An Intervention Analysis for the Reduction of Exposure to Methylmercury
from the Consumption of Seafood by Women of Child-bearing Age

C D Carrington and P M Bolger.

U.S. Food and Drug Administration

College Park, MD, USA.

# Abstract

# 

A previously developed exposure model was used (Risk Analysis
22:689-699, 2002) to assess the effectiveness of various advisory
scenarios on minimizing Hg blood levels via the consumption of
commercial seafood, both finfish and shellfish. This exposure model was
developed to predict levels of mercury (Hg) in blood in women of
child-bearing age in the US based on the frequency of seafood
consumption, the amount of seafood consumed per serving, and the types
of seafood consumed. Steady-state relationships that employed
descriptive statistics to account for toxicokinetic variation were used
to predict levels of Hg in blood. The model incorporates an uncertainty
dimension that is intended to represent the range of plausible
interpretations of the data. The predictability of the model was
confirmed via the use of NHANES blood Hg data. In the present analysis,
the model was used to predict the impact of limitations in the amount or
types of seafood consumed on blood Hg levels. Specifically, simulations
for various advisory scenarios were developed on the basis of
limitations on total consumption of seafood, elimination of the
consumption of certain species altogether, and/or a combination of both.
In the baseline model, the median (uncertainty) estimates for the
50^th^, 95^th^, and 99^th^ per capita population percentiles were 1.25,
8.2, and 16.1 ppb blood Hg, respectively in blood. After restriction of
seafood consumption to no more than 12 oz per week, the median
(uncertainty) estimates for the 50^th^, 95^th^, and 99^th^ per capita
population percentiles were 1.22, 6.8, and 10.6 ppb blood Hg,
respectively. Elimination of MeHg species, with average concentrations
above 0.6 ppm, resulted in very modest decrements in Hg blood levels, in
comparison to either the baseline or the reduced consumption scenarios.
These results suggest that strategies to reduce MeHg exposure by
reducing the amount of fish consumed (e.g., 12 oz/week) are more
effective at eliminating the high end of the exposure distribution than
are strategies intended to change the types of fish consumed.

# Introduction

Methylmercury (MeHg) is a well known environmental toxicant found in the
aquatic ecosystem. Inorganic mercury originates from anthropogenic and
natural sources. Once in the ecosystem inorganic mercury is converted to
methylmercury through bacterial activity and accumulates in fish and
other marine species to varying degrees, particularly in long-lived,
predators which are at the top of the marine food-chain. Depending on
the level of exposure MeHg can cause mild to severe neurological
symptoms such as paresthesia, ataxia, dysarthyria, hearing defects,
visual disturbances and death. Levels of exposure seen in some
fish-eating populations have been reported to be associated with
developmental delays in children whose mothers were exposed during
pregnancy. While high-level poisoning episodes in Minimata and Nigata,
Japan and in Iraq demonstrated pronounced MeHg-induced neurological
deficits there is also concern that MeHg can cause more subtle
developmental delays or other neurological effects at lower levels of
exposure more consistent with the usual patterns of fish consumption
seen in the U.S.

As part of its efforts to minimize the risks associated with such
outcomes the U.S. Food and Drug Administration issued a new advisory in
2002 that provided recommendations concerning the consumption of certain
fish species and for fish in general by pregnant women. The FDA advised
these women to avoid the consumption of four species of fish; namely
King mackerel, shark, swordfish and tile fish. In addition, it was
recommended that they include up to 12 oz of a variety of other fish
species over the course of a week. In order to better understand and
define what a variety of fish means the FDA conducted a series of
exposure assessments of various fish consumption scenarios that were
constructed to be consistent with the consumption of 12 oz of a variety
of fish. The scenarios differed in how "variety" of fish was defined. In
these assessments EPA's reference dose (RfD) was used as a measure of
the effectiveness of a variety consumption/exposure scenario was
effective in keeping weekly MeHg exposures of women who followed the
specific advise scenario below the RfD.

# Methodology

## The Baseline Model

The model employed in the present analysis is a modified version of a
model described previously (Carrington and Bolger, 2002). These
modifications are as follows:

-   The number of fish categories for which distributions were developed
    was expanded from 24 to 42. (see Table 1). Tuna was broken into
    three categories, corresponding to 1) light canned tuna, 2) albacore
    canned tuna, and 3) fresh/frozen tuna steaks.

-   Mercury concentration data was obtained for additional species,
    which are identified in Table 2. For tuna steaks, this data was used
    to construct an empirical distribution. For the remaining species
    for which additional data was obtained, modeled distributions were
    developed by fitting the distributions to the portions of the
    cumulative distribution above the levels of detection. A battery of
    ten distributions were fit to each data set and the four that
    provided the best fit were used to construct a probability tree (see
    Figure 1 for an example and Carrington, 1996 for further description
    of the methodology).

-   A range of 0.1 to 0.2 ppb was added to blood Hg levels in order to
    represent contributions from sources other than fish. This range
    reflected the levels at the low end of the NHANES survey. Since
    virtually everyone in the NHANES survey had a blood mercury level
    above zero, yet 10-20% of the NHANES survey population reported no
    seafood consumption, this suggests that there are contributions to
    blood Hg levels from other sources (e.g., dental amalgams) other
    than seafood. Since the present model is intended to represent
    methylmercury exposure, a range with an uncertainty bound including
    zero was introduced to acknowledge the possibility of minor
    exposures from sources other than seafood.

-   A correction factor (listed in Table 1) was applied to reflect water
    loss during food preparation. The values were based on water loss of
    11% for fried seafood, 21% for poached or steamed seafood, and 25%
    for baked or broiled seafood (EPA, 2000). Group-specific correction
    factors were calculated based on the frequency of use of different
    food preparation (e.g. baking, steaming, or frying) within each
    group, based on the CSFII survey. A default value of 0.8 was used
    for categories not represented in the CSFII survey. These are listed
    in Table 1. No correction factors were applied for canned-tuna since
    the MeHg concentration values, expressed as total Hg, were obtained
    after cooking and draining of water or oil from the can.

-   The model parameters used to extrapolate long-term frequency of
    consumption from short- term records were chosen to be consistent
    with the 30 day seafood consumption data collected by NHANES (see
    Figure 2). The percentage of consumers was also changed from 70-90%
    to 85 to 95% in order to be consistent with the NHANES survey.

-   The fraction of the annual seafood diet estimated from the
    individual dietary survey, as opposed to market share, was treated
    as an individual variable rather than as a population uncertainty.
    Also, instead of using a range of 20 to 80%, the range of individual
    repetitiveness was estimated using the NHANES survey, by calculating
    the fraction of total seafood consumption in the seafood category
    with the highest number of eating occasions. This produced a range
    of Repetition Ratios 12 to 100% (see Figure 3)

## Scenarios

In order to simulate the impact of consumer seafood advisories for women
of child bearing age who become pregnant, several scenarios were
developed that are intended to predict the expected impact of the
advisory on mercury blood. All the scenarios presumed full compliance
with the advisory. Seafood species were divided into three groups, as
listed in Table 2.

Using these groups, the following advisory scenarios were modeled:

-   *Total Seafood Consumption Limits* (see Table 3)*.* The consumption
    of seafood is limited to 6, 12, or 18 oz without regard to species.

-   *Species Consumption Limits* (see Table 4)*.* There is no limit on
    how much fish may be consumed. Seafood consumption is limited to
    either the middle or low groups (No High Hg), or the low group only
    (Low Hg Only). In either case, seafood from the restricted group(s)
    is replaced by a random selection from a market-share distribution
    of low mercury species.

-   *Total Seafood and Species Limit Combinations* (see Table 5)*.*

    -   *12 oz No High* Consumption of seafood is limited to 12 oz per
        week, high mercury fish are replaced with low mercury fish.

    -   *12 oz Variety* (see Table 5) *.* Seafood consumption is limited
        to 12 oz per week, with no more than 6 oz from the Middle Hg
        group. High Hg fish (shark, swordfish, and mackerel) and Middle
        Hg fish in excess of 6 oz are replaced with Low Hg fish.

    -   *12 or 6 Albacore* (see Table 5)*.* Same as 12 oz variety. In
        addition, for the purposes of calculating the 12 oz limit,
        albacore portions are doubled. As a result, the maximum amount
        of seafood that may be consumed is reduced by an amount equal to
        the amount of albacore consumed. For example, if 3 oz of
        albacore is consumed per week, then the total amount of seafood
        that may be consumed is 9 oz. As the most extreme example, if 6
        oz of albacore is consumed per week, then no additional seafood
        may be consumed.

    -   *12 Low or 6 oz Middle* (see Table 5)*.* Seafood consumption is
        limited to 12 oz per week, High Hg fish (shark and swordfish)
        are replaced with Low Hg fish. For the purposes of calculating
        the 12 oz limit, seafood portions from the Middle group are
        doubled. As a result, the maximum amount of seafood that may be
        consumed is reduced by an amount equal to the amount of seafood
        from the middle group consumed. For example, if 3 oz of Middle
        Group seafood is consumed per week, then the total amount of
        seafood that may be consumed is 9 oz. As the most extreme
        example, if 6 oz of Middle Group seafood is consumed per week,
        then no additional seafood may be consumed.

-   -   *12 oz Low* (see Table 5)*.* Seafood consumption is limited to
        12 oz, high and mid Hg fish are replaced with low Hg fish.

-   

-   

# Results

## Comparison of Baseline Model to NHANES

The results from the blood mercury exposure model were compared to
survey mercury blood values from the NHANES survey population between
1999 and 2000 (see Figure 4). The values are in very close agreement.

## Intervention Scenarios

The impact of various consumer advisories on mercury blood levels is
presented in Tables 3, 4, and 5. In each case, the impact of each
advisory is compared to current baseline blood mercury values.

### Total Seafood Consumption Limits

Table 3 shows the expected reduction in mercury blood levels following
the introduction of consumption limits ranging from 6 to 18 oz per week.
While a limit of 18 oz only slightly reduces the level of exposure at
the extreme tail (i.e. above the 99^th^ percentile), more aggressive
limits reduce exposure for a greater range of consumers and provide a
greater reduction at the tail.

### Advisories Concerning Specific Species

Table 4 shows the expected reduction in mercury blood levels following
the elimination of certain species, with either particularly high
mercury levels or any species with above average mercury levels.
Although the reductions on mercury exposure are not as dramatic, the
reductions in exposure may be noted across the entire distribution

### Advisories Combining Limits on Amount and Species

Table 5 shows the expected reduction in blood mercury levels with
several different scenarios where the advisory includes some combination
of limitation on the amount of seafood consumed with additional
limitations on the types of seafood consumed In the first scenario,
which reflects the current FDA advisory avoiding the consumption of high
methylmercury species and limiting seafood consumption to no more than
12 oz per week will eliminate the occurrence of blood mercury values
that are higher than 5 times the average. The simulations indicate that
more aggressive limits on what species are consumed would result in
greater reductions across the entire distributions of blood mercury
values, but only provide minor, further (in comparison with advisories
that only limit the amount of fish consumed) reductions in those
consumers with the highest levels of exposure.

CONCLUSIONS

Using the NHANES blood mercury data, the exposure model used to predict
blood levels for women of child-bearing age is validated. This does not
prove beyond any possible doubt that the model is entirely correct,
however, the comparison does indicate that the results of the model are
entirely plausible.

An advisory that eliminates consumption of certain species with High Hg
levels and limits consumption to 12 oz per week appears to result in the
most significant reductions in blood mercury levels. Further
restrictions in limiting certain species with Hg levels, exceeding 0.5
ppm Hg, results in minimal further reductions in blood mercury levels.

# 

# References

Carrington, CD (1996). Logical Probability and Risk Assessment. *Human
Ecology Risk Assessment* 2:62-78.

Carrington CD and Bolger PM (2002). An Exposure Assessment for
Methylmercury from Seafood for Consumers in the United States. *Risk
Anal* 22:689-699.

U. S. Environmental Protection Agency (2002). Estimated Per Capita Fish
Consumption in the United States.
<http://www.epa.gov/waterscience/fish/consumption_report.pdf>

U. S. Food and Drug Administration (2001). Mercury Levels in Seafood
Species. <http://www.cfsan.fda.gov/~frf/sea-mehg.html>.

Figure 1: Fitted Distributions for Hg in Cod

![](media/image1.wmf){width="5.916666666666667in" height="5.03125in"}

An example of a fitted distribution. 10 different distributions were fit
to the sample Hg data for Cod. The four best models were used to create
a probability tree that describes the frequency distribution with a
representation of model uncertainty.

Figure 2: Long-Term Frequency Extrapolation for Consumption

![](media/image2.wmf){width="6.4944444444444445in"
height="4.510416666666667in"}

The CSFII based projection employed the exponential function described
in Carrington and Bolger (2002b), using values of 0.696 and 0.356 for
the alpha and beta parameters, respectively.

**Figure 3: Repetition Ratio Distribution**

![](media/image3.wmf){width="5.177083333333333in"
height="4.479166666666667in"}

Figure 4: Quantile-Quantile Comparison of Simulation and Survey Blood Hg
Values

![](media/image4.wmf){width="6.493055555555555in"
height="4.855555555555555in"}

Table 1: Seafood Hg data

  ----------------------------------- -------------------- --------------
  Species                             Range (ppm)          Samples

  Bluefish^1^                         0.14 - 0.63          23

  Catfish                             ND - 0.31            29

  Cod                                 ND - 0.42            20

  Crawfish^1^                         0.01 -- 0.05         20

  Croaker, Atlantic^1^                0.01 - 0.10          20

  Croaker, Other                      0.18 - 0.41          15

  Flounder (Flatfish)                 ND - 0.18            17

  Grouper^1^                          0.07 -- 1.21         18

  Halibut                             ND - 1.52            31

  Lobster, Spiny                      ND - 0.27            8

  Orange Roughy                       0.01 -- 0.76         23

  Oysters                             ND - 0.25            34

  Pollock                             ND - 0.78            38

  Red Snapper^1^                      0.08 -- 0.44         13

  Sardines^1^                         0.00 -- 0.04         21

  Salmon                              ND - 0.19            57

  Sea Bass, Black^1^                  0.06 -- 0.35         20

  Shark                               ND - 4.21            240

  Shrimp                              ND - 0.5             25

  Swordfish                           0.05 - 2.98          280

  Tilefish^1^                         0.06 -- 1.12         13

  Trout, Sea^1^                       0.02 -- 0.88         13

  Trout, Freshwater^1^                0.02 -- 0.66         17

  Tuna, Albacore Canned^1^            0.02 - 0.85          175

  Tuna, Fresh                         0.01 - 1.13          181

  Tuna, Light Canned^1^               0.01 - 0.75          225

  Whitefish^1^                        0.03 -- 0.14         14
  ----------------------------------- -------------------- --------------

1- New data obtained since Carrington and Bolger (2000)

Table 2: Methylmercury (as total Hg) Distributions for Various Species

+-------------------+-------+------------+--------+----------+------+
| Species           | M     | Mean Hg    | Distri | Conce    | Advi |
|                   | arket |            | bution | ntration | sory |
|                   |       | (ppm)      |        |          |      |
|                   | Sha   |            | Type   | Factor   | G    |
|                   | re^1^ |            |        |          | roup |
+-------------------+-------+------------+--------+----------+------+
| Swordfish         | 0     | 0.988      | Emp    | 0.750    | High |
|                   | .0042 |            | irical |          |      |
+-------------------+-------+------------+--------+----------+------+
| Shark             | 0     | 0.982      | Emp    | 0.767    | High |
|                   | .0013 |            | irical |          |      |
+-------------------+-------+------------+--------+----------+------+
| King Mackerel     | 0     | 0.730      | Analog | 0.800    | High |
|                   | .0047 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Grouper           | 0     | 0.552      | M      | 0.800    | Mi   |
|                   | .0017 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Orange Roughy     | 0     | 0.485      | M      | 0.800    | Mi   |
|                   | .0020 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Tuna, Albacore    | 0     | 0.351      | Emp    | 1.000    | Mi   |
| Canned            | .0529 |            | irical |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Trout, Saltwater  | 0     | 0.340      | M      | 0.800    | Mi   |
|                   | .0006 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Tuna, Fresh       | 0     | 0.324      | Emp    | 0.798    | Mi   |
|                   | .0179 |            | irical |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Bluefish          | 0     | 0.318      | M      | 0.800    | Mi   |
|                   | .0009 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Lobsters,         | 0     | 0.310      | Analog | 0.765    | Mi   |
| American          | .0129 |            |        |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Sablefish         | 0     | 0.273      | M      | 0.823    | Mi   |
|                   | .0025 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Halibut           | 0     | 0.217      | M      | 0.750    | Mi   |
|                   | .0090 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Rockfish          | 0     | 0.204      | M      | 0.791    | Mi   |
|                   | .0039 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Crabs, Dungeness  | 0     | 0.170      | Analog | 0.766    | Mi   |
|                   | .0038 |            |        |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Haddock           | 0     | 0.170      | M      | 0.793    | Mi   |
|                   | .0062 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Lobsters, Spiny   | 0     | 0.165      | M      | 0.765    | Mi   |
|                   | .0082 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Snapper           | 0     | 0.154      | M      | 0.800    | Mi   |
|                   | .0046 |            | odeled |          | ddle |
+-------------------+-------+------------+--------+----------+------+
| Crabs, Blue       | 0     | 0.150      | Analog | 0.766    | Low  |
|                   | .0159 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Crabs, Snow       | 0     | 0.148      | Analog | 0.766    | Low  |
|                   | .0177 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Cod               | 0     | 0.143      | M      | 0.806    | Low  |
|                   | .0471 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Tuna, Light       | 0     | 0.135      | Emp    | 1.000    | Low  |
| Canned            | .1335 |            | irical |          |      |
+-------------------+-------+------------+--------+----------+------+
| Sea Bass          | 0     | 0.127      | Mode   | 0.791    | Low  |
|                   | .0004 |            | led^4^ |          |      |
+-------------------+-------+------------+--------+----------+------+
| Trout, Freshwater | 0     | 0.126      | Mode   | 0.800    | Low  |
|                   | .0069 |            | led^4^ |          |      |
+-------------------+-------+------------+--------+----------+------+
| Perch, Freshwater | 0     | 0.110      | M      | 0.785    | Low  |
|                   | .0004 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Crabs, King       | 0     | 0.092      | Analog | 0.766    | Low  |
|                   | .0040 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Pollock           | 0     | 0.071      | M      | 0.820    | Low  |
|                   | .1105 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Catfish           | 0     | 0.070      | M      | 0.870    | Low  |
|                   | .0477 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Whitefish         | 0     | 0.068      | M      | 0.800    | Low  |
|                   | .0022 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Perch, Ocean      | 0     | 0.056      | Analog | 0.785    | Low  |
|                   | .0049 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Croaker           | 0     | 0.054      | Mode   | 0.876    | Low  |
|                   | .0030 |            | led^4^ |          |      |
+-------------------+-------+------------+--------+----------+------+
| Scallops          | 0     | 0.050      | M      | 0.793    | Low  |
|                   | .0080 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Flatfish          | 0     | 0.046      | M      | 0.756    | Low  |
|                   | .0361 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Crawfish          | 0     | 0.028      | M      | 0.773    | Low  |
|                   | .0056 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Salmon            | 0     | 0.025      | M      | 0.758    | Low  |
|                   | .1067 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Shrimp            | 0     | 0.025      | M      | 0.773    | Low  |
|                   | .1514 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Clams             | 0     | 0.020      | M      | 0.754    | Low  |
|                   | .0169 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Tilapia           | 0     | 0.019      | M      | 0.800    | Low  |
|                   | .0187 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+
| Oysters           | 0     | 0.017      | Analog | 0.793    | Low  |
|                   | .0079 |            |        |          |      |
+-------------------+-------+------------+--------+----------+------+
| Sardines          | 0     | 0.016      | M      | 0.795    | Low  |
|                   | .0123 |            | odeled |          |      |
+-------------------+-------+------------+--------+----------+------+

1 -- As a result of species not included in the list, the sum of the
market share values is about 90%.

2 - *Empirical* -- Direct sampling of data set, used for large data sets
with very few values below the limit of detection. *Fitted* -- Modeled
distribution with uncertainty about model form (see text for additional
explanation). Used for data sets with a limited number of observations,
often with many values below the level of detection. *Analog* -- Two
distributional forms (lognormal or gamma) - mean value from 1978
National Marine Fisheries Survey, shape parameter by analogy (see
Carrington and Bolger, 2002 for additional explanation). Used when only
mean values are available.

3 -- These values reflect weight after food preparation as a percentage
of initial weight. Mercury concentrations for seafood as eaten were
calculated by dividing initial concentration by the correction factor.
No correction factor was applied for canned tuna, since the mercury
measurements were made after cooking. .

4 - Croaker, Sea Bass, and Freshwater Trout all had bimodal
distributions that were described with two different distributions. The
Croaker and Sea Bass data subsets corresponded to surveys taken at
different times and may reflect different species with the same common
name.

Table 3: Effect of Advisories Based on Seafood Consumption Limits on
Estimated Hg Blod Levels

  ---------- --------------- --------------- --------------- --------------
  Scenario   Baseline        18 oz/week      12 oz/week      6 oz/week

  Average    2.3 (2.1, 2.6)  2.2 (2.0, 2.5)  2.1 (1.9, 2.3)  1.7 (1.5, 1.8)

  Perc 0.10  0.2 (0.1, 0.3)  0.2 (0.1, 0.4)  0.2 (0.1, 0.4)  0.2 (0.1, 0.3)

  Perc 0.25  0.6 (0.4, 0.7)  0.6 (0.4, 0.7)  0.5 (0.4, 0.7)  0.6 (0.4, 0.7)

  Median     1.3 (1.1, 1.5)  1.3 (1.1, 1.5)  1.3 (1.1, 1.5)  1.2 (1.0, 1.4)

  Perc 0.75  2.9 (2.5, 3.3)  2.8 (2.4, 3.2)  2.8 (2.5, 3.2)  2.7 (2.4, 3.1)

  Perc 0.90  5.5 (4.7, 6.5)  5.4 (4.6, 6.4)  5.1 (4.4, 5.7)  5.5 (4.9, 6.2)

  Perc 0.95  7.7 (6.4, 9.2)  7.4 (6.2, 8.9)  6.5 (5.7, 7.2)  7.9 (7.1, 8.9)

  Perc 0.99  13.6 (10.8,     11.7 (10.2,     9.5 (8.4, 11.3) 13.0 (11.1,
             20.2)           14.4)                           16.4)

  Perc 0.995 16.4 (13.1,     13.7 (11.4,     11.5 (9.4,      16.2 (12.9,
             25.9)           17.1)           14.8)           25.6)

  Perc 0.999 26.3 (17.5,     20.7 (14.1,     18.8 (12.8,     23.8 (16.0,
             52.0)           35.4)           24.9)           37.8)
  ---------- --------------- --------------- --------------- --------------

All units are g Hg/L in blood with uncertainty bounds expressed as 5^th^
and 95^th^ confidence limits in parentheses.

Table 4: Effect of Advisories Based on Species Selection on Estimated Hg
Blood levels

  ----------- ------------------- ------------------- -------------------
  Scenario    Baseline            No High             Low Only

  Average     2.3 (2.1, 2.6)      2.3 (2.0, 2.5)      1.7 (1.5, 1.9)

  Perc 0.10   0.2 (0.1, 0.3)      0.2 (0.2, 0.3)      0.2 (0.1, 0.3)

  Perc 0.25   0.6 (0.4, 0.7)      0.5 (0.4, 0.7)      0.5 (0.3, 0.6)

  Median      1.3 (1.1, 1.5)      1.3 (1.1, 1.5)      1.0 (0.8, 1.2)

  Perc 0.75   2.9 (2.5, 3.3)      2.8 (2.3, 3.2)      2.1 (1.7, 2.3)

  Perc 0.90   5.5 (4.7, 6.5)      5.3 (4.6, 6.2)      3.8 (3.3, 4.4)

  Perc 0.95   7.7 (6.4, 9.2)      7.4 (6.3, 9.4)      5.4 (4.4, 6.7)

  Perc 0.99   13.6 (10.8, 20.2)   13.1 (10.5, 20.3)   8.8 (7.0, 14.3)

  Perc 0.995  16.4 (13.1, 25.9)   16.1 (11.8, 27.1)   10.4 (8.0, 16.7)

  Perc 0.999  26.3 (17.5, 52.0)   26.6 (17.9, 49.6)   14.4 (10.1, 24.7)
  ----------- ------------------- ------------------- -------------------

All units are g Hg/L in blood with uncertainty bounds expressed as 5^th^
and 95^th^ confidence limits in parentheses.

Table 5: Effect of Advisories with Species and Consumption Limits on
Estimated Hg Blood Levels

  ---------- ----------- ----------- ----------- ----------- ---------- ---------
  Scenario   Baseline    12 oz No    12 oz       12 or 6     12 or 6    12 oz Low
                         High        Variety     Albacore    Medium     

  Average    2.3 (2.1,   2.0 (1.8,   2.0 (1.8,   2.0 (1.8,   1.9 (1.7,  1.5 (1.3,
             2.6)        2.2)        2.2)        2.2)        2.1)       1.7)

  Perc 0.10  0.2 (0.1,   0.2 (0.1,   0.2 (0.1,   0.2 (0.2,   0.2 (0.1,  0.2 (0.1,
             0.3)        0.4)        0.4)        0.4)        0.4)       0.2)

  Perc 0.25  0.6 (0.4,   0.6 (0.4,   0.5 (0.4,   0.5 (0.4,   0.5 (0.4,  0.2 (0.1,
             0.7)        0.7)        0.7)        0.7)        0.7)       0.3)

  Median     1.3 (1.1,   1.3 (1.1,   1.3 (1.0,   1.2 (1.1,   1.3 (1.1,  0.5 (0.4,
             1.5)        1.5)        1.5)        1.5)        1.5)       0.6)

  Perc 0.75  2.9 (2.5,   2.8 (2.3,   2.8 (2.4,   2.8 (2.3,   2.7 (2.3,  1.0 (0.8,
             3.3)        3.2)        3.2)        3.1)        3.1)       1.1)

  Perc 0.90  5.5 (4.7,   4.9 (4.4,   4.9 (4.3,   4.8 (4.3,   4.7 (4.2,  2.0 (1.8,
             6.5)        5.5)        5.6)        5.4)        5.2)       2.3)

  Perc 0.95  7.7 (6.4,   6.3 (5.7,   6.2 (5.5,   6.0 (5.5,   5.7 (5.1,  3.6 (3.1,
             9.2)        7.0)        6.9)        6.7)        6.5)       4.0)

  Perc 0.99  13.6 (10.8, 9.0 (8.0,   9.1 (8.0,   8.8 (7.4,   8.0 (6.9,  4.6 (4.0,
             20.2)       11.2)       10.7)       11.3)       9.4)       5.3)

  Perc 0.995 16.4 (13.1, 10.6 (9.1,  10.7 (9.1,  10.6 (8.4,  9.3 (7.7,  6.3 (5.4,
             25.9)       13.7)       12.8)       14.1)       11.3)      8.2)

  Perc 0.999 26.3 (17.5, 17.8 (12.4, 15.3 (12.0, 17.8 (12.0, 12.7 (9.7, 6.9 (5.8,
             52.0)       25.7)       18.1)       23.9)       15.2)      8.8)
  ---------- ----------- ----------- ----------- ----------- ---------- ---------

All units are g Hg/L in blood with uncertainty bounds expressed as 5^th^
and 95^th^ confidence limits in parentheses.