coal mine workers from Tay Nam Da Mai Coal Joint Stock Company - VINACOMIN

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1. Ñaët vaán ñeà

Tieâu chaûy vaø nhieãm khuaån hoâ haáp caáp ôû treû em laø hai beänh coù tyû leä maéc vaø töû vong cao nhaát ôû nhöõng nöôùc ñang phaùt trieån. ÔÛ nöôùc ta, 80% töû vong do tieâu chaûy xaûy ra ôû treû em döôùi 2 tuoåi, bình quaân 1 treû döôùi 5 tuoåi moãi naêm maéc töø 0,8-2,2 ñôït tieâu chaûy, öôùc tính haøng naêm coù 1100 tröôøng hôïp töû vong [6], [5].

Veà NKHH, trung bình moãi naêm moät ñöùa treû maéc 4-9 laàn, tyû leä töû vong do NKHH chieám 1/3 (30-35%) so vôùi töû vong chung [1], [4]. Tyû leä maéc vaø töû vong cuûa hai beänh naøy raát cao nhöng hoaøn toaøn coù theå haïn cheá baèng caùch chuû ñoäng phoøng traùnh taùc nhaân gaây beänh vaø xöû lí kòp thôøi khi bò beänh. Ñeå phoøng choáng beänh, ngöôøi daân noùi chung vaø ngöôøi chaêm soùc treû noùi rieâng phaûi coù kieán thöùc ñaày ñuû veà phoøng beänh vaø caùch xöû lyù khi treû bò maéc beänh ñeå giaûm tyû leä maéc vaø töû vong.

Chính vì lyù do ñoù, chuùng toâi thöïc hieän nghieân cöùu:

“Kieán thöùc cuûa caùc baø meï coù con döôùi 5 tuoåi veà phoøng choáng tieâu chaûy vaø nhieãm khuaån hoâ haáp caáp tính ôû treû em taïi moät soá vuøng/mieàn Vieät Nam”, vôùi muïc tieâu moâ taû kieán thöùc cuûa caùc baø meï coù con döôùi 5 tuoåi veà phoøng choáng tieâu chaûy vaø nhieãm khuaån hoâ haáp ôû treû em taïi moät soá vuøng/mieàn Vieät Nam

naêm 2014. Töø ñoù coù theå ñöa ra moät soá khuyeán nghò phuø hôïp vaøo coâng taùc truyeàn thoâng phoøng choáng caùc beänh nhieãm khuaån cho treû em trong giai ñoaïn hieän nay.

2. Phöông phaùp nghieân cöùu

2.1. Ñòa ñieåm vaø thôøi gian nghieân cöùu

Nghieân cöùu ñöôïc thöïc hieän vaøo naêm 2014 taïi 3 tænh: Hoøa Bình, Haø Tónh vaø Kieân Giang, ñaïi dieän cho 3 mieàn Baéc, Trung, Nam cuûa Vieät Nam.

2.2. Ñoái töôïng nghieân cöùu Caùc baø meï coù con döôùi 5 tuoåi.

Tieâu chuaån löïa choïn: Laø caùc baø meï coù con döôùi 5 tuoåi, coù tinh thaàn minh maãn, töï nguyeän, hôïp taùc traû lôøi phoûng vaán.

Tieâu chuaån loaïi tröø: Tinh thaàn khoâng minh maãn hoaëc khoâng coù maët taïi hoä gia ñình trong thôøi gian nghieân cöùu hoaëc khoâng töï nguyeän, hôïp taùc trong quaù mothers being able to detect some severe signs of diarrhea and ARI was low. Only 6.6% of mothers recognized wrinkled skin signs (14.4 % in urban and 2.1% in rural region, respectively); 11 % of mothers recognized signs of dyspnea (25.9 % in urban and 1.5% in mountainous region). Mothers’

knowledge about prevention of diarrhea and ARI in urban was better than that of mothers in rural and mountain regions.

Keywords: Diarrhea, acute respiratory infections, knowledge, under 5-year-old child.

Taùc giaû:

1. Vieän ñaøo taïo Y hoïc döï phoøng vaø Y teá coâng coäng, tröôøng Ñaïi hoïc Y Haø Noäi Email: [email protected]

2. Cuïc phoøng choáng HIV/AIDS – Boä Y teá Email: [email protected]

3. CNYTCC4 naêm hoïc 2015-2016, Vieän ñaøo taïo Y hoïc döï phoøng vaø Y teá coâng coäng, tröôøng Ñaïi hoïc Y Haø Noäi Email: [email protected], [email protected]

4. Boä Y teá

Email: [email protected], [email protected]

Clinical characteristics of the respiratory symptoms of coal mine workers from Tay Nam Da Mai Coal Joint Stock Company - VINACOMIN

Duy Van Khuong¹, Chung Quang Le², Phuong Thi Bich Khuong³, Thuy Khuong Phuong⁴

Abstract

Objective: To describe respiratory symptoms of coal mine workers from Tay Nam Da Mai Coal Joint Stock Company - Vinacomin in 2019.

Methods: A cross-sectional study was carried out among 757 coal mine workers from Tay Nam

Da Mai Coal Joint Stock Company - Vinacomin. Face-to-face interviews were performed using modified standardized questionnaires to elicit information on occupational history, demographics, smoking habits, and respiratory symptoms.

Results: Workers of Tay Nam Da Mai Coal Joint Stock Company - Vinacomin had dust exposure,

with arithmetic mean of 6.4 mg/m

³

for current respiratory dust, and had many chronic symptoms such as breathlessness (14.0%), cough (53.6%), 2 weeks for period of the cough (63.8%), 2 months for the cough in one year (65.3%), 2 consecutive years with cough (70.2%) and ≤ 200ml of cough with sputum production per day (97.8%).

Conclusion: Prevalence of chronic respiratory symptoms of coal mine workers in Tay Nam Da Mai Coal Joint Stock Company - Vinacomin was at a high level. The coal mine workers had a high risk of Coal Workers’ Pneumoconiosis, therefore, leaders of Tay Nam Da Mai Joint Stock Company - Vinacomin need to raise awareness among policy-makers, workers and employers in the coal mining industry. It is also useful in setting priorities for prevention strategies.

Keyword: coal mine worker, respiratory symptom, breathlessness, cough, chest pain

1. Ha Noi Medical University, 2. Coal - Mineral Hospital, 3. K Hospital, 4. Master Student of RMIT

1. Introduction

Respiratory diseases have detrimental effects to the health of miners, with important implications for morbidity and mortality.

Respiratory symptoms are early manifestations of acquired respiratory diseases and examining such symptoms among miners is mandatory

during health surveillance of these dust-exposed

workers. Various studies from industrialized

countries have documented the relationship

between exposures to coal dust and increased

risks of respiratory symptoms. Both longitudinal

and cross-sectional studies

^1,2

have shown that

the occurrence of persistent cough and phlegm

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production, breathlessness and wheezing significantly relates to individual cumulative exposure to respiratory mixed coal dust.

The British Pneumoconiosis Field Research among 30,000 miners showed that coal dust contributes to the development of respiratory symptoms among younger workers. The US Coal Mine Health and Safety Act in 1969 set the legal respiratory mixed coal dust standard for coal mines in the United States at 3mg/m

³

, with a reduction to 2mg/m

³

in 1973. Despite these standards, studies in the United States showed statistically significant associations between cumulative exposure to respiratory dust and respiratory symptoms for miners joining the industry after 1970

³

.

Previous studies had examined respiratory symptoms in subgroups of miners who worked at different positions such as coal face, transport, maintenance

⁴

. However, the respiratory health of workers who create mining paths for miners to extract coal has not been studied explicitly. In the study of Mamuya SH, et al.

⁵

, this group of workers had the highest exposure to respiratory dust and quartz, indicating a high risk of respiratory symptoms and disorders. More information about these workers is considered to be important to development of interventions for mines, in order to avoid future respiratory disorders due to dust exposure in this group. In developing countries, and specifically among workers in intensive- labor coal mines, only a few studies have been conducted to investigate the relationships between respiratory symptoms and coal mine dust

⁵

. Therefore, this study aims to describe the prevalence of the respiratory symptoms of coal

mine workers in Tay Nam Da Mai Coal Joint Stock Company - Vinacomin in 2019.

2. Methods

2.1. Study design and participants

A cross-sectional study was carried out at a coal mine in Tay Nam Da Mai Coal Joint Stock Company - Vinacomin, in 2019. Among 1,389 workers in this mine, 628 workers were excluded. The excluded workers were managers, assistant managers, and heads of section who had a low exposure level to coal mine dust. In addition, workers in carpentry, masonry, garage, foundry, welding, etc. were excluded since they exposed to other types of dust. Office workers and temporary workers were also excluded.

Thus, 761 workers were invited to participate but 4 workers with insufficient clinical data due to bad radiographic quality were also excluded.

Finally, 757 workers participated in the study (650 men and 107 women), giving a response rate of 99.3%.

2.2. Questionnaire

The coal mine workers were interviewed

using a respiratory health questionnaire, that

was developed on the basis of St George’s

respiratory questionnaire

⁶

. The questionnaire

had three parts, including personal and work

characteristics, smoking habits, and respiratory

health symptoms. The questionnaire was

prepared in Vietnamese and pre-tested among

30 selected coal mine workers for clarification

and modification before the start of this

study. The questions on personal and work

characteristics included sex, age, education

level, employment history, years worked in the

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mine and years in dusty work elsewhere.

Workers were asked whether they had the following symptoms: dry cough, shortness of breath, cough with sputum during or after the previous shift. In statistical analysis, the responses were dichotomized to no (never) and yes (mild, moderate, severe, or very severe).

2.3. Standard diagnosis of Coal Worker’s Pneumoconiosis (CWP)

Based on Circular No. 15/2016/TT-BYT for CWP diagnosis of Viet Nam Ministry of Health

⁷

: 1) occupational history, 2) the duration of coal dust exposure and 3) chest radiography.

A standard set of radiographs reflecting the amount of coal retained in the lungs was used for comparison and diagnosis

^8,9

. Simple coal worker’s pneumoconiosis usually develops as small, rounded opacities first observed mostly in the upper lobes. These densities were classified as follows: p, q, r. The lung zones were identified as follows: RU, RM, RL, LU, LM and LL. Any nodular opacity greater than 1cm in diameter on radiographs was considered as complicated coal worker’s pneumoconiosis or progressive massive fibrosis. Subcategories for this group were as follows: A, B, C.

2.4. Cumulative dust exposure (CDE)

Dust-exposed service length: a dust-exposed length of service was counted in years from the 1st year of dust exposure, when participants had no occupational changes

¹⁰

. Dust-exposed lengths of service were collected from health record at Vinacomin hospital. Dust-exposed lengths of service were classified into four groups: < 10 years, 10–19 years, 20–29 years, and ≥ 30 years group

¹¹

.

CDE dose (mg/(m

³

·years)) was calculated as accumulated value of ∑ Ci×Ti (Ci: time- weighted average concentration in each year (mg·year/m

³

); Ti: dust exposure year).

2.5. Statistical analysis

The Statistical Package for the Social Sciences (SPSS) version 22.0 (IBM, Armonk, NY, United States of America) was used for the data analysis. P value ≤ 0.05 was chosen as the criterion for statistical significance. The independent t - test and F - test were used to compare continuous variables between coal workers with CWP and without CWP. The Chi- square test or Fisher-exact test were used to compare proportions in categorical variables. A p value < 0.05 was considered as statistically significant.

2.6. Ethical approval

Study protocols followed the ethical principles for medical research involving human participants of the Helsinki Declaration. The research permit was obtained from the Viet Nam National Coal - Mineral Industries Holding Corporation Limited (Vinacomin). There was institutional consent since the administration of the Tay Nam Da Mai Coal Joint Stock Company – Vinacomin was informed of the project and allowed the study to proceed. Each person was verbally informed about the aims of the study and the methods before being requested to consent to participate in the study voluntarily.

3. Results

3.1. Demographic characteristics and

breathlessness symptoms

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Table 1: Demographic characteristics, current and cumulative exposures to respiratory dust among coal mine workers

Exposure status

CWP workers (n = 216)

Without CWP workers (n =

541)

Total

p

SD SD SD

Age (years)a

Length of services (years)

^a

Current exposure (mg/m3)

^a

Cumulative dust exposure (mg/m3)

^a

Smoking status (n & %)

^b

- Current smoker - Ever smoker - Non-smoking

38.6 14.7 0.5 7.4

123 13 80

8.1 7.7 0.3 6.4

56.9 6.0 37.0

34.0 12.1 0.5 6.0

208 16 317

7.2 6.9 0.3 5.7

38.4 3.0 58.6

35.9 13.0 0.5 6.4

331 29 397

7.6 7.3 0.3 5.9

43.7 3.8 52.4

0.001c 0.001c 0.367c 0.004c

0.001d

a

Arithmetic mean (standard deviation).

^b

Number (percentage).

^c

Analysis of variance.

^d

Chi-square.

Table 1 shows the demographic characteristics and current and cumulative exposure to respiratory dust. Among workers with CWP, average duration of dust exposure age (14.7 ± 7.7mg/m

³

and 12.1 ± 6,9mg/m

³

, respectively) and cumulative dust exposures were (7.4 ± 6.4mg/m

³

and 6.0 ± 5.7mg/m

³

, respectively) higher compared with the group of without

CWP workers. The cumulative exposure was also considerably higher for the CWP workers. The number of years in the mine was significantly higher for workers with CWP than that of the group of without CWP workers. The prevalence of current smokers, ever-smokers and non-smoking were significantly different among the three groups (p < 0.001).

Table 2: Chronic respiratory symptoms among coal mine workers

Respiratory symptoms

Workers with CWP (n =

216)

Workers without CWP

(n = 541)

Total

p

n % n % n %

Breathlessness Yes

No

48 168

22,2 77,8

58 483

10,7 89,3

106 651

14,0

86,0 p = 0.0011

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Shortness of breath when:

Hurrying on level ground Walking with people of your own pace on level ground To stop for breathing when walking at your own pace on level ground

44 3 1

91,7 6,2

2,1

55 3

0 94,8 5,2

0,0

99 6

1 93,4 5,7

0,9

p = 0.6762

Cough Yes

No

140 76

64.8 35.2

266 275

49.4 50.6

406 351

53.6 46.4 p = 0.0011 Characters of the cough

Dry cough Cough with white sticky

phlegm’s

Cough with yellow, green phlegm’s

10 91

39 7.1 65.0

27.9 10 194

62 3.8 72.9

23.3 20 285

101 4.9 70.2

24.9 p = 0.1561

Duration for cough 1 week

2 weeks

> 2 weeks

7 79 54

5.0 56.4 38.6

11 182

75 4.1 67.7 28.2

18 259 129

4.4 63.8 31.8

p = 0.0791

Duration for cough in one year 1 month

2 months

> 2 months Do not remember

32 88 19 1

22.9 62.8 13.6 0.7

73 177

13 3

27.5 66.5 4.9 1.1

105 265 32

4 25.9 65.3 7.9 0.9

p = 0.022

Number of consecutive years with cough 1 year

2 consecutive years

> 2 consecutive years Do not remember

10 83 41 6

7.1 59.3 29.3 4.3

11 202

48 5

4.1 75.9 18.1 1.9

21 285

89 11

5.2 70.2 21.9 2.7

p = 0.0061

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Number of cough production per day

≤ 200ml

> 200ml Do not remember

135 2 3

96.4 1.4 2.2

262 4 0

98.5 1.5 0.0

397 6 3

97.8 1.5

0.7 p = 0.0602 Chest pain

Yes No

46 170

21.3 78.7

70 471

12.9 87.1

116 638

15.3 84.7 p = 0.0041 Chest pain areas

Front of chest

Back chest closed scapular Back chest under scapula

Unclear

28 11 6 1

60.9 23.9 13.0 2.2

39 18 10 3

55.7 25.7 14.3 4.3

66 27 16 4

57.8 25.0 13.8 3.4

p = 0.9332

1. Chi-square test between the two groups of workers 2. Fisher-exact test between the two groups of workers

For breathlessness, the significant difference was observed between CWP workers and without CWP workers (p = 0.001). There was no significant difference between CWP workers and the group of without CWP workers who were classified as having breathlessness (p >

0.05) (Table 2).

For cough symptoms, two groups of workers differed in cough and cough with sputum on most of days for as many as 2 consecutive months or more in a year (Table 2). The CWP workers had higher prevalence of cough over 2 consecutive months than the without

CWP workers (p = 0.020) and cough over 2 consecutive years (p = 0.006). There was no significant difference between the CWP workers and the without CWP workers for any of the cough production, period of cough and number of cough production symptoms (p >

0.05).

There was a significant difference between

the CWP workers and the group of without

CWP workers for symptom of chest pain (p =

0.004), but no statistical significance was found

between the two groups regarding chest pain

areas (p > 0.05) (Table 2).

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Table 3: The relation between cumulative respiratory coal dust exposure with some chronic respiratory symptoms

Chronic symptoms Exposure groups Exposure (mg.

year/m3) n %

Breathlessness

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

10 9 28 59

5.1 4.7 14.8 32.2

Shortness of breath when hurrying on level ground

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

7 8 27 57

70.0 88.9 96.4 96.6

Cough

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

16 106 137 147

8.2 55.8 72.5 80.3

Cough with yellow, green phlegm

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

2 16 33 50

12.5 15.1 24.1 34.0

2 weeks for period of the cough

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

11 68 93 87

68.8 64.2 67.9 59.2

2 months for cough in one year

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

9 70 94 92

56.3 66.0 68.6 62.6

2 years for consecutive years with cough

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

9 70 94 92

56.3

66.0

68.6

62.6

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Cough production per day: ≤ 200ml

First quartile Second quartile

Third quartile Fourth quartile

0.00 - ≤ 2.8 2.81 - 4.5 4.51 - 7.8

> 7.8

15 104 134 144

93.8 98.1 97.8 98.0 Table 3 shows that the proportions of coal

mine workers who were suffering from breathlessness, shortness of breath when hurrying on level ground, cough and cough with yellow, green phlegm’s were gradually increasing groups of cumulative respiratory coal dust exposure. The proportions of the 2 weeks for period of the cough, 2 months for cough in one year, and 2 year for consecutive year with cough were not different between exposure groups.

Discussion

Coal mine and silica dust may lead to impaired pulmonary function and also lung diseases which remain a relevant occupational hazard for miners

^2,12

. Our study findings show that average age and length of services of participants, cumulative dust exposure (mg/m

³

) were higher than findings in the study of Simon HD Mamuya, et al.

⁵

, and lower than findings in the study of Yinxia, et al.

¹³

. The fact that the group of CWP workers had higher cumulative dust exposure and higher occurrence of symptoms than the group of without CWP workers was found. Our study findings show a higher prevalence of chronic symptoms (cough, with white and sticky sputum…) than that in previous studies among miners from the United States, the United Kingdom and China. This might be explained by lower dust

exposure levels in our study and maybe sample size was different from that of other studies.

Workers in the mine team (coal face) had an average exposure of 0.66 mg/m

³

,

¹⁰

which was lower than those in previous studies in the United States (1.1 ± 0.5 mg/m

³

)

¹⁴

, Australia (1.51 ± 1.08 mg/m

³

)

¹⁵

and South Africa (0.9 - 1.9 mg/m

³

)

¹⁶

.

In our research, the frequencies of chronic symptoms were 14.0% for breathlessness, 53.6% for any cough, 4.9% for dry cough, 70.2% for any cough with white and sticky sputum, 24.9% for cough with yellow sputum, 93.4% for short of breath when working hard, and 21.9% for over 2 consecutive years with cough and 15.3% for chest pain. This was higher with studies in Tanzania and in South Africa and research of Wang M-F, et al.

^4,5,17

. In our study, the prevalence of dry cough of the mine workers (4.9%) was lower than in the result of Naidoo et al. in South Africa (5.3%) but higher in the CWP workers (dry cough:

7.1%)

^4,16

.

As a reminder, the frequencies of chronic symptoms of CWP workers in the our study were 22.2% for breathlessness, 2.1% for to stop for breathing when walking at your own pace on level ground, 64.8% for any cough, 27.9%