 chromium lead cadmium nickel titanium mice mortal tumor tissu level 700 mice live 5 ppm cadmium lead chromium nickel titanium drink water fed diet defici cadmium low metal tissu concentr compar man observ sex differ appear mortal femal unaffect mortal male cadmium lead nickel increas compar chromium group cadmium lead compar control longev oldest 10 sex lead titanium group male cadmium group compar control metal carcinogen incid tumor male cadmium lead femal nickel decreas bodi weight death greater titanium chromium lead group larg increment titanium moder increment cadmium nickel lesser increment chromium lead observ 5 organ compar control higher concentr cadmium titanium occur younger mice metal increas markedli tissu ag metal chromium exhibit sign innat toxic 