 However, even with considerable uncertainty, QMRAs are a good way to compare different risk scenarios.In a study comparing estimated health risks from exposures to recreational waters impacted by human and non-human sources of fecal contamination, QMRA determined that the risk of gastrointestinal illness from exposure to waters impacted by cattle were similar to those impacted by human waste, and these were higher than for waters impacted by gull, chicken, or pig faeces.Such studies could be useful to risk managers for determining how best to focus their limited resources, however, risk managers must be aware of the limitations of data used in these calculations.