Assessment of the estrogenic, antiestrogenic and mutagenic activity of two mixtures of environmental contaminants: Waste crankcase oil and municipal solid waste leachate

There is widespread concern that environmental exposure to chemicals with estrogenic and antiestrogenic activity may adversely affect reproductive health. Compounds with either of these potentials have been reported to exist in mixtures of environmental contaminants. In this study, two mixtures of crankcase motor oil and municipal solid waste leachate were investigated as examples of such mixtures, to assess both their estrogenic response modulating, and mutagenic potentials. Large amounts of WCO are frequently dumped into the environment resulting in significant pollution of both aquatic and terrestrial ecosystems. On the other hand, leachate contains degradation products of materials such as plastics, pesticides, petroleum products, metals, and pharmaceutical compounds that are disposed of as wastes. Some of these compounds have been reported to possess estrogenic, antiestrogenic or mutagenic potentials. Since both these environmental mixtures are ubiquitous, exposure to them is of significant public health concern. In this study, it was observed that new motor oil showed no estrogenic activity; WCO samples exhibited antiestrogenic potentials to different degrees, and caused concentration dependent DNA damage in MCF-7 cells; leachate from the USA was slightly estrogenic, whereas samples from Uganda exhibited no activity. The activity in the leachate was reduced by treating it with activated charcoal. All the tested leachate caused DNA damage. Mechanism of the WCO antiestrogenic activity was found to be due to two actions (1) increased metabolism of E₂ and (2) antagonistic binding of compounds in the WCO to the estrogen receptor (ER). WCO exhibited activity in MCF-7 cells that were transfected with a xenobiotic response element (XRE)-mediated reporter gene, suggesting that actions of the WCO were mediated through the aryl hydrocarbon receptor (AhR). Chemical analysis of the WCO, exhibited presence of polycyclic aromatic hydrocarbons (PAHs), but none in the new oil, suggesting that presence of PAHs in WCO may contribute to its antiestrogenic activity. All leachate samples exhibited presence of phthalates and phenols. Both mixtures have the potential to initiate cancer, although only one leachate sample exhibited potential to promote the process. These mixtures therefore can significantly impact public health through disruption of normal estrogen responses and/or being mutagenic, and exposure to them should be minimized.