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Cheryl Itkin and Susan Rieth U.S. EPA, ORD, NCEA Washington, DC U.S. EPA Annual QA Meeting San Antonio, TX May 14, 2009. Evaluating Secondary Data For Use In Chemical Risk Assessments . Outline. Chemical Risk Assessments/IRIS Database Study Types and Sources

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Cheryl Itkin and Susan Rieth

U.S. EPA, ORD, NCEA

Washington, DC

U.S. EPA Annual QA Meeting

San Antonio, TX

May 14, 2009

Evaluating Secondary Data For Use InChemical Risk Assessments

outline
Outline
  • Chemical Risk Assessments/IRIS Database
  • Study Types and Sources
  • Types of Secondary Data Used in Chemical Risk Assessments
  • Types of New Data Derived from Secondary Data
  • Secondary data QAPP
  • Literature Review Evaluation Criteria Checklist
  • Other Types of QA Assessments: Peer review
  • Case studies: Reject or Accept! You are the evaluator.
chemical risk assessments
Chemical Risk Assessments
  • Report on specific environmental substances and their potential to cause human health effects.
  • Each report represents a concise synthesis and evaluation of the most relevant science available. ________________________________________________

This presentation is based on IRIS risk assessments.

The Integrated Risk Information System (IRIS) is an electronic database of chemical risk assessments that provides both descriptive and quantitative information.

http://www.epa.gov/IRIS

Other chemical assessments that utilize secondary data include the Integrated Science Assessments (ISA), formerly called EPA Air Quality Criteria Documents for NAAQS pollutants.

study types and sources
Study Types and Sources
  • Types of studies: Epidemiological, toxicological, cancer studies, clinical, invitro studies, etc….
  • Resources:
    • Papers from the peer-reviewed literature
    • NTP Study Reports
    • Review documents, including health reviews prepared by ATSDR, Cal EPA, Health Canada, IARC
    • NIH
    • EPA Pesticides
    • NIEHS
    • Study Reports from Industry
    • Unpublished studies
types of secondary data used in chemical risk assessments
Types of Secondary Data Used in Chemical Risk Assessments

Quantitative –

  • e.g., mean & standard deviation, incidence data
  • Individual animal data with all endpoints reported is sometimes available. Typically provided for histopathology findings in NTP bioassays.

Qualitative – descriptive characterizations

types of new data derived from secondary data
Types of New Data Derived from Secondary Data
  • Quantitative – secondary data are used to derive values for IRIS oral RfDs and inhalation RfCs, and oral slope factors and inhalation unit risks for the carcinogenic effects of chemicals
  • Qualitative – secondary data used for assessment characterization (cancer weight-of-evidence characterizations)
secondary data qapp document the method for evaluating existing literature
Secondary Data QAPP: Document the Method for Evaluating Existing Literature

(Handout)

  • QA Project Plan Template for data selection from Literature Reviews; describe the process of identifying and justifying content relevant to the assessment.
  • Checklist included in QAPP template
planning document qapp
Planning Document (QAPP)
  • Document conducting a Literature Search:

Extracting, proofing, presenting data from literature. Here’s general guidance:

    • Source(s) of existing data/information and rationale for selecting the sources (selection criteria)
    • Non-quality constraints on existing data that affect its use in this assessment (CBI, legal, programmatic)
    • How the data/information will be used
    • Procedures for determining the quality of existing data (ie. accuracy, completeness, limitations, representativeness)
    • Validation procedures (calculations & equations)
literature evaluation criteria belongs in the qapp
Literature Evaluation CriteriaBelongs in the QAPP
  • Why is this a key study?
      • New research
      • Confirms previous key study
      • Replaces weaker previous study
      • Best or only available study
  • Address 9 aspects: hypothesis, overall design, stat methods and reporting results, unit specification, missing data, consistent reporting, discussion of results, credible facility, published in a peer-reviewed journal, peer reviewed.
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Literature Evaluation CriteriaQAPP: list specifics for evaluating animal studies from peer-reviewed literature
  • For studies in experimental animals, determine if the following are appropriately described:
    • Species, strain, # animals
    • Exposure protocol
    • Doses/concentration levels
    • Parameters monitored
    • All key/relevant findings
    • Numerical data accurately tabulated or reported in the text
    • NOAELs/LOAELs identified
    • Correct/appropriate inferences/conclusions
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Literature Evaluation CriteriaQAPP: specifics for evaluating epidemiological studies from peer-reviewed literature
  • For human exposure studies, determine if the following are appropriately described:
    • Study design
    • # subjects & controls
    • Exposure issues addressed
    • All key/relevant findings
    • Numerical data accurately tabulated or reported in the text
    • Correct/appropriate inferences/conclusions
other types of quality assurance activities
Other Types of Quality Assurance Activities

Peer review provides independent evaluation of scientific and technical work products.

  • assumptions
  • calculations
  • extrapolations
  • interpretations
  • methodology
  • acceptance criteria
  • conclusions
summary
Summary
  • Secondary data are being used effectively and frequently and can be qualitatively and/or quantitatively analyzed.
  • Document your methods for evaluating literature and reasons for accepting or rejecting a study.

Discuss Case Studies Next

case studies for discussion
Case Studies for Discussion

Carbon Tetrachloride (Sept ’09)

Edwards, 1941

Nagano et al., 2007

Thallium (next 2 months)

Wei, 1987

The external peer review drafts for both chemicals are posted on the IRIS web site under Recent Additions (2008)

questions for evaluation data quality objectives
Questions for Evaluation (Data Quality Objectives)
  • Is this study adequate for conducting quantitative analysis? (e.g., derive RfC, RfC, cancer slope factor)
  • Is this study adequate for a qualitative assessment? (develop weight of evidence characterization)
  • Discuss issues/concerns (for example):
    • Sufficient information provided for data analysis
    • Dosing period concerns
    • Reliability of incidence rate
    • Adequacy of study design
    • Strength of evidence (clear, some, equivocal, none, inadequate)
    • Occurrence of common vs uncommon neoplasia
    • Statistical significance
case study carbon tetrachloride
Case StudyCarbon Tetrachloride
  • Edwards,JE. 1941, Hepatomas in mice induced with carbon tetrachloride. J National Cancer Institute 2:197-199
    • Adequate for qualitative assessment of potential to induce liver tumors
    • Not adequate for qualitative assessment of effect other than liver tumors
    • Not adequate for quantitative analysis

Here’s why (issues):

    • Insufficient information provided to estimate administered dose
    • Single dose group
    • Dosing period too short for quantitative cancer assessment
    • Only liver tumor data provided
    • High tumor incidence in the only dose group tested (88 to 100%) does not support quantitative analysis
case study carbon tetrachloride17
Case StudyCarbon Tetrachloride
  • Nagano et al., 2007b, [Japan Bioassay Research Center (JBRC), 1998] Inhalation carcinogenicity and chronic toxicity of carbon tetrachloride in rats and mice. Inhalation Toxicology 19:1089-1103
    • Adequate for qualitative assessment and qualitative assessment of noncancer and cancer endpoints.

Here’s why:

  • Two-year inhalation bioassay published in a peer-reviewed journal
  • Used a robust study design that included adequate group sizeds (50 animals/sex/group) and examination of a thorough set of noncancer and endpoints.
  • Results were adequately reported.
case study thallium
Case StudyThallium
  • Wei,1987,Studies on Spermotoxicity of Thallium Carbonate in Drinking Water and its Effect o Reproductive Function of Mice. Institute of Environmental Health Monitoring, Chinese Acadamy of Preventive Medicine, Beijing. Zhongua Yufang Zazhi 21 (3): 141-143.
  • Not adequate to use for quantitative analysis. Study findings were not considered sufficiently reliable to serve as basis for RfD derivation.

Here’s why:

  • Low confidence in this study (non-reporting of several observations (water intake, body weights, behavior, and animal health)
  • # of animals examined for sperm and repro endpoints were indefinitively reported
  • Absence of reported sperm results and no explanation for loss of male mice
  • Supporting literature on the repro toxicity is limited
contact information
Contact Information

ITKIN.CHERYL@EPA.Gov

Director Quality Assurance,

NCEA, ORD, USEPA,

Washington, DC (Potomac Yards)

(703) 347-8557

RIETH.SUSAN@EPA.Gov

IRIS Team Leader,

NCEA-IRIS, ORD, USEPA,

Washington, DC (Potomac Yards)

(703) 347-8582