The smelter, from a photo taken between 1911 and 1916 (Via SMH).

When pricing a house next door to the contaminated site of a former uranium smelter, even a house with waterfront access, most realtors would aim low. In Sydney, though, one such house is on the market for roughly $3.6 million. The realtor describes the site nearby, full of radioactive dirt contaminated with "traces" of uranium and thorium, as just "a slight variation from the norm."

Not surprisingly, the house has been on the market for awhile. Many potential buyers have expressed interest, but so far nobody has purchased it (the crackle of Geiger counters from across the street may have something to do with this). As nuclear power expands, though, it is worth examining just how dangerous such contamination can really be.

Few specifics about the case in Sydney have been released, but it is possible to speak generally about the materials involved. Uranium is only mildly radioactive, and exposure even to high levels of uranium is not known to cause cancer (high levels, if ingested, can cause kidney and tissue damage, though). So, "traces" of it are unlikely to be dangerous. Thorium can give you cancer if you inhale it in large amounts (or possibly when you ingest it), but has not been known to cause birth defects or fertility problems, as some other radioactive materials can. Again, "traces" of thorium are likely harmless.

The wild card in this situation is the radioactivity from the soil. When certain types of powerful radiation encounter everyday materials, those materials can become "activated." In other words, they become radioactive (to a weaker degree) themselves. However, after nearly a century, the soil at this site in Sydney would have reverted to a very low, though perhaps above "background," level of radioactivity. (The New South Wales government and an independent consultancy say the radiation level is higher than background, but safe.)

While a higher than usual level of radiation in the area sounds scary, it is probably not all that dangerous. Many studies have found that constant exposure to low levels of radiation does not pose a health risk. One study, performed by the U.S. National Cancer Institute, found no increased cancer risk for people living near 62 large nuclear facilities. If nuclear power spreads, we should remain vigilant, but there is no need for paranoia.