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Int. J. Environ. Res. Public Health 2006, 3(4), 355-359;
Abstract: This study was designed to assess the impact of high particulate concentration on peak expiratory flow rate of lungs of sand stone quarry workers. The workers were engaged in different types of activities such as drilling, loading and dressing. These different working conditions had different concentrations of RSPM, leading to different exposure levels in workers. It was found that exposure duration and exposure concentrations were the main factors responsible for damage to the respiratory tracts of the workers. The particles were deposited at various areas of the respiratory system and reduced the peak flow rate. It was also revealed from the study that most of the workers suffered from silicosis if the exposure duration was more than 20 years.
The mining of various minerals and materials is going on since the man has thought about the development. In ancient age mining was done by the manpower and machinery involvement was negligible. Invention of new tools has increased mining activities but at the same time the pollution level also increased. The increase in the pollution level increases the chances of occupational diseases. The type of occupational diseases depends upon the type of pollutant. The consequence, of an inhaled particle depends on its inherent toxicity, its ability to penetrate the site at which it can exert its effects and the amount retained in the lung . The toxicity of the particles retained in the lungs depends upon the chemical composition of the particles . The sand stone quarrying has been established as the largest industry of Jodhpur (India). The quarrying of sand stone around Jodhpur has been going on prior to its inhabitation in the year 1459 AD . More than hundred thousands workers are employed for quarrying and its related activities. Jodhpur sand stone rests uncomfortably over a highly rugged basement of Malani Rhyolite and has been assigned Cambrian Age. Structurally Jodhpur rocks are undeformed, lithofacies and are almost horizontal which helps towards easy quarrying . The working capacity of workers starts decreasing with the increase of working duration in quarries. This decrease in working capacity is because of the damages in the respiratory tract due to deposition of RSPM. PEFR relates to obstruction of larger airways, if diagnosed earlier then preventive measure can be taken, before development of serious respiratory problems hence this parameter was taken for study. This study relates the reduction in PEFR due to exposure duration and RSPM concentration.
A comprehensive methodology was adopted for taking the observations. The various steps undertaken are:
Stone quarries were selected to cover all the deposits around Jodhpur.
Selection of workers: Selection of workers was based upon the exposure duration, type of works and socioeconomic factors. Persons having any respiratory problem were excluded from the study. Only male workers were considered because female workers percentage is negligible.
Development of questionnaire: The ATS-DLD (American Thoracic Society- Division of Lung Diseases) questionnaire was modified and prepared in ‘Hindi’ language
Respirable Particulate concentration in ambient air was measured with the help of ‘High Volume Air Sampler’ for every activity. These activities are designated as loading, dressing and drilling and the workers who perform these works are called labour, dresser and driller respectively. The concentrations of these activities are designated as 1, 2 and 3 for normal quarry environment (i.e. loading), dressing and drilling respectively.
The Peak expiratory flow rate (Maximum expiratory flow rate that can be achieved and sustained for a period of 1.0 sec) of workers engaged in different type of activities was measured with the help of Spirometer (Spiroweb, manufacture by drcdrecare, Hydrabad, India). The predicted value of Peak Expiratory Flow Rate (PEFRp- it depends upon height, weight and age of human) of each worker was calculated by using ERS -93 Equations. Table- 1 gives the average value of RSPM.
The control population was selected from the society of same socioeconomic status but these workers were not exposed to mine environment but they are exposed to normal ambient environment. The effect on respiratory tract is chronic therefore exposure duration was divided in four categories, 0–5 yr., 5–10 yr., 10–15 yr. and >15 yr. and these categories are designated as 1, 2, 3 and 4 respectively. Categories of workers, number of workers in each categories and exposure categories are given in table- 2.
The reduction in Peak Expiratory Flow Rate of lung is calculated and it is designated as IPEFR and is given by Eq-1. The values of PEFRp are calculated by ERS-93 Equation (i.e Eq 2 & Eq 3). The mean values of index (IPEFR) are shown in table- 3. The PEFR and other required parameters (i.e. height, weight, age and sex) of 419 workers were recorded out of which 374 were quarry workers and 45 were in the category of control population.
Morbidity Analysis: ATS-DLD questionnaire was used for study. The different types of respiratory problems found among the workers are given in table 4. The results are shown in terms of percentage of population suffering from different types of problems.
Regression Analysis for IPEFR
The mean values of index IPEFR are calculated for various cases and are shown in table 3. A multiple linear regression model with dependent variable Y and independent variables X1 and X2 is considered:
Where, β0,β1 and β2 are constants and are known as the parameters of the model. The dependent variable IPEFR is denoted by ‘Y’. The independent variables EXCAT (i.e. exposure categories of workers) and PCAT (i.e. particulate concentration categories) are denoted by X1 & X2 respectively. The regression analysis is done by using the data from table- 3. Let the estimates of β0, β1 and β2 are denoted by b0, b1 and b2 respectively. The values of b0, b1 and b2 are obtained by the principle of least squares. The data given in table -3 are analyzed and calculated statistical parameters are given in table 5.
Analysis of Variance for Regression
H0: β1 = β2 = 0 against H1: not all βk = 0: (k=1, 2)
From table-5 the value of calculated ‘F’ i.e.
F = 90.296 and Fk,n−k−1,α = 8.02
Here F > Fk,n−k−1,α; hence reject H0 at α level of significance therefore significance of individual β’s be tested by ‘t – test’.
t-test (for Testing Individual β’s of Multiple Linear Regression Model)
H0: βj = 0 against H1 : βj ≠ 0 : (j=1,2)
The calculated values for ‘t-statistics’ for β1 and β2 are given in table -5.
t (for β1) = 9.515
t ( for β2) = 9.490
The value of tn−k−1;α/2 = 2.26
Here t > tn−k−1;α/2 ; therefore reject H0. Hence β1 ≠ 0 and β2 ≠ 0
As the estimated b0, b1and b2 are
The estimated multiple regression equation for IPEFR is:
The value of R2 is 0.953 which means that about 95 % of variation in the dependent variable “Y” (IPEFR) is due to independent variables X1 and X2
Significance Test for Mean IPEFR (For two Population Means)
To investigate the significance of the difference between the means of two normal populations viz. exposed and controlled for IPEFR; t-test and Cochran-cox test are applied. The t-test for two independent samples is applied when variances of both the populations (exposed and controlled) are unknown but equal whereas the Cochran-cox test is applied for both the population, when the variances of both the populations are unknown and unequal. That is the choice between t-test and Cochran-cox test depends whether variances of both the populations are equal or not. Hence the equality of variances of both the populations can be tested by F-test (Variance Ratio Test).
For IPEFR the values of various test statistics: F, t, and Cochran-cox statistic, for different category of workers and controlled population are given in table 6. First F-test is applied for all the cases to test whether the variances of both the populations are equal. The value of F-statistics is given in col. (6) of the table. If the value of F-statistics is significant (such values are marked with *) the Cochran–cox test is applied and the value of test statistics tc, for different cases are given in col. (13). Whereas, if value of F-statistic is insignificant then t-statistics for different cases, are calculated and its values are given in col. (9). Significant values of these statistics are marked with *. The critical values for F, and Cochran-cox tests are given in cols. (7) and (12). The critical value of ‘t’ i.e.
tn1+n2−2;α is taken as 1.96 (i.e. for normal distribution) .
It is observed from table-6 that the values of ‘t’-statistics or Cochran-cox test statistics, as the case may be are significant for all the cases. Thus it is concluded that there is significant difference between the mean indices for exposed & controlled populations for IPEFR.
Noting further that the mean values of concerning index for exposed population is considerably higher than the corresponding value of control population. Therefore, it indicates that Peak Expiratory Flow Rate of lungs of stone quarry workers are reduced due to the particulate pollution in quarries.
The study was carried out to find the effect of particulate concentration on peak expiratory flow rate of lungs of stone quarry workers. The results indicates that as the exposure duration increases the peak expiratory flow rate of lungs decreases and if exposure duration is same but concentration of particulate matter increases then again the peak expiratory flow rate of lungs decreases. Therefore the decrease in the peak expiratory flow rate of lungs depends upon the exposure duration and particulate concentration.
The equation developed for the decrease in peak expiratory flow rate of lungs of stone quarry workers is given as eq-5 and the validity of the equation is tested statistically. The analysis indicates that decrease in peak expiratory flow rate of lungs of controlled and affected population has significant difference. This is because of working in the polluted atmosphere and this significant difference is statistically verified. It is revealed from this study that if the exposure duration is more than 15 years then the decrease in peak expiratory flow rate of lungs is 56% for labour, 60% for dresser and 65% for driller. The decrease in peak expiratory flow rate in such percentage leads to many respiratory problems like wheezing, cough, silicosis etc. It was found that 58.6% of workers are suffering from respiratory diseases.
|Table 1. Particulate concentrations for different activities|
|Activity||Particulate concentration||Concentration category|
|Normal Quarry Environment||4800 μg/m3||1|
|Table 2. Category of workers and exposure duration|
|Category of workers||Exposure duration in Years||Number of workers||Exposure category|
|Table 3. Mean values of index|
|No. of workers||Worker Category||EXP DUR||EXCAT||PCAT||Mean IPEFR|
(A) Males ( >18 years):(B) Males ( <18 years):
|Table 4. Prevalence of combination of different respiratory problems in quarry workers|
|Type of respiratory problem in combination||Prevalence in percentage|
|Wheezing, Dyspnoea, Cough, Silicosis||5.6|
|Dyspnoea, Silicosis, Asthma||5.3|
|Dyspnoea, Cough, Silicosis||3.5|
|Wheezing, Dyspnoea, Cough||4.1|
|Wheezing, Dyspnoea, Cough, Silicosis, Asthma||1.9|
|Wheezing, Dyspnoea, Cough, Silicosis, Tuberculosis||1.1|
|Wheezing, Dyspnoea, Cough, Silicosis, Asthma, Tuberculosis||1.3|
|Other combination of problems||1.1|
|Population with “No Problems”||41.4|
|Table 5. Values of Statistical parameters|
|Std. error of the estimate||0.0169062|
|Table 6. Tests for equality of means of exposed and control populations for IPEFR|
|Worker Category||Excat||n||MIPEFR||VRIMPEFR||F||Fν1, ν2,0.05||Sp||t||w1||t1α/2||tcr||tc||TEST|
*Significant values of the test statistic under consideration.**The critical value of ‘t’ i.e. tn1+n2−2;α is taken as 1.96 (i.e. for normal distribution)
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