Equations Used for Seafood Consumption Advisories
The equations used by Environmental Defense to generate consumption advisories come from the Environmental Protection Agency's "Guidance for assessing chemical contaminant data for use in fish advisories" (reference below). These allow us to calculate a safe number of meals to eat per month given specific body weights, portion sizes, and fish contaminant concentrations. The equations for mercury and PCBs are given below:
| Fish consumption equation for non-cancer effects due to mercury | Fish consumption equation for cancer effects due to PCBs |
|---|---|
| Meals/mo = RfD x BW x 35.2 x Tap Cm x MS |
Meals/mo = ARL x BW x 35.2 x Tap CSF x Cm x MS |
RfD = Reference Dose (0.0001 mg/kg-d)
BW = Body weight (kg)
Cm = Measured contaminant concentration (mg/kg or ppm)
35.2 = Meal size conversion factor (ounces/kg)
Tap = Time averaging period (30.44 days/month)
MS = Meal size (ounces)
ARL = Acceptable Risk Level (0.00001)
CSF = Cancer Slope Factor (2 mg/kg-d)-1
The reference dose (RfD) and cancer slope factors (CSF) are obtained from EPA’s Integrated Risk Information System. EPA defines them as follows:
Reference Dose -- an estimate of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.
Cancer slope factor -- an upper bound, approximating a 95% confidence limit, on the increased cancer risk from a lifetime exposure to an agent.
Our advice for probable carcinogens (e.g. PCBs) is based on an additional cancer risk, or acceptable risk level (ARL), of 1 in 100,000 over a 70-year lifespan, as recommended by EPA.
We list fish on our health advisories chart if they should be eaten less than once a week (4.35 times a month) by children or adults. We designate fish a ‘Health Concern’ on our Pocket Seafood Selector wallet cards for fish that receive a health advisory for adults (see Health Alerts).
Using our assumptions about body weight and portion size, and the constants described above, we can also calculate the ‘cut-off’ values for both mercury and PCBs that will generate a ‘Health Concern’ label. These values represent the average contaminant concentrations in fish above which once-weekly consumption is not recommended by EPA.
| Body weight | Portion size | Cut-offs for mercury (in parts per million) | Cut-offs for PCBs (in parts per million) | |
|---|---|---|---|---|
| Women | 144 lbs | 6 ounces | 0.269 | 0.013 |
| Men | 172 lbs | 8 ounces | 0.241 | 0.012 |
| Older Children | 67 lbs | 4.5 ounces | 0.167 | 0.008 |
| Young Children | 32 lbs | 3 ounces | 0.119 | 0.006 |
Posted: 01-Jan-1900; Updated: 20-Jan-2008
