 Contamination in one coastal region can lead to effects in areas thousands of miles away and having a nationwide monitoring program enables NOAA to track these effects.A performance based quality assurance process (QA) is used by the Mussel Watch Program to maintain data quality.The National Institute of Standards and Technology (NIST) and the National Research Council of Canada (NRC) assist analytic laboratories in exercises to ensure that data collected from all labs have comparable accuracy and precision.