How we determine our health ratings

The Environmental Defense Fund uses equations from the Environmental Protection Agency to determine how much seafood is safe for consumers to eat.

Our scientists rely on the advisory methodology of the Environmental Protection Agency (EPA). While the Federal Drug Administration (FDA) is charged with monitoring the nation's commercial seafood supply, its recommendations are based on 30-year-old science and balances consumer health risks against economic losses to the fishing industry. In addition, FDA only issues advice for methylmercury and ignores the risks associated with other seafood pollutants, such as PCBs.

EPA's risk-assessment approach is based solely on human health, and is rooted in more recent and rigorously reviewed science. Our unparalleled compilation of mercury data from over 300 government monitoring programs and scientific studies, coupled with the EPA's risk-assessment approach, provides consumers with a powerful tool for maximizing the health benefits of seafood.

These equations allow us to calculate a safe number of meals to eat per month given specific body weights, portion sizes, and fish contaminant concentrations. The equation for mercury is given below:

Fish consumption equation for non-cancer effects due to mercury
Meals/mo = RfD x BW x 35.2 x Tap 
                            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) is 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.

Using our assumptions about body weight and portion size, and the constants described above, we can also calculate the ‘cut-off’ values for mercury 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 weightPortion sizeCut-offs for mercury (in parts per million)
Women 144 lbs 6 ounces 0.269
Men 172 lbs 8 ounces 0.241  
Older Children 67 lbs 4.5 ounces 0.167
Young Children 32 lbs 3 ounces 0.119