THAT is impossible. Strontium 90 is still Strontium 90 if it is in the soil or in the plant or in your body.

If a pot plant picks up Strontium 90 or Cesium 137 and you smoke it you are inhaling that Strontium and Cesium into your lungs and irradiating your lungs. If deposited in your lungs, the particulate can be flushed up the trachea and then pass down the esophagus to the stomach where it will be digested and become part of the body waiting for its opportunity to cause cancer.

In the past 100 years the cancer rate has increased six fold per ratio of the population.