From a letter released today by Lisa Jackson, former administrator of the Environmental Protection Agency and now Apple’s environmental director:

Recently, we received some questions about whether the chemicals benzene and n-hexane are used in the manufacturing of our products. Apple treats any allegations of unsafe working conditions extremely seriously. We took immediate investigative action, sending specialized teams into each of our 22 final assembly facilities, and found no evidence of workers’ health being put at risk. We’ve updated our tight restrictions on benzene and n-hexane to explicitly prohibit their use in final assembly processes.

At the same time, Apple also released their Regulated Substances Specification to the public. The spec is complex and the list of regulated substances is both detailed and quite long. Benzene and n-hexane are both prohibited “from use in all final assembly manufacturing processes” and other uses are subject to specified breathing zone restrictions.

Hard to fault Apple’s methods here. They’ve laid it out for all the world to see. Now its all up to the supply chain auditing process to make sure these prohibitions are taking hold.