Some of the approved drugs are synthetic versions of the natural hormones, such as trenbolone acetate and zeranol. Just like the natural hormone implants, before FDA approved these drugs, FDA required information and/or toxicological testing in laboratory animals to determine safe levels in the animal products that we eat (edible tissues). Furthermore, FDA required that the manufacturers demonstrate that the amount of hormone left in each edible tissue after treatment is below the appropriate safe level. As described above, a safe level is a level which would be expected to have no harmful effect in humans.
The EC made the scientific claim that the hormones used in treating cattle remain in the tissue, specifically the hormone, 17-beta estradiol .  However, despite this evidence the EC declared there was no clear link to health risks in humans for the other five provisionally banned hormones. The EC has also found high amounts of hormones in areas where there are dense cattle lots. This increase in hormones in the water has affected waterways and nearby wild fish.  Contamination of North American waterways by hormones would not, however, have any direct impact on European consumers or their health.