Dirty Dozen pollutants enter air - study

'Dirty Dozen' chemicals, including the notoriously toxic DDT, are being freed from Arctic sea ice and snow through global warming, a study suggests.
The 'Dirty Dozen' - formally known as persistent organic pollutants (POPs) - were widely used as insecticides and pesticides before being outlawed in 2001.
They are extremely tough molecules that take decades to break down in nature. They also bio-accumulate, meaning that as they pass up the food chain, concentrations rise, posing a fertility threat to higher species.
In addition, they are insoluble in water and easily revolatilise, so can swiftly transit from soil and water to the atmosphere in response to higher temperatures.
The study, published on Sunday in the scientific journal, Nature Climate Change, looked at atmospheric concentrations of three chemicals - DDT, HCH and cis-chlordane - monitored between 1993 and 2009 at a station in Norway's Svalbard Islands and at another in the Canadian Arctic.

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