CAGAYAN DE ORO CITY, Philippines — Environmental watchdog BAN Toxics has issued a stern public health warning after discovering that prohibited skin-lightening products containing dangerous levels of mercury are openly flooding major public markets in this city. The group purchased 11 skin-lightening cosmetics from various beauty shops inside the Cogon and Carmen public markets between June 30 and July 2. Retailing for as low as P60 to P330, th…