Benzene and n-hexane (also called hexyl hydride) have been banned by Apple over concerns for the safety of its workers in its 22 third-party final assembly plants, 18 of which are located in China. Benzene is known to be a carcinogen and n-hexane may cause nerve damage. The chemicals are used to clean electronics in the final stages of assembly as they evaporate more quickly than alcohol.

A recent audit by Apple indicated that while 18 of the 22 factories already did not use the substances, the chemicals were found in the other four. The concentration of the chemicals was found to be within safe limits.

The chemicals are still used in downstream production and in other industries - benzene is used in production of nylon and polystyrene, for example – and Apple is not expected to ban its use totally throughout the supply chain. Workers’ exposure in the final assembly process, however, is much more acute and more likely to cause health problems, leading to the ban at that stage of the manufacturing process.

Pressure has been mounting on Apple and other electronic manufacturers to remove the substances from their subcontractors’ factories, most recently by China Labor Watch and Green America. In 2009, Taiwan-based Wintek, a subcontractorfor Apple, found that its workers were becoming ill after handling n-hexane and stopped the use of the chemical after this became known. In 2010, Apple required that the facility have better ventilation systems installed and stop using the chemical, though it did not ban the use of it as a company policy until now.

It is still unknown what will be used to replace the chemicals, but alcohol has been used in the past and that is what Wintek went back to when it stopped using n-hexane.

While no other manufacturers have banned the use of the chemicals as yet, pressure may mount to ban them industry-wide.