Background and objective: We previously assessed the prevalence of occupational asthma (OA) to snow-crab in production plant workers. We also showed that this type of OA is related to immediate immunological reactivity as demonstrated by skin reactivity and increased specific IgE antibodies. However, we did not show that snow-crab antigens causing immunological reactivity and OA could be found in the air sampling in the plants atmosphere. This was the purpose of the current work.
Material and methods: Area air samples worn by workers at four different worksites of a snow-crab producing plant were obtained on PVC filters with an SKC pump run at 1.5 L/min for 2 h. Snow-crab was being boiled and processed during the air sampling periods. Filters were analysed by RAST inhibition in a blind manner (i.e. without knowledge of the worksite where the filter originated).
Results: Eluate from one of the four sites (#2) had the highest protein concentration and yielded the highest per cent inhibition of RAST--13% inhibition with the snow-crab meat, 23% and 28% inhibition with the snow crab water RAST in two separate assays. An eluate taken from a filter at another site (#1) showed borderline reactivity (1% and 10% inhibition in two assays) whereas the two other ones and a control filter were negative. The two filters that contained snow-crab proteins were the ones nearest the boiling process, site #2 being the nearest followed by site #1. It was estimated that a 28% inhibition corresponded to approximately 8.6 micrograms of proteins and to approximately 1.5 micrograms of allergens on the filter.
Conclusion: This study suggests that airborne snow-crab-derived proteins, released during the boiling process, are the cause of immunological reactivity and of OA to snow-crab.