Even composites can be toxic. If they are direct cure ones - done by dentist, typically they are only 50-60% cured at best, which leaves close to 50% of toxic monomers that can leach and offgass into the body. You can find metacrylatese in the liver and other organs. Over time or based on the amount of exposure they can sensitise individuals and you can start having many allergies.
Better option is to go with ceramic fillings (Vita, Cerec, Ceramco, etc)- unfortunatelly these currenrtly might require more tooth removal and might need to be bonded with resin cement which works like a glues unless you go with porcelain fused to metal (crown) or Zirconia ceramic crown. Resin cements can be also toxic, but if used in small amounts and with small margins should be safe.
Nick, have you ever heard of tooth colored or composite fillings?