PERSISTENT ORGANIC POLLUTANTS: Melting Glaciers Release Frozen Toxicants

The melting of glacial ice that formed in the middle of the twentieth century may be a source of a cocktail of persistent, bio accumulative toxic substances that can threaten human health and the environment, according to a study by Christian Bogdal, a postdoctoral research fellow at the Swiss Federal Institute of Technology, Zürich, and colleagues in the 1 November 2009 issue of Environmental Science & Technology. Their findings, along with those of a handful of other studies, suggest the release of toxics once bound within glaciers may be a little-recognized consequence of ongoing climate change. The Swiss team analyzed sediment samples taken from Lake Oberaar, a glacier-fed lake in central Switzerland. They measured sediment levels of several pollutants that would have entered the lake over the period 1953–2006 and compared the measurements with those from three lower-altitude Swiss lakes that aren't glacier fed. The substances analyzed included 17 dioxins and furans, 18 polychlo-rinated biphenyls (PCBs), 10 synthetic musk compounds, DDT and two of its transformation products (DDE and DDD), 4 additional organochlorine pesticides (hexachloroben-zene, hexachloro cyclohexane, dieldrin, and heptachlor epoxide) and their transformation products, and polychlorinated naphthalenes. The Lake Oberaar and lower-altitude samples reflected a generally consistent pattern of increased influx of the compounds into the lakes from the 1950s through a peak in the 1960s–1970s, followed by a decrease to relatively low levels in the 1980s and 1990s. The exception was musk compounds, whose sediment influx was fairly steady from the 1950s to the mid-1990s. These patterns parallel the widespread increase in production and use of these substances from the 1950s through the 1970s, and the subsequent decline (except in the case of musk compounds) as concerns about toxic effects often resulted in restrictions or bans on use. These patterns also mesh with the premise that the primary source of the sediment toxics to that point was deposition of airborne pollutants generated in urban, industrial, and agricultural areas. Beginning in the late 1990s, however, the influx of all the compounds into Lake Oberaar—but not the lower-altitude lakes— increased moderately to sharply. In some cases, the new peak influxes were 2–5 times higher than the 1960s–1970s peaks. These increases coincide with a total reduction in Alpine glacier volume of about 12% between 1999 and 2008, according to a report by Daniel Farinotti and colleagues in the August 2009 issue of Global and Planetary Change. About one-quarter of that reduction …