SAN FRANCISCO (AP) ― Apple is banning the use of two potentially hazardous chemicals during the final assembly of iPhones and iPads as part of the company’s latest commitment to protect the factory workers who build its trendy devices.

The decision announced Wednesday comes five months after the activist groups China Labor Watch and Green America launched a petition drive calling on Apple Inc. to abandon the use of benzene and n-hexane in the production of iPhones.

A four-month investigation at 22 factories found no evidence that benzene and n-hexane endangered the roughly 500,000 people who work at the plants, according to Apple. No traces of the chemicals were detected at 18 of the factories and the amounts found at the other four factories fell within acceptable safety levels, the Cupertino, California, company said.

Nevertheless, Apple decided to order its suppliers to stop using benzene and n-hexane during the final assembly of iPhones, iPads, iPods, Mac computers and various accessories. What’s more, Apple is requiring all its factories to test all substances to ensure that they don’t contain benzene or n-hexane, even if the chemicals aren’t listed in the ingredients.

Benzene is a carcinogen that can cause leukemia if not handled properly and n-hexane has been linked to nerve damage. The substances are often found in solvents used to clean machinery and electronics.