They weren't sued because there was carcinogens in the chicken, but they were sued because of California's Proposition 65, which stated that if there's anything dangerous in the products then the companies had to give a clear warning.
チキンが発癌物質を含んでいたから訴えられたわけではなく 製品に危険性がある場合に明示的な警告を義務づける カリフォルニア州法Prop 65のため 訴えられたのです