drug imagery on reCaptcha

Hi have been using reCaptcha, but we just noticed that the reCaptcha is using a drug image! See attached (second on the right). How are the images get approved for usage on this and how can this be prevented from happening again? -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.