James Green, You are correct that correlation does not mean causation.  However, if there is a correlation, that is a reason to investigate to determine whether there is causation or not.  

The increase in cancer is correlated with an increase in the usage of glyphosate and atrazine.  Glyphosate is the most widespread pesticide used in the world.  The World Health Organization recently declared glyphosate to be probably carcinogenic.  Atrazine is in nearly 90% of drinking water in the US.   It has been linked with ovarian cancer, non-Hodgkin's lymphoma, hairy-cell leukemia, and thyroid cancer, prostate cancer, breast cancer, liver cancer, esophageal cancers, and childhood cancers.  

Studies are now being conducted to determine whether glyphosate and atrazine are causing cancer.  Studies should be conducted in Hawaii to determine whether the use of restricted use pesticides by agricultural entities are harming Hawaii residents.