GROUND-TRUTHING THE SHELLFISH SANITATION MODEL PEARL: USIING PUBLIC HEALTH SANITATION DATASETS FROM PACIFIC, GULF, AND ATLANTIC STATES OF THE UNITED STATES  

Pearl is designed to evaluate and manage shellfish growing area closures. The Pearl model can be used in one of two modes. In the standalone mode, Pearl can perform a multi‐year analysis using observed fecal coliform data collected from within shellfish growing areas to determine if shellfish harvested from those areas may pose a human health risk for shellfish consumers. Shellfish growing areas that are identified as at risk through a stand‐alone Pearl analysis are candidates for closure rule adjustments. Run in tandem mode with a previously released model, Aquarius, Pearl can be used to adjust closure rules and maximize the number of days a shellfish growing area can remain open to harvest with no increased risk of illness to shellfish consumers. Pearl's additional formula used to determine the Upper Limits of the Estimated 90^th Percentile increases the sensitivity of the existing National Shellfish Sanitation Program's closure assessment method, which only uses the Estimated 90^th Percentile values.

The Pearl model was used to analyze Public Health sanitation datasets from the coastal states of Washington, California, Texas, Alabama, Florida and Georgia to ground-truth its application nationally. In all six studies, of the 19,939 data points, the majority of fecal coliform data points (95.85%) for the estimated 90^th percentile values appeared below the Pearl Limit of 26 MPN/100 mL, and vast majority of the geometric values (99.21%) appear below the Pearl Limit of 8 MPN/100 mL, for a five-tube test. This demonstrates that the six states inadvertently employ the Pearl limits of 8/26 MPN/100 mL and not the NSSP 14/43 standard.

We hypothesize that state agencies initially establish closure rules based on the traditional NSSP 14/43 standard, but they may be adjusting the final harvest closure rules by just tightening the rules. They possibly do this based on the response of reported illnesses, and not by additional, more sensitive statistical analyses of bay conditions that could reveal potential public health threats. We have proposed that the existing NSSP 14/43 standard does not adequately protect the public from consuming contaminated shellfish. Our more sensitive Pearl analysis using the Upper Limits of the estimated 90^th percentile demonstrates that our test states are already inadvertently managing production bays below the Pearl limits. Therefore we propose that the existing NSSP standard should be adjusted to 8/26 MPN/100 mL for a five-tube test for our domestic shellfish industry and imported shellfish products. Preliminary unpublished analyses of Public Health datasets from three additional Atlantic Coast are showing similar results.