Respiratory Diseases and Associated Factors among Seafood Processing Workers in Vietnam: A Cross-Sectional Study

Abstract

Background:

Seafood processing workers are exposed to bioaerosols, seafood proteins, and chemical agents in cold and humid environments, increasing the risk of occupational respiratory diseases.

Aim:

This study aimed to determine the prevalence of respiratory diseases and associated factors among seafood processing workers in Vietnam.

Methods:

A cross-sectional study was conducted in 2025 among 576 workers directly involved in seafood processing lines at three enterprises. Data were collected through structured interviews, specialist clinical examinations (otorhinolaryngology and respiratory), and workplace assessments of temperature and humidity. Respiratory diseases were classified according to the International Classification of Diseases-10 criteria. Multivariable logistic regression was performed to identify associated factors.

Results:

The prevalence of at least one respiratory disease was 43.2%. Upper respiratory tract diseases were most common, including allergic rhinitis (27.1%), chronic pharyngitis (12.7%), and chronic laryngotracheitis (8.2%). Lower respiratory tract diseases included asthma (4.7%), bronchitis (3.8%), and chronic obstructive pulmonary disease (1.2%). Independent associated factors were female sex (adjusted odds ratio [AOR] = 1.62), work experience ≥11 years (AOR = 1.51–1.58), frequent overtime (AOR = 1.72), smoking (AOR = 2.12), inconsistent mask use (AOR = 1.60), and cold, humid workplaces (AOR = 1.63).

Conclusion:

Respiratory diseases impose a considerable occupational health burden among seafood processing workers in Vietnam. Preventive measures should focus on improving the workplace microclimate, strengthening personal protective equipment compliance, and integrating smoking cessation into occupational health programs.

INTRODUCTION

Occupational respiratory diseases represent a major category of noncommunicable conditions associated with hazardous workplace exposures. According to the World Health Organization (WHO), exposure to dust, toxic gases, bioaerosols, and chemical agents contributes substantially to the global burden of asthma and other chronic respiratory diseases.[1] Seafood processing is recognized as a high-risk occupational environment due to cold and humid working conditions and frequent exposure to aerosolized seafood proteins, microorganisms, proteolytic enzymes, and cleaning agents.[2,3,4]

Fish and shellfish proteins are potent allergens capable of inducing airway inflammation through both IgE-mediated and non-IgE-mediated mechanisms, potentially leading to occupational asthma and allergic rhinitis.[2,3,4,5] In addition, exposure to organic dust and bioaerosols has been associated with chronic respiratory symptoms and impaired lung function. Previous studies have reported that the prevalence of respiratory symptoms among seafood processing workers ranges from 2% to 36%, depending on the level of exposure and the effectiveness of environmental control measures.[6,7] In developing Asian countries, high work intensity and inadequate use of personal protective equipment may further increase cumulative exposure risks.[8]

In Vietnam, seafood processing is a key export industry that employs a large workforce, predominantly of female workers. However, epidemiological evidence regarding the prevalence of respiratory diseases and associated factors among seafood processing workers remains limited.[9] Therefore, this study aimed to determine the prevalence of respiratory diseases and identify associated factors among seafood processing workers in Vietnam, thereby providing scientific evidence to support occupational health surveillance and preventive strategies in this sector.

METHODS

Study design

This was a cross-sectional descriptive epidemiological study conducted to assess the prevalence of respiratory diseases and associated factors among seafood processing workers.

Participants

Between January and October 2025, we recruited 576 workers directly employed in seafood processing lines (preprocessing, sorting, freezing, packaging, and cold storage) at three private seafood processing enterprises: Ha Long Canned Food Company, Viet Truong Co., Ltd., and Hai Long Co., Ltd. Permission to conduct the study was obtained from the management boards of the participating enterprises before data collection.

Workers directly involved in production for at least 12 consecutive months who provided written informed consent were included.

Individuals with preexisting asthma, chronic obstructive pulmonary disease (COPD), or other chronic respiratory diseases diagnosed before seafood industry employment, as well as those with severe acute illnesses during the survey, were excluded.

Sample size

The sample size was calculated using the formula for estimating a population proportion.

In this formula, Z represents the 95% confidence interval (CI) (Z = 1.96), and p is the estimated prevalence of respiratory diseases from a previous study. Due to the lack of data on the prevalence of respiratory diseases among seafood processing workers in Vietnam, we chose p = 0.5 and d = 0.05 as the margin of error. The minimum sample size (n) was calculated to be 384 participants. A design effect of 1.5 was applied, yielding a final sample size of 576 participants.

Sampling method

Participants were selected using proportionate stratified random sampling. The three participating enterprises were considered as separate strata, comprising a total of 1,220 eligible workers.

The sample size for each enterprise was allocated proportionally using the formula:

In this formula, n_i represents the number of participants selected from enterprise i, N_i is the number of eligible workers at enterprise i, N is the total number of eligible workers across all three enterprises (1,220), and n is the overall sample size (576). Accordingly, 368 workers were recruited from Ha Long Canned Food Company, 109 from Viet Truong Co., Ltd., and 100 from Hai Long Co., Ltd.

At each enterprise, a list of all eligible workers was obtained from human resources records. Participants were then selected using simple random sampling within each stratum with random numbers generated through Microsoft Excel software until the required sample size was achieved. Workers who declined participation or did not complete the survey procedures were replaced by the next eligible individuals within the same stratum.

Data collection methods

A standardized procedure was followed, encompassing structured interviews, specialist clinical examinations, and an assessment of workplace environmental conditions.

Interviews: Using a questionnaire pilot-tested among 30 seafood processing workers at a similar seafood processing enterprise in Hai Phong City, who were not included in the final study sample, to ensure clarity, feasibility, and reliability of the questionnaire, researchers collected data on demographics, occupational factors (position, experience, overtime), smoking status, mask use, and respiratory symptoms (cough, wheezing, dyspnea, rhinorrhea) experienced in the previous 6 months.

Clinical examination: Otorhinolaryngology and respiratory specialists conducted examinations to diagnose conditions based on the International Classification of Diseases-10 (ICD-10) criteria, including upper (J00–J06, J30–J39) and lower respiratory tract diseases (J20–J22, J40–J47). Participants with at least one ICD-10 diagnosis were categorized as having respiratory disease.[10] Chest radiography was performed for all participants as part of the occupational health assessment to identify possible pulmonary abnormalities and support the clinical diagnosis of respiratory diseases.

Assessment of temperature and humidity: Workplace microclimate data were obtained from 2025 routine environmental monitoring records conducted by the enterprises’ occupational safety departments following current hygiene standards.

Data analysis

Data were entered and analyzed using SPSS software version 22.0 (SPSS Inc., Chicago, IL, USA). Continuous variables were expressed as mean ± standard deviation, while categorical variables were summarized as frequencies and percentages. Initially, univariate analysis using Chi-square tests was conducted to identify potential factors associated with respiratory diseases. Variables with P < 0.20 were subsequently included in a multivariable logistic regression model to determine independent associated factors while controlling for potential confounders. Adjusted odds ratios (AORs) with 95% CIs were calculated. P < 0.05 was considered statistically significant.

Ethical approval

The study received approval from the Ethics Committee of the Vietnam National Institute of Maritime Medicine (Decision No. 05/2025/QD-YHB). All participants provided written informed consent, and data were anonymized and kept confidential. Additionally, the study protocol was reviewed and approved by the occupational safety departments of the participating companies.

RESULTS

A total of 576 seafood processing workers were included in the final analysis [Table 1]. The study population was predominantly female (68.4%) with a mean age of 44.8 ± 8.1 years. More than half of the participants (57.8%) had over a decade of work experience. Regarding behavioral and workplace exposures, 26.6% were smokers, 29.7% reported frequent overtime work, and 22.4% operated in cold and humid microclimates. Although regular mask use was high (81.1%), nearly one-fifth of the workforce did not use masks consistently.

Table 1.

General characteristics of the study participants (n=576)

Variable	n (%)
Gender
Male	182 (31.6)
Female	394 (68.4)
Age (years)
20–29	35 (6.0)
30–39	118 (20.5)
40–49	217 (37.7)
≥50	206 (35.8)
Mean (SD); minimum–maximum	44.8 (8.1); 20–61
Work experience (years)
≤10	243 (42.2)
11–19	220 (38.2)
≥20	113 (19.6)
Mean (SD); minimum–maximum	16.3 (9.9); 2–37
Education level
Secondary school	73 (12.7)
High school	401 (69.6)
College	102 (17.7)
Smoking
Yes	153 (26.6)
No	423 (73.4)
Frequent overtime work
Yes	171 (29.7)
No	405 (70.3)
Regular mask use
Yes	467 (81.1)
No	109 (18.9)
Working in cold and humid environments
Yes	129 (22.4)
No	447 (77.6)

SD=standard deviation

The overall prevalence of workers diagnosed with at least one respiratory disease was 43.2% [Figure 1].

Figure 1.

Prevalence of respiratory diseases among seafood processing workers (n = 576)

Upper respiratory tract conditions predominated among the cohort, led by allergic rhinitis (27.1%), followed by chronic pharyngitis (12.7%) and chronic laryngotracheitis (8.2%) [Table 2]. Lower respiratory tract diseases were less frequent, comprising asthma (4.7%), bronchitis (3.8%), and COPD (1.2%) [Table 2].

Table 2.

Distribution of respiratory diseases among seafood processing workers (n=576)

Respiratory diseases	ICD-10 code	n (%)
Allergic rhinitis	J30.4	156 (27.1)
Chronic pharyngitis	J31.2	73 (12.7)
Chronic laryngotracheitis	J37	47 (8.2)
Acute pharyngitis	J02	33 (5.7)
Asthma	J45	27 (4.7)
Bronchitis	J40	22 (3.8)
COPD	J44	7 (1.2)

ICD-10=International Classification of Diseases-10, COPD=chronic obstructive pulmonary disease

Multivariable logistic regression analysis was performed to identify independent risk factors for respiratory diseases by adjusting for potential confounders. The analysis identified several significant factors across demographic, occupational, and behavioral categories. Regarding demographic factors, female sex was independently associated with a higher risk of respiratory disease (AOR = 1.62; 95% CI: 1.12–2.33; P = 0.01). Occupational risk factors included work experience of 11–19 years (AOR = 1.51; 95% CI: 1.03–2.21; P = 0.033) and ≥20 years (AOR = 1.58; 95% CI: 1.08–2.31; P = 0.018) compared with ≤10 years, frequent overtime work (AOR = 1.72; 95% CI: 1.19–2.46; P = 0.003), and working in cold and humid environments (AOR = 1.63; 95% CI: 1.09–2.45; P = 0.018). Finally, behavioral factors significantly associated with an increased risk were smoking (AOR = 2.12; 95% CI: 1.46–3.11; P < 0.01) and inconsistent mask use (AOR = 1.60; 95% CI: 1.05–2.45; P = 0.029) [Table 3].

Table 3.

Multivariable logistic regression analysis of factors associated with respiratory diseases among seafood processing workers (n=576)

Variable	n	With respiratory diseases, n (%)	Without respiratory diseases, n (%)	AOR (95% CI)	P
Gender
Male	182	61 (33.5)	121 (66.5)	1
Female	394	188 (44.7)	206 (52.3)	1.62 (1.12–2.33)	0.010
Age (years)
<40	153	55 (35.9)	98 (64.1)	1
40–49	217	99 (45.6)	118 (54.4)	1.43 (0.94–2.19)	0.097
≥50	206	95 (46.1)	111 (53.9)	1.48 (0.96–2.27)	0.075
Work experience (years)
≤10	243	81 (33.3)	162 (66.7)	1
11–19	220	101 (45.9)	119 (54.1)	1.51 (1.03–2.21)	0.033
≥20	113	67 (59.3)	46 (40.7)	1.58 (1.08–2.31)	0.018
Education level
Secondary school	73	29 (39.7)	44 (60.3)	1
High school	401	170 (42.4)	231 (57.6)	1.18 (0.71–1.96)	0.518
College	102	50 (49.0)	52 (51.0)	1.55 (0.84–2.83)	0.157
Frequent overtime work
No	405	159 (39.3)	246 (60.7)	1
Yes	171	90 (52.6)	81 (47.4)	1.72 (1.19–2.46)	0.003
Smoking
No	423	161 (38.1)	262 (61.9)	1
Yes	153	88 (57.5)	65 (42.5)	2.12 (1.46–3.11)	<0.001
Regular mask use
Yes	467	190 (40.7)	277 (59.3)	1
No	109	59 (54.1)	50 (45.9)	1.60 (1.05–2.45)	0.029
Working in cold and humid environments
No	447	177 (39.6)	270 (60.4)	1
Yes	129	72 (55.8)	57 (44.2)	1.63 (1.09–2.45)	0.018

AOR=adjusted odds ratio, CI=confidence interval. Statistically significant P values are presented in bold

DISCUSSION

Our study found that the prevalence of respiratory diseases among seafood workers was 43.2%. This finding is consistent with results from similar occupational and geographical settings in developing Asian countries, where high work intensity and environmental factors significantly impact worker health.[3,9] These results align with trends in the seafood and food industries, where employees are routinely exposed to bioaerosols, organic dust, seafood proteins, and industrial chemicals. International studies report respiratory symptoms ranging from 4% to over 36%. Specifically, research in Norway and India found prevalence rates of 20–40% among seafood workers. Our 43.2% prevalence underscores the significant respiratory health risks inherent in this sector.[11,12,13] Respiratory risk varies by task; raw material handling poses higher risks due to increased aerosolized protein exposure.[14] Additionally, individual factors like smoking significantly increase the risk of chronic bronchitis and lung function impairment. Recognizing these confounders is essential when assessing occupational exposures.[15,16,17] Our prevalence exceeds that of some European settings where engineering controls like exhaust ventilation are common.[12,15] In developing countries, inadequate environmental controls and a lack of surveillance contribute to high disease rates.[18] This 43.2% prevalence highlights a major health concern necessitating improved conditions.

Table 2 shows that allergic rhinitis (27.1%) and chronic pharyngitis (12.7%) predominated, while lower respiratory tract diseases were less frequent. This reflects the overlapping nature of occupational respiratory disorders. The predominance of upper respiratory tract conditions aligns with bioaerosols depositing on the nasal and pharyngeal mucosa. These findings mirror international trends where upper respiratory symptoms predominate over asthma. Studies in Northern Europe and India similarly found rhinitis and pharyngitis as the most common manifestations among seafood processing workers.[12,13] Our 4.7% asthma prevalence is lower than European reports (6%–10%), likely due to different ascertainment methods.[12,14] Occupational asthma is often underestimated without spirometry.[14] Lower frequencies of bronchitis and COPD are consistent with disorders requiring cumulative exposure and smoking.[19]

Multivariable analysis [Table 3] linked respiratory diseases to sex, work duration, overtime, smoking, mask use, and environmental conditions. These results reflect the multifactorial nature of diseases where biological, workplace, and behavioral factors interact closely.

Female workers faced higher risks (AOR = 1.62). Consistent with Asian studies, women often handle tasks involving direct contact with wet raw materials and cleaning agents.[13] Higher respiratory symptom rates among females involve both occupational and biological factors.[2,20]

Increased work experience showed a cumulative exposure–response relationship, supporting the hypothesis that prolonged bioaerosol exposure contributes to respiratory disorders.[2] Employment duration remains a key determinant for respiratory health problems in this industry.[15,21]

Frequent overtime work was associated with an increased risk of respiratory diseases (AOR = 1.72), highlighting the role of increased daily exposure duration. Studies on occupational exposures have demonstrated a dose–response relationship between exposure time and the risk of respiratory symptoms, particularly in environments with high concentrations of organic aerosols.[2,21]

Smoking was the strongest factor (AOR = 2.12), consistent with tobacco smoke impairing mucosal barriers and amplifying inflammatory responses.[19] Workers exposed to organic dust who smoke face significantly higher risks of respiratory symptoms compared to nonsmokers.[21]

Inconsistent mask use increased risk (AOR = 1.60), highlighting the importance of personal protective equipment. Poor compliance contributes to high rates of occupational asthma and inflammation.[14] Conversely, particulate-filtering masks can substantially reduce protein exposure and symptoms.[11,12]

Cold and humid environments increased risk (AOR = 1.63) by increasing aerosol persistence and inducing airway constriction. Respiratory symptoms and lung impairment are significantly higher in these conditions compared to dry and warm environments.[3,12]

Overall, our findings indicate that respiratory diseases among seafood processing workers result from multifactorial influences, including cumulative occupational exposures, adverse working conditions, and individual risk behaviors. Identifying these independent associated factors has important practical implications, suggesting that preventive interventions should focus on reducing exposure duration and intensity (e.g., limiting prolonged overtime and improving ventilation), strengthening appropriate mask use, improving the workplace microclimate, and integrating smoking cessation programs into occupational health services. This multilevel approach has been recommended in several studies on the prevention of occupational respiratory diseases in the food and seafood processing industries.[2,14,20]

Study strengths and limitations

This study has several strengths. It included a relatively large sample of seafood processing workers from multiple enterprises, enhancing the representativeness of the study population. Respiratory diseases were diagnosed through specialist clinical examinations using standardized ICD-10 criteria, improving diagnostic reliability. In addition, the integration of questionnaire data, clinical assessments, and workplace environmental information enabled a comprehensive evaluation of occupational and behavioral factors associated with respiratory diseases.

Nevertheless, several limitations should be considered. The cross-sectional design prevents causal inference between occupational exposures and respiratory diseases. Moreover, the absence of pulmonary function or allergy testing may have led to the underdiagnosis of certain conditions, such as occupational asthma. Finally, some variables, including smoking status, overtime work, and mask use, were self-reported and may therefore be subject to recall bias.

CONCLUSION

Respiratory diseases represent a common occupational health problem among seafood processing workers, with a prevalence of 43.2%. Independent risk factors include female sex, extensive work experience, frequent overtime, smoking, inconsistent mask use, and exposure to cold and humid environments. Comprehensive prevention requires improving workplace ventilation, ensuring mask compliance, and integrating smoking cessation into occupational health services. Additionally, periodic health screenings incorporating pulmonary function tests are essential for the early diagnosis and management of these respiratory conditions.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.