Will the radioactive isotopes be passed up the food chain?

From what I've read so far, the amount of I-131 in milk is 10 times higher than the sample collected at the creek. The reason we find I-131 in milk is because "the rain lands on grass --> cow eats the grass --> cow processes grass --> cow is milked --> milk is delivered to the store".
How about we eat steak then? How much of these radioactive isotopes can accumulate up the food chain? I understand than I-131 has short half life. We might not need to worry about it. But how about other radioactive isotopes such as Cs or other untested isotopes that has a very long half life? Do we need to worry about the food chain effect?

How about our vegetables? Do we need to worry about these radioactive isotopes staying in the soil?

Could somebody let know/ educate me, so that I can have peace of mind?

Thanks.