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Q: math conversion ( Answered 5 out of 5 stars,   1 Comment )
Subject: math conversion
Category: Science > Math
Asked by: deedeeski-ga
List Price: $5.00
Posted: 09 Oct 2005 06:50 PDT
Expires: 08 Nov 2005 05:50 PST
Question ID: 578155
if a fish has .11 ppm methyl mercury, how much methylmercury is in 85
grams of that fish.  please answer in grams or micrograms and show
math in simplest form possible
Subject: Re: math conversion
Answered By: livioflores-ga on 09 Oct 2005 07:47 PDT
Rated:5 out of 5 stars

PPM means part per million, and for this problem the relationship PPM
is 1 miligram [mg] per kilogram [Kg]:

Then if we have 0.11mg  of methyl mercury per 1Kg, then in 85g of
fish, that equals 0.085Kg we must have:
X = 0.085 * 0.11 = 0.00935 miligrams of methyl mercury 

If a fish has 0.11 ppm methyl mercury, there are 0.00935 miligrams of
methyl mercury in 85 grams of fish.

See for additional references the following pages:

"Parts Per Million, etc.":

"Parts per notation - Wikipedia, the free encyclopedia":

Search strategy at
"parts per million"

Hope this helps you. Feel free to request for a clarification if you need it.


Request for Answer Clarification by deedeeski-ga on 09 Oct 2005 09:53 PDT
thank you , I understand the math and can repeat this for my purposes
of determining the amount of Methyl mercury in a serving size of fish
(I have been all over the Internet and spoken to math professors
without figuring it out).  Here's where I cannot not reconcile it in
my head however, so let me explain my main purpose...

the EPA suggests a reference or safe dose of MeHg as the following: 
.1ug(or microgram) per kg body weight per day

do you multiply your weight in kg by .1 to get your daily level, if
so, all of this fish is lethal!

your example of .00935 mg = 9.35 ug, but my RfD is .1 x 40 = 4 ug a
day (and that .11 was supposed to be one of the lower ppms!)

I must still be doing something wrong and I need to understand this
for an important presentation, I have to explain it to a room full of
people!  Please remember i am NOT a math person, and I can pay another
five dollars for finally understanding this!!

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. "

For additional references see:
"Mean Tissue Mercury Concentrations in Non-commercial Fish from Advisory Sites":

"Consumption Advice - Fish Advisories -- U.S. EPA":

"What You Need to Know about Mercury in Fish and Shellfish"

"Fact Sheet: Methylmercury - Human Health Water Quality Criteria - U.S. EPA":

Hope this helps you.

deedeeski-ga rated this answer:5 out of 5 stars
thanks you went above and beyond!

Subject: Re: math conversion
From: wwwsurfer-ga on 09 Oct 2005 07:03 PDT
x = (.11 / y) * 85

where x is the amount of mercury
where y is the fish in grams

for example: the fish is 100 grams total

y = 100

.11 / 100 = .0011
.0011 * 85 = .0935 is how much methylmercury is in the fish

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