Gas chromatography-mass spectrometry study of polycyclic aromatic hydrocarbons in grass and milk from urban and rural farms

Polycyclic aromatic hydrocarbon (PAH) levels were studied in grass and milk sampled at two farms, one located in a non-contaminated, rural area, and another located in a urban area close to PAH sources such as highways, busy roads, fuel-powered trains and a steel plant. PAH concentration were measured by gas chromatography coupled to mass spectrometry (GC-MS) using internal deuterated standards. In grasses, unexpectedly, although the sum of PAH concentrations was only slightly higher at the urban farm (83.1 ± 16.1 ng g^-1) than the rural farm (51.8 ± 10.6 ng g^-1), this difference was not observed for all PAH members. This absence of a striking difference of PAH levels between urban and rural grasses suggests that atmospheric PAH sources, for example, vehicle exhausts and chimney fumes, could be rapidly diluted by winds. In milk, PAH concentrations were not significantly different at urban and rural farms.