assessing and managing the risks associated with eating seafood

June 8, 2004 Seafood: Assessing the Benefits and Risks 1 of 17

Assessing and Managing the Risks Associated With Eating

Seafood

Don Schaffner, Ph.D.

Professor and Extension Specialist

Rutgers - The State University of NJ


Overview

- Understanding risk analysis, risk assessment and risk management

- The steps in risk assessment• Special attention focusing on exposure and dose-

response• Using Methyl Mercury (MeHg) as an example

- Risk management• Continue with MeHg example• Show how FDA Foods Advisory Committee

feedback was used to improve the risk message


Risk Analysis Components

- (Quantitative) Risk Assessment• How big is the risk, what factors control the risk?• Scientific process

- Risk Management• What can we do about the risk?• Political process

- Risk Communication• How can we talk about the risk with affected

individuals?• Social and psychological process


Risk Assessment

- Hazard Identification • What agents, food(s) and people are involved?

- Exposure Analysis • What is the chance of exposure?• What is the level of exposure

- Dose-Response Analysis • What is the human health effect of the exposure?

- Risk Characterization • Complete picture of the assessed risk


Hazard Identification

- Agent: Developing neurological system is very sensitive to toxicity of methyl mercury

- Food: Mercury is a naturally occurring and also released into the air through industrial pollution. Mercury can accumulate in streams and oceans. Bacteria transform mercury into methyl mercury. Fish absorb methyl mercury as they feed. Methyl mercury builds up more in some fish than others depending on what they eat.

- People: Women (of child-bearing age, who are pregnant, who could become pregnant, who are nursing mothers) and young children


Dose-Response Analysis

- Reference dose (RfD) is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime.


Background on MeHg RfD

- EPA derived a MeHg RfD in 1995 based on a MeHg poisoning incident in Iraq.

- Congress mandated (1997) that EPA fund a National Research Council study to determine if the RfD was scientifically justifiable

- NRC panel found RfD to be scientifically justifiable (2000) but suggested EPA revisit the issue using new 3 new studies

- The three new studies are the Seychelles Islands study, Faroe Islands study and the New Zealand study.


Data used for RfD- Seychelles Islands (-)

• 779 mother-infant pairs, infants followed from birth to 5.5 years, standardized neuropsychological endpoints, maternal hair mercury concentrations.

- Faroe Islands (+)• About 900 mother-infant pairs, Children tested w/ variety

of tasks at 7 years of age, cord blood mercury and maternal hair mercury measured.

- New Zealand (+)• 38 children of mothers with hair mercury levels during

pregnancy greater than 6 ppm matched with children whose mothers had lower hair mercury concentrations, 237 children were assessed on a number of neuropsychological endpoints (similar to Seychelles study) at 6 years of age


RfD determination

- There are several ways to determine a RfD, and one is to used a Benchmark Dose (BMD)

- BMD calculations use a model to relate exposure to effect, but to use it we need to know• how low is “abnormal”• If exposed, chance of becoming abnormal

- Add uncertainty factor• Intra-human variability

- RfD was determined to be 0.1 ug/kg/day, which corresponds to 5.8 mg MeHg/L blood


Exposure assessment

- What foods are responsible for the exposure?

- What is the chance of a particular individual being exposed?

- If exposed, what is the level of exposure?

- If enough data are available, a computer model can be used to predict exposure, and to investigate interventions.


Exposure assessment model

MeHg by Species

Speciesmarket share

Seafoodconsumptio

n

MeHgExposure

MeHg BloodLevels

MeHg HairLevels

Diet-bloodratio

Blood-hairratio


Exposure scenarios

- Divide fish into high, medium and low MeHg species

- Run different computer simulations including:• No dietary exclusions at all• Consumption from the Medium and Low

groups, but not High• Consumption from the Medium and Low

groups, limiting the amount from the Medium group

• Consumption Low group, no Medium or High


Exposure model summary

- Model appears to predict the National Health and Nutrition Examination Survey (NHANES) data from the JAMA article

- Model will be peer reviewed, and can be used to inform risk management decisions


Risk Management

- The results of the exposure and dose-response assessments have given us a picture of the situation

- Now we must weight competing issues• Fish is…

• a good source of protein, provides important nutrients and is generally affordable

• Fish may also contain substances that are harmful to health


Risk Management

Hg in Blood (ppb)

0 5 10 15 20 55 60

Fre

quen

cy

0.00

0.02

0.04

0.06

0.08

0.10

NHANES data

EPA RfD

Faroe BMDL

- About 8% of at-risk population above the RfD

- Objective: reduce this %, and still keep fish in the diet


Improved risk message

- As a results of feedback FDA received from it’s Foods Advisory Committee (FAC)

- FDA and EPA should combine their two independent advisories

- Tell people what “eat a variety of fish” mean?

- People want to know about canned tuna… so tell them!

- Unify commercial and recreational fish message

- Create specific advice for children


Summary

- The risk analysis process and it’s components

- The step in risk assessment, included examples from exposure assessment and dose-response for methyl mercury

- The nature of risk management and the approach used by FDA and EPA in creating their new (March 2004) advisory for methyl mercury in fish for women and children

assessing and managing the risks associated with eating seafood

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