An emerging body of research literature has shown a strong association between respiratory health problems and certain occupations [1]. Acute as well as chronic occupational exposures to chemicals have found to be lethal for the workers in industrial plants [2]. Although these chemicals are known to invariably affect all body systems, lungs are most vulnerable to air–borne hazards which are caused due to exposure to wood dust which is produced in sawmills, furniture industries, cabinet making, and carpentry [3]. Studies which had been done earlier have reported that exposure to wood-dust had caused adverse symptoms like cough, malaise, chest pain, dyspnoea and headache in wood workers [4]. A few studies have commented on the role of wood-dust in inducing occupational asthma, chronic bronchitis, pnuemonitis, nasopharyngeal and lung malignancies, but data is relatively inconclusive [5].
Many researchers have observed a reduced PEFR (Peak Expiratory Flow Rate), a forced vital capacity (FVC) and a forced expiratory volume in first second (FEV1) in wood workers as compared to those in general population [6]. In view of a dearth in information on this issue, it was necessary to carry out the present research as a detailed study, on effects of wood dust on peak expiratory flow rate (PEFR), which were caused by work exposure, which was lacking in this geographical region.
The aim of present study was to know the values of PEFR in healthy, non-smoking carpenters and the influence of age, height, weight, body surface area and duration of exposure on these PEFR values and to compare these values with those of healthy non–smoking persons who were engaged in works other than carpentry.
Material and Methods
This study was conducted in the Department of Physiology, Rajindera Medical College, Patiala, India. The subjects comprised of 150 randomly selected, male carpenters who were in the age group of 18–45 years. Their ages, smoking habits, duration of exposure, physical status and health conditions were recorded by using a questionnaire. After recording their brief history, they were examined as per the proforma, which was attached. The ethical committee’s clearance and informed consents of the subjects were obtained.
Healthy persons with a previous history of respiratory illnesses and persistent cough or expectoration and smokers were excluded from this study, because smoking is a more important cause of respiratory symptoms and reduction in the ventilatory capacity than wood dust. The study group was divided into two different groups i.e. Group A and Group B on basis of their profession. Group A (study subjects) consisted of 150 healthy, non-smoking carpenters who were working in Patiala District. Group B (control subjects) consisted of 150 healthy, non–smoking persons who were engaged in works other than carpentry.
Further, study and control subjects were categorized according to their age, height, weight, body surface area and duration of exposure to wood dust. PEFR was determined by using a Mini Wright’s peak flow meter. The testing procedure was quite simple and non–invasive and it was harmless to the patients. It was explained to subjects, followed by a demonstration of its performance. The test was done with the subjects in standing position. The subjects were instructed to take a maximal inspiration and to blow into the instrument rapidly and forcefully. A close watch was made to ensure that a tight seal was maintained between the lips and mouthpiece of the device. The test was repeated 3 times and the highest of these readings was considered for the purpose of analysis as litre/min. All the observations of age, height, weight, body surface area and PEFR were recorded in the proforma.
The data was analysed by using the computer softwares, Microsoft Excel and Statistical Package of Social Sciences (SPSS, version 15.0). The mean and standard deviation (SD) were calculated and reported for the quantitative variables. The statistical difference in the mean values was tested by using Student’s t-test. A p-value of < 0.05 was considered as statistically significant.
Observation and Results
[Table/Fig-1] shows the mean and standard deviation of PEFR in study and control subjects. Mean PEFR of study subjects was less than that of the control subjects and this difference was statistically significant (p<0.01).
Comparison of Mean and SD of Pefr in Study and Control Subjects Groups
| Subjects | Range of PEFR (in Lts./min.) | Mean ± SD of PEFR (in Lts./min.) | ‘t’ value | ‘p’ value |
|---|
| Study | 300 – 490 | 393+ 52.14 | 16.44 | <0.01 |
| Control | 390 – 570 | 485.53+45.10 |
[Table/Fig-2] shows the mean ± standard deviation of PEFR in study and control subjects according to the three age groups. Mean PEFR of study subjects was less than that of the control subjects in all 3 groups and this difference was statistically significant (p<0.01).
Comparison of Mean and SD of Pefr in Study and Control Subjects According to Age Groups
| Age groups (in years) | Study | Control | ‘t’ value | ‘p’ value |
|---|
| No. of subjects | Mean ± SD of PEFR (in Lts./min.) | No. of sub. | Mean + SD of PEFR (in Lts./min.) |
|---|
| 18-27 | 47 | 429.36 ± 40.72 | 49 | 495.31 ± 45.42 | 7.48 | <0.01 |
| 28-36 | 57 | 383.33 ± 47.97 | 47 | 486.38 ± 46.13 | 11.09 | <0.01 |
| 37-45 | 46 | 367.83 ± 47.93 | 54 | 475.93 ± 42.67 | 11.93 | <0.01 |
[Table/Fig-3] shows the mean and standard deviation of PEFR in study and control subjects according to three height intervals. Mean PEFR of study subjects was less than that of the control subjects in each height interval and it was statistically significant (p<0.01).
Comparison of Mean and SD of Pefr in Study and Control Subjects According to Height Groups
| Height intervals (in cms) | Study | Control | ‘t’ value | ‘p’ value |
|---|
| No. of subjects | Mean ± SD of PEFR (in lts./min.) | No. of sub. | Mean + SD of PEFR (in lts./min.) |
|---|
| <155 | 36 | 383.61 ± 50.55 | 54 | 473.89 ± 42.22 | 9.18 | <0.01 |
| 156 – 168 | 84 | 381.43 ± 46.20 | 61 | 487.21 ± 41.68 | 14.17 | <0.01 |
| >169 | 30 | 436.67 ± 48.02 | 35 | 500.57 ± 51.16 | 5.16 | <0.01 |
[Table/Fig-4] shows the mean and standard deviation of PEFR in study and control subjects according to three weight intervals. Mean PEFR of study subjects was less than that of the control subjects in each weight interval and it was statistically significant (p<0.01).
Comparison of Mean and SD of Pefr in Study and Control Subjects According to Weight Groups
| Weight intervals (in kgs) | Study | Control | ‘t’ value | ‘p’ value |
|---|
| No. of sub. | Mean + SD of PEFR (in Lts./min.) | No. of sub. | Mean + SD of PEFR (in Lts./min.) |
|---|
| <54 | 45 | 392.44±47.63 | 32 | 483.75±46.96 | 8.34 | <0.01 |
| 55 – 69 | 85 | 383.65±50.35 | 88 | 479.32±43.70 | 13.66 | <0.01 |
| >70 | 20 | 434.00±51.95 | 30 | 505.67± 42.72 | 5.33 | <0.01 |
[Table/Fig-5] shows the mean and standard deviation of PEFR in study and control subjects according to three body surface area sub groups. Mean PEFR of study subjects was less than that of the control subjects according to BSA in each sub- group and it was statistically significant (p<0.01).
Comparison of Mean and SD of Pefr in Study and Control Subjects According to Body Surface Area
| BSA groups (in m2) | Study | Control | ‘t’ value | ‘p’ value |
|---|
| No. of sub. | Mean ± SD of PEFR (in lts./min.) | No. of sub. | Mean ± SD of PEFR (in lts./min.) |
|---|
| <1.55 | 53 | 385.85 ± 48.45 | 45 | 472.67± 43.24 | 9.28 | <0.01 |
| 1.56– 1.80 | 80 | 387.5 ± 50.40 | 80 | 486.25 ± 45.46 | 13.01 | <0.01 |
| >1.81 | 17 | 441.18 ± 48.59 | 25 | 506.4 ± 40.4 | 4.73 | <0.01 |
[Table /Fig-6] shows the mean and standard deviation of PEFR in study subjects according to three duration of exposure groups in the study subjects. Mean PEFR decreased with an increase in duration of exposure in study subjects.
Comparison of Mean and SD of Pefr in Study Subjects According to Duration of Exposure Groups
| Group No. | Duration of exposure (in years) | No. of subjects | Range of PEFR(in lts./min.) | Mean + SD of PEFR (in lts./min.) |
|---|
| 1. | 1 – 5 | 50 | 300 – 490 | 430.8 + 39.48 |
| 2. | 6-10 | 77 | 300 – 490 | 384.16 + 47.61 |
| 3. | 11-15 | 23 | 300 – 390 | 340.43 +26.54 |
Discussion
The present study was undertaken to establish the effect of wood dust on the respiratory health status of carpenters by measuring their peak expiratory flow rate (PEFR) values. Cases consisted of 150 non-smoking carpenters who were in age group of 18-45 years, while 150 non -smoking persons who were engaged in works other than carpentry served as controls. The observations were analysed statistically. Comparison of PEFR in study and control subjects was done and data was collected. Also influence of age, height, weight, body surface area and duration of exposure on PEFR of carpenters was studied. Prediction equations were formulated to determine PEFR.
PEFR is the largest expiratory flow rate which is achieved with a maximal forced effort from a position of maximal inspiration, which is expressed in litres/min. Since it can be easily carried out at work place, this parameter is often used to detect the severity of lung diseases.
PEFR and Age: In the age group of 18–27 years, mean PEFR was found to be 495.31 + 45.42 litres/min, which declined with age to reach values of 486.38 + 46.13 litres/min (for age group of 28-36 yrs) and 475.93 + 42.67 litres/min (for age group of 37-45 years)[Table/Fig-2]. Therefore, the present study revealed that mean PEFR in study subjects decreased with an increase in age. Also, when mean PEFR of study subjects was compared with that of control subjects according to three age sub–groups, it was found to be less than that of control subjects and this difference was statistically highly significant. The results were consistent with those of another study which was conducted [6].
PEFR and Height: As shown in [Table/Fig-3],there was a positive correlation between PEFR and height in the control subjects (r=+0.269). The mean PEFR in study subjects and control subjects increased with an increase in height. This result was corroborative with those of the studies which were conducted by researchers [7]. On comparison, according to three height sub–groups, mean PEFR of study subjects was found to be less than that of control subjects and this result was statistically highly significant.
PEFR and Weight: In this study, there was a positive correlation between PEFR and weight in study group (r=+0.224) and controls (r=+0.224), which meant that the mean PEFR in study subjects and control subjects increased with an increase in weight. This observation was in accordance with that of other study [8]. Moreover, when mean PEFR of study subjects was compared with that of control subjects according to three weight sub groups, it was found to be less than that of control subjects, which was found to be highly significant [Table/Fig-4].
PEFR and Body Surface Area: The mean PEFR in study subjects and control subjects increased with an increase in body surface area, as shown in [Table/Fig-5]. Our finding was in accordance with those of other studies [9]. When mean PEFR of study subjects was compared with that of control subjects according to three body surface area sub groups, it was found to be less in study subjects than in control groups, which was found to be highly significant.
PEFR and duration of exposure: The present study revealed that mean PEFR in study subjects decreased with an increase in duration of exposure to wood dust, as shown in [Table/Fig-6]. This observation was consistent with that of another study [10] and it was found to be statistically significant(p<0.01).This was probably due to adverse effects of wood dust on respiratory status of carpenters.
Conclusion
The mean PEFR of study subjects was less than that of the control subjects in each sub group of age, height, weight and BSA and these results were statistically highly significant. The decrease in PEFR in carpenters was probably caused by a continuous occupational exposure to wood dust, which had caused an adverse effect on their respiratory functions. His/her working conditions are important for a person’s respiratory health.
Mostly, all the carpenters work in confined spaces without protective devices. In order to prevent the ill effects of wood dust on the respiratory health of carpenters, we suggest a medical observation which includes pre-employment medical check-ups, provision for a good ventilation at work place and encouragement on use of personal protective equipment like masks. Further regular lung monitoring should be done to detect any ill effects on respiratory system at an early age and to prevent spread of the disease.