industrial health, 1995, 33, 101-117 101 green tea workers

Industrial Health, 1995, 33, 101-117 101

Some Aspects of Occupational Safety and Health in

Green Tea Workers

Seyed Mohammad MIRBOD1~*, Setsuya FUJITA1,

Kazuhisa MIYASHITA2~, Ryoichi INABA1 and Hirotoshi IWATA1

1) Department of Hygiene, Gifu University School of Medicine, 40 Tsukasa-Machi, Gifu 500, Japan

2) Department of Hygiene, Wakayama Medical College, Wakayama 640, Japan

(Received March 17, 1995 and in revised form August 21, 1995)

Abstract: The objectives of this study were to evaluate the health and safety conditions of 36 male and 27 female green tea workers who were aged 40-69 years and had worked for at least 5 years in green tea production procedures. The Mean ± SD of age was

57.1 ± 5.8 years in males and 54.4 ± 6.4 years in females. The mean working career was 26.1 ± 9.5 years and 24.3 ± 9.1 years, respectively. The most commonly subjective

complaints developed while at work was pain in the lower back at a rate of 72.2% in males and 63.0% in females. Regarding persistent subjective complaints, female workers

had significantly (P < 0.05) higher prevalence rate for breath shortness (25.9%) compared to that of male workers (5.6%). It was observed that the male workers whose

occupational career was equal to or more than 28 years had significantly higher

prevalence rates for stiffness in the neck and pain in the arms, compared to those of male workers whose occupational career was less than 28 years. The prevalence of nasal

allergy was 11.1% either in the male or female workers. The total rate of accidents

during working hours in the male workers was 22.2%, and that in the female subjects was 18.5%. The mean frequency weighted vibration magnitude produced by using tea-

leaf plucker was in the range of 2.4-3.5 m/s2. The mean equivalent A-weighted noise level while using the same equipment was 100.6 ± 5.0 dB(A). The need for occupational

safety and health programs in these small farm settings are discussed.

Key words: Green tea workers - Subjective complaints - Respiratory diseases - Accidents - Segmental vibration - Noise

INTRODUCTION

Tea is one of the three major non-alcoholic beverage in the world. The annual world tea production is 2.5 million metric tons: about 75% as black tea and 25%

* To whom correspondence should be addressed.

102 S. M. MIRBOD et al.

as green tea and oolong tea. The main black tea producing countries are India, Sri Lanka and Indonesia, and the main green tea production countries are China, the former Soviet Unions, and Japan. The green tea production in Japan is about 94,000 metric tons. Tea production requires a number of outdoor and indoor processes during which workers have to work in an uncomfortable condition (non-natural posture of trunk), and operate various types of mechanical machines during their working activities. Occupational health hazards of tea workers have been the subjects of a few re-

ports. Most of these studies have been focused on the effect of a fine dust known as tea fluff on respiratory function of workers occupationally exposed to black tea dust1_4~. Attack of allergic diseases was also described by Ebihara5~ in two workers employed in a green tea garden. Besides exposure to tea dust, accidents

(falls and injuries) and exposure to high levels of noise, vibration and heat have been reported. In a study by Kurulashvili and Fedorov6~ the physiological effects of vibration, noise and dynamic physical load associated with the use of tea-

plucking machines were reported. In two studies by Sen et al.'' 8) the workloads and ergonomic aspects of manual tea plucking operations have been reported. In two Japanese studies9° 10) noise levels of tea harvesting machines have been re-

ported between 81 dB(A) and 101 dB(A). Noise at a level of more than 90 dB(A) has also been reportedly among workers engaged in sifting or screening process

(indoor activities). The objectives of this study were as follows: (a) to evaluate subjective com-

plaints among male and female green tea workers who use hand-held tea-leaf pluckers as a part of their daily job activities; (b) to measure segmental vibration and noise levels associated with the use of tea pluckers (during actual job pro-cesses); and (c) to give recommendations for the improving of green tea workers' working conditions.

Background on green tea production

Useful consideration of the occupational health hazards among green tea work-

ers requires background information concerning harvesting and production proce-

dures of green tea. A brief explanation on these processes may be given as fol-

lows.

1. Green tea harvesting

There are three periods of green tea harvesting; first crop late April to mid May,

second crop in late June and third crop from late July to early August. The main

outdoor activities during these periods are tea plucking and tea pruning.

Plucking. There are three methods of plucking; (a) manual plucking (by hand),

(b) plucking by using mechanical hand-held tea plucker, and (c) tea plucking by means of plucking tractor. The amount of new shoot which one person can harvest

per day is from 10 to 15 kg by hand plucking, from 60 to 100 kg by hand-held

HEALTH AND SAFETY CONDITIONS OF GREEN TEA WORKERS 103

plucker, and from 400 to 500 kg by plucking tractor. It should be mentioned that the usage of hand-held tea-leaf pluckers requires three workers to be involved. These include two workers who have to carry and to hold the equipment in a moderately bending forward posture of trunk and to keep the tool in a constant height while walking along a row of tea bushes. The third worker has to carry a large bag connected to the tool, in order to collect the shoots plucked. Pruning. In the course of the perennial growth of tea there is a continual re-moval of the vegetative organs of the plant, at short intervals by the process of skiffing and at long intervals by pruning. The objective of pruning is as follows:

(a) to refresh the plant vigor of an old tea field; and (b) to keep the height of the plucking surface within the bounds of easy and efficient plucking.

2. Manufacturing of green tea The primary goal in the manufacture of green tea is the preservation of the leaf catechines. The steps after plucking include, rapid enzyme inactivation by steam-ing or pan firing, rolling, and high temperature air drying. Glycosides of aromatic and terpene alcohols found in the growing leaf are rapidly hydrolyzed after plucking to form the free volatile alcohols. In Japan, enzyme inactivation is generally carried out by steaming in large rotating cylinders for 20-50 sec followed by a series of twisting and drying steps designed to produce a desirable appearance and reduce moisture gradually to about 3%. Tea so produced is called "sencha" and is graded into several quality categories".

MATERIALS AND METHODS

Subjects and questionnaire In May 1993, by several field visits, personal interviews, and by means of a

questionnaire, information on subjects' age, working history as well as subjective complaints of 39 male and 28 female green tea workers affiliated to the Depart-ment of green tea of Gifu Agricultural Research Center were collected. For these workers the use of tea harvesting machines (in addition to their daily working activities) and working in a tea factory was confirmed by their supervisor. The occupational history comprised questions on the number of years subjects worked as green tea workers, working hours in a day (throughout the year), and the total number of days in a year during which hand-held tea harvesting machines were used. From these workers 36 male and 27 female workers were considered for this study. The criteria for inclusion were as follows: (1) age of 40 to 69 years, (2) at least 5 years of occupational career in green tea production, and (3) using hand-held tea harvesting equipment as a part of their job activities. The questions on subjective symptoms were classified into three main categories: symptoms devel-oped while at work (13 items), persistent subjective complaints (11 items), and any

past and/or present history of allergic, bronchial asthma or other respiratory dis-


eases (7 items). Each subjective symptom was coded 2 if the subject had a symptom and was 1 if he or she did not have the symptom. Both male and female workers were divided each into two subgroups by their occupational career, i.e., those with the working experience of less than 28 years and those with the occupational career of equal to or more than 28 years. The prevalence of sub-

jective complaints in the subgroups of each gender were then compared. Using the same questionnaire, the subjects were asked if they had accidents during their working hours and if the answer was positive, they were requested to point out the exact location of the injury due to the accident(s).

Noise and vibration measurements The most frequently hand-held tools used by the subjects were the tea-leaf pluck-

ers, types V8-New Z 1070 and V8-New Z 1210 (Ochiai Co, Shizuoka). Regard-ing plucking or pruning procedure, the blade of the tools may be changed and the length of the handles can be adapted at the most comfortable position for the users. A brief characteristics of these tools might be given as follows: weight of the tools was about 12.1-12.9 kg, the RPM of each tool was 1;700, and the antivibration materials had been mounted on the handles of the tools. The frequency-weighted vibration levels were measured during actual job processes while hand-held tea

pluckers were being used. The vibration measurements were made on the right and left hands of workers as well as on the handle of the tools used (Fig. 1), by means of a vibration dosimeter, type VB-03 (Rion Co., Tokyo) connected to an accelerometer, type PV-90 H (Rion Co.). For the vibration measurements on the tool, the accelerometer was glued to the handles as close to the hands of workers, but not to disturb the subject while working. As for the vibration measurements on the hand, the accelerometer was fixed in a small pick-up case and then mounted on the back of the hand using a simple palm band, such as athletic wrist sup-

Fig. 1.

up was

The hand-held tea-leaf plucker used by green tea workers (vibration pick-mounted on the hands of workers #1, #2 and on the handles #1, #2).


porter. The vibration measurement time ranged from 13 to 46 min during which the equivalent frequency weighted vibration acceleration [(ah,w)eq,t, (t = 13-46 min)], as well as the four and eight hours normalized equivalent frequency weighted vibration acceleration, i.e., (ah,W)eq,4 and (ah,W)eq,8 were obtained. With respect to the place of the vibration pick-up, the results obtained (in m/s2) were averaged and the mean ± SD as well as the ranges were derived. Detailed information on vibration measurements were reported elsewhere12~. During subjects' working activities noise measurements were conducted using the sound level meter (SLM), type NA-24 (Rion Co.) connected to a 112-inch-sized

piezoelectric microphone, type UC-52 (Rion Co.) and 1/3-Octave Band Real-Time Analyzer, type SA-27 (Rion Co.). The SLM accuracy and its decibel reading based on the A and C networks were ± 0.2 dB, 30-130 dB(A), and 35-130 dB(C), respectively. The noise level was sampled and stored by adjusting the sampling

period of SLM to 0.1 sec (fast response). During the course of tea plucking or tea pruning, the set of SLM connected to the frequency analyzer was carried by the observer and the microphone of SLM was kept at the ear level of worker. The time for noise monitoring (n = 10) ranged between 13 and 50 min, during which the equivalent continuous A- and C-weighted noise levels [(Leq,t), (t = 13-50 min)] were recorded. It should be mentioned that the equivalent continuous A- or C-weighted noise level shows the level of a steady sound which, in a stated time

period and at a stated location, has the same A- or C-weighted sound energy as the time-varying sound. Using the stored data, the sound pressure levels (SPLs) in the 1/1 octave-band center frequencies from 31.5 Hz to 8.0 kHz were also derived. More information on the noise measurement procedures was reported

previously13' 14)

Statistical methods To test level of significance, Student's t-test and the x2 test were used. When the frequency of a symptom was low (below 5), Fisher's exact test was used. The significance level was set at P < 0.05.

RESULTS

Subjects' characteristics Table 1 shows the Mean ± SD and ranges of age and occupational history of subjects. The mean age was 57.1 ± 5.8 years for the male subjects and 54.4 + 6.4 years for the female subjects. The mean occupational career of male workers was 26.1 ± 9.5 years and that of the female workers was 24.3 ± 9.1. Age and occupational career of either male or female workers were not significantly cor-related. The hand-held tea harvesting machine usage was 17.2 ± 16.3 days/year for male workers and 16.7 ± 12.7 days/year for female workers. The male workers


with a longer occupational career (equal to or more than 28 years) reported to use vibrating tools more often than the other male subgroup (P < 0.05). The mean values of working time (throughout the year) in male and female workers were

quite comparable (4.6 ± 1.8 h/day and 4.8 ± 2.1 h/day, respectively). The age and occupational history of the subgroups are also shown in the same Table.

Subjective symptoms The most commonly subjective complaints developed while at work was pain in the lower back at a rate of 72.2% among male and 63.0% among female workers

(Fig. 2). The prevalence of pain in the shoulders was noted at a rate of 44.4% in male and 51.9% in female workers. Pain in the neck was reported by 22.2% of males and 25.9% of females. Pain in the wrists and arms was more prone to occur in females compared to the male subjects, and the two groups showed a significant difference (P < 0.05) in the prevalence of pain in the wrists (males: 25.0% and females: 55.6%). Finger cold sensation had a lower figure in males compared to that of female workers (5.6% and 25.9%, respectively, P = 0.06). In the male workers (n = 36) occupational career was significantly correlated with

pain in the shoulders (r = 0.40, P = 0.01), stiffness in the neck (r = 0.36, P = 0.03), and pain in the arms (r = 0.35, P = 0.03). The prevalence of pain in the wrist among male workers was somewhat correlated with their occupational ca-reer (r = 0.31, P = 0.06). No significant correlation was found between the occupational career and subjective complaints in the female workers. In Table 2 the prevalence of subjective symptoms developed while at work are

shown for male, and female subgroups. In general, the male subgroups with the occupational career of equal to or more than 28 years complained more about sub-

Table 1. The mean ± SD of age and occupational history of male and female green tea workers. (The ranges are given within parenthesis.)


Fig. 2.

work in

Comparison males (n =

in 36)

the prevalence

and females

of subjective (n = 27). (*

complaints P < 0.05)

developed while at

Table 2. The numbers and percentage

developed while at work among male

occupational career.

prevalence and female

(%) of subjective symptoms green tea workers by their


jective symptoms developed while at work, compared to male subgroup with the occupational career of less than 28 years. These two subgroups showed signifi-cant differences (P < 0.05) in the prevalence of neck stiffness and pain in the arms. Regarding the female workers, the female subgroup with the occupational career of equal to or more than 28 years complained more about finger stiffness, pain in the arms, and stiffness in the neck. However, the two female subgroups showed no significant differences in their prevalence of various subjective complaints . In Fig. 3 the prevalence of persistent subjective symptoms are depicted. As

can be seen, the female workers had significantly (P < 0.05) a higher prevalence rate for breath shortness (25.9%), compared to that of male workers (5.6%). Two female workers (7.4%) but no male subjects complained of finger blanching. The

prevalence of leg cold sensation in females (51.9%) was higher than that in the males (30.6%), however the difference between the two groups was not statisti-cally significant. The prevalence rates of easy fatigability, eye strain and tinnitus among two groups were comparable and higher than the other persistent subjec-tive symptoms. The distribution of the persistent subjective symptoms by occupational career are shown in Table 3. In both male and female workers, some of the persistent subjective symptoms such as leg cold sensation, sore throat, insomnia, headache or dull head, and tinnitus were more prone to occur among subgroups with longer

Fig.

(n =

3. 36)

Comparison in the prevalence of persistent subjective symptoms in and females (n = 27). (* P < 0.05)

males


occupational career, while this was not true for some symptoms such as weak stomach and easy fatigability. No significant differences in the prevalence rates of

persistent subjective complaints in the subgroups could be seen. Table 4 shows the numbers and percentage prevalence of the current and/or past history of allergy and asthma among male and female workers (total subjects). There were 4 (11.1%) men and 3 (11.1%) women with nasal allergy. Bronchial asthma was found in 3 (8.3%) male workers but no females had this symptom. Allergic conjunctivitis was found in 3 (11.1%) female workers, while no one of male subjects had such a symptom. Also, 2 females (7.4%) but no male workers

Table 3. The number and percentage prevalence (%) of persistent subjective complaints among male and female green tea workers by their occupational career.

Table 4. The numbers and percentage prevalence

history of respiratory diseases and allergy among

(%) green

of the past and/or present

tea workers.


had allergic contact blepharitis. Eczema and dermatitis were reported in 1 (2.8%) male workers but no female subjects had this symptom.

Reported accidents among workers There were 8 (22.2%) male and 5 (18.5%) female workers who had injuries due to accidents during their working activities. The injuries among male workers were as follows: 3 subjects had injuries on the anterior part of the left thigh, one worker had injury on the posterior medium part of the right thigh, one worker had suf-fered from knee injury, and 2 workers had injuries on their fingers (thumb, index or middle fingers). In the female workers group, two workers had suffered from injury on the anterior part of the right thigh, one worker had injuries on her left

thigh as well as on her knee, and two workers had finger injuries (index and middle fingers). By pooling the numbers of accidents for males and females, it was revealed that the prevalence of accidents was 12.7% on the lower extremities and

6.3% on the upper extremities.

Segmental vibration The results of vibration magnitude measured on the tool (handles #1 and #2: see Fig. 1) are shown in Table 5. The mean equivalent frequency weighted vi-bration acceleration [(ah,W)eq,t] measured on the handle #1 (close to the engine) had

Table 5. The results (Mean ± SD) of vibration magnitude measured on the hands of workers and on the handles of hand-held tea harvesting equipment.

HEALTH AND SAFETY CONDITIONS OF GREEN TEA WORKERS i l l

a higher vibration magnitude [3.5 ± 0.3 m/s2, range: 3.2-3.8, (t = 13-28 min)]

compared to that measured on the handle #2 [2.9 ± 0.6 m/s2, range: 2.4-3.5, (t = 14-27 mm)]. The (ah,w)eq,t measured on the right hand of worker # 1 was 1.5 ± 0.1 m/s2 [range: 1.4-1.5, (t = 25-40 min)] and that on the left hand of the same

worker was 1.9 ± 1.0 m/s2 [range: 1.5-2.3, (t = 25-40 min)]. Regarding worker #2, these values for the right and left hands were recorded at the levels of 1.7

± 0.3 m/s2 [range: 1.4-2.0, (t = 25-46 min)] and 1.5 ± 0.3 m/s2 [range: 1.1-1.9,

(t = 27-46 min)], respectively. This Table also shows the 4 h and 8 h normal-ized (ah,w)eq,t. The mean values of (ah,w)eq,4 measured on the handles were in the range of 0.8-1.0 m/s2, while those measured on the hands of workers were be-

tween 0.5 m/s2 and 0.6 m/s2. Regarding the (ah,w)eq,8 these values decreased to 0.6-

0.7 m/s2 and 0.4-0.5 m/s2, respectively.

Noise levels Figure 4 shows the mean ± SD of the equivalent A- and C-weighted noise levels

as well as the equivalent decibel readings obtained for the octave-band center

Fig. 4. The equivalent A- and C-weighted noise levels [Leq,t (t = 13-50 min)] and the octave-band center frequency noise levels measured while the tea-leaf pluckers were being used. The values are given as the mean ± SD (n = 10).


frequencies (on the C scale) while hand-held tea harvesting machines were being used. As can be seen, the over-all mean values of Leg, t (t = 13-50 min) were 100.6 ± 5.0 dB(A) and 104.5 ± 7.0 dB(C), and during all noise measurements the equivalent C-weighted noise levels were typically 4-5 dB higher than the measured dB(A) levels. Spectral analysis of the equivalent C-weighted noise levels revealed that noise levels of tea harvesting machines were mostly in the range of 0.5-4 kHz at levels of 91.0-97.0 dB(C). It should be noted that subjects were exposed to a lower levels of noise when the hand-shear tea-leaf plucker was in idling posi-tion, or workers had to refuel the gasoline-powered tea plucker. During these con-ditions the measured noise levels (n = 6) were in the range of 81-84 dB(A) and 71-76 dB(A), respectively. The later value might be regarded as the ambient or background noise level. As already mentioned, in addition to the two workers who had to hold the hand-held tea-leaf plucker, a third person also had to carry a large bag (connected to the tool) in order to collect the shoots plucked. This means that the third person might also be exposed to a high level of noise, though he walked within 0.5-1.0 m distance from the two other workers. Hence, we measured the noise levels

adjacent to the third worker for whom the recorded values (n = 6) were in the range of 87-89 dB(A) and 94-97 dB(C). The direct decibel readings (n = 5) in the green tea factory demonstrated that the mean noise levels inside the factory were in the range of 78.5-82.3 dB(A) and 84.0-87.3 dB(C). These values reached 91.4 dB(A) and 93.1 dB(C) while an alarm inside the factory could be heard.

DISCUSSION

Occupational health in the agricultural sectors encompasses the anticipation, recognition, diagnosis, treatment, prevention, and community health aspects of health problems peculiar to agricultural populations. Many farmers still function as small independent businessmen for whom the occupational safety and health service has not been bound yet. Consequently, the information and inspection functions that form an important part of health and safety programs in other occupational sectors are generally missing in the small agricultural arena. The lack of specific health and safety programs in many farming operations resulted in an estimated 120,000 farm related injuries in 1989 in the USA15>. An

incidence rate of 48.8 occupational illnesses per 10,000 full-time agricultural workers was reported for 1988 by the Bureau of Labor Statistics15~. This illness figure is conservative in that the mentioned survey did not include farms with fewer

than 11 employees. Therefore, the magnitude of health and safety hazards con-fronted by agricultural workers on the numerous small farming operations that are characteristics of rural areas is not precisely known.


In this preliminary investigation we collected the information on some aspects of occupational safety and health in male and female green tea workers. These subjects reported to use mechanical tea-leaf pluckers as a part of their daily job activities.

Subjective complaints In the present study we demonstrated that about 72.0% of male and 63.0% of

female workers reported to suffer from low back pain. The prevalence of this symptom in male workers was comparable to the 76.0% prevalence rate reported

by Sakai et al. 16) among workers in local agricultural sectors. Among other sub-

jective symptoms developed while at work, fatigues in the shoulders, neck, arms, and wrists were also frequently complained about. With a view to gathering information on working condition of green tea workers, we made several field visits to green tea gardens during which ergonomic aspects of plucking operation were evaluated. Regarding the weight of the tea-leaf plucker machine (12-13 kg), two workers have to grip the handles strongly in order to keep the tool in a balanced position, and consequently, to have good shoots of tea-leaves. During this operation the neck is rotated to the left or right and workers have to keep a moderately bend-

ing position of the trunk (more than 20°). It was observed that there were some work-stoppage (i.e., weighing the shoots plucked, drinking tea, and refueling the engine), and the subjects reported to use the tea-leaf pluckers the longest 75 days

per year, however, these subjects are also engaged in various other job activities before and after the plucking periods. These include skiffing and pruning of green tea bushes, deep plowing, and fertilizer application, which either of these activi-ties require loads upon the back, shoulders, arms; and neck. Therefore, it becomes very difficult to identify the characteristic features of their individual job activi-ties. However, non-neutral postures of trunk could be postulated. In several stud-ies the relationship between non-neutral postures and fatigue in the back and lower back has been reported17' 18). Also, it has been reported that the incidence of back and low back pain is high during the most productive years of life (age 25-60

years)19~. To protect these workers from developing localized fatigue, it may seem that bad work postures of green tea workers might be improved by some ergo-nomics interventions as well as health education of farmers such as shortening of a spell of plucking work and physical exercise to accelerate recovery from local-ized fatigue.

A comparison in the prevalence of subjective symptoms between the males and female workers revealed that for some symptoms such as pain in the wrists, fin-

ger cold sensation, and pain in the arms, a female preponderance exits. This could be explained, to some extent, by the physical capacity of females which in gen-eral is lower than that of males. We speculate that some activities such as holding


the tea-leaf plucker machine puts a high load on the arms and wrists of the female workers. As a result, the females had significantly a higher prevalence of pain in the wrists compared to that of male workers. For some of the mentioned symptoms male workers with a longer working career had higher prevalence rates compared to other male subgroup. An accumulative work-related subjective complaints might be postulated. This hypothesis could be supported by some of our results, i.e., there were significant positive correlation between the male workers' occupational career and development of some symp-toms such as pain in the shoulders, neck stiffness, and pain in the arms. Regarding the persistent subjective symptoms, leg cold sensation stand out as having caused the most female subjects to complain about. Also, we observed that about 30% of male or female subjects complained about some symptoms such as leg cold sensation, easy fatigability and eye strain. The exact cause of these disorders could not be clarified in the questionnaire or during interview with the subjects. However, the nature of the job, physical capacity (as already mentioned), the small number of subjects in each group, and individual susceptibility might be attributed to the result obtained. We suggest that occupational health programs such as periodic health examinations, evaluation of working environment, and training on correct posture of the body during working hours should be applied to these small farm settings. The associated subjective complaints may also vary with topography, climate, the economy and social factors. As our subjects were from the same district, comparative studies from some other areas should be carried out. With the benefit of such studies there would be confidence that proper decisions could be made for the health and safety of all concerned.

Respiratory diseases Respiratory disease related to occupational exposure to tea dust was first de-scribed as "tea factory cough" and "tea taster's disease" by Castellani and Chalmers20~. The symptoms being loss of weight, tiredness, and cough with mucopurulent expectoration. Uragoda3~ found a higher prevalence of chronic bronchitis and asthma in tea workers than that expected in the general population. Al-Zuhair and Cinkotai21 and Castellan et al.22~ reported shift reductions for FEV1 in tea workers related to tea dust exposure. Ebihara5~ described two patients working in a tea garden who were considered to have allergic symptoms of headache, cough, expectoration, stridor, dyspnoea, and rhinitis which he thought were caused by airborne cilia from tea leaves. In two studies by Mackay23, 24) a high prevalence of respiratory diseases in tea garden workers was reported. In the present study, the prevalence of nasal allergy was about 11.0% among either male or female workers, and that of bronchial asthma was 8.3% only among male subjects. Although the data set is small, we recommend that medical surveillance be required to prevent irreversible changes in respiratory function. Medical su-

pervision serves as a means of detecting those workers sensitive to dust (in a tea


garden and/or in a tea factory), since there is a large variation in individual susceptibility to chronic respiratory diseases. Such an examination would prevent a sensitive person from working in those processes that carry the risk of respi-ratory allergy, chronic obstructive lung disease, or any other respiratory diseases.

Accidents Agricultural technology increasingly has emphasized mechanization, and machines have been responsible for the majority of farm traumas2S~. The accidents may occur in a locations (such as a barn lot or field) which is not easily reached by con-ventional emergency rescue vehicles. The total rate of accidents in the present study was 18.5% in the female and 22.2% in the male subjects. Although the exact

causes of accidents could not be detected, falls and injuries caused by agricultural implements of the cutting and digging type were mentioned by some subjects. This is not unexpected, considering the steep slopes on which tea is generally grown and the type of work involved in the processes of clearing, uprooting and prun-ing. Additional research should be carried out to identify factors or circumstances that might be attributed to the causes of accidents. The possibilities of taking active safety measures such as education, training, and equipment design should also be taken into account.

Hand-arm vibration It has been well recognized that exposure to hand-arm vibration may cause an

entity called hand-arm vibration syndrome (HAVS) which is disturbances in the

peripheral circulation, peripheral nerves, muscles, bones, and joints of the hands and arms. The most prominent component in HAVS is the finger blanching called vibration-induced white finger (VWF), which seems to be brought on by cold. The only source of hand-arm vibration for the subjects of this study was identified as the gasoline-powered hand-held tea harvesting machines which has been shown to cause considerable shifts in vibration sensitivity and markedly influence the pe-ripheral vessels6~. We demonstrated that the equivalent frequency weighted accel-eration level [(ah,W)eg,t, (t = 13-46 min)] of the tools used by the subjects was in the range of 2.4-3.5 m/s2 on the handles and 1.4-2.0 m/s2 on the hands of work-ers. It should be noted that antivibration materials had been mounted on the handles, though, during the course of observation non of the subjects was seen to use anti-vibration gloves. Regarding the vibration magnitude, the mean work-ing time (less than 5 h/day), and the period during which the hand-held tea har-vesting machines are being used (i.e., April to August with an outdoor air tem-

perature of 14-27°C)12~, exposure to hand-arm vibration seems not to be a serious problem among subjects. The cause and latency of finger blanching (in two females) could not be de-tected, since they could not remember the beginning time of the disorder. Thus, it was difficult to differentiate VWF from idiopadic Raynaud's phenomenon in the


two subjects. As already mentioned, adopting an ergonomic working posture and an ergonomics training (such as mild gripping posture and the use of antivibration

gloves) could be helpful in reducing the transmission of vibration energy from the hand tool through the hands into the upper extremities.

Noise levels A number of investigators have reported increased hearing loss in farmers as

compared to other occupational groups or to the general population26, 27). Although older farmers generally show higher hearing threshold281, impairment has also been documented among younger individuals29~. In a study by Jones and Oser30~, the overall noise levels of 20 farm equipment were between 90 dB(A) to 114 dB(A). The Leq noise level reported in this study was 100.6 dB(A) (except during work-ing-stoppage, i.e., idling or refueling) which also falls in the range of the results reported by Jones and Oser. Our results were also comparable to those reported

by Takamatsu et al. 10) Although the effect of aging on hearing ability should be taken into account (presbycusis), we speculate that the prevalence of tinnitus reported in male and female workers (25%-30.0%) may, to some extent, be re-lated to exposure to the high level of noise31, 32) We suggest that these workers should have a pure tone audiogram done periodically. Hearing-protection devices represent the most commonly applied noise control at the point of receiver, how-ever, non of our subjects used such a device. Ensuring that such devices are readily available and maintained in a sanitary condition, and that the subjects are

properly trained in their use, represent significant challenges in the setting of the typical small farm.

ACKNOWLEDGMENTS

The authors are grateful to Mrs. T. Nakano, Department of green tea, Gifu

Agricultural Research Center, for her generous help in this study.

REFERENCES

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