Question

I have always enjoyed eating tuna fish. Unfortunately, a study of the mercury content of canned tuna in 2010 found that chunk white tuna contains 0.6 ppm Hg and chunk light tuna contains 0.14 ppm. The U.S. Enviromental Protection Agency recommends no more than 0.1 ug Hg/kg body weight per day. I weight 68 kg. How often may I eat a can containing 6 ounces of chunk white tuna so that I do not average more than 0.1 ug Hg/kg body weight per day? If I switch to chunk light tuna, how often can I eat one can?

Answer 1

1 ounce = 28.3495 g    , 6 ounces = 6 x 28.3495 = 170.097 g

white tuna fish has 0.6 ppm Hg which means 0.6 x 10^ -6 g of Hg per 1 g

6 ounces white tuna fish has    ( 0.6 x 10^ -6 / 1) x 170.097   = 0.000102 g Hg .............(1)

light tuna fish 6 ounces has   ( 0.14 x 10^ -6) x 170.097 = 2.38 x 10^ -5 g Hg ................(2)

recomended level = 0.1 ug /Kg = 0.1 x 10^ -6 g /Kg = 10^ -7 g /Kg

Body mass = 68 kg , hence for person recomded level = 68 kg x 10^ -7 ( g/Kg) = 6.8 x 10^ -6 g per day.......(3)

From ( 1) ( 2) we see that 1 can white tuna has 0.000102 g while we need 6.8 x 10^ -6 g per day

Hence number of days 1 can can be consumed = ( 0.000102/6.8x10^-6) = 150 days

Thus for 150 days 1 can completely can be consumed.

From ( 1) ( 3) we see that number od days 1 can can be cosnumed = ( 2.38x10^ -5) / ( 6.8x10^-6) = 3.5

thus for 3.5 days one can can be consumed for light tuna