Food contamination by C20–C50 mineral paraffins from the atmosphere

Most foods from plant origin usually contain 1–10 mg/kg (dry weight) of non-resolved isomeric alkanes in the range of the n-alkanes C20–C50 which are assumed to be residues from mineral oil products (in addition to the natural paraffins). In edible vegetable oils, concentrations may exceed 100 mg/kg. Since it was suspected that this contamination was mostly of environmental origin, particulate matter from air was analysed for the same range of paraffins. In a road tunnel, around 5 μg/m3 of such paraffins were found, corresponding to about 3% of the fine dust (PM10). The composition corresponded to that found in the particulate matter from the exhaust of diesel engines, which in turn largely corresponded to engine (lubricating) oil. In Swiss cities, the C20–C50 mineral paraffins in the PM10 from ambient air amounted to 0.1–1.5 μg/m3 (about 1% of the dust) and seemed to primarily originate from incomplete combustion of heating and diesel oil, lubricating oil, and road tar debris. On the countryside, the concentrations were around 0.03 μg/m3 (0.3% of the dust). Soil contained 0.5–10 mg/kg of these paraffins. The similarity of the molecular weight (volatility) distribution suggests that the food contamination with paraffins, is mostly from the air. A substantial proportion probably consists of lubricating oil. If this hypothesis is confirmed, measures should be investigated to reduce this contamination.