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Three groups of eight volunteers were administered stable isotope-labelled phthalate diesters in a single dose and the amount of the corresponding phthalate monoesters excreted in the urine was measured. Amongst the phthalates administered were the symmetrical dibutyl-, di-2-ethyl- and diisooctyl- phthalates along with the unsymmetrical benzylbutylphthalate. The control group received no dose, the low dose group received 168-255 microg of each phthalate and the high dose group received 336 to 510 microg of each phthalate. The excreted phthalate monoesters were measured by LC-MS following hydrolysis of conjugates. The bulk of phthalate monoester was excreted in the first 24 hour period following the dose. For dibutylphthalate, 64% and 73% on a mole basis of the low, and high dose respectively was excreted as monobutylphthalate. For dioctylphthalate (sum of the 2-ethylhexyl and the isooctyl species) the yield was 14 and 12% of the low and high dose excreted as monooctylphthalate. For benzylbutylphthalate, 67% and 78% was eliminated as monobenzylphthalate and only 6% (measured for the high dose only) was eliminated as monobutylphthalate. These conversion factors can be used in future studies to assess exposure to phthalate esters via measuring urinary levels of the monoester metabolites.

Factors affecting polycyclic aromatic hydrocarbon (PAH) concentrations in oils and fats, cereals and related foodstuffs have been investigated. Levels of PAHs were low in retail fish and animal-derived oils and fats, such as butter, where the mean benzo(a)pyrene concentration was 0.06 microgram/kg. Higher and more variable amounts were present in retail vegetable oils for which the mean level of benzo(a)pyrene was 1.29 micrograms/kg. Margarine was the major dietary source of PAHs in the oils and fats total diet group accounting for 70% of the benzo(a)pyrene intake from these commodities. The levels of benzo(a)pyrene were less than 0.1 microgram/kg in white flour and similar amounts were found in bread showing that PAHs are not formed to any significant extent during baking of bread. Higher concentrations of up to 2.2 micrograms/kg benzo(a)pyrene were detected in cereal-derived products containing higher levels of edible oils such as pudding-based desserts, biscuits and cakes. The presence of vegetable oils as an ingredient also appeared to increase PAH levels in infant formulae as the mean benzo(a)pyrene content of 0.49 microgram/kg was four times higher than that found in skimmed milk. The mean value in the feed, after reconstituting the formulae with water, would however have been less than 0.1 microgram/litre. Investigations of rape seed drying showed no increase in any PAHs when cold, or electrically-heated air was used. Combustion gas drying had no effect for the larger PAHs such as benzo(a)pyrene but caused mean increases of between 41% and 126% for fluoranthene, pyrene and chrysene. These increases did not correlate with reductions in moisture content of the rape seed implying that the combustion conditions were more important to PAH contamination than the degree of exposure to combustion gases. Concentrations of these three PAHs and also benz(a)anthracene were all significantly reduced by up to a factor of five when crude oils were refined suggesting that carefully controlled direct drying need not contribute PAHs to refined oils and fats.

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