Indium Takes An Atmospheric Downturn

Indium is widely used in electronics and energy technologies—for example, transparent and conductive films of indium tin oxide are used in televisions and other electronic displays. As use of indium has grown, so too have concerns about its potential toxicity and environmental fate. At least so far, however, it appears that older industrial processes released more indium into the atmosphere than modern ones, according to a study of a bog in Massachusetts (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b03182). MIT researchers Sarah Jane O. White, Carrie Keach, and Harold F. Hemond extracted a core sample from Gowing’s Swamp, a wetland noted by philosopher Henry D. Thoreau in his famous journal about Walden Pond and its environs. They sliced the core, dated the slices using radioisotope techniques, and analyzed them for indium and other metals. They found that indium deposition started rising in the late 1800s and peaked around 1970, when the U.S. implemented stricter controls on particulate emissions to the atmosphere by activities such as coal combustion and metal smelting. Since then, indium concentrations in the bog have dropped significantly. The study suggests that release of indium to the atmosphere by current electronics manufacturing and product disposal is considerably lower than historical sources in North America.