Samples taken from each worker and from the air in an unnamed fish processing plant were tested for herring antigens, mould spores and endotoxins (toxins released when bacteria break down). Bacteria and even matter from inside fish intestines can find their way into workers’ airways and onto their skin, found the Swedish study.
The scientists from Sahlgrenska University Hospital, Gothenburg, claimed theirs was the first ELISA sensitive enough to test 0.1 nanograms per ml of herring parvalbumin (the allergen that can enter workers’ airways).
ELISA (enzyme-linked immunosorbent assay) is a quality control test that uses antibodies to recognise the presence of specific macromolecules.
Culprits: exploding herring and high-pressure sprays
Allergies and breathing problems including asthma among workers in the fish processing industry coincided with the introduction of high-pressure cleaning hoses which disperse food particles into the air, said the study’s authors.
On the first day of the test, concentrations of particles in the air were so high they went beyond the measuring range of the researchers’ equipment.
“The workers at the herring plant reported feeling worse during the night shift when the day shift workers had cleaned the floor with a high-pressure sprayer,” said the study.
Workers’ symptoms also worsened when they were handling herring that had eaten krill (small crustaceans). "If the herring had eaten krill or seaweed, their bellies were swollen and sometimes burst after capture,” said the report. On these occasions, endotoxin concentration in the air was at its highest.
To combat the problems of high-pressure spray and bursting fish, the scientists advised that better ventilation was vital. Additionally, when the plant followed advice to replace the high-pressure sprayer with a hose, this “resulted in a reduced exposure to fine bioaerosols”.
“Visible fog” of fish
The study also compared equipment, finding that newer workstations generated fewer airborne fish particles.
“When measuring particle exposure during two hours of work stationed at either the new filleting machines or the old filleting machines, the levels differed significantly,” said the findings.
The average exposure per worker was 986 nanograms of herring allergens per m3 at old filleting workstations, and 725 nanograms per m3 at newer machines, although these figures were found to even out over longer shifts.
The explanation was that “the old-style filleting machines generated a visible fog over the line of machines, whereas the new machines were fully encapsulated.”
Working outside the processing room was found to be much safer than either type of workstation, with allergen levels dropping to 130 nanograms per m3.
“Levels of herring parvalbumin were nearly an order of magnitude lower in the loading and packing areas compared with the filleting and controlling/inspection workstations,” said Dahlman-Höglund, et al.
Occupational asthma can affect people who work intensively with flour, animals, chemicals and metals. If it is treated early, it can be reversed, but if workers remain in an environment that aggravates their symptoms, occupational asthma can cause life-long problems.
Herring is the most commonly caught fish in Sweden. Its popularity is expected to spread to the rest of Europe, since herring is not endangered and is considered good for heart health.
Source: Annals of Occupational Hygiene, May 23, 2013, doi:10.1093/annhyg/met021
Title: “Exposure to Parvalbumin Allergen and Aerosols among Herring Processing Workers”
Authors: Anna Dahlman-Höglund, Anne Renström, Fernando Acevedo and Eva Andersson.