都市の雑草にみられる有毒植物の危険性

―東大阪市を中心とした河川と教員・保育士の意識調査から―

抄録

  Higashiosaka, which is located on the east side of Osaka, is an industrial city in Japan. Many rivers flow through it and for this reason, it is perceived as an ideal natural environment in which children can play. Riverside weeds are an immediate and recognizable nature source to city-dwelling children.

  Ranunculus silerifolius and R. sceleratus are species of flowering plant in the buttercup family. Ranunculaceae is found at the riverside and in a flood-control system that yields green patches alongside the riverbanks. They are toxic due to the presence of the substance, protoanemonin. Toxic weeds are predominant in the cracks of riverside concrete blocks, where they grow prolifically, owing to little competition from other weeds. These poisonous weeds have unique shapes, which are fascinating to children, placing them at an increased risk of acquiring dermatitis.

  Following the administration of a survey questionnaire, it was found that most primary school teachers and childcare personnel can’t differentiate these poisonous weeds with edible plants and prickly seeds, with which they permitted the children to play with.

  Since 2010, nutrias (river rats) (Myocastor coypus) in Higashiosaka’s rivers have been consuming the nontoxic weeds, leaving the poisonous weeds, which continue to grow and spread. In recent years, poisonous plants are proliferating in the city rivers because the nutria have broadened the habitation area of cities in western Japan.

  Thus, prompt measures are urgently needed to prevent the acquisition of dermatitis, triggered by poisonous river weeds.