In vitro studies: what is their role in toxicology?

Many epidemiology studies have reported associations between inhaled environmental pollutants, especially particles, and mortality or morbidity. Despite these impressive associations, fundamental uncertainties exist as to the underlying pathophysiological mechanisms responsible for mortality or morbidity following exposure to air pollutants. In vitro toxicology provides a powerful approach to describe these mechanisms at the cellular, biochemical, and molecular level. This manuscript will describe some advantages and limitations of in vitro toxicology studies in comparison with epidemiology studies, and human and animal exposure studies. A recent example will also be presented which demonstrates that the response of cultured cells to air pollution particles is similar to the response seen following in vivo exposure to the same particles. This coherence between an in vivo and in vitro response provides relevance to additional in vitro studies that characterize the mechanisms by which these particles cause adverse health effects.