Apple says it makes the "the most environmentally responsible products in our industry," and an independent study has backed up this claim. iFixit and Healthystuff.org dissected 36 smartphones and analyzed their chemical composition using X-ray fluorescence spectrometry. The study graded the phones based on the presence of known hazardous chemicals like bromine, mercury and lead.
Over the years, Apple has steadily improved its products moving from a "high concern" rating for the original iPhone to a "low concern" rating for the iPhone 4S and the iPhone 5. The iPhone 3G and the iPhone 4 are both in the "moderate concern" level, with the iPhone 4 (2.95) falling just under the 2.81 score of the "low concern" Samsung Evergreen.
[Source: TUAW - Read more there]