Exposure To Desert Cyanobacteria May Pose A Risk To Human Health

Abstract

Studies on the occurrence of cyanotoxins in desert environments are relatively rare, compared with aquatic environments. Cyanobacteria are, however, important primary-producers in desert environments where they grow rapidly after seasonal rains, stabilizing and fertilizing arid habitats. As cyanobacteria can produce toxins, we tested whether desert cyanobacteria presented a risk to human health. Cyanobacterial crust coverage was measured using random quadrats, and representative samples of cyanobacterial crust from wadis and sabkha were removed for analysis. Extracts were produced using standard methods and toxins were measured by hplc, uplc, mass spectrometry, elisa and enzyme inhibition assays. Cyanobacterial crusts were found to cover 80 percent of the state of qatar, and up to 87 percent of the land was covered with cyanobacteria. The neurotoxic amino acids β-n-methylamino-l-alanine (bmaa) and 2,4-diaminobutyric acid (dab) were detected in the crust material. Microcystins were detected at concentrations between 3.8 and 238 ng/g crust, equivalent to between 7 and 40µg/m2. Pcr products for the mycd gene for microcystin biosythesis were detected after amplification of dna from desert crust samples. In addition, the presence of anatoxin-a(s) was inferred by acetylcholine esterase inhibition assay. Based on the concentration of microcystins detected in crust, with reference to previously published inhalation toxicity for microcystins, in combination with the amount of dust potentially inhaled by a person, the dose of microcystins could exceed a tdi value of 3ng/kg/day for an average adult. The presence of cyanotoxins in desert crusts has important implications for human health and further studies are required to monitor desert dust storms which may contain these crusts. Furthermore, an understanding of the risks of inhaling particles containing cyanotoxins is warranted.