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 a nother located in a urban area close to PAH sources such as highways, busy roads, fuel-powered trains and a steel plant. PAH concentration were measur ed by gas chromatography coupled to mass spectrometry (GC-MS) using interna l deuterated standards. In grasses, unexpectedly, although the sum of PAH c oncentrations 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 no t observed for all PAH members. This absence of a striking difference of PA H levels between urban and rural grasses suggests that atmospheric PAH sour ces, for example, vehicle exhausts and chimney fumes, could be rapidly dilu ted by winds, In milk, PAH concentrations were not significantly different at urban and rural farms.