What can i do about my kids dad letting my kids be around severe 2nd hand smoke?

my kids ages 3 and 5 go with their dad and everytime they come back they smell and look like they have been rolling around an ash tray. where he lives they all smoke and when my kids are eating or sleeping they are puffing away with no care in the world. what can i do im in need of help and what can i tell the judge on an upcomming court hearing about the severe not just secondhand smoke but severe secondhand smoke. please help me i truly believe this is child abuse and child endangerment but the dad does not. I addressed my concern to him but i either end up being hung up on or looking at the end of a vehicle.