence was still higher (27.0 %) with odds ratio of 9.6, whereas in the past grinders, the prevalence of tuberculosis was as high as 53.7 % and the odds ratio was 30.3. This indicates that the grinders had 10 30 times higher odds of developing tuberculosis as compared to the controls.

It is further seen that there is no silicosis or silico-tuberculosis among the control subjects, as they are not exposed to the silica dust. On the other hand, the prevalence was higher among the remaining categories due to the exposure to the silica dust either indirectly as in community, family members and other workers or directly as in the present and past grinders. The odds ratio for silicosis and silico-tuberculosis was calculated keeping the prevalence of community subjects as the reference. The prevalence of silicosis showed significant linear increase from the community subjects to the past grinders with increasing risk of developing silicosis as suggested by the odds ratio increasing from 1.0 in the community subjects to 8.4 in the past workers. The prevalence of silico-tuberculosis though lower than that of silicosis, also showed significant linear increase among all the categories with still higher odds ratio as compared to silicosis. In general, the community, family and other workers behaved similarly with respect to their odds ratio. The same was true about the past and present grinders.

Table 15: Prevalence of silicosis, tuberculosis and silico-tuberculosis among the study subjects according to the category 

Category

N

Tuberculosis

Silicosis

Silico-tuberculosis

n (%)

OR

n (%)

OR

n (%)

OR

Control

841

31

(3.7)

1.0

0

(0.0)

-

0

(0.0)

-

Community

748

150

(20.1)***

6.6 (4.3-10.0)

51

(6.8)

1.0

21

(2.8)

1.0

Other workers

314

59

(18.8)***

6.1 (3.7-9.8)

28

(8.9)

1.3

12

(3.8)

1.4

Family

127

25

(19.7)***

6.4 (3.5-11.7)

14

(11.0)

1.7

8

(6.3)

2.3

Present grinders

397

107

(27.0)***

9.6 (6.2-15.0)

116

(29.2)***

5.6 (3.9-8.2)

59

(14.9)***

6.0 (3.3-8.6)

Past grinders

341

183

(53.7)***

30.3 (19.6-47.0)

130

(38.1)***

8.4 (5.8-12.3)

93

(27.3)***

13.0 (7.7-22.0)

 

N = Total number of subjects in the category    

n = Number of subjects in the subgroup having silicosis, tuberculosis or silico-tuberculosis

OR = Odds ratio   

*** = p < 0.001

Table 16 shows the prevalence of silicosis among the grinders according to the duration of grinding. It is seen that the prevalence of silicosis among the present grinders increased significantly with the duration of grinding. Though the linear trend with regard to duration of grinding was seen as judged by the chi square in the past grinders, the odds ratio was not significantly higher in 5 8 and 13 16 years exposure group. 

Table 16: Prevalence of silicosis among the grinders according to duration of grinding (years)
           

Grinding (Years)

Present grinders

Past grinders

N

n (%)

OR

N

n (%)

OR

04 & less

90

5

(5.6)

1.0

138

39

(28.3)

1.0

05-08   

110

16

(14.5) *

2.9

90

34

(37.8)

1.3

09-12   

64

22

(34.4) ***

8.9

(2.9-29.1)

58

31

(53.4) **

2.9

(1.5-5.8)

13-16   

42

17

(40.5) ***

11.6

(3.5-40.3)

28

11

(39.3)

1.6

17 & more

91

56

(61.5) ***

27.2

(9.4-84.7)

27

15

(55.6) **

3.2

(1.3-8.0)

 

N = Total number of subjects in the group    

n = Number of subjects in the group having silicosis

* = p < 0.05, ** = p < 0.01, *** = p < 0.001

 

Past history and family history of pulmonary tuberculosis was enquired in all the subjects. The resulting prevalence of pulmonary tuberculosis is presented in Table 17. It is seen that the prevalence of past history of pulmonary tuberculosis in the study subjects as well as in their family members was significantly higher in all the categories as compared to the controls. However, the community, other workers and family categories had comparable past as well as family history of pulmonary tuberculosis. It is also seen that the family, community and other workers had lower prevalence of pulmonary tuberculosis in the past than the grinders.

Table 17: Category - wise prevalence of pulmonary tuberculosis according to the past and family history among the study subjects
 

Category

Past history

Family history

n (%)

n (%)

Control (N = 841)

10

(1.2)

4

(0.5)

Community (N = 748)

69

(9.2)

98

(13.1)

Other workers (N = 314)

37

(11.8)

43

(13.7)

Family (N = 127)

9

(7.1)

20

(15.7)

Present grinders (N = 397)

68

(17.1)

89

(22.4)

Past grinders (N = 341)

144

(42.2)

96

(28.2)

X2

317.7***

200.17***

 

N = Total number of subjects in the category    

n = Number of subjects in the category having past or family history of pulmonary tuberculosis

*** = p < 0.001

Table 18 shows the prevalence of silicosis, tuberculosis and silico-tuberculosis among the study subjects in relation to their past history of tuberculosis. It is seen that prevalences of all the three diseases were significantly higher in the subjects having past history of pulmonary tuberculosis as compared to those who never had tuberculosis in the past. Among the subjects with past history of tuberculosis the odds were at least 9.3 times higher for tuberculosis, 5 times for silicosis and 6.2 times for silico-tuberculosis than those not having the past history of tuberculosis.

Table 18: Prevalence of silicosis, tuberculosis and silico-tuberculosis among the study subjects having past history of tuberculosis      

Past history of tuberculosis

Tuberculosis

Silicosis

Silico-tuberculosis

No (N = 1606)

286

(17.8)

187

(11.6)

81

(5.0)

Yes (N = 327)

238

(72.8)

152

(46.5)

112

(34.3)

Odds ratio

12.3

(9.3-16.4) ***

6.6

(5.0-8.7) ***

8.6

(6.2-12.0) ***

N = Total number of subjects in the group    

Figures in parenthesis indicate percentages

*** = p < 0.001 

The subjects were divided into two categories (i) with tuberculosis and (ii) without tuberculosis for analyzing the results of serum ACE and copper estimations. Further, they were grouped on the basis of profusion grades 0, 1, 2, & 3 of small opacities on chest x-ray.  SACE levels according to the category of silicosis and subjects without tuberculosis (only silicosis) are given in Fig. 12. The increasing SACE were observed from profusion 0 to profusion 3. The SACE levels show higher values in corresponding profusion grades in subjects with tuberculosis Fig. 12. Serum copper in subjects without tuberculosis and subjects with tuberculosis in different profusion grades is given in the Fig. 13, which showed an aggravated increase in subjects with tuberculosis in corresponding profusion grades. From result of analysis of variance it is seen that ACE and Cu levels differing significantly  (p<0.005) according to tuberculosis status and profusion grade. Multiple regression analysis was carried out with profusion grade as dependant variable and age, SACE, Copper and tuberculosis status as independent variable. The results are presented in Table 19. The regression coefficient of age, SACE and Copper are significant and positive.  Thus data suggest increasing trend in SACE, Copper with profusion grade. The adjusted R2 indicate that 30% of variation in profusion grade is explainable by Age Copper and tuberculosis code. Since lysyloxidase an enzyme responsible for collagen cross-linking requires copper as an activator ion significantly increased copper levels with profusion grade can be explained. 

 The levels of serum ACE (Fig. 12) and copper (Fig. 13) significantly increased with the increasing grade of profusion in silicosis and silico-tuberculosis. The multiple regression analysis with profusion grade as dependent variable and age, ACE, copper and tuberculosis status as independent variable showed that regression coefficients of age, ACE and copper are significant and positive. Further, adjusted R2 indicated that 30 % variation in profusion grade is explained by ACE, copper, age and tuberculosis status. However, the contribution of ACE is highest as suggested by the regression coefficient. Hence, serum ACE can be used as a good indicator of progression of profusion of small opacities in workers exposed to the silica dust.  

Figure 12: Serum ACE levels in silicosis and silico-tuberculosis patients

 

Figure 13: Serum copper levels in silicosis and silico-tuberculosis patients

Table 19. Multiple regression analysis with profusion grade as dependent variable and ACE, copper, age, and tuberculosis status as independent variables

 

Variable

Coefficient (B)

SE (B)

Significance

ACE

0.25356

0.003275

P<0.005

Copper

0.004523

0.001749

P<0.05

Age

0.017593

0.004063

P<0.005

TB status

0.223050

0.113867

P<0.1

Constant

-2.203662

0.316299

P<0.005

 Adjusted R2 = 0.3013, P<0.005

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 Conclusions

 

The significantly higher prevalence of the respiratory and non-respiratory symptoms and clinical respiratory signs among the exposed subjects as compared to the controls suggested that the exposure to the silica dust is responsible for these findings. Further, the present or past grinders who are directly exposed to the dust due to their occupation were having the highest prevalence, but those having the indirect exposure to silica dust such as the family, community or other workers also had high prevalence of these conditions. Similarly, the prevalence of silicosis, silco-tuberculosis and tuberculosis was significantly higher among all the categories as compared to the controls. For the indirect exposure groups the chances of developing tuberculosis were as high as 6.1 to 6.6 as compared to the controls, whereas for the present and past grinders the chances were still higher (9 and 30 times, respectively) as suggested by the odds ratio. The chances of developing silicosis and silico-tuberculosis though comparable were higher in the family and other workers than the community, the present and past workers had much higher chances of developing these diseases when compared to the community subjects. 

 The biochemical data suggest increasing trend in SACE and copper with profusion grade. When adjusted R2 (0.3013, P < 0.005) is considered, it indicates 30% variation in profusion grade due to age, SACE, copper and tuberculosis status with clearly evident highest contribution of SACE. Based on these observations, it is suggested that SACE can be used as a biomarker in silicosis and silico-tuberculosis.

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