Claim: Air pollution in California associated with childhood cancer — So where was all the childhood cancer in the 1950s, 60s and 70s?

If this association were true, there would have been a huge spike in childhood cancer during the 1950s and 1960s. This is junk science because the weak statistical associations are based on unknown exposure data (exposure data is only guesstimated) and the biological implausibility of lumping different types of cancer together (i.e., if an exposure causes cancer, it probably causes one sort of cancer not all sorts).