sediments have been used by the EPA in the past. Categories have been characterized as “good” for zero ERL exceedances, “intermediate” if there are ERL exceedances but zero ERM exceedances, and “poor” for any ERM exceedance. The EPA credits the ERL and ERM as valuable benchmarks that assist in providing a uniform context for evaluating contaminant levels within estuaries. Reliability Long and colleagues, using both "effects" and "no effects" data, determined measures of the accuracy of the guidelines by calculating the percent incidence of effects occurring within the ranges delineated by ERL/ERM. The percent incidence of effects was calculated by dividing the number of effects entries by the total number of entries and multiplying by 100. For trace metals, the guidelines for copper, lead, and silver were the most accurate - below the ERL concentration, there was less than a 10% incidence of effects. A steady increase was seen between the ERL and ERM concentrations, and above the ERM, the incidence of effects was greater than 83%. The organic contaminant guidelines also appeared to be very accurate for all classes of polycyclic aromatic hydrocarbons (PAHs) and most of the individual PAHs. The incidence of effects was 25% or below when the concentrations were below the respective ERL value, with only (fluorene as an exception, while the incidence of effects was 75% or greater at concentrations above the respective ERM, excepting dibenzo(a,h)anthracene, p,p’-DDE, total dichlorodiphenyltrichloroethane (DDT), and total Polychlorinated biphenyls (PCBs). Importantly, one hundred percent effects were seen in concentrations above the ERM for acenaphthylene, 2-methyl naphthalene, and low-molecular weight PAHs, and ninety percent or greater effects in this range were seen for chromium, lead, silver, benz(a)anthracene, and fluoranthene. Contaminants that were reported as having low accuracies included nickel, mercury, chromium, total PCBs, p,p’-DDE, and total DDT. Comparison to other SQGs (case studies) Multiple case studies have been conducted to compare different sediment quality guidelines (SQGs) and their ability to predict sediment toxicity. The original intent of NOAA in developing ERL/ERMs was to create a ranking system for sediment site toxicity in order to compare one site to another. Although not the original intent, these guidelines have been compared to other SQGs to assess their ability to predict sediment toxicity in different organisms. Long and co-workers also conducted a meta-analysis using 1068 sediment toxicity assays to evaluate the predictive ability of the ERL/ERM, PEL (predicted effects level), and TEL (threshold effects