Apple has banned two chemicals from being used in the final stages of manufacturing its devices following pressure from activist groups and an investigation at 22 factories. The two chemicals in question are benzene and n-hexane, which manufacturers use as a cleaning and solvent agent respectively, but have been linked to health problems.

In March, China Labor Watch and Green America began pressuring Apple to stop using the chemicals, arguing that alternatives were available. Apple proceeded to conduct its own investigation into the use of the two chemicals at the 22 factories, reports the Associated Press. The company found 18 of the factories weren't using the chemicals, while the other four were within safety limits. Even so, it ultimately decided to ban the chemicals. The ban encompasses the final stages of assembling iOS devices and Macs, the AP says, though can be used at factories earlier on in the manufacturing process.

"This is doing everything we can think of to do to crack down on chemical exposures and to be responsive to concerns," Apple's vice president of environmental initiatives Lisa Jackson told The AP in an interview. "We think it's really important that we show some leadership and really look toward the future by trying to use greener chemistries."

N-hexane has proven controversial for Apple in years past. One of its manufacturing partners Wintek used it for cleaning iPhone screens due to the fact that it evaporates faster than alcohol. 137 workers who were exposed to the chemical were hospitalized, and a number of them threatened to sue the company claiming long term illnesses. Apple reported the incident in its 2011 Supplier Responsibility progress report, and noted that it required the facility to overhaul its ventilation systems and stop using the chemical, though the company didn't ban it outright. In benzene's case, the solvent has been identified as carcinogenic, though is still an important part in the production of polystyrene and nylon fibers in other industries.