Workers in the salmon industry are at risk of developing allergies and respiratory diseases, including asthma, due to occupational exposure to bioaerosols, i.e. biological agents such as allergens, enzymes and endotoxins, in their work environment. The overall objective of this intervention trial is to identify effective and feasible control measures (interventions) that reduce exposure to these bioaerosols. The project comprises nine salmon processing factories in northern, central and western Norway. The factories are allocated to either one of the two intervention arms or the control group. In all factories, an assessment of exposure to bioaerosols will be performed. In addition, employees will be invited to undergo a health examination and fill out a self-administered questionnaire including information on demographics, work tasks, health and health promoting factors. The intervention trial is part of a broader study that comprises several substudies including the identification of clinically relevant allergens, investigation of exposure-response relationship between the exposure to individual bioactive agents in bioaerosols and investigations of prevalence of airway symptoms, altered lung function, skin symptoms or immunological responses indicating hypersensitivity. Finally the project includes the identification of health promoting factors that are present in the salmon processing industry. The project is an interdisciplinary multi-center study that places great emphasis on a close dialogue between the researchers and industry in all phases of the project.
The intervention trial is part of a broader study on assessment of exposure and health of workers in the salmon industry. Measurements of exposure, health examinations and questionnaire data serve as a basis for both intervention- and other substudies. The intervention trial itself is a parallel group, three-arm non-randomized superiority trial with a 1:1:1 allocation. Processing of salmon includes two main processes: 1) in the slaughtering department, the fish are slaughtered, sorted, automatically or manually gutted, and washed before further processing; and 2) in the filleting department, the salmon is filleted and skinned by machines before manual trimming of the fillets. The main source of exposure to fish proteins is by inhalation of wet bioaerosols containing a heterogeneous mixture of proteins, enzymes, endotoxins and microorganisms. It is hypothesized that a reduction in exposure will cause a decrease in the prevalence of symptoms from the airways and skin, as well as sensitization, in workers of factories that implement the exposure-reducing measures.Hence, the overall aim of identifying effective and feasible control measures (interventions) that reduce exposure to these bioaerosols is to lower the risk of, or preferably prevent, the development or chronification of respiratory diseases, eczema and allergy among salmon processing workers. The main hypothesis behind the interventions is that control measures that aim at using less water, at reduction of bioaerosol generation or at shielding workers from the production line have the potential to reduce bioaerosol exposure. The three arms of the trial are therefore 1) technical intervention targeting alteration of nozzles or nozzle function along the production line (NZ), 2) behavioral or technical intervention related to cleaning of surfaces (CS), or 3) no intervention (control). Each of the intervention arms represents a general intervention category in which details for the actual intervention are to be developed in collaboration with the factory staff to maximize the effect of the interventions. The intervention arms NZ and CS imply measures that have the potential to reduce bioaerosol exposure for the employees, while factories in the CTR arm will not receive any active intervention measures. NZ targets alteration of nozzles or nozzle function along the production line, e.g. by manipulation of nozzle dimensions, alteration of operating pressure or shielding of the nozzle's output stream. CS focuses on reduction of bioaerosol exposure for the employees while cleaning their personal operating areas during working operations or while cleaning floor areas . This can include increased use of swabbing instead of flushing with water hoses or alterations in use of water hoses for cleaning. Examples for the latter are a reduced flushing frequency, reduction of number of employees executing the work, alterations of hose dimension or nozzles on hoses. Suggestions from employees regarding details of the intervention will be taken into account for the final design of the intervention. This can include local specific characteristics, specific location of intervention or others. Randomization of intervention arms is not feasible due to different premises of factory infrastructure. The nine participating factories (three from each geographical region) will therefore be allocated to the study arms by the project group, reassuring that each region will cover all three study arms. Data assessment will be done by questionnaires, exposure measurements and health examinations before (T1) and after the intervention period (T2). Interventions will start 5-8 weeks after T1, permitting technical adjustments where necessary. Interventions are to be continued until follow-up measurements at T2, 12 months after T1. Two phone calls and one physical visit are to be carried out during the intervention period. Questionnaire data relevant for the intervention trial include background demographics, questions relevant for exposure assessment (work tasks, department, etc), as well as questions on symptoms from the eyes, the respiratory system and skin. Health examinations will include spirometry (lung function), skin prick testing (allergic sensitization) and blood sampling (sensitization, inflammation). Exposure assessment will be done by personal exposure measurements collected in the breathing zone of workers, as well as by stationary sampling. While all workers (approx. 1500-2000 subjects), will be eligible for answering the questionnaires, the number of invitees for health examination and exposure assessments will be much lower (ca 900 and 216, respectively), due to logistical and timely constraints. Sample size calculations was performed for the primary outcome; the effect of interventions in reducing the concentration of bioaerosols (total protein) in salmon processing plants. The inclusion of 24 workers with 2 repeated measurements in each of the three intervention arms (see section on inclusion criteria above) will give a total of 432 measurements (144 measurements in each of the intervention arms). According to the sample size calculations, 133 exposure measurements of total proteins in each of the intervention arms give a power of 80% of detecting a 20% reduction of exposure (significance level of 0.05). The corresponding number of measurements needed to detect a reduction in exposure of 40 and 30% were 34 and 59 measurements, respectively. Hence, 144 measurements as aimed at in the present study will ensure a buffer of about 8% in order to account for rejection of measurements due to sampling errors. The number of exposure measurements per work shift will also be limited by logistical constraints.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
2,000
Technical intervention targeting alteration of nozzles or nozzle function along the production line, e.g. by manipulation of nozzle dimensions, alteration of operating pressure or shielding of the nozzle's output stream. How the intervention is to be carried out in detail in the respective factory is to be developed in collaboration with the factory staff. This can include local specific characteristics, specific location of intervention or others.
Behavioural or technical intervention. This can include increased use of swabbing instead of flushing with water hoses or alterations in use of water hoses for cleaning. Examples for the latter are a reduced flushing frequency, reduction of number of employees executing the work, alterations of hose dimension or nozzles on hoses. How the intervention is to be carried out in detail in the respective factory is to be developed in collaboration with the factory staff. This can include local specific characteristics, specific location of intervention or others.
University Hospital of Nothern Norway
Tromsø, Norway
Change of salmon processing workers' personal exposure to inhalable protein
Change in inhalable total protein (ug/m3) in the workers' breathing zone from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences in mean concentration of full shift measurements (8 hours) between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change of salmon processing workers' personal exposure to proteases
Change in concentration of proteases (ng/m3) in the workers' breathing zone from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences in mean concentration of full shift measurements (8 hours) between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change in area concentration of airborne total protein (stationary measurements)
Change in total protein (ug/m3, inhalable aerosol fraction) from stationary measurements in relevant areas of the salmon production line from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences in mean concentration of full shift measurements (8 hours) between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change of salmon processing workers' personal exposure to airborne fish allergens
Change in concentration of total aerosol fraction of fish allergens (ng/m3) in the workers' breathing zone from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences in mean concentration of full shift measurements (8 hours) between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change of salmon processing workers' personal exposure to airborne endotoxins
Change in mean concentration of inhalable total endotoxin units (EU/m3) in the workers' breathing zone from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences in mean concentration of full shift measurements (8 hours) between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' self-reported symptoms from the upper airways
Since the investigators expect to have a significant "loss to follow-up" from T1 to T2,the investigators will analyze change in prevalence of self-reported symptoms from the nose from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Prevalence of symptoms from the respiratory system will be assessed using information reported by participants through a questionnaire that includes standardized questions on respiratory symptoms (upper and lower airways), allergic status and malaise (European Community Respiratory Health Survey, ECRHS). Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Data collected at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' self-reported symptoms from the lower airways
Since the investigators expect to have a significant "loss to follow-up" from T1 to T2, the investigators will analyze change in prevalence of self-reported symptoms from the chest from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Prevalence of symptoms from the respiratory system, as well as the asthma symptom score (0-5) will be assessed using information reported by participants through a questionnaire that includes standardized questions on respiratory symptoms (upper and lower airways), allergic status and malaise (European Community Respiratory Health Survey, ECRHS). Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Data collected at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' self-reported eye symptoms
Since the investigators expect to have a significant "loss to follow-up" from T1 to T2, the investigators will analyze change in prevalence of self-reported symptoms from the eye pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Prevalence of eye symptoms will be assessed using information reported by participants through the a set of standardized questions in a questionnaire.Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Data collected at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' lung function at group level (FEV1 in % of predicted)
Change in proportion of participants having a decline in maximum forced expired volume in 1 second (FEV1 in % of predicted), from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' lung function at individual level (maximum forced expired volume in 1 second (FEV1)/forced vital capacity (FVC) ratio)
Mean of individual change in maximum forced expired volume in 1 second (FEV1) in % of forced vital capacity (FEV1/FVC ratio), from pre-intervention (baseline, T1) to post-intervention (follow-up, T2) for individuals, provided low loss-to follow up. Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Data collected at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' cross-shift lung function (FEV1)
Change in mean difference between pre-shift values and post-shift values (cross-shift) in maximum forced expired volume in 1 second (FEV1, in liter and % of predicted) of individual salmon processing workers from pre-intervention (baseline, T1) to post-intervention (follow-up, T2) .Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' cross-week lung function (FEV1)
Change in mean difference between pre-shift values on Monday and post-shift values on Thursday (cross-week) in maximum forced expired volume in 1 second (FEV1, in liter and % of predicted) of individual salmon processing workers from pre-intervention (baseline, T1) to post-intervention (follow-up, T2) .Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Incidence of salmon processing workers' sensitization to salmon
Registration of number of salmon workers that are newly sensitized to salmon at follow-up. Sensitization will be assessed by serum immunoglobulin E (IgE) specific to salmon proteins. Individuals that are negative for specific immunoglobulin E (IgE) at pre-intervention (baseline, T1) and positive at post-intervention (follow-up (T2) will be registered as an incidence case. Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Measurements at T1 compared to T2, 12 months after T1.
Change in salmon processing workers' self-reported skin symptoms
Since the investigators expect to have a significant "loss to follow-up" from T1 to T2, the investigators will analyze change in prevalence of self-reported skin symptoms from pre-intervention (baseline, T1) to post-intervention (follow-up, T2). Skin symptoms will be assessed using information from a questionnaire that includes standardized questions on eczema, other symptoms from the skin and urticaria (Nordic Occupational Skin Questionnaire, The Nordic Occupational Skin Questionnaire NOSQ-2002). Differences between intervention groups and between intervention groups and control group will be analyzed.
Time frame: Data collected at T1 compared to T2, 12 months after T1.
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