LONDON, ENGLAND - AUGUST 06: In this photo illustration the rear of an Apple iPad is seen on August 6, 2014 in London, England. iPad maker Apple is selling fewer units than in the same quarter in 2013, it is reported. (Photo illustration by Peter Macdiarmid/Getty Images)

Apple will stop using two chemicals -- n-hexane and benzene -- in the last stages of its manufacturing process, following calls from labor and environmental groups to halt the use of the substances in its factories. The changes will take effect Sept. 1.

The chemicals are common in solvents and even gasoline but are used in electronics manufacturing as cleaning and de-greasing agents. Both can be toxic -- or even lead to higher rates of cancer -- when improperly handled or over long periods of exposure. Their use has been on the decline since those health risks were discovered, analysts said, but have remained in use in the electronics world.

Since 2010, there have been several reports of workers in Apple's supply chain falling ill after exposure to n-hexane; similar reports have surfaced at factories run by Apple rival Samsung, as well. This past March, labor watchdog China Labor Watch and nonprofit environmental group Green America gathered more than 23,000 signatures asking Apple to stop using both of the chemicals altogether.

Lisa Jackson, Apple's vice president for environmental initiatives, said in an online letter that Apple " treats any allegations of unsafe working conditions extremely seriously."

After the most recent round of questions about the chemicals, Jackson said, Apple sent "specialized teams into each of our 22 final assembly facilities, and found no evidence of workers’ health being put at risk." Still, the firm has decided it is best to stop use of the chemicals at its 22 final assembly plants, which employ approximately half a million workers.

The company will continue using the chemicals in other parts of its manufacturing, Jackson said, but it will also tighten restrictions for the chemicals' use. Apple also released a full list regulated substances that it uses in its factories, and its safety standards for workers using those materials.

"Greater transparency like we are seeing from Apple will help drive a bigger discussion on replacement or elimination of chemicals from the manufacturing supply chain with its stakeholders," said Gary Cook, a technology analyst for Greenpeace. He also urged other electronics manufacturers to follow suit.

Green America, one of the original organizers of March's petition, said in a statement that it was pleased with Apple's initial steps. But, the group said, Apple should go further and disclose all of the chemicals it uses in its factories to the public.

"This announcement and the preceding investigation shows that Apple listens to its customers," said campaigns director Elizabeth O'Connell in a statement. "However, Apple needs to go further to create a safe environment at all factories in their supply chain for the health and safety of all 1.5 million workers."

(This story has been updated to reflect that labor groups collected 23,000 signatures asking Apple to stop using  n-hexane and benzene.)