Frankfurt - German chemicals group BASF said it launched a legal challenge against the European Commission's ban of BASF's insecticide fipronil, imposed in July on concern its use as seed treatment is linked to declining bee populations.BASF has filed legal action with the General Court of the European Union because "valid scientific studies and evidence were not properly taken into account," BASF said in a statement on Tuesday.The European Union in July added fipronil to its blacklist of substances suspected of playing a role in declining bee populations. A risk assessment published in March by the European Food Safety Authority found that fipronil is highly toxic to honey bees.Bees are exposed to toxicity through nectar, pollen and guttation fluid, the assessment said.Growing concernThe ban follows similar EU curbs imposed in April on three of the world's most widely-used pesticides, known as neonicotinoids, and reflects growing concern in Europe over a recent plunge in the population of honeybees critical to crop pollination and production. According to BASF the decline in bee populations is caused by multiple and complex factors and that the restriction of the pesticide will not contribute to protecting bees."The decision regarding fipronil was derived from an assessment that focused heavily on new technical areas for which no established regulatory evaluation criteria are yet available," said Jürgen Oldeweme, Senior Vice President Global Product Safety, BASF Crop Protection in July. "Moreover, sound data from field studies that underpin the safe use of our product for bees were not considered sufficiently."