Serotonin can’t past the blood-brain barrier.

You have two serotonin households and it serves different regulation purposes in your body and brain.

I don’t know. As a lack of proper inspections is a key aspect to the issue, i wouldn’t trust it not to be the case.

I can only speak about Germany, but Germany is one of the largest pork producers and consumers.

There is at least one mayor scandal every year about malpractice, lack of hygiene and/or abuse of workers at industrial animal farms and slaughterhouses. The number of government inspectors only is enough to allow for inspections about once every 20 years or so per business. Also in many cases inspections are done by the local veterinarians, who also have the farmers/slaughter houses as customers and have a clear conflict of interest.