The impacts of land use on the prevalence of allergic sensitization to olive pollen: a case study in Alentejo

Abstract

Allergic diseases are a serious public health problem mainly in industrialized countries. In Portugal, pollen allergy affects about 20% of the population, with grasses and olive trees being among the most allergenic. The growing increase in the cultivation of olive groves in Alentejo as well as its use as an ornamental plant may have an impact on exposure to allergens, which may influence the risk of sensitization to which the population. Nowadays, the prevalence of allergic sensitization to olive pollen in Alentejo is still unknown. Thus, the aim of this study was to characterize the prevalence of allergic sensitization in the population in relation to the pollen level in Alentejo. A retrospective analysis (2011-2021) of the available data on sensitization of the population found at Clinidata®XXI, Hospital de Beja, was performed; the levels and type of specific IgE for the different allergen groups, with a special focus on olive tree pollen were collected. The pollen levels were collected from https://lince.di.uevora.pt/polen/index.jsp, University of Évora. Analysis of the association between the two variable was be performed. The land use, particularly, the extension of olive cultivar groves was obtained from Pordata and EDIA (https://www.pordata.pt; EDIA, https://www.edia.pt). The extension of cultivar groves increased between 2011-2021 in Alentejo, having almost tripled around the Alqueva basin (from ~20,000ha to >70,000ha). The annual pollen index presents a tendency to increase in the last year. Interestingly a tendency to diminish between 2011 (~10,500 pollen/m3) and 2018 (~4000 pollen/m3) while it tended to increase between 2018 and 2021 (>15,000 pollen/m3), not following the steady increase profile of olive cultivar groves. Considering, the prevalence of positive olive sIgE also followed a biphasic pattern, reaching a nadir in 2017 – 2018, the years with the lower levels of olive pollen, followed by an increase between 2019 and 2021. When the mean levels of sIgE is considered, a 5-fold and a 2-fold increase were observed in 2021 compared to 2018 and to 2011, respectively, in keeping with the high pollen levels. In conclusion, these results suggest that the exposure to highest concentration of olive pollen favours the increase of sensitization of the population, particularly children. Other data should be analised to validate the observations in this case study.