Apple has banned the use of two chemicals, benzene and n-hexane, in final assembly of its iPhones and iPads, the Associated Press reports. The company has drawn criticism in the past for using both potentially hazardous chemicals — workers reported n-hexane-related sicknesses in 2010, and by 2011, workers at an Apple manufacturing partner wrote a letter regarding their concerns and health issues due to n-hexane exposure. Though Apple claims an investigation at 22 factories revealed no evidence that either chemical endangered workers, the company is requiring all factories to test substances for the two chemicals on top of the general ban. “This is doing everything we can think of to do to crack down on chemical exposures and to be responsive to concerns,” said Lisa Jackson, Apple’s vice president of environmental initiatives. “We think it’s really important that we show some leadership and really look toward the future by trying to use greener chemistries.” Apple also released a new message from Jackson on the company’s decision to ban the two controversial chemicals.