Occupational Health Issues in the Seafood Industry Due to Biological Exposures: A Narrative Review

Abstract

Climate change, along with the global shift toward more sustainable seafood production, is giving rise to novel occupational exposures. Anticipated changes in the types and quantities of seafood produced, as well as evolving methods of production and processing, are driven by increasing demands for resource efficiency and environmental impact mitigation. Aquaculture, particularly land-based farming of fish and shellfish, is becoming more prevalent and introduces distinct occupational health challenges related to the animals, their associated microorganisms, feed, and production settings.

In this literature review, we aim to identify and categorize the occupational exposures that have been reported to adversely affect human health during the handling and industrial processing of fish and shellfish. The primary focus is on biological exposures occurring within processing facilities. Bioaerosols, which may contain infectious agents, allergens, or toxins, represent a key area of concern. For the purposes of this review, we group biological exposures into these partially overlapping categories. Consideration is also given to the broader context of the green transition, emphasizing sustainability and recent developments within the seafood industry. We find that the potential for zoonotic transmission is considerable, the risk of occupational asthma and allergies is well-documented, and that workers are exposed to a range of potentially toxic substances. Furthermore, significant developments in seafood production, driven by climate change and the pursuit of more sustainable practices, are likely to introduce new occupational exposures for which the industry may not be fully prepared.

1. Introduction

Global consumption of seafood is steadily increasing, as is the variety of seafood. On a broader agenda, the industry aims for a balanced consideration of the environment, animal welfare, and the health and safety of the individuals involved. This aligns with the concept of “One Health” [1], which also encompasses occupational health. Changes in the occurrence of seafood in nature and increases in the prevalence of pathogenic microorganisms and parasites have been documented as a consequence of climate change [[2], [3], [4]]. This may have implications for the occupational environment. Further, in the context of the growing focus on the green transition, there is an increasing ambition to utilize and exploit organic materials and other resources as efficiently as possible. Waste and by-products from the seafood industry are expected to be recycled to a greater extent, which may introduce new or increased occupational health challenges. For example, shells from shrimp and crabs could lead to elevated exposure to chitin and similar substances, which are known to cause occupational asthma and allergies [5,6].

Most dietary guidelines [e.g., the World Health Organization (WHO), European dietary recommendations, and dietary guidelines from various countries] recommend eating at least two servings of seafood per week [7]. Eating seafood from sustainable sources (responsibly farmed or caught) can help reduce the environmental footprint associated with terrestrial meat production (especially beef and pork), which has been reported to have a significantly higher impact on climate change due to land use, water consumption, and greenhouse gas emissions [8].

In the fishing industry, there are several occupational health challenges, one of which relates to exposure to biological hazards from fish, shellfish, and associated microorganisms. These exposures can lead to various health issues, such as allergies, respiratory diseases, infections, and other illnesses. For preventive measures, it is of importance to understand how employees are exposed to these hazards. A primary exposure route is via the air–exposure to bioaerosols. Bioaerosols are small droplets containing biological material that can become airborne during seafood handling, cutting, waste disposal, or facility cleaning. Bioaerosols can be a) inhaled and affect the respiratory system, b) swallowed and affect the gastrointestinal system, or c) deposited on the skin or mucosal surfaces. Similarly, employees can also be exposed to larger droplets and splashes that directly land on them. In addition, exposure may occur through direct hand contact with the seafood. Substances in seafood can also be absorbed into the body and exert effects on organ systems. Furthermore, exposure duration, frequency, and amounts are also important aspects to be considered in a hazard assessment of substances in seafood.

In this literature review, we aim to identify which exposures have been reported to cause health problems in the handling and processing of fish and shellfish. Our focus is on biological exposures in industrial processing facilities. Bioaerosols may contain harmful agents that can cause infections, allergic reactions, or toxic effects. For the purposes of this review, we found it appropriate to categorize the exposures into these partially overlapping groups. In the discussion, we will also address preventive measures that are well-supported by evidence of their effectiveness. Additionally, we also incorporated aspects of the green transition, sustainability, and recent developments within this industry.

2. Methods

We conducted a narrative review to explore biological exposures in the fishing industry, with a particular emphasis on recent developments, sustainability, and occupational diseases. Literature searches were performed using the PubMed and Web of Science databases up to April 1,2025. Search terms included combinations of keywords such as fishing industry, seafood processing, and fish processing with green transition, sustainability, climate change, environmental impact, innovations, and new developments. Additional searches were carried out using the names of major seafood types combined with terms such as occupational health, infections, allergies, allergens, and toxins. A specific search was also conducted using the keyword aquaculture in the title in combination with occupational health.

The reference lists of relevant articles were manually screened to identify additional sources. The search strategy was limited to articles published in English or Danish. Potentially relevant articles were first screened by title and abstract, followed by full-text assessment where applicable. Articles meeting these criteria, as well as relevant references cited within them, were included in the review.

All titles were initially screened by the corresponding author (LA) and selected articles were subsequently read by LA and at least one coauthor. Both original research articles and review papers were considered. The structure of this review follows the guidelines for narrative reviews as outlined by Baethge et al [9], using the Scale for the Assessment of Narrative Review Articles (SANRA).

3. Results

When handling seafood, including the processes of cutting, gutting, portioning, packaging, preparing, and cleaning facilities and equipment, there is a risk of exposure to harmful bioaerosols and splashes. These bioaerosols and splashes may contain organic material from the seafood itself or microorganisms, and parasites in the seafood.

Considerable differences exists between various occupational settings. In aquaculture, where live fish are handled, feed may be the primary risk factor for occupational exposure and associated allergies. In manual processing plants, where fish and shellfish are gutted and processed, large quantities of bioaerosols containing allergens and microorganisms may surround workers throughout their shift.

3.1. Exposure measurements

Occupational exposure to various bioaerosol components with potential adverse health effects has been documented in seafood processing facilities. These include airborne bacteria, fungi, endotoxin, and different fish allergens (Fig. 1). Some studies have focused on personal exposure measurements, while others on work area concentration measurements.

Fig. 1.

Possible exposures in the seafood industry. ∗Virus, bacteria, fungi, algae (phytoplankton) or parasites, ∗∗fish or shellfish (mollusks and crustaceans).

Airborne bacteria and fungi have been measured in some sectors of the seafood industry, mainly due to their sensitizing or toxic properties, but recently also due to their infectious potential. Thus, a study published in 2005 found a median exposure to microorganisms of 1500 to 5000 colony-forming units (CFU) per m³ in the shrimp industry, 5000 to 8000 CFU per m³ in the whitefish industry, and 4000 CFU per m³ in the salmon industry [10]. With the development of improved methods for the identification of microorganisms, concentrations of fungi and bacteria have been obtained in working stations at the species level in nine salmon processing plants. In general, the concentrations of bacteria and fungi were low, with the highest bacterial concentrations in slaughtering stations, while fungal concentrations were highest during fillet trimming. A total of 125 gram-negative, 90 gram-positive bacterial species, and 32 fungal species were identified in air samples. Nineteen different bacterial species belonging to risk class 2 (can cause human disease and may pose a hazard to workers) were found in airborne samples in different workstations [11].

Establishing dose-response relationships for infectious microorganisms is challenging due to variability in transmission routes and host susceptibility. Process water in seafood facilities can also harbor substantial loads of pathogens. For example, Klebsiella pneumoniae has been detected at 10⁶ CFU per mL and Pseudomonas fluorescens at 4 × 10³ CFU per mL in industrial water, while contaminated gutting machine water contained Aeromonas hydrophila, K. pneumoniae, and Pseudomonas spp. at 3 × 10⁹ CFU per mL [12]. Vibrio cholerae has been found in fish intestines (∼5 × 10³ CFU/g) [13], and filter-feeding shellfish may accumulate concentrations up to 100-fold higher than ambient water [14]. Thus, process water is a potential source of occupational exposure.

We have not identified any studies documenting airborne viruses in seafood processing environments. However, norovirus levels in oysters from U.S. commercial beds ranged from 10³ to 10⁸ copies/g [15], and in Spain, norovirus concentrations in shellfish were generally higher in farmed than wild populations [16]. Notably, even low levels of norovirus in shellfish have been associated with gastroenteritis in humans following oral exposure.

Exposure to endotoxin has been measured across various industries, with concentrations varying by location and type of seafood. Mean concentrations in the air (measured by the Limulus Amoebocyte Lysate assay) ranged from 0.14 to 136 EU (EU-endotoxin units) per m³ in facilities processing fishmeal [17] and seafood species such as cod, shrimp, salmon, herring, and crab [5,10,18,19]. During the processing of king crabs, measurements in certain areas of the factory have shown mean levels exceeding 6000 EU/m³ [5]. These levels could be interpreted as very high in the context of the Dutch occupational exposure limit of 90 EU per m³ [20]. In contaminated water from a gutting machine at a trout-processing factory, endotoxin concentrations of 1 μg per mL were found [12].

Some studies have specifically addressed the measurement of airborne allergens. For instance, airborne tropomyosin and trypsin have been detected in the crab processing industry [5]. Parvalbumin concentrations of up to 816 ng per m³ have been measured in the salmon industry, and up to 9800 ng per m³ during herring processing [21]. Tropomyosin levels during the processing of crabs and prawns have been reported to be as high as 102 μg per m³ [22]. Both trypsin and parvalbumin have also been detected in the air during fish processing on board Norwegian fishing trawlers [23]. Often total protein concentrations have been used as a proxy for potential allergen levels, although this approach is not ideal, as it assumes a correlation between total protein and the presence of allergens, which may not always be the case [23]. In the Norwegian salmon processing industry, airborne protein concentrations ranged from 0.76 to 12.6 μg per m³ [24]. In two South African factories processing anchovy, pilchard, and rock lobster, total protein levels were measured at 0.7 μg per m³ [25]. In Greenland, exposure to inhalable total protein among seafood processing workers varied by species: 6.1 μg per m³ for fish, 20.3 μg per m³ for snow crab, and 50.0 μg per m³ for shrimp [18]. These are mean values, indicating that workers may experience substantially higher concentrations in specific areas or during shorter time periods.

Evidence from larger automated facilities has demonstrated that cleaning activities, especially the use of high-pressure washing, generate substantial amounts of inhalable aerosols posing a potential risk of respiratory and skin exposure [26].

Certain types of seafood are associated with a higher prevalence of occupational health issues than others. The incidence of work-related asthma is, for example, significantly higher in facilities processing crabs and other shellfish compared to those handling fish [27].

In the following sections, we have categorized biological occupational health issues based on the type of exposure and the associated symptoms and diseases, as illustrated in Fig. 1. These categories are not always sharply defined, and the figure attempts to indicate some degree of overlap between them. For instance, an individual may develop an allergy to a fish parasite such as Anisakis, or experience a toxic reaction to certain bacteria. Similarly, inflammatory stimulation of the immune system can be triggered by toxins, allergens, and microorganisms.

3.2. Infectious microorganisms

Fish and shellfish, like all other animals, harbor naturally coexisting microorganisms. Additionally, they may carry parasites and pathogenic bacteria, molds, and viruses. Upon the death of the host, there can be a proliferation of spoilage bacteria. In some cases, these microorganisms can be transmitted to humans, leading to localized or systemic infections–referred to as zoonoses [28].

There are few studies on the transmission of pathogenic microorganisms from fish and shellfish to humans in occupational settings. However, as many of these infectious microorganisms are transmitted through oral ingestion, risk assessments should consider that aerosols and splashes landing on the skin, respiratory tract, or in the mouth and nose may facilitate transmission.

The European Food Safety Authority and the European Centre for Disease Prevention and Control highlight in their recent report on zoonoses in the EU that norovirus in crustaceans, shellfish, molluscs, and products containing them, as well as Listeria monocytogenes in fish and fish products, are significant concerns [29]. Some of the most relevant exposures in the fishing industry and during the handling of fish and shellfish are reviewed below and summarized in Table 1.

Table 1.

Main infectious agents from occupational handling of seafood

	Characteristics
Bacteria
Erysipelothrix rhusiopathiae	A saprophyte associated with marine fish, molluscs and crustaceans. The bacterium survives and grows on the exterior mucoid slime of fish or shellfish, without causing disease in the fish themselves [32]. Infections with E. rhusiopathiae occur via contamination of cutaneous wounds and typically result in localized, painful, self-limiting cellulitis, with purple discoloration and edema [33].
Vibrio species	Vibrio species are widely distributed in coastal and estuarine environments and have the potential to cause disease in both aquatic organisms and humans. V. cholerae, the causative agent of cholera, is of paramount global health significance. Additionally, V. parahaemolyticus and V. vulnificus are frequently found in seafood and water and can cause severe infections in humans. Human cases typically involve wound infections and gastrointestinal disease, the latter often characterized by watery diarrhea.
Listeria monocytogenes	L. monocytogenes, found in soil and marine environments, is primarily a foodborne bacterium, but it has also been reported to cause occupational skin infections. The bacterium exhibits high resilience, and is capable of growing at low temperatures and withstanding variations in pH and salt concentration. Noninvasive infection includes symptoms such as fever, headache, diarrhea, and muscle pain.
Mycobacterium marinum	M. marinum is a globally distributed bacterium found in both saltwater and freshwater environments, including swimming pools and fish tanks. Due to its environmental reservoir, occupational exposure can lead to infection, typically presenting as localized skin lesions in the form of single or multiple nodules or ulcers. M. marinum belongs to the same genus as M. tuberculosis and M. leprae, the causative agents of tuberculosis and leprosy, respectively [48].
Streptococcus iniae	S. iniae, found in freshwater and marine environments, is a zoonotic bacterium that causes disease outbreaks in both freshwater and marine fish, leading to significant economic losses in aquaculture. In humans, S. iniae infection occurs through percutaneous exposure during the handling of fresh fish. The most common clinical manifestation is cellulitis of the extremities; however, more severe invasive diseases, including sepsis, toxic shock, pneumonia, osteomyelitis, arthritis, infective endocarditis, and meningitis, have been reported [34,36].
Aeromonas hydrophila	A. hydrophila and other Aeromonas species are ubiquitous in freshwater environments and have been implicated in both occupational and community-acquired infections. Wound infections associated with handling of seafood, particularly during shellfish shucking, can lead to cellulitis, muscle necrosis, or septicemia, primarily in immunocompromised individuals but occasionally also in immunocompetent hosts. Additionally, various Aeromonas species have been isolated from the air in salmon processing plants, highlighting potential occupational exposure risks [11,33,34].
Clostridium botulinum	C. botulinum is a ubiquitous bacterium found in soils, aquatic sediments, and anaerobic environments. It is present on fish surfaces, with spores persisting in freshwater and marine sediments for decades. Additionally, the bacterium can inhabit the intestines of healthy fish, where it may produce highly potent botulinum neurotoxins. Botulism, which may result from ingestion or inhalation of aerosolized toxin, manifests with symptoms such as diarrhea, vomiting, dizziness, dysphagia, bloating, and constipation.
Edwardsiella tarda/Edwardsiella piscicida	E. piscicida, found in freshwater and marine environments, is primarily a fish pathogen but can also cause foodborne and waterborne infections in other animals and humans. E. piscicida was previously classified as E. tarda, E. tarda is now recognized as a nonfish pathogen [49]. Both species have the potential to infect humans, primarily causing gastroenteritis. However, extra-intestinal infections, including wound and liver infections, cholecystitis, peritonitis, meningitis, myonecrosis, osteomyelitis, sepsis, and bacteremia, may also occur.
Virus
Norovirus	Norovirus (NoV) is a major cause of gastrointestinal infections, accounting for approximately 58% of foodborne illnesses in the United States [41]. Infection often occurs through the consumption of contaminated water or food, particularly shellfish [50]. NoV is highly resistant and can remain infectious for weeks. As NoV can be transmitted via droplets and aerosols, and the infectious dose is relatively low, occupational transmission cannot be excluded [51].
Hepatitis E & A	Hepatitis A virus (HAV) and Hepatitis E virus (HEV) are foodborne pathogens frequently detected in shellfish. HAV is a major cause of foodborne viral outbreaks worldwide, whereas HEV is an emerging pathogen with a significant global health burden [52]. Currently, HEV is considered the most common cause of acute viral hepatitis globally [53]. While both viruses are transmitted via the fecal-oral route, waterborne transmission remains a key factor in large HEV outbreaks.
Fish parasites
Anisakis species	Anisakis spp. are marine nematodes that can infect humans through the consumption of raw or undercooked fish containing viable third-stage larvae. Infection can lead to anisakiasis, which varies in severity from mild to severe and presents as gastric, intestinal, ectopic, or allergic manifestations [43]. Anisakiasis has been described as an emerging zoonosis due to cultural shifts, climate change, and ecological transformations [44]. Common symptoms resemble food poisoning, but allergic reactions can also occur independently of infection through inhalation or direct contact. Occupational exposure to Anisakis simplex poses a significant health concern for individuals handling fish due to hypersensitivity reactions [46].

3.2.1. Bacteria

Zoonotic infections with Erysipelothrix rhusiopathiae from fish, molluscs (e.g., oysters, mussels, and octopuses) and crustaceans (e.g., crabs, lobsters, shrimp, and prawns) and other animals are well-documented. The bacterium is present in the epidermal mucus of fish, and transmission to humans occurs through direct skin contact, typically via cuts or abrasions. Human infection is primarily associated with occupational exposure, such as in slaughterhouse workers and fish handlers. While the cutaneous form (erysipeloid) of E. rhusiopathiae infection is common, invasive infections are rare [[30], [31], [32]].

Several Vibrio species are known to cause disease following the ingestion of or contact with fish and shellfish. The most notorious among them is V. cholerae, a natural inhabitant of aquatic environments and the causative agent of cholera. Studies have demonstrated that fish and shellfish can act as carriers and transmit V. cholerae [13]. Due to their filter-feeding mechanism, shellfish can concentrate Vibrio bacteria to levels exceeding 100 times that of the surrounding water [14]. Other Vibrio species, including V. parahaemolyticus and V. vulnificus, are typically transmitted through the consumption of seafood, particularly raw oysters. Although the primary clinical manifestation of infection with these species is gastroenteritis, they can also cause wound infections and, in the case of V. vulnificus, septicemia, particularly in individuals with liver disease or compromised immune systems [33]. V. vulnificus is commonly found in warm coastal waters and has been isolated from seawater, sediments, plankton, and shellfish in the Gulf of Mexico and along the U.S. Atlantic and Pacific coasts. The prevalence of pathogenic Vibrio species varies with environmental factors such as water temperature, salinity, and phytoplankton concentration. In Europe, Vibrio spp. have also been detected, generally at low levels, except in bivalves [34]. Surveillance studies from the U. S. have shown a rise in vibriosis incidence over the past 15 years, possibly due to increasing water temperatures [2].

L. monocytogenes is a highly resilient bacterium capable of growing at temperatures ranging from 1 to 50^oC and tolerating significant variations in both pH and salt concentration. Due to its ability to survive under extreme conditions, the substantial challenges it presents in the seafood industry, and its major role as a foodborne pathogen, the European Union has classified L. monocytogenes as a microorganism of particular concern [29]. Infection with L. monocytogenes can result in febrile gastroenteritis and flu-like symptoms. The most common symptoms include fever, headache, diarrhea, and muscle pain, typically occurring after the ingestion of contaminated food. In more severe cases, invasive listeriosis may develop, leading to bacterial spread into the bloodstream, liver, or cerebrospinal fluid. Mycobacterium marinum can cause fish handler's disease (also known as “swimming pool granuloma” or “fisherman's finger”). Infections with M. marinum and other related species can occur after contact with contaminated water or infected fish, particularly through wounds or abrasions in the skin. In 2013 and 2014, this bacterium caused an outbreak with at least 98 cases of infection in individuals handling fish in New York [35]. A range of other Mycobacterium species have also been reported to cause infections following contact with contaminated water or fish [33,34].

The bacterium Lactococcus garvieae has been reported to cause endocarditis and other infections following the consumption of raw fish or occupational exposure. For a review, see Gauthier (2015) [33]. Similarly, Weinstein et al (1997) [36] identified zoonotic infection with Streptococcus iniae in nine individuals who handled raw fish. Cellulitis of the hand was observed in eight cases, while one case presented with endocarditis.

Clostridium botulinum, the bacterium responsible for botulism, is a commensal organism in the intestines of numerous fish species worldwide and is present in environmental sediments and decaying organic matter. The disease is caused by potent neurotoxins produced during bacterial growth. Cases of intoxication have been documented in humans following the consumption of fish products [33] and following inhalation of aerosolized toxin [37]. Botulism is primarily an intoxication rather than an infection, as the disease results from the ingestion, inhalation, or absorption of botulinum neurotoxin rather than from bacterial proliferation within the host [33,37].

Other bacteria, such as Escherichia coli and species of Aeromonas, Salmonella, and Edwardsiella, have been reported to cause infections in humans, for example, in association with seafood handling and shellfish shucking. These infections often occur in individuals with compromised immune systems. For an overview, see Gauthier 2015 [33].

Lastly, the emergence of antibiotic resistance in bacteria represents a significant concern, with potential implications for the treatment of infections in both humans and animals. Although substantial quantities of antibiotics are utilized in aquaculture production, data on the scale of their use remain scarce. Consequently, there is a need for improved surveillance and stricter regulation of antibiotic use in the aquaculture industry, including monitoring potential occupational exposure to antibiotic-resistant bacteria [38].

3.2.2. Virus

Norovirus is notorious for inducing gastroenteritis following the consumption of contaminated foods [39]. Shellfish, particularly mussels and oysters, are frequently implicated in such outbreaks. Furthermore, bivalve mollusks like mussels and oysters are capable of bioaccumulating contaminants present in their surrounding waters, thereby elevating the risk of infection in cases of fecal contamination. Given the minimal infectious dose, transmission in occupational settings through handling and exposure to aerosols or splashes from contaminated seafood is also likely [40].

Hepatitis A is a common foodborne disease caused by the hepatitis A virus, which is primarily transmitted through the fecal-oral route. The virus is known to cause large-scale foodborne outbreaks, particularly in areas where sanitation and hygiene standards are insufficient. The virus targets the liver and can lead to an array of clinical manifestations. Typically, the infection is characterized by an incubation period of approximately 2–6 weeks, after which patients may experience fever, malaise, and anorexia. Similarly, hepatitis E virus has also been implicated as a cause of disease resulting from contaminated water and contamination of various foods, including fish and shellfish [41,42]. Most cases of infection are asymptomatic, which contributes to the underdiagnosis of this condition.

3.2.3. Parasites

Over the past two decades, the geographic range of fish-borne zoonotic helminths has expanded, posing an increasing public health burden [43]. More than 40 species of fish parasites are known to infect humans, with major parasitic organisms including tapeworms (e.g., Diphyllobothrium spp.), flukes (e.g., Opisthorchis spp.), and roundworms (e.g., Anisakis spp.) [1]. The most well-known of these is the nematode family Anisakidae. This parasite is often an unwelcome guest when fish are inadequately prepared, and its presence in anchovies, in particular, has been frequently cited as a common source of gastrointestinal infection. Infection can lead to anisakiasis, manifesting as mild to severe gastrointestinal symptoms, including gastric, intestinal, and allergic reactions [44,45].

With climate change expected to contribute to the increased spread of these parasites, fish-borne helminthic diseases represent an important and growing public health challenge [3]. Whether occupational exposure can lead to infections remains uncertain; however, the contents of droplets that are inhaled can end up in the gastrointestinal tract, which constitutes the natural transmission route in humans. Nevertheless, Anisakis present in fish is known to cause sensitization and allergic reactions in occupational settings [46].

Since a parasite's life cycle is directly associated with that of its host, fluctuations in host populations have a direct impact on parasite populations. Consequently, climate change is among the most important factors influencing the distribution and prevalence of these zoonotic parasites [47].

3.2.4. Fungi

Some fungal species have been reported to originate from fish and seafood and cause zoonosis, but this is not well-documented and has not yet been described as a problem in the fish industry [3].

3.3. Toxins from fish or microorganisms

Exposure to various toxins may occur during the handling, processing, and preparation of seafood, as well as during the cleaning of facilities and equipment. These toxins may originate from the seafood itself or from associated microorganisms. Certain fish accumulate toxic algae through their diet, while filter-feeding mollusks concentrate neurotoxin-producing dinoflagellates, leading to severe health risks.

Ciguatera fish poisoning (CFP) is caused by ciguatoxins derived from dinoflagellates, which bioaccumulate in fish species. Ciguatoxin is heat-stable and thus resistant to cooking. Symptoms appear within 1 to 6 hours postingestion and can persist for days, months, or even years. Clinical manifestations include gastrointestinal distress (diarrhea, vomiting), neurological disturbances, and cardiovascular complications. CFP affects up to 50,000 individuals annually [54]. Paralytic shellfish poisoning (PSP) results from neurotoxins, primarily saxitoxin, produced by dinoflagellates. These toxins affect the nervous system, leading to nausea, vomiting, diarrhea, tingling sensations, and even muscular paralysis. PSP accounts for a significant portion of seafood-related fatalities. Diarrhetic shellfish poisoning (DSP) is caused by okadaic acid and related toxins from dinoflagellates, leading to severe gastrointestinal symptoms such as diarrhea, nausea, and abdominal pain [50].

Bacterial toxins, such as botulinum toxin from C. botulinum and endotoxins from various gram-negative bacteria, may pose serious health hazards. Endotoxins, biologically active lipopolysaccharides (LPS), trigger inflammatory responses leading to organic dust toxic syndrome (ODTS) with asthma-like symptoms. Endotoxin exposure has been documented at fish, crab, and shrimp processing plants, linking occupational exposure to pulmonary illnesses [55,56].

Histamin (scombroid) poisoning arises from improperly stored fish where bacterial conversion of histidine into histamine leads to pseudoallergic reactions. Commonly implicated fish include mackerel, tuna, herring, sardines, and anchovies [57]. Workers in the fish processing industry may be exposed to histamine-containing aerosols [58]. Occupational histamine poisoning has been documented in ten workers handling spoiled fish flour, with inhalation, as well as skin and eye exposure. Within 30 minutes, the affected workers developed allergy-like symptoms involving the skin, eyes, gastrointestinal tract, respiratory system, and cardiovascular system [59]. Histamine is not degraded by cooking.

Chitin is an abundant polysaccharide and a key structural component of the exoskeletons of shellfish, such as prawns, crabs, and lobsters. In the seafood industry, chitin and its derivative chitosan, which is particularly abundant in crab shells, have been associated with airway inflammation and are suggested to contribute to the development of asthma and occupational allergies [5,6].

Hydrogen sulphide (H₂S) is a toxic gas produced during anaerobic decomposition of fish. It is a significant contributor to work-related sudden deaths and can cause damage to the respiratory tract and nervous system [60]. Also, during aquaculture, H₂S exposure is an occupational health concern [61,62].

3.4. Allergy and allergens from seafood

Allergy is an inappropriate immune response to typically harmless substances, known as allergens, such as pollen, enzymes, food proteins, or animal dander. This reaction is mediated by immunoglobulin E (IgE) antibodies, which trigger inflammatory responses upon allergen exposure. Sensitization is the initial phase in allergy development, where the immune system mistakenly recognizes an allergen as a threat, priming the immune system for a future allergic reaction upon re-exposure to the allergen. Sensitization can occur via food exposure, leading to an allergic reaction upon occupational exposure, or vice versa (REF). The WHO projects that by 2050, up to 50% of the global population may be affected by some form of allergy [63]. In particular, shellfish allergy has become an increasing health concern over the past decade [64].

Occupational asthma and allergy related to industrial work with fish, mussels, oysters, prawns, and crabs have been documented as early as the 1980s [12]. Food allergies to fish and shellfish are well known; however, exposure to allergens in bioaerosols and splashes during processing and handling is not widely acknowledged.

It is noted that irritant nonallergic effects may give symptoms similar to allergic effects both in terms of dermal and inhalation exposure. An important aspect of seafood allergies is that clinical symptoms may occur not only during consumption of seafood but also during food processing and preparation.

In the fish and shellfish processing industry, the prevalence of occupational allergic contact urticaria or protein contact dermatitis ranges from 3 to 11% worldwide [65], that of work-related allergic rhinitis from 5 to 24% [66], and that of work related allergic asthma from 2 to 36% [60,66,67]. Occupational allergic asthma seems to be more often associated with shellfish (4–36%) than with fish (2–8%) [68].

3.4.1. Fish

In the fish industry, exposure can occur by inhalation of aerosols generated during cutting, scrubbing, and cleaning, or on the skin as a result of direct handling of the fish. Upon inhalation or splashing into the mouth and face, potential allergens often end up in the gastrointestinal system due to the mucociliary escalator, which transports particles and impurities from the airways to the throat, where they are swallowed. Furthermore, exposure can occur through the skin, and allergens may cause harm via wounds, lesions, or other breaches in the skin barrier. When working with aquaculture, the feed may also contain allergens that can lead to occupational allergy [62].

Inhalation of bioaerosols containing fish proteins has been linked to occupational asthma [22,69,70], estimated to affect 2–8% of exposed individuals [26,71]. A study examining nine fish species identified codfish, salmon, pollock, and herring as the most allergenic and cross-reactive species, whereas halibut, flounder, tuna, and mackerel exhibited lower allergenic potentials [72].

Parvalbumins, collagens, aldolases, enolases, and vitellogenin are key fish allergens, with parvalbumin as the primary cause of occupational asthma in fish processing workers [54,66]. According to Davis et al [73], over 72 seafood allergens have now been registered with the International Union of Immunological Societies. In Table 2, we present key characteristics of the major allergens from fish and shellfish.

Table 2.

Main allergens in occupational exposures from handling of seafood

	Characteristics
Fish
Parvalbumin	Parvalbumin, a thermostable protein found in fish muscle tissue, is considered the primary fish allergen [56]. Inhalation of parvalbumin is the main route of sensitization [71]. Parvalbumin levels vary among fish species, with migratory fish (e.g., tuna, swordfish) containing lower levels than sedentary species (e.g., cod, carp, sea bass). Personal exposure measurements have confirmed that workers in sea trout processing plants in Denmark, fishermen aboard Norwegian trawlers, and employees in salmon and herring processing plants are exposed to airborne parvalbumin [21,23].
Collagen	Collagen is a major structural protein in fish, present in connective tissue, tendons, skin, and bones. It was identified as a fish allergen in the early 2000s. A 2016 Japanese study found that 50% of fish-allergic patients exhibited IgE reactivity to mackerel collagen [78]. When fish is cooked, collagen denatures and converts into gelatin, which is less allergenic. However, exposure to raw fish, such as in sushi and sashimi consumption or occupational settings in the fishing industry, suggests that collagen is a significant allergen in these contexts.
Enolases & aldolases	Enolases and aldolases are allergenic muscle enzymes involved in glycolysis, the metabolic pathway responsible for sugar degradation and energy production. Compared to parvalbumin, enolases and aldolases exhibit significantly lower thermal stability and appear to be present exclusively in raw fish [79]. Furthermore, Kuehn et al. [79] reported that more than half of individuals sensitized to parvalbumin also exhibited sensitization to enolases and aldolases.
Vitellogenin	Vitellogenin, a precursor of yolk proteins, is synthesized in the liver of fish and transported via the bloodstream to oocytes, where it accumulates during oocyte growth [80]. It is a major protein component in salmonid roe and has been identified as a potential food allergen in various fish species. Clinical reactivity to vitellogenin varies and is often specific to certain types of caviar, with cross-reactivity reported between salmon roe and herring roe [57]. Vitellogenin has also been detected in raw, intestine, and shell extracts of crabs but is absent in cooked meat extracts [27].
Trypsin	Trypsin is a widely distributed digestive enzyme (protease) that catalyzes protein hydrolysis in both vertebrates and invertebrates. Exposure to trypsin has been associated with inflammatory responses in cell models and is suspected to contribute to allergic reactions, including seafood allergies. Airborne trypsin has been detected in processing areas within the crab and salmon industry work environments [5,74].
Anisakis	Anisakis is a parasitic nematode, commonly found in marine fish (herring, cod, mackerel, salmon, and tuna) and squid. Anisakis is associated with IgE-mediated allergic reactions following secondary exposure. It can cause both gastrointestinal infections (anisakiasis) and allergic reactions. Sensitization to Anisakis allergens can lead to allergic responses without prior infection. This occurs through inhalation or direct contact in domestic or occupational settings [45].
Shellfish
Tropomyosin	Tropomyosin, a water-soluble muscle protein, is a major allergen found in crustaceans and mollusks. It has been identified as the primary allergen in crab and shrimp processing environments, contributing to occupational allergies [73]. Tropomyosin is heat-stable, retaining its allergenicity even after cooking, and workers appear to be more sensitized to boiled crustacean extracts than to raw ones [27]. Occupational exposure to airborne tropomyosin during crab and prawn processing can be significant, indicating a potential risk for sensitization and allergic reactions in exposed workers [22].
Arginine kinase	Arginine kinase (AK) has been identified and characterized in various crustaceans, including shrimp, crabs, lobsters, and prawns, as well as in mollusks such as octopuses. Studies indicate that 10–51% of shrimp-allergic individuals exhibit IgE binding to AK [73]. AK is an enzyme involved in cellular adenosine triphosphate (ATP) regulation and energy metabolism in invertebrates. AK is a heat-labile protein, with studies indicating reduced allergenicity following thermal and pH treatment. AK is known to contribute to clinical cross-reactivity between crustaceans, mollusks, and other invertebrate allergen sources, including house dust mites, cockroaches, and parasites [68]. Occupational exposure to aerosolized AK has been documented in various seafood processing environments, where inhalational exposure has been linked to sensitization and allergic responses [27].
Sarcoplasmic calcium-binding protein	Sarcoplasmic calcium-binding protein (SCP) is a heat-stable shellfish allergen first identified in shrimp and prawn [54,81]. Although considered a minor allergen, it elicits IgE binding in 29–50% of shrimp-allergic patients. SCPs are found exclusively in invertebrates and serve as functional analogues to vertebrate parvalbumin, playing a crucial role in calcium regulation within the muscle cells of crustaceans. SCP has been extracted from cooked crab meat, emphasizing its stability and potential allergenicity even after heat processing. SCP has been associated with occupational asthma [82].
Myosin light chains	Myosin light chain (MLC) has been identified as an important allergen in various crustaceans, including shrimp, crab, and lobster. MLC is considered a minor allergen; it is heat-stable and resistant to degradation, with sensitization rates ranging from 19% to 55%. Studies have demonstrated that MLC is recognized in both raw and boiled shrimp extracts [83]. MLC has been implicated in cases of shrimp allergy, including severe reactions such as anaphylaxis, where it was the sole responsible allergen [84]. Additionally, exposure to steam from boiling shrimp can trigger asthmatic episodes, suggesting that aerosolized MLC may contribute to respiratory symptoms [83]. Furthermore, recent studies have identified MLC as an important fish allergen, exposure to which may lead to occupational rhinitis and asthma [85].

Many proteases have the potential to trigger allergic responses in sensitized individuals. However, nonallergenic proteases are also believed to contribute to airway inflammation. Additionally, proteases can enhance the effects of other harmful agents in bioaerosols by disrupting epithelial barriers, thereby facilitating allergic sensitization [74].

Several studies have documented occupational asthma, including in salmon processing workers [56], while airborne monitoring has confirmed the presence of salmon parvalbumin [22,24].

Anisakis is a parasitic nematode responsible for IgE-mediated allergic reactions upon secondary exposure. Clinical manifestations include urticaria, angioedema, asthma, and, in rare cases, anaphylaxis in highly sensitized individuals [46]. Sensitization occurs through the ingestion of contaminated fish or through occupational exposure, with specific IgE detected in 12–50% of affected workers and skin prick test positivity ranging from 8% to 46% [46].

Studies indicate that Anisakis allergens exhibit high resistance to heat, pepsin digestion [75], and freezing [43]. Moreover, crude extracts contain cross-reactive allergens shared with other nematodes, crustaceans, insects, and mites. Sensitization prevalence varies globally based on geography, diet, and occupational risk [46].

3.4.2. Shellfish

Shellfish allergy is a common food allergy with a prevalence of up to 3% in the adult population, although significantly higher in regions with high seafood consumption and among seafood processing workers. For a comprehensive review see Ruether et al [54]. Unlike many other food allergies, shellfish allergy is typically lifelong, being persistent in up to 90% of affected individuals [73].

Occupational exposure to shellfish allergens is a well-documented risk, particularly in the crustacean processing industry, where workers may develop allergic reactions through ingestion, skin contact, or inhalation of aerosolized proteins during processing [27]. Studies report high rates of respiratory symptoms, including asthma, in seafood workers, with up to 50% experiencing asthma-like symptoms and 42% reporting other allergic reactions such as rhinitis, conjunctivitis, and skin reactions [76].

Tropomyosin, a heat-stable muscle protein, is the primary allergen in crustaceans, being responsible for cross-reactivity between different shellfish species [64]. Tropomyosin is found across various invertebrates, including mollusks, and displays structural conservation. Studies suggest that tropomyosin levels are higher in cooked crab than in raw crab, making processed shellfish more allergenic [66].

In addition to crustaceans, occupational allergy from contact with squid has been reported, with cases of asthma, rhinitis, conjunctivitis, and contact urticaria documented in seafood production workers [77]. Additional allergens include arginine kinase, myosin light chain, and sarcoplasmic calcium-binding protein.

3.5. Traditional seafood industry and aquaculture in transformation

Climate change has already affected ocean temperatures and the distribution of fish and shellfish. One example is the decline of the once-abundant and economically important shrimp in the marine waters of New England [4].

On average, seafood has a lower carbon footprint than other animal protein sources, as fishing does not require farmland or livestock management. A significant portion of the greenhouse gas emissions associated with wild-caught seafood originates from fuel consumption. However, the environmental impact varies among different fish and shellfish species. Fisheries targeting anchovy, mackerel, and similar species are the most fuel-efficient, using less than 80 liters of fuel per ton of catch when purse seines encircle large schools. In contrast, crustaceans like Australian tiger prawns and Norway lobster can require over 10,000 liters per ton due to the high fuel demand of dragging prawn nets and moving between lobster traps [86].

It is essential that we adapt our production methods and behaviors to mitigate the impact on our planet. Our food production system is one of the largest sources of greenhouse gas emissions, accounting for 20–30% of the global carbon footprint (REF). Thus, the fishing industry is undergoing transitions that account for the shifting distribution of seafood and the demand for more sustainable production and distribution methods. As the global population and the demand for seafood continue to increase, it will become increasingly critical for fisheries and aquaculture operations to minimize their contribution to global emissions.

The significant and growing demand for fish and shellfish, driven by their excellent nutritional properties and the desire to enhance sustainability in production systems, has resulted in a global shift where more seafood is now cultivated in controlled and physically confined environments–aquaculture–than is harvested from wild populations in lakes and oceans [87].

Various types of aquaculture systems exist, ranging from large enclosures and anchored structures in marine and freshwater bodies to land-based facilities with massive tanks and aquaria. There is ongoing research and experimentation aimed at advancing land-based aquaculture techniques to reduce environmental impact and improve sustainability, for instance, by recycling water and utilizing less resource-intensive feed. These facilities require advanced technologies for water purification, continuous hygiene management, and sustainable energy supply.

The impact on the working environment and potential exposures depends on numerous factors, such as the production species, feed, type of facility, and the level of automation. However, there may be benefits to occupational exposure due to the more controlled conditions, where improved hygiene may result in fewer infections, less toxin and allergen exposures originating from the animals, their water, and cultivation environment. Conversely, if production facilities are not fully controlled, there is a risk of accumulation of potentially harmful microorganisms and allergens, which could pose health risks to exposed workers. Additionally, new types of exposures may arise, including large quantities of cleaning and disinfection agents, pharmaceuticals, and exposures from novel production species.

Occupational exposures in aquaculture have been found to involve similar risks to those present in the broader seafood industry, with additional hazards specific to aquaculture operations. These include risks associated with feed handling, cleaning of land-based systems, and a potential lack of well-developed preventive measures (safety climate) to address occupational health and safety challenges in this emerging sector [61,88,89].

An increased risk of zoonoses and other occupational diseases and injuries has been documented in aquaculture operations [3,62]. Notably, asthma, other respiratory symptoms, and skin infections are common following biological exposures in this sector.

4. Discussion

The seafood industry is currently shaped by three major trends. Firstly, global demand for seafood has increased significantly and is projected to continue rising in the coming years. Secondly, the industry is heavily impacted by climate change, which alters ocean currents and affects the distribution of many marine species, including fish, shellfish, and associated microorganisms. Finally, the sector is influenced by the growing emphasis on sustainability, with a strong societal and political drive. This is observed especially among informed consumers and policymakers. The emphasis involves a) producing seafood in ways that minimize environmental impact, b) reducing energy consumption, c) reducing the use of nonrenewable resources, and d) ensuring the protection of both animal welfare and human health.

In 2022, global fisheries and aquaculture production reached a record high, with per capita aquatic animal food supply increasing from 9.1 kg in 1961 to an estimated 20.7 kg, representing about 15% of global animal protein intake. Aquaculture has grown by 6.6% since 2020, now accounting for over 57% of aquatic animal products consumed directly by humans [87]. For the first time, aquaculture production has surpassed capture fisheries. By 2032, aquatic animal production is projected to increase by an additional 10%. The fisheries and aquaculture sector employed approximately 61.8 million people in 2022. The role of aquatic foods in supporting food security, nutrition, and poverty reduction is increasingly emphasized in global platforms such as the UN Food Systems Summit and the UN Framework Convention on Climate Change (UNFCCC). Food and Agriculture Organization (FAO) is developing guidelines for sustainable aquaculture and supporting initiatives focused on occupational safety [87].

4.1. Climate change and new exposures

El Niño Southern Oscillation (ENSO) events, driven by changes in sea surface temperature and upwelling, alter marine ecosystems, affecting fish stocks and habitats. El Niño events are associated with declines in fish catches across multiple fisheries. Climate models indicate that extreme ENSO events will likely become more frequent under global warming scenarios [87].

Climate change, encompassing rising sea temperatures and sea levels, ocean acidification, harmful algal blooms, extreme weather events, and shifts in the distribution and abundance of seafood species as well as their associated microorganisms and parasites, will significantly affect both fisheries and non-land-based aquaculture production. Due to climate change, there is a heightened risk that Vibrio infections, including cholera, will increase in frequency and expand into previously unaffected regions [50]. Similarly, the abundance and distribution of norovirus in shellfish-growing waters will be influenced by changes in rainfall, river flows, salinity, and water temperature [16].

4.2. Occupational health

In the fishing industry, workers may be exposed to hazards that can lead to infections, toxic effects, and allergic reactions. The primary exposure routes are through aerosols and splashes, which can be inhaled or deposited on the skin. It is essential to protect workers as effectively as possible, and the classic hierarchy of controls provides a relevant framework for prevention. Exposure should be eliminated where possible, for instance, through the use of enclosed systems and mechanization. If elimination is not feasible, exposure should be minimized using technical and administrative measures, or mitigated through the use of personal protective equipment. The use of high-pressure cleaning and open mechanical systems, such as those used for cutting or crushing, that generate aerosols containing potentially harmful materials should be limited.

Continuous monitoring to identify and enable the prevention of occupational health risks, along with a workplace culture that promotes awareness and knowledge of potential hazards, is crucial for ensuring a safe working environment.

4.3. One Health - aquaculture

One Health in aquaculture involves the health of the workers, the animals, and the shared work environment, as well as risk assessments and measures for maintaining a safe workplace [90,91].

The sustainability of aquaculture in its current form may warrant skepticism; the quantities of small forage fish, such as anchovies and sardines, used to feed larger farmed species often exceed the biomass of the fish produced, approximately one-sixth of all wild-caught fish being used as feed in aquaculture [92].

To achieve increased seafood production within a responsible, environmentally sustainable, and safe industry that promotes both occupational health and well-being, we must maintain a strong focus on the significant transitions ahead. A recent UN report on Sustainable Development Goal 14 (Life Below Water) highlights that overfishing has depleted more than one-third of global fish stocks, urging swift and coordinated global action [93]. This calls for a heightened commitment from key stakeholders across society, academia, and industry to expand and disseminate knowledge about the various risks associated with this sector. Understanding these evolving challenges and their potential consequences is essential to ensuring a resilient and sustainable seafood industry for the future.

Different perspectives on future sustainable food production include the increased use of recirculating aquaculture systems (RASs), which enable seafood cultivation in controlled environments with minimal water usage, reduced environmental impacts, and cost-efficiency. Furthermore, alternative production organisms such as algae and seaweed are expected to become more prominent, as they offer significantly lower production costs, more efficient yields of protein and other essential nutrients, and substantially reduced environmental impacts [94].

5. Conclusion

We find that the potential for zoonotic transmission is considerable, the risk of occupational asthma and allergies is well-documented, and workers are exposed to a range of potentially toxic substances. Furthermore, significant developments in seafood production—driven by climate change and the pursuit of more sustainable practices—are likely to introduce new occupational exposures for which the industry may not be fully prepared. The One Health concept, which encompasses the interconnection between animal, human, and environmental health, should be integrated with appropriate consideration of occupational health. The seafood industry is undergoing significant changes as climate change introduces both new opportunities and emerging risks. New species are being utilized, and novel microorganisms, allergens, and parasites are becoming part of the bioaerosols to which workers are exposed. This development should be closely monitored, both technologically and in terms of occupational medicine, with continuous implementation of risk management strategies.

5.1. Limitations

This study is a narrative review. Although we have applied a systematic approach to the literature search, there may still be relevant areas or key studies that we have inadvertently overlooked. In addition, the included articles were not systematically assessed for bias and confounding variables, but were instead appraised by the authors, acknowledging the inherent limitations of this approach.

CRediT authorship contribution statement

Lars Andrup: Writing – review & editing, Writing – original draft, Resources, Project administration, Funding acquisition, Formal analysis, Data curation, Conceptualization. Niels Hadrup: Writing – review & editing, Validation. Anne Mette Madsen: Writing – review & editing, Validation, Methodology, Conceptualization.

Statement on the use of AI tools

AI-assisted technologies has only been used to improve readability and language.

Conflicts of interest

The authors declare no conflicts of interest.