An international team of scientists has detected low concentrations of toxic, carcinogenic chlorine compounds known as Polychlorinated biphenyls (PCBs) in samples taken from America's highest mountain in the Andes.
The snow samples taken at an altitude of 6200 metres on Aconcagua Mountain in the Andes are among the highest traces found anywhere in the world of these substances, which have been banned since 2001.
In particular, the samples contained more persistent compounds like hexachlorobiphenyl (PCB 138) and heptachlorobiphenyl (PCB 180).
Mountain ranges could be a natural trap for persistent organic pollutants that are transported by the atmosphere all over the world, according to scientists from IIQAB in Barcelona, the UFZ in Leipzig and the University of Concepcion in Chile.
The PCB concentration on Aconcagua was less than half a nanogram per litre.
Compared with the values measured in other mountain and polar regions, the concentrations on the mountain peak in the Andes were relatively low.
The PCB concentrations measured around the peak of Mount Aconcagua were approximately one-tenth of those found in earlier samples taken from Sierra Velluda, a mountain just 3500 metres high on the west side of the Andes in Chile.
"This could be because of the way in which these pollutants accumulate in the snow. But it could also have something to do with the three hydroelectric power stations on the lower slopes of Sierra Velluda. Their transformers are potential sources of PCBs," suggested Ricardo Barra of the EULA-Chile Centre for Environmental Research at Concepcion University.
"However, detecting PCBs in the snow on top of Aconcagua clearly shows that these compounds are transported to the Andes by the atmosphere and accumulate there," he added.
According to the researchers, these findings highlight the need to investigate further the role of mountains in the spread of these pollutants and the associated risks.
PCBs are among the 'dirty dozen' persistent organic pollutants banned worldwide under the Stockholm Convention.
Until the 1980s, PCBs were used primarily in transformers and capacitors and as hydraulic fluids and diluents.
As well as causing chronic effects like acne, hair loss and liver damage, PCBs are also a suspected cause of male infertility.
The toxin also represents a danger to a large number of animals because it accumulates in fatty tissue and is passed on via the food chain.