Among the most promising approaches for discovery of emerging environmental pollutants involves non-target screening by high resolution mass spectrometry. Using non-targete, samples are screened without a priori knowledge of the contaminants of interest. The approach has only been possible recently with the development of ultra high-resolution mass spectrometers. Non-target screening has been successfully applied to abiotic samples such as water and sediment but its application to biological samples is limited. One reason is the presence of endogenous compounds, which are difficult to differentiate from environmental pollutants. ACES has recently developed a novel strategy which uses time trends to flag bioaccumulative contaminants from chronological datasets of biological samples. The approach is coined ‘non-target time trend screening’.