Workers at a Chinese factory making iPhones were poisoned by the chemical n-hexane in a medical scare last year, according to the Guardian newspaper.
Dozens of staff at the factory in Suzhou were affected by the chemical, which was used to clean some components of the device.
Prolonged exposure to n-hexane can cause extensive damage to the peripheral nervous system and eventually the spinal cord, an expert told the Guardian.
The factory is owned by Taiwanese electronics firm Wintek, which makes the iPad and the iPhone.
One worker, using the name Wu Mei, was hospitalized early last year after using the chemical.
“I found it very hard to go upstairs and if I squatted down I didn't have the strength to get up. Later my hands became numb and I lost my balance – I would fall over if someone touched me,” she said.
She was one of the first to use n-hexane as a cleaning agent and so was one of the worst affected. More than 60 workers needed medical care and many spent months in hospital.
Paul Whitehead, a toxicology consultant and member of the UK's Royal Society of Chemistry, said recovery could take a year or more.
The chemical's risks are well-known in the industry, but Wintek had switched from alcohol to n-hexane for cleaning without proper ventilation.