Dietary intake and physical activity of elementary school children in Ha Nam and Dien Bien provinces in 2020

-■c -ÍM Qỉ ugc V Hl


ACKNOWLEDGEMENT

I -am indebted to my tutor. Ass. Prof. Le Till Thanh Xuan from the Department
of Occupational Health. School of Preventive Medicine and Public Health. Hanoi
Medical

University

for her exemplaiy

guidance,

monitoring and constant

encouragement throughout the course of this thesis. I am also indebted to members of
Department of Occupational Health allowing me to use a part of data as my thesis. I
also wish to take this opportunity to express a deep sense of gratitude to the Board of
Directors. Training Department of School of Preventive Medicine and Public Health for
their cordial support, valuable information and guidance which helped me in
completing this task through various stages. I would like to express my deepest thanks
to the Managing Board. Department of Training. Hanoi Medical University who had
created a favorable and wonderful environment in the scliool for the past 6 years. I wish
to thank all the teachers in the Department of Occupational Health. School of
Preventive Medicine and Public Health Hanoi Medical University for their valuable
information provided by them in their respective fields. I am gratefill for their
cooperation during the period of my assignment. Lastly. I would like to express my
deepest thanks to my loving family, relatives and friends for their constant
encouragement without them this thesis would not be possible.

Hanoi. May 2021
Student

Pham Duv Thanh

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SOC I ALIST REPUBLIC OF VIETNAM
Independence-Freedom - Happiness

CONFIRMATION
To:
-

Management Board of Hanoi Medical University.

-

Department of Undergraduate Training Management and Department of Student
Affairs. Hanoi Medical University.

-

Institute for Preventive Medicine and Public Health. Hanoi Medical University.

-

Department of Occupational Health, Hanoi Medical University.

-

Examination Committee for Graduation Thesis 2020-2021
I here by declare that this research was originally done by myself and was a part

of national research on silicosis where the principal investigator approved for my
participation. The data handling and analysis were objectively completed with honesty.
The results of this stud}’ have not been published in any document.

Hanoi. May 2021

Student
Pham Duy Thanh
•


LIST OF ABBREVIATIONS
ILO
WHO

International Labor Organization
World Health Organization


TABLE OF CONTENTS

CONFIRMATION
ABSTRACT

INTRODUCTION

REFERENCES
APPENDIX 1
APPENDIX 2
APPENDIX 3
APPENDIX 4
LIST OF TABLES
Table 2.1. List of variables and indicators among employees of Coc factory in

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LIST OF FIGURES

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Abstract
Silicosis is an occupational lung disease that causes lung fibrosis, progressive
and irreversible in workers who inhale free silica dust. Coc factory is a manufacturing
industry that also generates a lot of silicon dust, which significantly affecting the health
of employees, especially problems related to occupational pulmonary dust respiratory
disease. Therefore, the health protection and prevention of occupational diseases for

employees is very necessary.
We conduct the topic "The prevalence and some associated factors of silicosis
among employees working in one factory in Thai Nguyen province. 2020" with two
following specific objectives: identifying the prevalence of silicosis among employees
and analysing some factors associated with the prevalence of silicosis among
employees working in Coc factory in Thai Nguyen province. 2020.
A cross-sectional study was applied. All employees of Coc factory were working
directly in the production lines matching with inclusion criteria as above. All qualified
employees to participate in the research, agreed to participate in the study and frilly
examined the research items were recruited. In totaL we selected 336 workers among
341 employees of the company at the study time.
After
Coc
Factory
analysing,
inand
Thai
the
Nguyen
prevalence
in
2020
silicosis
was
10.1%.
in
Gender
at
of
workers.

statistically
The
prevalence
significant
of
factor
silicosis
related
in3.14
male
to
silicosis
workers
was
4.32
1.60
times
11.6).
higher
When
than
analyzing
that
of
multivariate
female
workers
regression,
(95%
CI

the
higher
rate
than
of
silicosis
that
of
female
in
male
workers
workers
(95%
was
CI
was
times
1.05-1.24
X
tire
<0.05.
comparison
No
statistically
was
statistically
significant
significant
association

with
between
p was
other
factors
silicosis
was
found.
INTRODUCTION

Silicosis is an occupational lung disease tíiat causes lung fibrosis, progressive
and irreversible in workers who inhale free silica dust [1], [2]. It is incurable and the
most common of all occupational diseases in developing countries [3]. Exposure to
large amounts of free silica may go unnoticed because silica is odorless, does not cause
irritation and does not cause any immediate health effects. Chronic exposure to silica
also increases the risk of tuberculosis [4]. [5]. [6] - a major health problem in
developing countries, including Vietnam
According to the ILO International Labor Organization, it is estimated that every
year about 2.2 million people die from occupational diseases, equivalent to about 5.500

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deaths per day [7].
In developed countries, due to good labor protection, silicosis tends to decrease
gradually. In developing countries, according to the consulting conference of silicon
pneumoconiosis. Geneve 1989: due to ineffective measures to prevent dust, high
concentrations of respiratory dust, workers often have to work hard, making them be
dangerous. As a result, the risk of silicosis increases among those workers [8].

According to the World Health Organization (WHO), the prevalence of silicosis in
developing countries among workers exposed to silica dust was about 20-50%.
Incidence rates also varied between countries and occupations [9]. In Vietnam as of
2016. there were 34 occupational diseases entitled to social insurance. of which silicosis
was recognized for compensation since 1976 and is the most common occupational
lung disease [10]. The disease accounted for 88;% of all occupational diseases assessed
in Vietnam in the period 1976-1997 [9]. [11]. According to the summary' data of the
National Institute of Occupational Health and Environment - Ministry of Health in
2015. out of a total of 28.659 cases of occupational diseases detected across the country,
silicosis was accounted for 76.29% (12].
Thai Nguven is a province in northeastern Vietnam bordering Hanoi capital.
Thai Nguyen is a major socio-economic center of the Northeast and the Northern
Midlands and Mountains region. In 2008. the Department of Preventive Medicine and
Environment, the Ministry' of Health directed the investigation of status and risk factors
for occupational pneumoconiosis - silicosis in five key industrial cities / provinces, in
including Thai Nguyen. Besides high-tech zones. Thai Nguyen still has mam - industrial
zones operating with old and outdated technological lines, including the metallurgy
industry’.
Coc factory was established on September 6. 1963 as an auxiliary unit in the
metallurgical line of Thai Nguyen Iron and Steel Joint Stock Company. The factory's
main task is producing metallurgical coke as raw material for iron production.
Coc factory is a manufacturing industry that also generates a lot of silicon dust,
which significantly affecting the health of employees, especially problems related to

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occupational pulmonary dust respiratory disease. Therefore, the health protection and
prevention of occupational diseases for employees is very necessary'.

Therefore, we conducted the topic "The prevalence and some associated factors of
silicosis among employees working in one factory in Thai Nguyen province. 2020" with
two following specific objectives:
1. To identify- the prevalence of silicosis among employees working in Coc
factory in Thai Nguyen province. 2020
To analyse
some employees
factors
with
prevalence
of
Nguy
silicosis
en province,
among
2020 associated
working in
Cocthe
factory
In Thai
Chapter 1
LITERATURE REMEW

1.1.

Concepts associated with the employees, working environment and
silicosis

1.1.1. The employees
According to clause 1, article 3 of the Labor Code 2012 defines an employee as

a person aged full 15 years or older, capable of working, working under a labor
contract, paid and subject to management, of the employer.
According to Law No. S4/2015 / QH13 - Law on Occupational Safety and
Hygiene, an employee is defined as an officer, public servant, employee, person of the
people’s aimed forces and those who work under compliance co-labor: probationer:
apprentices and apprentices to work for the employer and for t hose who do not work
under 1 abor contracts.
l.u. Working environment
Working environment is the space of the working area in which employees work
together with means of serving labor. Workers' health and the environment also have a
close relationship. A polluted working environment will impair the workers' health
possibly even death. Worker’s health status is a general measure of working
environment [1].

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Working environment includes physical, chemical, microbiological psychosocial
and accidental factors. Workers working in different occupations are exposed to
different factors of the working environment, and thus suffer from different impacts and
disease patterns.
1.13. Dust in labor
Dust in the working environment is generated from the production process. Dust
is a collection of many molecules of small size and longstanding in tire air as flying
dust, settling dust and multi-phase aerosol systems of vapor, smoke, and mist formed
from the debris of objects substances caused by natural forces or by manufacturing
processes. Dust less than 0.1 urn suspended in the air. do not stay in the alveoli. Dust
from 0.1pm to 5pm in size stays in the lungs, accounting for 80-90%. Dust from 5 to 10
pm enters the lungs but is retained in the bronchi and transported by tile hairs of the

bronchial cells to the throat. Dust greater than 10pm collects in the nasal wall. Thanks
to the respiratory system, humans can block and eliminate 90% of dust over 5um in
size. The harmful effects of dust to the respiratory system are highly dependent on the
particle size, chemical composition and sedimentation rate. The most dangerous
harmful effect of dust is causing lung fibrosis. It is a hallmark of lung diseases [14].
1.1.4. Silica (lust
Free silica dust lias the chemical symbol of SÌO2. SĨO2. also known as silica, isa common mineral in the earth's crust, accounting for 27.7%. It is found abundantly in
nature in the form of sand or quartz, is a major component of some types of glass and is
the main substance in concrete [15].
Silica rarely exists in atomic form it is often combined with oxygen in the form of
silicon dioxide (SĨO2) consisting of 2 bodies:
The unconjugated
silicon
oxide,
silicon
dioxide,
form
isanhydric
called
free
silicon,
silicon
quartz,
(or
free
crystalline
silica)
silica)
insilicon
two

forms:
or
amorphous
polymorphic
(amourphous
crystal
silica).
(free
In
which:
cause
10%
amorphous
form,
inactive,
less
toxic
and
not

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1
2

disease. The crystalline form accounting for 90% is the pathogenic form. The common
order is alpha, quartz, cristobatite. and tridi mite.
Structural and surface activity characteristics are related to dust toxicity'.- quartz

lias a four-sided structure with high fibrosis potential, while S- sided cristobatite does
not cause fibrosis.
The hydration properties of free silicon lead to the formation of OH groups Oil
the dust surface and this bond reacts with the phospholipids of the cell membrane,
causing damage to this cell. If the surface of the silica is suirounded by aluminum salts,
substance p204. the toxicity of SĨO2 will be reduced. Silica dust containing aluminum
salts did not cause experimental silicosis.
Combination form: is silicon dioxide (SĨO2) combined with other cations such
as Mg. Ca. Na, K. Fe.... to form silicates such as Feldspars (K. Na. Ca). Kaolin. Mica...
The standard allows to be applied in the determination of the concentration of
dust containing silicon (free silicon dioxide - SĨO2) and assessment of dust pollution
containing silicon in tile air of the working environment in Decision 3733/2002 / QDBYT [16].
7.7.5. Occupational diseases
According to the Law on Safety. Hygiene and Labor 2015. occupational disease
is a disease caused by harmful working conditions of the occupation affecting the
employee [19]. In Vietnam by May 2016. there were 34 diseases recognized as
occupational diseases and entitled to the insurance regime, divided into 5 main groups,
including:
Group I: Occupational pulmonary and bronchial diseases.
Group 2: Occupational poisoning diseases.
Group 3: Occupational diseases caused by physical factors.
Group 4: Occupational skin diseases.
Group 5: Occupational diseases caused by microorganisms.

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1
3

1.1.6. Silicosis
The term Silicosis was firstly used by Visconti when he found SÍO2 in cadaveric
lungs in 1871 [20]. In 1915, Colis et al. showed that quartz was the cause of silica dust.
The 1930 International Conference in Johannesburg identified the cause of silicosis as
SĨO2 and defined: “Silicosis is a lung condition caused by breathing in silicon bioxide
(SĨO2) or free silicon. Anatomically characterized by fibrosis and growth of granules ill
the two lungs, clinically difficult to breathe, and radio graphically the lungs have a
distinctive image of damage” [2].
In the opinion of the ILO expert group at the Fourth International Conference on
Pneumoconiosis (Bucarest. 1971). pneumoconiosis is defined as: “Dust accumulation in
the lungs and the response of the organization with ingress of dust". Thus, silicosis is a
difluse fibrosis occupational lung disease, which develops and does not recover in
employees who breathe in dust containing silicon every day and the silicon content in
rocks is also very different, as in sandstone. The content of agar, granite and shale
ranges from 20 to nearly 100%. Classification according to ICD-9 silicosis lias code
502. and according to ICD - 10 codes are J02.0 [2].
1.1.7. Diagnosis tlie silicosis
According to Circular 15/2016 / TT - BYT on occupational diseases and social
insurance, guidelines for diagnosis of silicosis are as follows:
- Occupational
riskSpecifically:
factors:
Workers
must
work the
in dust
exposure
size
of particles,

occupations
free
whose
silicon
concentration,
content
exceed
quantity
and
permissible
limit.

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1
4

• Minimum exposure: respiratory dust concentration containing free silicon is
greater than 0.1 mg / m3 for 8 hours (or according to current regulations).
• Minimum exposure time: 3 months for acute cases: 5 years for chronic cases.
• Guarantee period: for acute silicosis, the maximum duration of illness after
cessation of exposure is 1 year. For chronic silicosis, maximum onset of illness
alter cessation of exposure: 35 years.
- Clinical feature: may have the following symptoms:
• Difficulty breathing with exertion, then frequent difficulty in breathing:
• Civ st pain, cough, and sputum production;
• There maybe explosive rales, moist rales (possibly acute).
- Subclinical feature:

• Images of lesions on a straight chest x-ray (film and digital film);
+ There are small opacities round notes denoted p, q. r: small uneven opacities
denoted s. t. u or ideal large blur A. B. c (according to the sample film of the
International Labor Organization (ILO) 2000 or the 2011 ILO digital sample film).
•

Can see emphysema, cant)' necrosis, eggshell calcification.

•

Respiratory dysfunction (if any): Restricted or obstructive pulmonary ventilation
(when bronchitis is present), or mixed.

•

Lung CT scanner when needed.

l.l. s. X-ray images of th e si licosis
• Small cloud:
Dimension cloud:

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• Regular round opacities: the symbols of p. q. r are used; small cloud p is a cloud with
size less than 1.5mm; small cloud q is a cloud of size from 1.5 to 3.0 nun: small haze
r is a cloud of sizes between 3.0 and 10.0 mm.
• Non-circular opacities: the symbols s. t and u are used: small uneven opacities cloud
s is tlie opacities cloud with the largest spot size up to 1,5mm: small uneven cloud t

is a cloud with the widest spot size from 1.5mm to 3.0mm; small uneven cloud u is
the opacities cloud with the widest spot size from 3.0 to 10.0 nun.
- The density of tile cloud: depending on the density of the cloud, the classification of
ILO - 2000 is divided into 4 main groups: 0. 1. 2. 3; Each main sub-category
includes 3 sub-categories.
• Large cloud:
- Large cloud type A is a cloud with the size from 10.0 to 50mm or the total size of the
large fiizzies not exceeding 50mm.
- Large cloud type B is a cloud of size over 50mm but not exceeding the upper area of
the right lung or the total size of the cloud is greater than 50mm but not exceeding
the upper area of the right lung.
- The large cloud of type c is the haze having dimensions greater than the area of the
right lung or the total size of the opacities exceeding the area on the right lung.
Oilier abnormalities that can be seen on x-rays include:
- Aortic loop atherosclerosis.
- Thick pleura in the apical region.
- Small cloud adhesion.
- Oxidation of the pleura.
- Heart failure.
- Tensile organs in the chest.
-

Lime of the hilum or mediastinal lymph nodes.

-

Lymph node lung enlargement.

-

Image of blurred bands and lines on the lung parenchyma.


-

Pictures of gas spillage, pleural effusion.

-

Other diseases or abnormalities [10] (21 ].

1.1.9.

Respiratory junction evaluation parameters
Respiratory function measurement is a technique commonly used in the diagnosis,

assessment of severity and treatment monitoring of respirator}' diseases. The teclinique
helps to record parameters related to lung function, thereby helping to evaluate ventilator}'
disorders: obstruction, restriction and mixed.
• Some key respirator}' indicators:
-

FEV1 (Forced Expiratory Volume in One Second): Tire volume of air that can be
exhaled for the first 1 second of exertion is the volume of air that can be exhaled
during the first second of forced expiration. FEV1 is an important, easy-to-measure.
low-volatility index used to determine and evaluate the degree of obstruction.

-

FVC (Force vital capacity): forced vital capacity is the total volume of forced

exhalation air in one breath.

-

VC (Vital capacity): fixing capacity. VC is an important indicator of restrictive
syndrome identification.

-

TifTmeau FEV1 / VC is normal ằ 70%.
Gaensler FEV’l / FVC index is normally t> 70%.
Diagnose the degree of limitation according to the standard of A TS / ERS based on

FVC[22J:
• Low: % F VC = 60 - <80% of theoretical value.
• Medium: % F VC = 40 - <60% of theoretical value.
•

High: % FVC = <40% of theoretical value.
Diagnosis of airway obstruction according to .4 TS / ERS based on FEV1 [22]:

•

Low: % FEV1 £ 70% of theoretical value

•

Average: % FEV1 = 60 - 69% of the theoretical value

•

Little high: % FEV1 = 50 - 59% of theoretical value

•

High: % FEV1 = 35 - 49% of theoretical value


•

Very high: % FEV1 = <35% of theoretical value
Diagnosis of obstruction is based on GOLD 2014 standards (FEM value after

bronchodilator test) [23].
•

Stage 1 - Low: FEV1 £ so% of theoretical value

•

Srage 2 - Average: 50% s FEV1 <80% of theoretical value

•

Stage 3 - High: 30% ắ FEV1 <50% of theoretical value

•

Stage 4 - Very high: FEV1 <30% of theoretical value.

1.2.

The prevalence in silicosis among employees exposed to silica dust 1.2.1.
Global

The first international conference on pneumoconiosis was held in 1930 in
Johannesburg - South Africa, to discuss the pres ention of silicosis that is very common
among mining workers. The ILO-held pneumococcal disease conferences over tire past
eight decades have contributed greatly to the advancement of respiratory medicine
worldwide [8].
In the weekly
(MMWR)
US.
according
report,
to
in
the
the16305.
2005
period
Morbidity
1968
and Mortality
2002.
out
million
primary
death
cause

certificates,
of
death
with
silicosis
which
was-reported
toof
be74
the
98% of whom are male. Between 1968 and 2002. the number of deaths from silicosis
decreased from 1157 to 148. or 93%. respectively [24].
According to the SWORD program in the UK. in the 22-year period from 1996 to
2017. there were 216 reported cases of silicosis belonging to 8 occupational groups in direct
contact with silica dust in the labor environment, of which tire metal production and
quarrying accounted for the highest percentages of 21% and 19%ụ respectively. The median
age of those reported was 61 years (between 23-89). and 98% were male [25].
A 2011 Italian study of a workshop using mostly artificial stones reported silicosis
with a prevalence rate of 54.5% (6 out of 11 workers), where The largest dust comes from
the cutting and polishing of football [26].
In. 2014. a study in Spain by Perez-Alonso A et al. Showed that the use of new
building materials such as quartz increases tire incidence of silicosis due to occupational
exposure. Specifically. 46 men were diagnosed with the disease with an average age of 33
years and an average age of 11 years [27],


A 2014 study of agate grinder respiration in Iran found that: Onyx grinding workers
are at risk of respiratoiy diseases, especially silicosis and chronic bronchitis. The rate of
silicosis in onyx workers was 12.9%: 43.3% of subjects had limited ventilation disorder
[2S].

Another study in Australia in 2016 showed that in the 5 years from 2011-2016 there
were 7 cases of silicosis related to artificial stone - a new material present in Australia since
the 2000s exposure to artificial rock dust until symptoms were 7.3 years. All 7 people have
symptoms of cough, difficulty breathing increases gradually with exertion [29].
In 2017. Tsao Y. c et al. Conducted a descriptive study on the clinical characteristics
and history of silicon dust exposure of workers in several Taiwan ceramics manufacturing
facilities. Tire results showed that: 78.7% of subjects with small opacities lesions had
density of main subgroups 1 and 2. and 21.3% of subjects with small opacities lesions had
density of main subgroups 3 and lesions, laige opacities haze on x-ray. There are 52.9% of
subjects with limited RLTK with FVC <80%. 49.3% with FEV1 <80%. For airway
obstruction 49.3% had predicted an FEV1 <80%. 25.8% had an FEV / FVC ratio <75%. and
29.6% had predicted an MMEF <60% [30].
India is a country with a large mining industry. In 1999. the Indian Medical Research
Council reported that about 3.0 million workers had a high risk of exposure to silicon: Of
which about 1.7 million workers were in the quanying industry. 0.6 million were in the
production of non-metal products (refractory bricks, clay, glass, mica ...) and 0.7 million
were in the metal industry. There was very little epidemiological research on silicosis in
India where the incidence of silicosis varies from 3.5% in the material manufacturing
factories to 54.6% in the shale pencil industry [31].
In 2015. Prabodh Pancliadhvayee et al conducted a study on pneumoconiosis in
Indian among jewelry polishing workers. The results showed that silicosis in jewelry
polishing workers was found to be more severe and progressive than that of other
occupational exposures silicosis. Specifically, tire exposure time to silica dust of jewelry
polishers was significantly less than that of other workers (3.4 X 1.7 vs 9.3 X 4.1: p =
0.001). the mean duration (months) of jewelry polishers was also less than other workers


(14.9 X 5.8 with 28.5 ± 16.5: p = 0.04) [32].
In 2017.
stone

crushing
another
units
study
were
in at
India
risk
also
ofunits
showed
silicosis,
that
with
workers
rates
inXgreater
42.5
(from
than
35-49
8%.
In
years
old).
the
75%
average
of
workers

age
of
with
diagnosis
the
disease
was
have
ray
images
been
working
of
patients
inwhich,
stone
with
crushing
die
disease
showed
for
18-30
that:
years.
small,
round
cloudy
image accounted for 87.5%; Eggshell calcification occurs in 50% of cases and pleural
thickening was 62% [33].

In 2003. Xiao GB et al’s study on dry sludge exposure at Tatami carpet production in
China showed tliat: the average free silicon content in the settling dust in the workplace was
25.6%. There are 2.57% of subjects with a cloud density of 1/0 or more on x-ray [34].
In Vietnam
In 2003. research by author Nguyen Thi Bich Lien on clinical symptoms and CNHH
exploration on 83 quarry workers in Binh Dinh with the age of> 5 years showed that: the
rate of silicosis was 9.6% with the majority (50%) having mild illness (1/0 p); 1.2% had
silicosis combined with tuberculosis; there are 2 prominent functional symptoms: chest pain
(80.7%) and difficulty breathing (75.9%) followed by sputum production, coughing and
coughing up blood [37],
According to a study by Nguyen Bach Ngoc et al in 2003 on silicosis among quarry
workers in Binh Dinh. 19 workers were found and diagnosed with silicosis, accounting for
3.23% and mainly in the 1/0 p form 100% of cases are at work age> 5 years [38].
According to authors Nguyen Lieu and Pham Van To (2004), among the diseases
acquired by coal mining workers in Quang Ninh, lung and bronchial diseases account for
the highest proportion at 40.8% [39].
A study was done by the authors Huynh Thanh Ha and Trinh Hong Lan (2008) found
that the rate of silicosis of workers working in some construction materials manufacturing
facilities in Binh Duong was 11.97%. Of which, the rate of workers in the stone quarrying
and processing workshop w as much higher than that in the brick production area (p <0.05).
22.13% of the employees had abnormal development results, in which the mixed ventilation
disorders accounted for the highest percentage of 11.27% and only 0.64% were jammed
ventilatory disorders [40].
According to authors Nguyen Van Thuyen and Hoang Viet Phuong (2014). the rate
of general respirator.- disorders among workers in some factories of repairing and building
defense ships in the sou til was 22.ss%. mainly limited ventilatory disorders accounting for


15.47%. mixed ventilatory disorders were 5.01%. and the remaining 2.4% were jammed
ventilator}’ disorders. The rate of occupational silicosis was 21.35%. of which 17.43% was

pure silicosis, and silicosis combined with tuberculosis accounts for 3.92%. Research has
also shown that there was an association between occupational age and risk of disease [41].
In 2016. a study by author Trinh Van Tuan on the current situation of Silicosis in
some facilities exploiting, processing stone and producing building materials in Binh Dinh
province showed tliat; the overall prevalence rate is 44.5%. of which the incidence of
suspected infection (0/1. 1/0) is 37.2%. incidence rate 1/1 p / p or more is 7. 3% [42].
Research on the state of silicosis of workers in some iron-smelting factories in 20IS
by Ta Till Kim Nhung and Nguyen Ngoc Anh shows that the incidence of silicosis of two
iron refining factories in Tliai Nguyen province was 11.5% and 12.3%, respectively [43].
1.3.

Some factors associated with the prevalence of silicosis among employees

exposed to silica dust
There
sex.
occupational
have
been
many
age.
studies
history
conducted
of
chronic
respiratory
that
the
age.

disease,
dust
protection
smoking,
measures
exposure
among
history,
employees
andshowing
the
related
degree
toof
use
of
respirator}'
of
workers
in
disease
direct
in
contact
general
with
and
silica
silicosis
dust

in
particular
the
labor
environment.
1.3.1.
Global
Akgun et ai (2008) showed that the risk and severity of silicosis correlated with
seniority (r = 0.48; p <0.001). exposure time (r = 0.25; p <0.01) and number of working
places (r = 0.32; p <0.01) [36].
Sillicosis in onyx grinder workers in Iran (2014) mainly occurs in workers> 40 years
old and those with exposures> 25 years, and tile disease was also linked 10 unsecured
personal protective measures [28].
A study by Gizzaw z et al in Ethiopia in 2015 showed that gender, age. education
level, work position, age. smoking, history of chronic respiratory disease and training
knowledge about occupational hygiene to prevent respirator.’ diseases are factors related to
chronic respirator)’ symptoms that the workers of Dejen Cement Factory suffer. The
relationship was significant for both univariate and multivariate analysis (p <0.05).
specifically, men had a risk 2.07 times higher than women (95% CI; 1.18-3.63); workers
aged 45 and over had a 4.02 times higher risk of contracting workers under 30 years old
(95% CI: 1.94-9.12); workers with education below grade 8 have a risk of 4.07 times higher
than the group with higher education (95% CI: 1.86-8.92); workers working in the cement


department have a risk of 3.72 times higher than that of raw parts (95% CI: 1.92-7.21);
workers with the occupational age of more than 5 years have a risk of 5.44 times higher than
that of the group with the occupation age less than or equal to 5 years (95% CI: 3.09-9.59);
smokers had a 5.38 times higher risk of contracting than a non-smoker group (95% CI: 1.4220.39); workers with a history of chronic respirator)’ disease were 7.79 times more likely to
be infected than workers with no history of the disease: workers who were not trained in
occupational hygiene to prevent respiratory diseases were at risk of 2.73 times higher than

that of trained workeis (95% CI: 1.41-5.29) [44].
In 2016. a study of coal workers in Australia concluded that symptoms and
manifestations of occupational pneumoconiosis varied depending on the composition of the
inhaled dust, duration of exposure, stage of illness, and other factors related to the subject's
geomorphology [29].
The 2019 study of respiratory disease incidence among iron production workers in
India found an association with the history of family chronic respiratory disease (OR =
0.47%. 95% CI: 0.24-0.91) and worker education level (OR = 0.34; 95% CI: 0.12-0.94).
literate people had the rate of disease lower than the illiterate [45].
1.32. In Vietnam
Research by the author Dao Xuan Vinh et al (2006) in die building material
manufacturing facilities whose working time was exposed to the labor environment with the
concentration of silicon dust exceeding the permined standard at least 5 consecutive years
shows that there was a correlation between the incidence of silicosis with occupational
groups, in particular, the group of quarry workers, producing refractory bricks with silicosis
accounted for the highest rate of 6.4% followed by is the group of cement producers and the
lowest was 3.8% in the group of casting, concrete drilling, mechanical... [46].
According
to
research
by the
author
Nguyen
Ngoc
Son.
Le
Hoai
on
2012.
workers

The
study
suffering
indicates
from
silicosis
that
higher
at
the
age.
Saigon
the
Shipyard
higher
the
in
proportion
workers
with
of
occupational
workers
with
age
pulmonary
£the
5
years
disease.

lias
the
The
rate
rate
of
ofCam
ventilatory
age
group
5-10
disorders
years
of
13.8%.
highest
increasing
is
37.7%
to
23.1%
in
the
in
age
the
group
2
10
years.

Theand
higher the occupational age plus the dust pollution level, the greater the prevalence of
silicosis [47].
Authors Nguyen Van Thuyen and Hoang Viet Phuong (2014). researching on workers
with silicosis at some shipbuilding and repair factories in the south showed that the higher
the occupational age. the higher the rate of silicosis. Specifically, the occupational age group


£ 10 years has the lowest rate of disease (10.86%), increases to 22.06% in the age group 1120 years and the highest is 35% in the age group> 20 years. [41].
A study by Nguyen Ngoc Anh and Ta Thi Kim Nhung (2018) also showed a
correlation between silicosis and age (95% CI: 1.7-11.3) and history of respiratory disease,
chronic absorption of employees (95% CI: 1.6-114.3) [43],
1.4.

Overview of the study sites

•
Thai Nguyen is a province in northeastern Vietnam, bordering Hanoi capital. Thai
Nguyen is a major socio-economic center of the Northeast and the Northern Midlands and
Mountains region. In 2008. the Department of Preventive Medicine and Environment. the
Ministry of Health directed the investigation of status and risk factors for occupational
pneumoconiosis - silicosis in five key industrial cities

f

provinces, in including Thai

Nguyen. Besides high-tech zones. Thai Nguyen still has many industrial zones operating
with old and outdated technological lines, including the metallurgy industry. Coc factory is a
manufacturing industry’ that also generates a lot of silicon dust, which significantly

affecting the health of employees, especially problems related to occupational pulmonary
dust respiratory disease. Therefore, the health protection and prevention of occupational
diseases for employees is very necessaiv.
Chapter 2
RESEARCH SUBJECTS AND METHODOLOGY
2.1.

Research sites

The study was done in Coc factory. Cam Gia ward. Thai Nguyen province.
Coc factors- was established on September 6. 1963 as an auxil iary unit in die
metallurgical line of Thai Nguyen Iron and Steel Joint Stock Company. The factory's main
task is producing metallurgical coke as raw material for iron production.
Currently, the company lias 341 workers.
The main products of company: metallurgical coke, steel widgets, bitumen,
naphthalene, phenol.


Figure 2.1: study location
Research subjects

2.2.

Employees were working in Coc factory.
Inclusion criteria:
-

Directly exposure to silica dust.

-

The employee fully participated in the examination items required by the study,
including attending questionnaire, clinical examination. Xray film and respiratory
functions.

-

Agreed to participate in research.

-

Working time at the company at least one year at the study time.
Exclusion criteria:
Those working in the administrative department of the company, the pregnant female

employees.


Metallurgical coke making process:

Steel making process:

Figure 2.2: Metallurigical coke and steel making process
2.3.

Research times

-

The study was conducted from June 2020 to May 2021

-

Data were aggregated in November 2020

2.4.

Research design
A cross-sectional study was applied.

2.5.
•

Sample size and sampling
Sample size: The entile sample was selected.
All employees of Coc factory were working directly in the production lines matching

with inclusion criteria as above.
•

Sampling

A list of all employees directly engaged in production was made. All qualified employees to
participate in the research, agreed to participate in the study and fully examined the research
items were recruited. In total, we selected 336 workers among 341 employees of the


company at the study time.
2.6.

Variables and indicators
Demographic characteristics: age. gender, specialized work...

Table 2.1. List of variables and indicators among employees ofCoc factory
in 2020
Variables,
indicators

Definition. Variable Type

Technique for
data collection

General information
Number of years from birth to 2020
Age

Gender
Variables,
indicators

(according to solar calendar), including 5

Face-to face

age groups: under 20. from 20-29. from 30-

interview by

39. from 40-49 and over 50 years old

Questionaire

Male Female
Definition. Variable Type

Questionaire
Technique for
data collection

Including: construction materials; mining
and processing ores: exploiting,
Specialized

manipulating stone, metallurgy; production

work

of ceramics, porcelain and glass; exploiting

Questionaire

granite stone; other

Years of working at the factory (from the
Occupational age

beginning to 2020). including 4 groups: <5
years. 5-9 years. 10-19 years and £ 20 years

Questionaữe