International Journal of
Environmental Research
and Public Health
Article
The Cotton Dust-Related Allergic Asthma: Prevalence and
Associated Factors among Textile Workers in Nam Dinh
Province, Vietnam
Tran Thi Thuy Ha 1 , Bui My Hanh 2 , Nguyen Van Son 3 , Hoang Thị Giang 1 , Nguyen Thanh Hai 1 ,
Vu Minh Thuc 4 and Pham Minh Khue 1, *
1
2
3
4
*
Faculty of Public Health, Haiphong University of Medicine and Pharmacy, Haiphong 04212, Vietnam;
tttha@hpmu.edu.vn (T.T.T.H.); htgiang@hpmu.edu.vn (H.T.G.); nthanhhai@hpmu.edu.vn (N.T.H.)
Department of Tuberculosis and Lung Disease, Hanoi Medical University, Hanoi 11521, Vietnam;
buimyhanh@hmu.edu.vn
Department of Occupational Diseases, National Institute of Occupational and Environmental Health,
Hanoi 11611, Vietnam; nguyenvansonbnn@yahoo.com
Department of Research and Training, Tam Anh Hospital, Hanoi 11813, Vietnam;
vuminhthuc2010@gmail.com
Correspondence: pmkhue@hpmu.edu.vn; Tel.: +84-943-080-138
doi.org/10.3390/ijerph18189813
Abstract: Objective: To determine the prevalence of cotton dust-related allergic asthma and associated
factors among textile workers in Nam Dinh province, Vietnam. Methods: A cross-sectional study was
performed with 1082 workers in two textile garment companies using the asthma diagnostic criteria
of the GINA (Global Initiative for Asthma) 2016 guidelines. Results: Among study participants, 11.9%
had suspected asthma symptoms, 7.4% were diagnosed with asthma, and 4.3% (3.6% in men and 4.5%
in women) were diagnosed with cotton dust-related allergic asthma. Overweight, seniority more than
10 years, history of asthma, allergic rhinitis, family history of allergy, and exposure to cotton dust
from more than one hour per day in the working environment were found to be important predictors
of cotton dust-related allergic asthma among textile workers. Conclusions: Textile workers in two
companies in Nam Dinh, Vietnam had a high prevalence of dust-related allergic asthma compared to
estimates from the general population. There is a need to design appropriate measures of prevention,
screening, and care for dust-related asthma in the textile industry. Further evaluation with better
exposure assessment is necessary.
Academic Editor: Luigi Vimercati
Keywords: allergic asthma; cotton dust; textile workers; Nam Dinh; Vietnam
Citation: Ha, T.T.T.; Hanh, B.M.; Van
Son, N.; Giang, H.T.; Hai, N.T.; Thuc,
V.M.; Khue, P.M. The Cotton
Dust-Related Allergic Asthma:
Prevalence and Associated Factors
among Textile Workers in Nam Dinh
Province, Vietnam. Int. J. Environ. Res.
Public Health 2021, 18, 9813. https://
Received: 1 August 2021
Accepted: 12 September 2021
Published: 17 September 2021
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4.0/).
1. Introduction
Asthma is a common non-communicable chronic respiratory disease and occurs in
all countries regardless of the level of development. The definition of asthma still has
many different opinions and statements. According to WHO, asthma is characterized by
recurrent attacks of breathlessness and wheezing, which vary in severity and frequency
from person to person [1]. According to Gina’s report based on various data sources, there
are approximately 358 million people with asthma in the world (with global prevalence
ranging from 1 to 22% of the population) [2]. In addition, 26.2 million disability-adjusted life
years (DALYs) are estimated to be lost due to asthma, representing 1.1% of the total burden
of disease. Finally, 495.000 deaths worldwide are due to asthma every year [3]. Asthma
continues to be a major source of global burden in terms of both social and economic
(including direct and indirect costs) aspects. Asthma leads to high direct medical costs
(hospital admissions, physician visits, and medications) and indirect costs due to its impact
on productivity loss and premature death [1,4].
The strongest risk factors for developing asthma are inhaled substances and particles
that may provoke allergic reactions or irritate the airways, in which chemical irritants in the
Int. J. Environ. Res. Public Health 2021, 18, 9813. https://doi.org/10.3390/ijerph18189813
https://www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2021, 18, 9813
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workplace are a typical example [1]. When a substance or condition at work causes asthma,
it is called work-related asthma. Work-related asthma (WRA) comprises two major entities,
occupational asthma (OA-, asthma induced by sensitizer or irritant work exposures) and
work-exacerbated asthma (WEA-pre-existing or concurrent asthma worsened, but not
caused, by work factors: aeroallergens, irritants, or exercise . . . ) [5,6]. In the textile
industry, work-related asthma is considerable and several agents such as cotton dust and
dyes may cause this condition [7]. The prevalence of work-related asthma among textile
workers has been studied in several countries: 9.1% in Thailand [8], 0.9% of women and
1.1% of male textile workers in Croatia [9], 4.0% and 5.0% in Pakistan in 2013 and 2015
respectively [10,11]. Meanwhile, work-exacerbated asthma is more common with about
25% to 50% of working adults with known asthma causing exacerbations with asthma
symptoms related to their workplace [12]. These symptoms include wheezing, cough, chest
tightness, and/or shortness of breath.
Vietnam has a developed textile industry with more than 3800 companies, more than
2 million workers, and ranks fifth in the world in textile and apparel exports [13]. The
textile working environment has a lot of factors (such as cotton dust, noise, humidity, lack
of light . . . ) that contribute negatively to the health of workers despite the regulations
on annually measuring the working environment and periodic medical examinations
for the workers [13]. Indeed, in Vietnam, well-being at work is an issue of increasing
concern. Currently, the list of occupational diseases covered by insurance has expanded
to 34 [14], including occupational asthma, which is a major occupational problem in the
textile industry.
Nam Dinh province located in the center of the Southern Red River Delta region of
Vietnam is called “The Textile City” of Viet Nam, with about 480 companies and more
than 200,000 active workers, accounting for 8% of textile companies in the country [15].
Currently, besides traditional businesses such as Nam Dinh Textile Factory, Song Hong
Garment Joint Stock Company . . . , the whole province has two operating industrial
parks, including Bao Minh and Hoa Xa, attracting many textile enterprises, a large-scale
garment at home and abroad, creating jobs for many workers. In addition, the province
has 24 district-level industrial clusters established, of which 19 industrial clusters with
a total area of 352.5 ha have been put into operation, providing space demand for the
first textile enterprises production development and business investment. There is a
school specializing in training high-tech workers for the textile industry, Nam Dinh Textile
Industry College, that uses modern high-tech equipment compared to textile vocational
training schools in Vietnam. In recent years, there have been many studies assessing the
working environment and the health status of textile workers [13,15]. However, in the last
fifteen years, there have not been any studies to assess asthma disease and asthma-related
allergies to cotton dust among textile workers. Thus, there is a need to understand the
prevalence of cotton dust-related allergy asthma, and other respiratory conditions as well as
relevant health hazards in this industry to strengthen the existing system to protect workers’
health. The object of this study is to determine the prevalence of cotton dust-related allergic
asthma and associated factors among textile workers in Nam Dinh province, Vietnam.
2. Materials and Methods
2.1. Study Design
A descriptive cross-sectional survey was performed between May and November
2016 to ascertain the cotton dust-related allergic asthma and some potential explanatory
variables among workers in two textile companies (Nam Dinh Yarn and Song Hong
Garment) of Nam Dinh, Vietnam.
2.2. Eligibility Criteria
We selected all workers (1125) who participated in all stages of the production process
(harvesting, preparatory processes, spinning, weaving, and finishing) of 2 companies and
meet the following criteria:
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− Directly participate in the production process,
− Have worked in their current position for at least 12 months, and
− Agree to participate in the study.
A total of 1082/1125 (368 in Nam Dinh Yarn and 714 in Song Hong Garment) workers
participated in this study.
2.3. Criteria for Making the Diagnosis of Asthma and Cotton Dust-Related Allergic Asthma
Diagnosis criteria for asthma are based on GINA (Global Initiative For Asthma)’s
guidelines updated in 2016 with 2 key defining features: a history of respiratory symptoms
such as wheeze, shortness of breath, chest tightness, and cough that vary over time and in
intensity, AND variable expiratory airflow limitation [16].
Criteria for determining allergic asthma associated with cotton dust in the workplace [17]:
− have been diagnosed with asthma according to the criteria above,
− have a family or personal history of allergy,
− serum IgE > 100 UI/mL, AND
− positive for skin test (Prick test) with cotton dust.
2.4. Data Collection Instruments
We used the following tools to collect data:
− A sociodemographic questionnaire was used to collect general information, such as age,
gender, height, weight, marital status, smoking status, personal history of asthma across
their whole life, family history of allergy, and work-related information, including seniority,
working position, and time of cotton dust exposure per day.
− An asthma screening questionnaire was developed based on GINA guidelines for the
diagnosis of asthma.
− Respiratory function measurement tool: CHEST HII 801 spirometer (2012, Japan) and
Ventolin Inhaler 100mcg for bronchodilator reversibility test.
− Materials to serve the prick test [16] with cotton dust allergen.
− Materials for blood collection to quantify serum IgE concentration.
2.5. Research Progress
This study went through the following stages:
Step 1: We worked with the trade unions of 2 companies to build the research plan,
organizational processes and provided an information sheet to all their 1125 workers before
the study. The survey was set within the workers’ annual medical checkup sessions of the
companies. In total, 1082 workers agreed to participate in the study, signed the consent
forms, and were then interviewed about socio-demographic information, occupational
characteristics, and asthma screening (symptoms, history of asthma, history of allergy).
Parallel to the interview, all participants were examined for allergic rhinitis and allergic
sinusitis performed by the otorhinolaryngology specialists of the National Otorhinolaryngology Hospital. There were 129 workers with suspected asthma symptoms. The total
timing of this step took place in 3 weeks with 8 trained interviewers per day.
Step 2: The respiratory function was measured in those with symptoms and a history
of suspected asthma. The following parameters were measured:
− vital capacity (VC)
− forced vital capacity (FVC)
− forced expiratory volume in the first second (FEV1)
− Gaensler index is calculated by the following formula: Gaensler = FVC/FEV1.
A person exhibits obstructive ventilatory disorders when: FEV1 <80% and Gaensler
index <75% of the theoretical value.
People with obstructive ventilation were given a bronchodilator reversibility test with
Salbutamol (Ventolin Inhaler 100 mcg). This test is considered positive when the FEV1
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at the second measurement (after Salbutamol spray) increases ≥ 12%
≥ more compared to
the first test and/or the absolute value of the FEV1 is greater than 200 mL. A total of 80
workers had obstructive ventilation and were positive at the bronchodilator reversibility
test (i.e., diagnosed with asthma).
Step 3: People with diagnosed asthma had a prick test with cotton dust allergen and
a determination of IgE concentration for the purpose of diagnosing allergic asthma in
association with cotton dust. Forty-six workers were found to have allergic asthma in
association with cotton dust.
The study processes are presented in Figure 1.
Figure 1. The study processes. (+): positive.
2.6. Statistical Analysis
SPSS version 22.0 software (SPSS Inc. IBM, Armonk, NY, USA) was used for data
analysis. Quantitative variables were described as mean/median and standard deviation.
Prevalence (number, percentage, 95% confidence interval) of cotton dust-related allergic
asthma in each category according to sociodemographic, occupational, and allergic rhinitis
and sinusitis variables was calculated. A chi-square test (or Fisher’s exact test) for qualitative variables was used to compare characteristics of the sample according to cotton
dust-related allergic asthma. Multiple logistic regression was used to study the associated
factors of cotton dust-related allergic asthma. A stepwise backward selection strategy was
applied along with multivariate logistic regression to have reduced models. This strategy
used a p-values threshold of <0.2 at a log-likelihood ratio test for predictors included. The
level of significance was set at a p-value of less than 0.05.
2.7. Ethics
All study procedures involving human subjects were approved in advance by the
Institutional Review Boards at the Vietnam National Institute of Occupational and Environmental Health. Data collection procedures also were approved by the directors of the
two companies. Written informed consent was obtained from all participants.
3. Results
3.1. Characteristics of The Study Population
Among the workers participating in the study, 69.1% were female (748/1082). The
mean age was 34.8 years (SD = 8.6), half of them were between the ages of 30 and 39
(49.3%) and half had a working experience of more than 10 years (50.3%). Most of them
were married (96.65%) and non-smokers (98.3%). Percentage of asthma history and family
history of allergic reaction were 0.6% and 5.9% respectively, while 4.3% had allergic sinusitis
and more than half (52.1%) had allergic rhinitis. Fifty-six dot 9 percent of workers were
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exposed to cotton dust from 5 to 8 h in 1 working day and 25.3% from 9 to 11 h. The
percentage of non-exposed to cotton dust in the working environment was 12.9% (Table 1).
Table 1. Demographic and cotton dust-related allergic asthma characteristics among workers.
Cotton Dust-Related Allergic Asthma
Variables
N = 1082
Yes
n (%)
p-Value
No
n
%
n
%
Gender
Male
Female
334 (30.9)
748 (69.1)
12
34
3.6
4.5
322
714
96.4
95.5
0.473
Age group (years)
20–29
30–39
40–49
≥50
221 (20.4)
533 (49.3)
215 (19.9)
113 (10.4)
5
21
14
6
2.3
3.6
6.5
5.3
216
512
201
107
97.7
96.1
93.5
94.7
0.152
Overweight **
Yes (BMI ≥ 25)
No
48 (4.4)
1034 (95.6)
7
39
14.6
3.8
41
995
85.4
96.2
<0.01
Seniority
≤5 years
6–10 years
>10 years
242 (22.4)
296 (27.3)
544 (50.3)
4
6
36
1.7
2.0
6.6
238
290
508
98.3
98.0
93.4
0.001
Working position
(location of company)
Yarn Factory
Garment comp.
368 (34.0)
714 (66.0)
22
24
6.0
6.4
346
690
94.0
93.6
0.043
Marital status
Others
married
37 (3.4)
1045 (96.6)
1
45
2.7
4.3
36
1000
97.3
95.7
0.527 *
Smoking
smoke
Non-smokers
38 (1.7)
1044 (98.3)
5
41
13.2
3.9
33
1003
86.8
95.1
0.006
History of asthma
Yes
No
16 (1.5)
1076 (98.5)
4
42
25.0
3.9
12
1024
75.0
96.1
0.004 *
Family history of allergy
yes
No
191 (17.7)
891 (82.3)
32
14
16.8
1.6
159
877
83.2
98.4
<0.001
Allergic rhinitis
yes
no
564 (52.1)
518 (47.9)
41
5
7.3
1.0
523
513
92.7
99.0
<0.01
Allergic sinusitis
yes
No
46 (4.3)
1036 (95.7)
4
42
8.7
4.1
42
994
91.3
95.9
0.127 *
Time of cotton dust
exposure per day
no
1–4 h
5–8 h
9–11 h
140 (12.9)
52 (4.8)
616 (56.9)
274 (25.3)
2
1
23
20
1.4
1.9
3.7
7.3
138
51
593
254
98.6
98.1
96.3
92.7
0.004
*: Fisher’s Exact Test. **: According to the IDI and WPRO classification.
3.2. Prevalence of Cotton Dust-Related Allergic Asthma
In a total of 1082 workers, 129 (11.9%) had suspected asthma symptoms, 80 (7.4%)
were diagnosed with asthma, and 46 (4.3%) were diagnosed with cotton dust-related
allergic asthma.
The prevalence of cotton dust-related allergic asthma was 3.6% in men and 4.5% in
women (p = 0.473). This prevalence tended to increase with age (p = 0.152), seniority
(p = 0.001) and time of cotton dust exposure per day (p = 0.004). People marked overweight
had a higher prevalence than non-overweight people (14.6% versus 3.8%, p < 0.01). Finally,
workers with a history of asthma, a family history of allergic and a diagnosed allergic
rhinitis had a statistically significantly higher prevalence of cotton dust-related allergic
asthma than workers without history (all p-values less than 0.01) (Table 1).
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3.3. Associated Factors with Cotton Dust-Related Allergic Asthma among Textile Workers
A p-value of less than 0.2. univariate was used in analyses first used to find the
factors that are potentially associated with cotton dust-related allergic asthma. These
factors were put into the multivariate model of logistic regression. Final model results
showed that overweight, seniority of more than 10 years, history of asthma, allergic rhinitis,
family history of allergy, and duration of exposure to cotton dust per day were statistically
significantly associated with cotton dust-related allergic asthma.
In detail, overweight had OR = 5.11, p = 0.002 (reference category was non-overweight);
compared to a seniority under 5 years, workers with a seniority over 10 years had the
highest prevalence of cotton dust-allergic asthma with an OR = 4.12 and p = 0.012; people
with current allergic rhinitis or a history of asthma, a family history of allergy had a higher
prevalence of cotton dust-related allergic asthma compared to those without allergy, with
an OR and p values respectively at 3.67, 0.011; 8.11, 0.009 and 9.64, <0.001; workers exposed
to cotton dust for 1–8 h (OR = 4.52, p = 0.029) and 9 to 11 h (OR = 2.91, p = 0.004) per day
had a higher prevalence of cotton dust-related allergic asthma compared with workers not
exposed to cotton dust (Table 2).
Table 2. Factors associated with allergic asthma among textile workers.
Crude OR a
OR (95%CI)
Adjusted OR b
OR (95%CI)
No (reference)
-
-
Yes
4.35
(1.84–10.32)
5.15
(1.86–14.28)
≤5 years (reference)
-
-
6–10 years
1.05
(0.35–3.16)
1.32
(0.57–3.95)
>10 years
2.54
(1.05–6.14)
4.12
(1.37–12.38)
Garment company
(reference)
-
-
Yarn Factory
1.83
(1.01–3.31)
1.45
(0.72–2.93)
Independent Variables
Overweight
Seniority
Working position
(location of company)
History of asthma
Allergic rhinitis
p-Value
0.002
0.520
0.012
0.297
No (reference)
-
-
Yes
8.13
(5.52–26.26)
8.11
(1.71–18.55)
No (reference)
-
-
Yes
8.04
(3.15–20.52)
3.67
(1.34–10.03)
0.011
Yes
12.61
(6.58–24.16)
9.64
(4.73–19.64)
<0.001
No (reference)
-
-
1–8 h
2.57
(0.6–11.0)
4.52
(1.17–17.49)
0.029
9–11 h
5.43
(1.25–23.59)
2.91
(1.41–5.99)
0.004
Non (reference)
-
Smoke
12.61
(6.57–24.16)
0.009
No (reference)
Family history of alergy
Time of cotton dust
exposure per day
Smoking
2.15
(0.67–6.91)
Abbreviation: OR, Odds Ratio; CI, Confidence Interval; a Univariate analysis; b Multiple logistic regression.
0.199
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4. Discussion
The prevalence of work-related asthma is poorly defined in Vietnam. To the best of
our knowledge, this study is the first study estimating asthma prevalence among textile
workers using four different criteria i.e., physician-diagnosed (according to GINA 2016),
respiratory function assessment, skin prick test with cotton dust allergen, and quantification
of serum IgE concentration. Furthermore, this study was carried out with a large number of
participants (1082 textile workers). These strengthened its capacity to provide meaningful
information to better understand the prevalence and associated factors of cotton dustallergic asthma in Vietnam.
In this study, we found 129 (11.9%) workers with suspected asthma symptoms. Among
them, eighty (7.4%) were diagnosed with asthma. More than half of all asthma cases (46/80)
were associated with cotton dust allergies (3.6% in men and 4.5% in women) following a
lung function assessment, skin prick test, and serum IgE quantification. This prevalence of
asthma is higher than what is found in the general population in Vietnam. For example,
one research conducted in Hanoi in 2010 among 7008 adults aged 21 to 70 years old using
a self-reported questionnaire showed that the prevalence of all-cause asthma was 5.6% [18].
Another study performed in Dalat using a questionnaire plus a lung function assessment
mentioned that the prevalence of asthma was 2% [19]. One notes that all the textile workers
are required to undergo a medical examination before being employed, to be sure that
they are all healthy and able to perform textile works. Our results show that the working
environment might have an important influence on the asthma rate of workers.
However, the results found in our study are similar to those of several studies conducted in other countries. A cross-sectional study of Nafees et al. in 2013 among 372 adult
male textile workers from the spinning and weaving sections of 15 textile mills in Karachi,
Pakistan indicated a low prevalence of asthma (4%) out of 8% having obstructive disorders [10]. In Tunisia, the prevalence of occupational asthma among textile workers was 8%
according to research studies compiled by Chaari et al. in 2011 [7], and 4% in another study
by the same author on 600 apprentices in a textile and clothing vocational training center in
the Monastir area [20]. Likewise, in the Czech Republic population, the rate of occupational
asthma and occupational allergic rhinitis of total asthma and rhinitis incidence has been
shown to fluctuate between 5–15% [21]. Nevertheless, the results of the study in Pakistan
showed that the asthma prevalence in the textile workers was much lower than that one
found in the general population (up to 20%), possibly due to some protective effect of
endotoxin exposure [10]. This suggests that there is a need to implement specific measures
of prevention, screening and care for dust-related asthma given its high prevalence among
workers in the textile industry.
To take into account factors that may be related to cotton dust-related allergic asthma,
a multivariate regression model was conducted after eliminating the variables individually
associated with asthma with p-values greater than 0.2. The results showed that overweight,
seniority more than 10 years, history of asthma, allergic rhinitis, family history of allergy,
and exposure to cotton dust from 1 to 11 h in the working environment were relevant
factors compared to the reference categories. Two other factors (working position and
smoking) were significantly associated with allergic asthma in bivariate analyses but these
factors were not significantly associated in multivariate analyses. These findings were
reported for the first time in Vietnam but have also been recorded in many other studies
around the world. Many studies have provided evidence of an association between overweight/obesity and respiratory disorders, including asthma. Although the understanding
of the mechanisms of asthma in obese patients is still unclear, most studies conclude that
being overweight and having asthma are associated. A study conducted in the United State
of America based on 3 national time trends studies on obesity among adults with asthma
indicated that the prevalence of obesity was higher in the asthma group (21.3–32.8%) compared with the non-asthma group (14.6–22.8%) [22]. A retrospective study of 143 adults
found a similar association between obesity prevalence and asthma severity [23]. Based on
the evidence on this association, and evidence of chronic inflammatory response linking
Int. J. Environ. Res. Public Health 2021, 18, 9813
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overweight/obesity and asthma will help to address overweight/obesity issues in asthma
control [24]. Regarding seniority, workers who worked more than 10 years had a higher
risk of asthma than those who worked less than 5 years. This result is similar to the results
of some other studies. The Pakistani study of 327 workers showed that the duration of
work ≥10 years in the textile industry was an important predictor of asthma [10].
Of the factors that cause or are related to occupational asthma, especially in the textile
industry, dust is an important allergen, through its content of latex particles, cotton, pollens,
dyes, solids suspended in air . . . [7,25]. Cotton dust among textile workers, both in terms
of time and concentration exposure, leads to impaired lung function. A study by Ali et al.
set among 303 adult male textile workers has shown that every mg/m3 increase in dust
concentration was associated with a 5.4% decline in FEV1 (forced expiratory volume in
the first second) and therefore may be associated with asthma [26]. Another study by
Hinson et al. in 2016 aimed to evaluate the respiratory medical among the textile workers
exposed to cotton dust involved 656 subjects exposed to cotton dust and 113 non-exposed
subjects in a Beninese cotton industry company. The main results revealed that subjects
exposed to cotton dust have more respiratory symptoms than unexposed subjects (36.9% vs.
21.2%); and the prevalence of chronic cough, expectorations, dyspnea, asthma, and chronic
bronchitis are higher among the exposed in comparison with unexposed subjects [27].
Personal history and family history of asthma, allergic asthma, and allergies increase
the probability that the respiratory symptoms are due to asthma [2]. A study by Darika
Wortong et al. showed that the highest risk factors of asthma were a family history of
asthma and a history of atopy [28]. Among working adolescents, Erkan Cakir et al. found
that a family history of allergy, history of allergic rhinitis, and active smoking were risk
factors for asthma and related symptoms [29].
Allergic rhinitis subjects have been found to have a 3-fold increased risk of asthma
compared to subjects without allergic rhinitis (23.8 and 7.5%, respectively) [30]. A study
by Dorothée Provost et al. among the French working population revealed that 72.5% of
current asthmatics had allergic rhinitis [31]. In a review, Mike Thomas stated that allergic
rhinitis is very common in patients with asthma, with a reported prevalence of up to 100%.
His article also pointed out that comorbid allergic rhinitis is a marker for more difficulty
in controlling asthma and with worse asthma outcomes [32]. Allergic rhinitis is not only
associated with the occurrence and symptoms of allergic asthma, but also a factor that
influences the management and treatment of asthma.
Our study shows that workplace exposure to cotton dust increases the likelihood
of allergic asthma. However, because this is a cross-sectional study, it is not possible to
accurately assess whether the duration of exposure increases the risk of allergic asthma. A
study by Boubopoulos et al. on 443 cotton workers concluded that despite the reduction
in cotton dust concentration, asthma, respiratory symptoms, and pathology are the most
common findings in cotton workers and that it depends on the duration of exposure
whether workers are smokers or not and whatever the nature of the cotton dust [33].
Therefore, in order to reduce respiratory diseases for cotton workers, it is necessary to
comprehensively intervene on many factors and to focus on the groups of high seniority
and family allergic antecedent workers.
Weaknesses and Strengths of the Study
One of the strengths of this study is that it is one of the first studies on asthma among
cotton workers not only in Vietnam but also in Southeast Asia. The study had a large
sample size for a cross-sectional description with a variety of demographic characteristics.
In addition, the study used many standard tools to serve the diagnosis of allergic rhinitis,
allergic sinusitis, and atopic asthma according to the guidance of GINA. This is a good
reference for researchers in the field of occupational health and preventive medicine. It is
also an important source of data for managers of textile companies to improve the health
of their employees.
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Besides the above-mentioned strengths, the study has weaknesses that need to be
considered in further research work on the topic. Due to the cross-sectional study design,
causal relationships between relevant factors and allergic asthma have not been established.
Sampling was only conducted at 2 textile factories in Nam Dinh province; this may make
the sample not representative of all cotton workers in the province in particular as well
as in Vietnam in general. Calculation of the minimum sample size for a cross-sectional
study should also be performed. Further, recall bias might be also encountered during
direct interviews with study participants. Yet, the interviewers were well-trained, and the
questionnaire was pre-tested before being used in the study. This has probably mitigated
the study’s weaknesses. This study also has not mentioned other allergen factors, other
types of dust, and the nature of cotton dust such as its concentration.
This study used the GINA criteria for asthma diagnostics, which are community
diagnostic standards, not exclusive to occupational asthma. In addition, due to resource
constraints, repeated measurements of respiratory function to assess changes in FEV1 at
different times of the day have not been performed, which has somewhat reduced the
quality of the diagnosis. However, when referring to similar studies in the world, we
found that spirometry’s role is primarily used for screening, not necessarily for giving a
clinical judgment.
The above limitations are also the foundation for recommendations for further studies
on allergic asthma in order to obtain consistent results and provide more useful results for
clinicians and public health professionals.
5. Conclusions
This study has revealed a high prevalence of allergic asthma and cotton dust-related
allergic asthma among textile workers in Nam Dinh, Vietnam compared to the general
population, and has also pointed out several factors that are potentially associated with
the last condition. The working environment is probably playing an important role in the
occurrence of asthma in this population. Prevention and care of dust-related allergic asthma
among workers in the textile industry in Vietnam is needed. Future in-depth studies with
more relevant designs are necessary to supplement the limitations of this study.
Author Contributions: T.T.T.H. and V.M.T. are initiators of the research, they conceived and designed
the protocol. T.T.T.H. and P.M.K. performed and implemented the protocol at the workplace and
analyzed the data. B.M.H. performed the interpretation of the lung function tests. T.T.T.H. and P.M.K.
and N.T.H. wrote the paper. T.T.T.H., P.M.K., B.M.H., N.V.S., H.T.G., N.T.H. chaired the research
implementation. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: All study procedures involving human subjects were approved in advance by institutional review boards at the Vietnam National Institute of Occupational and Environmental Health. All authors have read and agreed to the published version of
the manuscript.
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.
Data Availability Statement: The EXCEL/SPSS data used to support the findings of this study are
available from the corresponding author upon request.
Acknowledgments: We thank all the participants for their contributions and also the leader of the
companies. This study was supported by the National Institute of Occupational and Environmental
Health of Vietnam.
Conflicts of Interest: The authors declare that there are no conflict of interest regarding the publication of this paper.
Int. J. Environ. Res. Public Health 2021, 18, 9813
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