Oil-sand mining may also release PAHs: between 19, the concentration of PAHs in sediments at the bottom of Canada’s Athabasca river rose by 41 per cent, in line with increased mining in the region ( Environmental Science and Technology, DOI: 10.1021/es104375d). Preliminary surveys suggest that, following last year’s Deepwater Horizon oil spill, sediments in the Gulf of Mexico contain higher than usual quantities of PAHs. They may also stunt the growth of fetuses by damaging their DNA.Ī 2002 study of beluga whales in Canada’s Saint Lawrence Estuary suggested that PAH pollution caused over a quarter of the 263 deaths reported there between 19, by inducing various cancers. In humans they have been shown to cause infertility by killing egg cells in the ovaries. Many of them are harmful to humans and wildlife. There are over 100 polycyclic aromatic hydrocarbons (PAHs) found in oil, coal and tar, which are readily released into the environment when fossil fuels are burned. “If PAHs became incorporated into actual bone collagen, we should be able to extract that.” That evidence may be found by analysing the bones for PAHs, says Carl Wendt at California State University, Fullerton, who was not involved in the study. Sholts says the team accepts the idea is still a hypothesis that requires more evidence. “I’m certainly not excluding the possibility, though – it’s a very interesting idea,” she says. However, she says that the idea that bitumen poisoned the Chumash lacks direct evidence. Patricia Lambert of Utah State University in Logan, who has studied the health of the Chumash, confirms that their stature declined over time. “It’s pretty clear that health was compromised over time on the Californian Channel Islands,” says co-author Sabrina Sholts of the University of California, Berkeley. This has been suggested before, but this is the first time bitumen has been considered as a contributor to this decline. The decreasing stature of the Chumash suggests declining health, says Wärmländer’s team. Previous studies have shown femur length declined over this period too.
The women’s skulls decreased from 3180 cm 3 to 2980 cm 3 ( Environmental Health Perspectives, DOI: 10.1289/ehp.1103478). They found that, over the generations, the skulls of men decreased from 3370 cubic centimetres to 3180 cm 3. Wärmländer and his colleagues measured 269 adult skulls from burials made between 6500 BC and AD 1780 on Santa Cruz and Santa Rosa islands off California’s coast. Most symptoms of health problems caused by PAHs reveal themselves in the flesh, but studies have suggested that mothers who are exposed to PAHs during pregnancy give birth to smaller than average babies, who become shorter than average adults. Wärmländer’s team then turned to the Chumash’s bones to see whether the tar balls had had an effect on their health. They found the tar contained 44 PAHs, including many known carcinogens. To find out whether California’s tar balls had the potential to damage the Chumash’s health, Sebastian Wärmländer of Stockholm University in Sweden and colleagues analysed samples taken from Californian beaches and from the La Brea tar pits in Los Angeles. We now know that bitumen can be a source of polycyclic aromatic hydrocarbons (PAHs) – pollutants that have been linked to a number of health problems (see “Poisonous ingredients”).
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