iPhone 2G, though, contains the most toxics.
The study, which was performed in order to discover what hazardous chemicals are found in popular smartphones, found that modern handsets generally contain fewer harmful chemicals than their predecessors.
Researchers carried out an X-ray fluorescence spectrometric analysis of 36 devices and assigned a rating on a scale of 0 to 5 (lowest being the best), as well as a ranking by chemical, component and "overall."
The process itself consisted of chemical analysis testing for 12 common hazardous chemicals, including bromine, mercury and lead. Component testing, meanwhile, was based on a breakdown by case, screen, solder, circuit board and other significant parts. The final stage of analysis constituted an overall assessment of each device.
Although the iPhone 2G was found to be the least environmentally friendly smartphone, the iPhone 4S and iPhone 5 were labelled a "low concern" at 2.69 and 2.75, respectively.
Other smartphones branded environmentally friendly were the LG Remarq, and the Motorola Citrus, in addition to Samsung's Captivate and Evergreen. The device that contained the least toxic chemicals with a score of 2.56 was the Citrus.
However, the report added that major cellphone manufacturers shouldn't "rest on their laurels" as "many toxics remain" in discarded handsets.
"The 'low concern' Samsung Reclaim had a 'high concern' proportion of arsenic. Twenty-four of the phones (nearly 70%) had a 'high concern' proportion of copper," said repair experts iFixit. "There is a trend of less toxics overtime, it looks like—especially for Apple. That’s good, but it’s not good enough."