A study on blood eosinophil level and ventilatory pulmonary function of the workers exposed to storage grain dust.

The workers engaged in storage grain handling are exposed to storage grain dust and suffer from different respiratory symptoms like, cough wheezing, chest tightness, eye and nasal irritations. It has been reported abroad and the present study results noted that the grain handlers have allergic symptoms like redness of eyes, itching, sneezing, skin rash, breathlessness and decrement of pulmonary function test values. According to their nature of job, the workers of storage grain godowns were divided into four categories i.e., load handling worker (LHW), ancillary, quality control and depot administration workers. The pulmonary function tests (PFT) and the differential count of leucocytes were carried out among the workers by standard technique. Decrement of pulmonary function test values was noted with the increment of blood eosinophil level.The PFT results were presented according to the blood eosinophil level. The decrement of mean PFT values were noticed as the blood level of eosinophil gradually increased from, up to -4%, >4-10% and above 10%. The maximum numbers of workers in different job categories are belonged to >4 -10% of eosinophil level. The percentage figure of workers in different departments were LHW 48.38%, (n=45), ancillary 38.88%, (n=7), quality control 54.54% (n=6) and depot administration workers 47.05% (n=16) are belonged to that range. Among the total workers the higher figure was found >4-10% ranges 47.43% (n=74) workers. The allergic manifestations like redness, itchiness and watering of eyes, sneezing, cough, breathless etc. are reported. These workers have blood eosinophil level and low pulmonary function test values. The respiratory impairments among the workers are restrictive, obstructive and combined restrictive and obstructive type.

INTRODUCTION

Dutch investigator[1] has previously suggested increased bronchial responsiveness and atopy in predisposed subjects to develop chronic obstructive pulmonary diseases (COPD). Earlier studies have identified environmental irritants are associated with COPD,[23] but the relationship between markers of allergy and airway inflammation and pulmonary function results has not been extensively studied. A number of studies have demonstrated the association between the reversibility of obstructive pulmonary function impairments and the number of eosinophil in peripheral blood.[45] Peripheral blood eosinophilia has generally being regarded as an allergic trait. Storage grain workers also sufferfrom different types allergic symptoms induced by grain dust which may cause eosinophilia. The present study was undertaken to evaluate the pulmonary function impairments associated with increment of peripheral blood eosinophil of the workers exposed to storage grain dust.

MATERIALS AND METHODS

The regular male employees of a grain storage depot were considered as the subject of the study. The suitable statistical techniques were followed to select the sample size and the sample. The lists of the total workers were collected from the authority (n=654) and select every fourth worker for the study. But some selected fourth workers did not agree to do the investigations (pathological and pulmonary function tests (PFTs)). They were unwilling and were avoiding testing by raising different reasons. Because of the non-cooperation, the number of subjects has been reduced. Total 156 workers participated in the study. According to their job. 1) Load handling workers (LHW)-engaged in loading and unloading, stacking and rearranging of grain sacks. 2) Quality control (Q.C) - picking the samples of food grains from grain sacks and categorically divide them according to quality, identified the grains for pesticides treatment etc. 3) Ancillary-refilling of bag, sweeping the floor, brushing over grain sacks to clear the pesticide tablets, covering the plastic sheets over the stacks of grain sacks for fumigation etc. 4) Depot administration (Admin.)-Looking after the loading, unloading, pesticide treatment etc. These workers were posted and seated inside the godowns to look after the work at the site of loading and unloading of grain sacs. The institutional ethical committee has ethically approved the main project proposal. Before examination of the subjects a consent form was issued to each subject and their written consent was taken to carry out the investigations.

The personal and occupational history of the workers was recorded with the help of a proforma designed for this purpose. Due stress were given to know the detailed occupational history and smoking habit of the workers were noted. The questionnaire was prepared and duly approved by scientific advisory committee of the institute looking into the problems related to the exposure to storage grain dust [Regional Occupational Health Center, (National Institute of Occupational Health), Annual report 20026]. All subjects were clinically examined. The total investigations including the filling of proformas, clinical examinations, collection of blood samples, pulmonary function tests were carried out at the dispensary unit of the storage grain depot. The differential count of white blood cells was done in our center by standard procedure of eosin and hematoxlin staining method.

Allergic manifestations in skin, conjunctiva, larynx, nose was recorded by clinical examination and by asking among the workers with due care. Clinical examination, occupational and personal history helps in the medical diagnosis. Allergic manifestation was assessed by redness, itchiness and watering of eyes, running nose, stuffiness, cough, sputum, breathlessness etc.

The PFTs were carried out by spirometric method .Slow vital capacity (SVC) and forced vital capacity (FVC) was recorded by Spirovit -SP-10 (Schiller Health Care Pvt. Ltd., Switzerland) and Peak Expiratory Flow Rate by Wright's Peak Flow meter (Clement and Clarke, UK). Forced expiratory volume in one second (FEV1) and the third second (FEV3), Forced expiratory volume in the first and the third second as the percentage of FVC (FEV1% and FEV3%), forced expiratory flow at 200-1200 ml, 25-75% and 75-85% was calculated from the same tracing. Before the recordings were taken all subjects were made well-motivated thus ensuring recording at optimum levels.[6] The reproducible maneuver was selected according to the standard technique (Morgan and Seaton[7]). Each subject was carried out the tests at least three times and best of the three was selected for the calculation. The reproducible maneuver was selected according to the standard technique.[89] The PFT measurements were made in a comfortable standing position. The body height and body weight were measured with a standard scale without footwear. All measured lung volumes obtained was expressed in body temperature pressure saturated with water vapor (BTPS). Body surface area was calculated from the Dubois and Du-Bois[10] formula. PFT values were predicted from the standard prediction equation of the Kolkata normal subjects (VC= -0.024.xage+ 0.044xHeight - 2.704, Age-years, height-centimeter).[11]

The criteria followed for categorization of the severity of restrictive impairment are based upon the ratios between predicted and observed values of VC and obstructive impairment based on observed FEV1%.[9] The level of significance was presented in the footnote of the respective table only in those comparisons, which were found statistically significant. The data were analyzed statistically according to job category and different blood eosinophil level.

RESULTS

The physical characteristics of the workers are presented in Table 1. The mean age, height and weight of the workers are comparable when compared in between the different categories of workers. Total and differential counts of leucocytes were carried out in all 156 subjects and the values were presented in Table 2. Mean values of total leukocytes of the exposed workers as a whole are within the normal range. In differential count of leukocytes the neutrophil, lymphocytes and monocytes count are with in normal range but eosinophil count is found higher compared to the normal range in some workers among the all four categories of workers. The blood eosionophil levels in the comparisons between LHW and depot administration workers and quality control and depot administration workers are found statistically significant. All other comparisons are statistically not significant.

Table 1

Physical characteristics of storage grain handling workers of different categories (Mean ± SD)

Table 2

Total and differential leukocyte count among the different categories of storage grain handling workers

Observed values of blood eosinophil are categorically divided into three groups-up to 4% (normal range of eosinophil), >4-10% and above10%, there is a gradual decrement of flow rates were noticed, as eosinophil level is increased. Sordrager et al.[12] evidenced that elevated eosinophil count might induce immunologic and cytotoxic process causing asthma in pot room workers. In the present study result is corroborated with the study of Sordger et al.[12] that the elevated eosinophil level workers showed lowered PFT values of obstructive in nature compared to the low eosinophil level workers. Table 3 represents the distribution of blood eosinophil level of grain workers of different categories. It has been found the blood eosinophil level of up to 4%, >4-10% and above 10% were found among the total storage grain dust exposed workers were 25.64%, 47.43% and 26.92% respectively. Among the workers of different working categories; the maximum numbers are having the eosinophil count of >4-10% level. Pulmonary function test values of the workers as a whole according to different blood eosinophil level are depicted in Table 4. Mean values of FEV1 of three different blood eosinophil levels are 85.23 ± 9.74, 84.38 ± 7.47 and 82.64 ± 8.21 respectively. Similarly mean values of peak expiratory flow rates (PEFR) according to blood eosinophil level are also reduced gradually 476 ± 112.22 l/min, 463 ± 87.35 l/min and 452 ± 77.88 l/min respectively. None of the comparisons of PFT values found statistically significant when compared between different levels of blood eosinophils .The [Figure 1] represents the comparison of flow rates of storage grain workers according to different blood eosinophil level. Among the workers of blood eosinophil level of up to 4%, >4-10% and above 10% blood eosinophil level, the mean values of different expiratory flow rates like FEF.2-1.21ml, are 6.90 ± 2.24 l/sec, 6.85 ± 1.86 l/sec 6.00 ± 1.75 l/sec Similarly the FEF 25-75% are 4.08 ± 1.62 l/sec, 3.87 ± 1.41 l/sec and 3.59 ± 1.21 l/sec and FEF 75-85% are 1.53 ± 0.73 l/sec, 1.36 ± 0.61 l/sec and 1.32 ± 0.53 l/sec respectively. Mean values of flow rates are found higher in low eosinophil level workers [Figure 1]. It has been found that the lung volumes of the workers according to blood eosinophil level found significantly higher in >4-10% level compared to the other two categories.

Table 3

Distribution of workers according to blood eosinophil level of different categories of workers

Table 4

Lung volumes of storage grain handling workers as a whole according to different blood eosinophil level (Mean ± SD)

Figure 1

Comparison of flow rates in workers according to job category and different blood eosinophil levels

Table 5 represents the lung volumes, FEV1% and PEFR of the workers of different job categories according to different blood eosinophil level. It has been found that the lung volumes and PEFR values showed no gradual trend of decrement of values according to the blood eosinophil level. In some categories of workers with high eosinophil level showed higher lung volumes compared to the corresponding low eosinophil level workers. Only the difference between up to 4% and above 10% showed significant changes other comparisons of mean values showed mean differences of values but they are statistically not significant. [Figure 2] represents the flow rates of the exposed grain workers with different job categories according to different blood eosinophil level. It has been found that the flow rates of all categories of workers are not declined gradually with the increase of blood eosinophil level. Figure 3 showed the respiratory impairments amongst the workers as a whole according to the blood eosinophil level. In up to 4% level category 4.8% of workers showed both restrictive and obstructive type of disorder. No combined type of impairments was noticed in that category. In >4-10 % level category only the 2.70% obstructive impairments were found. No other varieties of respiratory impairments were noticed among this group of workers. But in the next higher blood eosinophil group (above 10%) the respiratory impairments are found more compared to the other groups. The percentages of impairments are 9.52% restrictive type, 4.76% obstructive type and 2.83% combined restrictive and obstructive type respectively.

Table 5

Pulmonary function tests values of the workers of different job categories according to the blood eosinophil level (Mean ± SD)

Figure 2

Comparison of flow rates in workers according to job category and different blood eosinophil level

Figure 3

Pulmonary function impairments in workers according to different blood eosinophil levels

DISCUSSION

Workers reported some specific allergic symptoms related to different parts of the body during working condition. Some of the workers feel breathlessness due to such allergic manifestation. Allergic manifestation facilitates and increasing the number of blood eosinophil count.[13] Total count of leukocytes of the total number of exposed workers as well as workers with different job categories are with in the normal level. Similarly differential count of neutrophil, lymphocytes and monocytes also found with in the normal range but only the eosinophil count is found higher than the normal range. Maximum percentage of exposed storage grain dust workers have the eosinophil level of >4-10% and they are belonged to quality control group of workers. The number of the workers in that particular category is very less because the requirement of staff in that is also less to run the work. No considerable changes in lung volumes of the workers are noted with eosinophil level. It has been found that in the eosinophil level of >4-10%, the lung volumes are significantly higher than in the up to 4% category, the reason is not clear to us. But significantly lowered lung volumes were noticed when up to 4% and >4-10% level categories of workers are compared with the above 10% category. The allergic manifestations are common in this type of work like itchiness, redness and watering of eyes, running nose, sneezing, cough, breathlessness etc. In such subjects of different disciplines of work the blood eosinophil level was evaluated and the level was found higher than the normal range. In those subjects blood IgE level was also measured and found higher which are common among the subjects those who have the allergic symptoms. In such subjects the pulmonary function tests were assessed and found lower compared to the non-allergic symptomatic subjects. So these allergic manifestations might be probable reasons of high blood eosinophil level and lowered pulmonary function test results.

Among the flow rates PEFR showed no significant differences with different levels of blood eosinophil. The finding of the present study relating eosinophilia to respiratory symptoms and lower level of pulmonary function is in agreement with the theory of the “Dutch hypothesis” by Fletcher and coworkers,[3] which was originally formulated by Orie and coworkers.[2] This hypothesis describes both reversible and nonreversible pulmonary function impairments manifested by eosinophilia, airway hyper responsiveness and possibly by the IgE mediated allergy. The assumption of eosinophilia is an independence risk factor remains controversial. Vander Lande et al.,[4] Kauffman et al.[14] have previously reported and inverse association between blood eosinophil count and the level of pulmonary function. It might be inferred from this study that eosinophilia is more important for pulmonary function impairments, which is associated with the changes of different flow rates. In our present study a significant difference of FEF.2-1.21ml, FEF25-75% and FEF75-85% are noted among the exposed to storage grain dust workers having normal blood eosinophil level to high eosinophil level. Earlier studies evidenced that high eosinophil level resulted into obstructive type of pulmonary dysfunction, the present study results are corroborated with their findings. Restrictive type and combined both restrictive and obstructive type of respiratory impairments was also noted higher particularly in high eosinophil group workers (above 10%). The findings of this study suggested that storage grain dust exposure increases blood eosinophil level, which results restrictive and obstructive and combined type of pulmonary function impairments.