Five months after Chinese and American labor watchdog groups petitioned Apple to investigate the use of potentially hazardous materials in its iPhone and iPad assembly process, the company has announced that it will make changes banning the use of at least two chemicals, the Associated Press reported today. The chemicals in question are benzene and n-hexane, which are tied to lukemia and nerve damage, respectively.

After conducting a four-month study, Apple says it determined that there was no evidence to suggest that these chemicals posed a threat to workers assembling its devices in twenty-two factories, but announced that it would take steps to ensure that it would not become a problem in the future. To that end, both benzene and n-hexane have been banned from the assembly line.

The move is likely too late to have much of an impact on the assembly of some iPhone 6 units, as two versions of that model entered production over the past few weeks. As more iPhone 6 units are produced, the change will help ensure the continued safety of the half a million workers assembling the device.

Update: Lisa Jackson has published a letter on the Apple website explaining the decision to remove these toxins from the assembly process and the company’s continued commitment to eliminating harmful chemicals. Along with the letter, Apple published its Regulated Substances Specification, which outlines the rules it holds its suppliers and manufacturers to regarding use of potentially hazardous substances.

The full letter is below:

Eliminating the risks from toxic substances in the products we all use has always been a passion of mine, and today it is one of our top three environmental priorities here at Apple. We continue to lead the industry in this area as we are committed to keeping both people and the environment healthy. That’s why we’ve removed many harmful substances from our product designs and go to great lengths to make sure they stay that way.

Our pursuit has led to the creation of greener materials and more earth-friendly products, like power cords made without PVC, mercury-free displays, and enclosures that don’t contain brominated flame retardants (BFRs).

We require our suppliers to follow our Regulated Substances Specification and we hold our supply chain responsible with rigorous testing, by our own experts as well as independent labs. And today, for the first time, we are releasing our Regulated Substances Specification to the public.

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. You can learn more about our commitment to safe handling of chemicals and toxic substances here.

Our history proves that the electronics industry can make use of green chemistry. It’s time now to do even better, and we are eager to take on this challenge.

We’ll invest in research on new materials and technologies. We’ll assemble a new advisory board composed of leaders in safer chemicals and pollution prevention to advance our efforts to minimize or eliminate toxins from our products and supply chain. And we’ll listen — convening roundtables with stakeholders to seek out the best science, data, and solutions.

We’re committed to removing toxins from our products and processes. Because everyone has the right to a safe product and a safe working environment.