Clarification of Answer by
livioflores-ga
on
09 Oct 2005 14:48 PDT
Hi again!!
I researched and found the same info that you gave in your request:
The reference dose for the methylmercury is 0.0001 mg (or 0.1 ug) per
kg of body weight per day [mg/Kg-d].
Just to clarify, recall that reference dose is the minimum safe dose
of a chemical that is very unlikely to have adverse effects. It is
measured in units of milligrams per kilogram of body weight per day.
EPA assumes that the average body weight of adult males and females
combined in the US population is 70 Kg. Then for an average individual
the critical dose is 0.007 mg per day.
With a concentration of 0.11 PPM we have 0.11 mg of methylmercury per
Kg of fish, then to get only 0.007 mg of methylmercury we need:
X = 0.007/0.11 = 0.0636 Kg or 63.6 grams of fish (or 2.25 oz) less
than the 85 grams (3 oz) that you have.
But you must note that 85 grams of fish with 0.11 ppm of methylmercury
this not necessarily means a lethal dose. EPA presents risk-based fish
consumption limits which relate the number of fish meals that can be
eaten per month to fish tissue concentrations of methylmercury.
Eventually this consumption limits are colapsed to the number of fish
meals that can be eaten per week or day. Let me explain that, if the
reference dose for the methylmercury is 0.0001 mg/Kg-d, for an average
individual the critical dose is 0.007 mg per day or 0.049 (0.007x7) mg
per week or 0.2 (~0.049x4) mg per month.
With a meal size of 225 grams (~ 8 oz), uncooked size, you can safely
eat (at 0.11 PPM) 1.82 Kg of fish per month, that is approximately 8
meals per month or 2 meals per week.
See the following document for reference:
"Origin of 1 Meal/Week Noncommercial Fish Consumption Rate in National
Advisory for Mercury":
"-Risk Based Fish Consumption Limits-
US EPA, 2000, Table 4-3 (see attachment) presents risk-based fish
consumption limits which relate the number of fish meals that can be
eaten per month to fish tissue concentrations of methylmercury. The
inputs used in the
development of Table 4-3, are described in Section 3.3 of the same
document (US EPA, 2000). These include:
Reference Dose (RfD): 1x10^-4 mg/kg-d
Meal Size: 8 oz., uncooked corresponding with 6 oz. cooked as used in
the national advisory.
Body Weight: 70 kg, average body weight of adult males and females
combined, in the U.S. population.
-Derivation of Safe Fish Consumption Rate-
US EPA, 2000, Table 4-3 (see attachment) presents safe fish
consumption rates corresponding to various ranges of mercury
contaminant concentrations. While Table 4-3 is quite detailed, most
states have issued fish consumption advisories according to a more
coarse consumption rate categorization, i.e.: no consumption, 1
meal/month, 1 meal/week, and 2 meals/week. At this categorization,
states typically collapse the 2-4 meals/month consumption rates to a
single 1 meal/week category. That is, by Table 4-3 (US EPA, 2000), one
can safely consume 2 meals/week at concentrations ranging from >0.078
ppm to 0.12 ppm, and should consume no more than 1 meal/month at
concentrations ranging from >0.47 ppm to 0.94 ppm. As can been seen
from Table 1, below, the vast majority of fish species with
contamination data (27 out of 34 species) have concentrations within
the coarse 1 meal/week range (i.e. 2-4 meals/month range or > 0.12 ppm
- 0.47 ppm). Thus, the general consumer should be advised to eat no
more than 1 meal/week of noncommercial fish in the U.S. "
http://www.epa.gov/waterscience/fishadvice/1-meal-per-week.pdf
For additional references see:
"Mean Tissue Mercury Concentrations in Non-commercial Fish from Advisory Sites":
http://www.epa.gov/waterscience/fish/advisory.html
"Consumption Advice - Fish Advisories -- U.S. EPA":
http://www.epa.gov/waterscience/fish/advisory.html
"What You Need to Know about Mercury in Fish and Shellfish"
http://www.epa.gov/waterscience/fishadvice/advice.html
"Fact Sheet: Methylmercury - Human Health Water Quality Criteria - U.S. EPA":
http://www.epa.gov/waterscience/criteria/methylmercury/factsheet.html
Hope this helps you.
Regards,
livioflores-ga
