[Goal and Background] Risk assessment of environmental contaminants relies on scientific evidence from animal toxicity testing and epidemiological studies which can be time consuming, costly and provides limited mechanistic information.High throughput in vitro methods are needed to accommodate the need for testing large number of chemicals known or suspected to pose risk to human health.US Environmental Protecting Agency (EPA) initiated a Toxicity Forcaster (ToxCast) program in 2007, aiming to identify a battery of such predictive in vitro high throughput screening methods to reduce and eventually replace animal testing for better human health risk assessment.Due to its unique advantage of non-invasive and real time cell analysis (RTCA), impedance based screening methods were incorporated and utilized as a key component of the ToxCast program to evaluate general toxicity, nanoparticle toxicity, and potential endocrine disruptor characteristics of testing substances.