Detection of androgenic activity in emissions from diesel fuel and biomass combustion

The present study evaluated both diesel fuel exhaust and biomass (wood) burn extracts for androgen receptor–mediated activity using MDA‐kb2 cells, which contain an androgen‐responsive promoter‐luciferase reporter gene construct. This assay and analytical fractionization of the samples were used as tools to separate active from inactive fractions, with the goal of identifying the specific compounds responsible for the activity. A significant androgenic response was detected from the diesel emission. High‐performance liquid chromatographic fractionation of the sample indicated that significant androgenic activity was retained in three fractions. 4‐Hydroxybiphenyl was identified from the most active fraction using gas chromatography/mass spectroscopy. This purified compound was then tested at doses from 1 nM to 100 μM. 4‐Hydroxybiphenol exhibited antagonist activity at low concentrations and agonist activity at high concentrations. A competitive‐binding assay confirmed binding to the androgen receptor, with a median inhibitory concentration for radioligand binding of approximately 370 nM. Significant androgenic activity also was detected in the wood burn samples, but we were unable to identify the specific chemicals responsible for this endocrine activity. The present study demonstrates that in vitro bioassays can serve as sensitive bioanalytical tools to aid in characterization of complex environmental mixtures.