Your driveway could be the source of cancer-causing dust particles in your home, a new study has discovered. Some driveways, and especially public car parks, have a covering of coal tar-based sealcoat, a source of the harmful contaminants PAHs (polycyclic aromatic hydrocarbons), which are known to be carcinogenic, or cancer-causing. Scientists from the US Geological Survey have discovered that homes had very high levels of PAHs if they were close to public car parks and playgrounds that have the coal tar covering, or if their driveways had been coated. Coal tar has around 50 per cent higher levels of PAHs than other coverings and sealants, although, in tests, dust on the surface of the car parks had 530 times higher concentrations of PAHs than car parks that had different surfaces. The researchers believe that people are bringing the PAHs indoors after they've walked across driveways, playgrounds or car parks that have the coal tar surface. (Source: Environmental Science & Technology, 2010; 100111160908036; doi: 10.1021/es902533r).