NSF/ANSI STANDARD 61
FRAMEWORK FOR
RISK ASSESSMENTS
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Cost of Risk Assessment
Development
• Company with products to Certify
– Enabling certification of their product
• Certifier
– Has identified a risk assessment need to better
serve their clients
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Risk Assessment Developers
• Certifiers with Toxicology Staff
• Company with products to Certify
– Primarily larger chemical manufacturers with
Toxicology Staff
• Risk Assessment Contractor
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External Peer Review
• Health Advisory Board
• Facilitated by NSF International
• Maintain a panel of Toxicologists who are
experts in their field
• Review about 30 documents per year
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Incorporation into Standard
• Joint Committee maintains the Standard
• New criteria that pass the Health Advisory
Board are submitted to the Joint Committee
for adoption into the Standard
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Framework
• Certified Companies provide the funds to
support Risk Assessment development
• Directly through individual risk assessments
• Indirectly through service with the
Certifiers
• Certifiers facilitate the external peer
review
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NSF RISK ASSESSMENT
PROCEDURES FOR THE
EVALUATION OF
CHEMICAL SUBSTANCES
IN DRINKING WATER
BASED ON U.S.
ENVIRONMENTAL
PROTECTION AGENCY
GUIDELINES
Incorporated Into
NSF/ANSI Standards 60
and 61, ANNEX A
APPROACHES
• Use a published and peer reviewed
assessment
• Perform a qualitative or a quantitative risk
assessment
• For a quantitative risk assessment, use noncancer or cancer procedures
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NSF RISK ASSESSMENT
VALUES (NSF/ANSI 61)
• Total Allowable Concentration (TAC)
• Single Product Allowable Concentration
(SPAC)
• Short Term Exposure Level (STEL)
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USE OF A PUBLISHED AND
PEER REVIEWED
ASSESSMENT
• U.S. EPA MCLs and Health Canada MACs
accepted, other assessments evaluated
• Has to be publicly available
• Has to have undergone external peer review
• Has to reflect the oral route of exposure
• Has to follow U.S. EPA or International
guidelines
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MINIMUM STUDY QUALITY
FOR RISK ASSESSMENTS
• Studies evaluated for use in risk assessments
should be performed in accordance with
OECD or U.S. EPA guidelines.
• Studies should be evaluated for compliance
with Good Laboratory Practice guidelines.
• Some judgment is allowed regarding
hazard to human health in evaluating
older, non-compliant, studies.
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REVIEW REQUIREMENTS
FOR A NEW OR UPDATED
RISK ASSESSMENT
• Although NSF/ANSI Standards 60 and 61
specify minimum requirements for a new or
updated risk assessment, all available
information regarding a chemical should be
considered.
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QUALITATIVE RISK
ASSESSMENT
• Done when data are not available to do a
quantitative risk assessment.
• Minimum required studies are a gene
mutation assay (bacterial reverse mutation)
and a chromosomal aberration assay
(in vitro preferred), both with and
without exogenous metabolic
activation.
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QUANTITATIVE RISK
ASSESSMENT
• Same requirements as a Qualitative study,
plus a minimum of a subchronic toxicity
study (90-day repeated dose) in a rodent
species, preferably by the oral route.
• Includes carcinogenic or non-carcinogenic
endpoints.
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QUANTITATIVE RISK
ASSESSMENT KEY
COMPONENTS
•
•
•
•
•
Chemical’s Critical Effect
NOAEL/LOAEL/Benchmark Dose
Uncertainty Factors
Generate Reference Dose (RfD)
Calculation of Water Criteria (TAC,
SPAC, sometimes STEL)
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Uncertainty Factors
• Uncertainty factor of 1, 3, or 10 are
selected to cover various areas of
uncertainty (e.g. interspecies & intraspecies
variation, short-term to long-term
extrapolation, data base deficiencies, etc.)
• These uncertainty factors are
multiplied together to give the total
uncertainty factor
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EXAMPLE CALCULATION:
REFERENCE DOSE (RfD)
RfD (mg/kg-day) =
NOAEL or LOAEL or BMDL (mg/kg-day)
Total Uncertainty Factor
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EXAMPLE CALCULATION:
TAC CALCULATION
TAC =
[RfD x Body Weight] – [other sources]
Drinking Water Intake (L/day)
RfD is in mg/kg-day
Other sources are in mg/day
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STEL CALCULATION
• Not to be used for linear carcinogens, and
used only on a case-by-case basis, as
appropriate, for non-linear carcinogens with
an additional uncertainty factor
• Based on 10 kg body weight and 1 L/day
drinking water intake of a child, otherwise
similar to TAC calculation, although
a shorter-duration study may be used
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THRESHOLD OF
EVALUATION
• Used when data are insufficient to do even a
qualitative risk assessment (i.e. no
mutagenicity and/or chromosomal aberration
study is available)
• TAC is 0.003 mg/L, SPAC is 0.0003 mg/L
and STEL is 0.01 mg/L
• Not used if structure activity
relationships or other data suggest
an adverse healthForeffect
at those levels
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CLASS-BASED EVALUATION
CRITERIA
• Used when some members of a class (i.e.
aliphatic ketones) have data sufficient to
conduct quantitative risk assessments, but
the chemical of interest does not
• Level for the class shall not exceed the
lowest MCL or TAC and SPAC
identified for the chemicals of
known toxicity
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DIFFERENCES FROM
REGULATORY LEVELS
• NSF levels are based on health effects only,
while regulatory levels may include
analytical capability to detect the chemical,
technical feasibility, and other
considerations
• Regulatory agencies may require data
gaps to be filled, while NSF bases
its levels on existing data with
additional uncertainty factors to
account for deficiencies
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