Some brass fittings may come with a rather alarming cancer warning. This warning is most likely due to cadmium plating on the brass, and while it does pose a risk, the risk is not severe.
A thin layer of cadmium plating may be added to metal fixtures in order to prevent the metal from corroding. Cadmium is quite effective at this and can significantly increase the longevity of metal fixings.
Cadmium is itself toxic and many compounds including cadmium are known carcinogens. Cadmium can also cause developmental problems in children. In general, exposure to cadmium should be minimized.
What Are The Dangers?
The risks of suffering cadmium poisoning from a cadmium plated fixture are fairly small. The metal does not easily leach off of the fixings.
What to Do?
The only place where cadmium fixings need to be completely avoided is where they would come into contact with food and drink. In other environments, the risk of the metal getting into the body is minimal.
What Should I Do?
Avoid using the cadmium plated brass fittings in the kitchen. You may also want to avoid using them in the bathroom, but that is less critical.