(Beyond Pesticides, May 8, 2008) New research shows that melting Antarctic glaciers are releasing once frozen stores of persistent organic chemicals, now banned in many parts of the world. Marine biologist, Heidi Geisz, a Ph.D. student at the Virginia Institute of Marine Science studying the fate and effect of organic contaminants in the Antarctic, has found that DDT concentrations in penguins has remained at the same levels as they were 30 years ago, when DDT was widely used.
Arctic animals such as whales, seals and birds have had a significant decline in their DDT levels during the past decades, while the more stationary Antarctic penguins have not. The study, â€śMelting Glaciers: A Probable Source of DDT to the Antarctic Marine Ecosystem,â€ť published in Environmental Science and Technology (DOI: 10.1021/es702919n), identifies the melting snow and ice as the continued source of total DDT in this southern ecosystem.
The release of DDT also means that other persistent organic pollutants (POPs), including PCBs and PBDEs â€“ industrial chemicals that have been linked to health problems in humans, are also being released.
“DDT is not the only chemical that these birds are ingesting and it is certainly not the worst,” Ms. Geisz says.
Ms. Geisz and her team sampled AdĂ©lie penguins and found similar DDT concentrations to those found when the penguins were sampled in a 1964 survey.Â She found that the ratio of DDT metabolites, p,pâ€˛-DDT to p,pâ€˛-DDE declined over time. This shift indicates that the birds are exposed to the remnants of older DDT deposition. After examining glacial records, Ms.Â Geisz found a likely explanation for the high concentrations of DDT. During the 1950s and 60s, a time when DDT use peaked, the Antarctic glaciers swelled, potentially locking in chemicals like DDT. However, average winter temperatures on the Antarctic Peninsula have warmed 6 Â°C in the past 30 years, and glaciers now melt faster than they grow. They estimate that DDT reenters the ecosystem at a rate of 1 to 4 kg per year.
DDT and other POPs follow atmospheric paths to the Antarctic and the Arctic and eventually are deposited there in snow and ice. Animals there sequester these contaminants in their fat. These toxic chemicals persist in the environment, bioaccumulate in food chains and are common contaminants in fish, dairy products and other foods. Many human and animal populations now carry enough POPs in their bodies to cause subtle but serious health effects, including reproductive and developmental problems, cancer, and disruption of the immune system. Indigenous communities in the Arctic region carry alarmingly high levels of these contaminants.
However Arctic and Antarctic communities are not the only ones at risk. A survey conducted by the National Oceanic and Atmospheric Administration (NOAA) found that fish caught in Californiaâ€™s Los Angeles county waters contain the worldâ€™s highest-known DDT concentrations (See Daily News of February 1, 2007). These findings contradict the belief held by some scientists that DDT on the ocean floor has been breaking down into less toxic compounds and would soon disappear from marine life. Earlier this year, the National Park Service (NPS) released a report detailing high levels of DDT and other POPs contamination within park boundaries.
DDT and its metabolites have been identified as endocrine disruptors. DDT acts as an estrogen mimic and wreaks havoc on biological systems, with adverse health effects showing up later in an organismâ€™s development.