In my research over the internet everyone is telling that brass is not safe but still there are solenoid valves, joints, and piping made of brass used in everything like coffee machines, water dispensers etc.
It always depends on the concentration and where you place the copper within the human body.
In my opinion, the most interesting example are implants which are coated with copper and implanted within the human body. The idea behind this is, that copper is toxic at very low concentrations for bacteria, and the toxic concentration for human cells is slightly higher. If you hit the window between these two concentrations, you can prevent bacteria from settling down on your implant.
Furthermore, the human body needs copper. The recommendations about the daily intake differ. Some studies in the US have shown that the general copper intake in the USA is too high, others showed that it's too low (Wikipedia).
Some more information are provided by WHO (WHO - copper).
During designing a product, it gets more complex since the amount of released copper is influenced by complex corrosion processes which highly depend on the medium, time, etc. I think e.g. copper pans are coated most often (Copper pans) to prevent copper from entering your body.