ACUTE SKIN IRRITANT EFFECTS OF CYANOBACTERIA (BLUE-GREEN ALGAE) IN HEALTHY VOLUNTEERS

Abstract

Introduction Skin exposure to cyanobacteria and their toxins may occur during recreational water activities, but their effects have been difficult to quantify in previous studies. The aim of this study was to assess the dermal irritant effects (induced erythema) of a range of laboratory grown cyanobacterial species using skin patch testing on human volunteers. Methods Solutions of Microcystis aeruginosa (non-toxic strain), Anabaena circinalis and Nodularia spumigena were applied to 64 volunteers and Microcystis aeruginosa (toxic strain), Apanocapsa incerta and Cylindrospermopsis raciborskii were applied to 50 volunteers. Six concentrations of each organism ranging from less than 5000 to over 200,000 cells/mL, were applied using adhesive skin patches (“Finn Chambers”). Two sets of each cyanobacterial species, whole cells and lysed cells, were used, along with positive (sodium lauryl sulphate) and negative (culture media) controls. Patches were removed after 24 hours and a skin specialist using direct observation made clinical assessments of erythema. Subjects filled in a questionnaire regarding their medical history and current medication prior to patch application. People who suffered from eczema, hay fever, asthma or who had been diagnosed as atopic were included in the study Results Between 10% and 40% of both atopic and non-atopic individuals reacted to at least one of the active patches of each of the six cyanobacterial species studies across the concentration range tested. This was the case for both whole and lysed cells with little difference in reaction rates between these two skin treatments. No difference in the irritant effect between the six species was observed. No consistently sustained dose response relationship was identified for any of the cyanobacterial species tested. Conclusion Erythema was induced in a small number of participants by skin contact, but no threshold or dose response was demonstrated. Further research is required to better characterise individuals who might be susceptible.