By Jonathan Stempel (Reuters) – Mars Inc has been sued by a consumer who claims that Skittles candies are unfit to eat because they contain a known toxin that the company had pledged six years ago to phase out. In a proposed class action filed on Thursday in the Oakland, California federal court, Jenile Thames accused Mars of endangering unsuspecting Skittles eaters by using “heightened levels” of titanium dioxide, or TiO2, as a food additive. The lawsuit also said titanium dioxide will be banned in the European Union next month after a food safety regulator there deemed it unsafe because of “…