How many ppm (Parts Per Million) are there in 1mg (one miligram)?

Question

if you found this out, try this question:

If an oyster has 200ppm of zinc, how many oysters would it take for an adult to reach the recommended daily intake of zinc, 12mg ???

Answer 1

A value in ppm can't be translated directly into an absolute weight.

At 200 ppm zinc, there are 0.0002 g of zinc per gram of oyster. That works out to 0.2 mg of zinc per gram of oyster.

A person would have to consume 60 grams of oysters to get 12 mg of zinc.

How many oysters that would be depends on the size of the oysters.

Answer 2

This question can't really be answered, 'cause measuring the milligrams of an ingredient with PPMs depends on the density of not only that ingredient but on the density of all the other components of a given sample. The problem you seem to be having is to do with what PPM means. One part per million is equal to 0.0001%. (but only when talking about numbers of discrete items, such as atoms) One PPM is not equal to a certain small amount of grams. Let me modify your original question like this....

If oysters are 0.02% Zinc, then how many oysters do you need to get 12mg of Zinc?

What can you tell from this? You can tell that if you piled up oysters until you had 12 milligrams of zinc in there, that the oysters would have to weigh 60,000 milligrams... 'cause twelve divided by 0.02% (that is, divided by 0.0002) equals 60,000..... This is 60 grams of oysters. But if you don't know how much one average oyster weighs then how can anyone say how many oysters are in a 60,000 milligram pile of oysters? I s'pose you could try and google what an average oyster weighs but what breed of oyster?  .....and how old are they?  ......the oysters could be any size, weight and density in this question.

As for an example of what I mean about the density of components in a sample having an effect on the average weight (milligrams etc.) of the entire sample, imagine if you had a crate with 1,000,000 glass marbles in it. If I took out 200 of them and replaced them with 200 steel ball bearings of the same size, then your crate contents would be 200PPM ball bearings. (and 999,800 PPM marbles.) But your crate is now heavier. The average weight of the balls in the crate has gone up.  And while it is now true to say that 0.02% of the balls are steel, steel now accounts for more than 0.02% of the crates weight.



Just remember that PPMs are like percent..... not like grams.