A tool for evaluating exposure and the potential for adverse health effects resulting from exposure to lead in the environment.
LeadSpread was created to run on Microsoft Excel®
Background: Historically, LeadSpread has been a tool used by DTSC to estimate blood lead concentrations resulting from exposure to lead via dietary intake, drinking water, soil and dust ingestion, inhalation, and dermal contact. In past versions of LeadSpread (through the LeadSpread 7, January 2009 Update), each of these pathways was represented by an equation relating incremental blood lead increase to a concentration in an environmental medium, using contact rates and empirically determined ratios. The contributions via the five pathways were added to arrive at an estimate of median blood lead concentration resulting from the multi-pathway exposure. Ninetieth (90th), ninety-fifth (95th), ninety-eighth (98th), and ninety-ninth (99th) percentile concentrations were estimated from the median by assuming a log-normal distribution with a geometric standard deviation (GSD) of 1.6.
In 2007, CalEPA’s Office of Environmental Health Hazard Assessment (OEHHA) developed a new toxicity evaluation of lead replacing the 10 µg/dL threshold blood concentration with a source-specific “benchmark change” of 1 µg/dL (http://oehha.ca.gov/public_info/public/kids/pdf/PbHGV041307.pdf). One ug/dL is the estimated incremental increase in children’s blood lead that would reduce IQ by up to 1 point. In light of the updated CalEPA lead toxicity criterion, as well as the need for revision to ensure that the model is adequately protective of women of child-bearing age, a new version of the DTSC LEAD RISK ASSESSMENT SPREADSHEET (LeadSpread 8; 2011) has been developed.
DTSC LeadSpread 8: DTSC LEAD RISK ASSESSMENT SPREADSHEET
(LeadSpread 8; 2011) is a Microsoft Excel® workbook. It is designed as two self-contained worksheets. Worksheet 1 (DTSC PB8 [child]) is a revision of LeadSpread 7, and should be used for evaluating residential land use scenarios. Worksheet 2 (Modified USEPA ALM [adult]) is a modified version of USEPA's 6/21/09 Adult Lead Model (ALM) which incorporates DTSC recommendations for evaluating industrial worker exposures to lead in soil. Worksheet 2 is not DTSC’s LeadSpread model, but has been included as a separate worksheet of the DTSC LeadSpread 8 Excel® file for convenience. Please consult the “LeadSpread 8 User’s Guide and Recommendations for Evaluation of Lead Exposures in Adults” (which can be downloaded below) for additional information. Detailed information on USEPA’s ALM can be accessed at: http://www.epa.gov/superfund/lead/products.htm.
The risk-based soil concentration developed in LeadSpread 8, based on the OEHHA incremental blood lead criterion, is meant to be implemented as an estimate of the Exposure Point Concentration (EPC) usually based on the 95 percent confidence limit on the arithmetic mean, not as a 'not to exceed' soil concentration. Please see the User's Guide on this web page. Background exposures to lead, and media other than soil/dust which may be impacted by lead are not considered in either worksheet. If lead is present at levels above background in media other than soil (e.g. water, air) or if the home grown produce pathway is anticipated at the site, please contact the HERO toxicologist. DTSC’s LeadSpread model is currently undergoing additional revision, and we hope to incorporate additional exposure pathways and environmental media in the near future.
Download the LeadSpread 8 Microsoft Excel® workbook (bloodpb8.xls) using the link below. Documentation for Worksheets 1 and 2 is contained as comments for various cells within each worksheet. For convenience, major comments and notes are also contained in the “LeadSpread 8 User’s Guide and Recommendations for Evaluation of Lead Exposures in Adults” which can be downloaded using the separate link below.
NOTE: If you have comments on LeadSpread 8 or evaluation of lead exposures, please include them in an e-mail message to Michael Wade at firstname.lastname@example.org