On February 20, the peer-reviewed journal Environmental Health Perspectives published a study which concluded that the health risks arising from a lifetime exposure to the levels of polyaromatic hydrocarbons (PAH) found in water distribution systems are of low public health concern (Blokker et al.). Exposures were found to be below the Tolerable Daily Intake (TDI) of 30µg/d/kg bodyweight developed by Baars et al in 2001.
The researchers took samples in 120 different locations over a period of 17 days and under a variety of conditions including flushing, repair and normal operation. They measured 20 different PAHs. Only after flushing of the piping system by the water companies and mains repair PAH levels were found to be higher than the drinking water quality standards of 0.1µg/L, but also declined rapidly afterwards. During normal operation the levels of PAHs were below the limit of detection, which was between 0.005 µg/L and 0.05 µg/L depending on laboratories and PAHs. To estimate whether levels were safe, the researchers applied the method used by EFSA to evaluate the risk of PAH contamination in food. Both oral intake and inhalation exposure were considered. The margins of exposure estimated were below PAH levels that are considered of low concern.
Water distribution systems were historically coated with coal tar and bitumen, coatings which may release PAHs into the water. Today distribution pipes are coated with cement. Exposure to PAHs is of public health concern because of PAHs mutagenic and carcinogenic potential.
Blokker, M et al. “Health Implications of PAH Release from Coated Cast Iron Drinking Water Distribution Systems in the Netherlands.” Environ Health Perspect (published online February 20, 2013): .doi:10.1289/ehp.1205220