A team of scientists has rather alarmingly discovered that the "surprisingly high rate" of hermaphroditism in polar bears can be directly linked to pollution, the Independent reports. The researchers - who examined 139 bears across the Arctic region - noted that around one in 50 female bears on Norway's Svalbard islands has both male and female sex organs.

The toxic compounds currently giving the greatest cause for concern are polybrominated diphenyls (PBDEs) - flame retardants used to treat furniture and carpets. The team, with members from Alaska, Canada, Denmark and Norway, says that "significant deposits" have turned up in polar bears' fatty tissue, notably in eastern Greenland and the aforementioned Svalbard islands. Studies on mice suggest PBDEs attack "sex and thyroid glands, motor skills and brain function".

The compounds travel northwards from the US and Europe - especially on southerly winds. The moist air carrying the toxins then condenses when it hits the cold arctic air, thereby allowing the deposited chemicals to get into the food chain.

Colin Butfield of the Worldwide Fund for Nature said: "The Arctic is now a chemical sink. Chemicals from products that we use in our homes every day are contaminating Arctic wildlife." The use of such chemicals, combined with the risk of global warming, means many Arctic polar bear populations could disappear by the end of the century.

The problem is simple: levels of toxic waste increase the further you travel up the food chain. The polar bear study, published in December in Environmental Science and Technology , explains how one chemical compound was "71 times more concentrated in polar bears than in the seals they normally feed upon".

PBDEs are not, however, the only risk. Derek Muir, of Canada's Environmental Department, said that there is evidence that another retardant - Hexabromocyclododecane (HBCD)- has made its way into the Arctic food chain. He warned: "It's a chemical that needs to be watched, because it does biomagnify in the aquatic food webs and appears to be a widespread pollutant."

Humans, meanwhile, are also being warned about the possible toxic effects of flame retardants. The Detroit Free Press reports that a study carried out by the US-based Ecology Center, released yesterday, demonstrated levels of PBDEs and plastic-softeners called phthalates in cars at around five-times higher than those normally found in houses. The chemicals - detected in "randomly selected 2000-2005 model year cars and trucks made by 11 manufacturers" - were deposited as dust "on floors and windows of cars and trucks, especially in hot weather".

Although scientists are unsure of the implications of these findings, due to "uncertainty over safe levels of the chemicals", they noted the news "adds to a growing sense of worry that the widely used chemicals may be accumulating at dangerous levels in humans - damaging developing fetuses and children in ways that are only starting to be understood".

Related links

2003 Defra statement on HBCD

Some background info on PBDEs