Why is use of calcium carbide as an artificial fruit ripening agent banned? Fruits like mangoes can be ripened using agents like ethylene, acetylene or calcium carbide. Of these, the latter is dangerous and is banned in most countries. Wikipedia says it is because calcium carbide has traces of arsenic and phosphorus. Is there any other reason?

Will it still be unsafe if pure calcium carbide is used?
According to Anwar et al. the use of $\ce{CaC2}$ is discouraged due to 


  dangers of explosion and carryover of toxic materials like arsenic and phosphorus to consumers, thus making the healthy fruit poisonous. Since no technical knowledge is considered necessary for its anomalous use, higher quantity of calcium carbide needed to ripen immature fruit, makes them 
  tasteless.


For references and more information, see: Anwar, R., A.U. Malik, M. Amin, A. Jabbar and B.A. Saleem, Int. J. Agri. Biol. 2008, 10, 35–41. Available at researchgate.net.