Intake fraction distributions for indoor VOC sources in five European cities.

UNLABELLED: Distributions of intake fractions for indoor air emissions were estimated for five cities in the EXPOLIS study (Athens, Basel, Helsinki, Oxford, and Prague). Intake fractions are an expression of the mass of a pollutant that reaches a target compared with the mass emitted by a source. They facilitate direct comparisons of the relative impact of different sources on individual or population exposure and dose. The computation of the distributions was obtained through Monte Carlo simulations, based on distributions of residence volume, air exchange rates and time-activity data, calculated from the EXPOLIS database, as well as on distributions from the literature. Some approximations were made that are valid for persistent pollutants and continuous sources, such as emissions from building materials, pesticides, molds, as well as for certain non-continuous sources such as cooking or cleaning products. For these categories of sources, intake fractions are approximately independent of the actual indoor concentrations and irrespective of the source. Intake fractions in the five populations examined followed approximately lognormal distributions. The mean individual intake fractions exhibited some variability across cities, ranging from 1.5x10(-3) in Athens to 4.5x10(-3) in Helsinki. Intake fractions for all the people in a household followed similar distributions, with mean values ranging from 4.6x10(-3) in Athens to 11.8x10(-3) in Helsinki. This modest variability mostly reflects the differences in climates and consequent air-tightness of the buildings. The 95th percentile of the distributions were two to three times the mean values, indicating substantial homogeneity within each population as well. These results compare well with previous estimates for environmental tobacco smoke and cooking, and are two to three orders of magnitude larger than estimates for outdoor sources. PRACTICAL IMPLICATIONS: Emissions from indoor sources were estimated to be approximately 1000 times more likely to reach a human target than emissions from outdoor sources. Strategies to reduce exposure to indoor sources can only realistically focus on reducing the strength of the emissions.

Differential effect of several inducers on hepatic and mammary benzo(A)pyrene metabolism in rat and hamster.

Rat and hamster mammary gland, in comparison with the liver, were examined for their in vitro ability to metabolize polycyclic aromatic hydrocarbons, and for the effects of pretreatment with various mixed function oxidase inducers on this metabolism. Hamster mammary microsomal benzo(a)pyrene (BP) hydroxylase activity was 4-fold greater than that in the rat, and this activity was induced 3- to 5-fold in the hamster, and 7- to 13-fold in the rat, by pretreatment with 7,12-dimethylbenz(a)anthracene, beta-naphthoflavone, Aroclor 1254 or 3-methylcholanthrene. Hamster hepatic microsomal BP-hydroxylase activity was 80-fold greater than in the rat. Whereas pretreatment with these enzyme inducers enhanced rat hepatic activity by 20- to 30-fold, little effect of "inducers" was observed on the hamster hepatic enzyme, even when the formation of the various BP metabolites was determined by high pressure liquid chromatography.