Occupational airborne exposure, specific sensitization and the atopic status: evidence of a complex interrelationship

Abstract

Background: We have investigated the relationship between atopic status and long-term occupational exposure to latex proteins or methyl diethyl diisocyanate (MDI) as high and low molecular weight asthma-inducing agents, respectively.

Methods: This study is based on retrospective analyses of two groups of symptomatic outpatients: 184 healthcare workers with latex exposure and 156 workers with isocyanate (MDI) exposure. We analysed atopic and non-atopic subgroups according to exposure duration and the frequencies of specific sensitization.

Results: 45% of the healthcare subgroup specifically sensitized to latex were atopic, whereas in the non-sensitized healthcare subgroup only 26% were atopic. On the other hand, subjects specifically sensitized to MDI were rarely atopic (only 15%), whereas in the subgroup non-sensitized to MDI atopy was present in 38%. After prolonged durations of exposure, the proportion of atopics was further elevated in most healthcare subgroups but it decreased in the MDI-exposed subjects.

Conclusions: We hypothesize that latex proteins as sensitizing agents might promote the development of atopy, whereas exposure to the low molecular weight MDI might inhibit the atopic status.

Figure 1

A. Pathomechanic scheme of work-related asthma. Specific sensitization and atopy represent response variables of the main risk variable ‘occupational exposure’ as well as explanatory variables of the definite response variable ‘work-related asthma’. For details see text. ¹⁾ Broadening of sensitization to related allergens. B. Pathomechanic scheme of allergic asthma. Specific sensitization as a main mechanism of work-related asthma by exposure to high molecular latex allergens. The structural relations between factors are simplified in the case of a main pathomechanism. C. Pathomechanic scheme of isocyanate asthma. The main pathomechanism is unknown. The schema of Figure  1A cannot be principally simplified.

Figure 2

I: Percentage of atopy grade 1 in the latex and MDI subgroups: (A – all; B – specifically sensitized; C – not specifically sensitized). Healthcare workers sensitized to latex were significantly more frequently atopic than non-sensitized healthcare workers. The converse relationship was found for MDI workers. II: Percentage of atopy grade 2 in the latex and MDI subgroups. Differences between occupational subgroups were more pronounced for atopy grade 2, e.g. none of the 20 MDI-sensitized workers and only 8% of the non-sensitized latex workers were designated atopy grade 2.

Figure 3

Total IgE levels in the latex and MDI subgroups. I: Percentage of subjects with elevated total IgE serum levels ( > 100 kU/L) in the latex and MDI subgroups. The relationship between the proportions of subjects with elevated total IgE levels in the sensitized and non-sensitized groups was similar to their respective atopy relationships in Figure  2, but less pronounced. II: Absolute total IgE serum level (medians) in latex and MDI subgroups. The relationship between absolute total IgE values in sensitized and non-sensitized subgroups was similar to the relationship between percentages of atopics in Figure  3.I.

Figure 4

Specific sensitization and atopy in the subgroups with different exposure durations. The trend of relationship between atopy and specific sensitization across the subgroups is explicitly opposite for latex and isocyanate exposure.