Also note that far more things "are known to cause cancer in California" than anywhere else!
For various interesting/historic reasons, California has exceptionally tight environmental restrictions (for pollutants etc), and one of the lowest thresholds for labeling products as "suspected" or "known" to cause cancer.
I'm in no position to judge whether California is "reasonable" or "over cautious", but for people who want to stir up panic, they'll always cite contamination levels (e.g. in water) compared to California's limits!